ANATOMY REVIEW

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=22 BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="041000d2egerdp.png"> <div> </div> </td> </tr><tr> <td valign="top" width=145 BGCOLOR="#333399" TEXT="#080000" background="040a2c00erkjzj.png"> <div> <IMG SRC="096e39f0.png" border=0 width="227" height="159" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div>  <a href="HTMLobj-151/Enya_-_Storms_in_Africa.mp3"><u>Enya_-_Storms_in_Africa.mp3</u></a>  </div> </td> <td valign="top" height=458 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <FONT SIZE="5" COLOR="#336600" FACE="Times New Roman" ><I>cardio5</I></FONT><FONT SIZE="1" COLOR="#663399" FACE="Times New Roman" >    </FONT> |    <B> </B><FONT SIZE="2" COLOR="#0000BF" FACE="Times New Roman" ><A HREF="index.htm" TARGET="_top" TITLE="cardio5"><U><B>home</B></U></A></FONT></div> <div> <A HREF="id22.htm" TARGET="_top" TITLE="DEF"><U>DEF</U></A>   |   <B>ANATOMY REVIEW</B>   |   <A HREF="id18.htm" TARGET="_top" TITLE="VALVULOPATHY"><U>VALVULOPATHY</U></A>   |   <A HREF="id25.htm" TARGET="_top" TITLE="mitral valve"><U>mitral valve</U></A>   |   <A HREF="id21.htm" TARGET="_top" TITLE="VALVULOPATHY2"><U>VALVULOPATHY2</U></A>   |   <A HREF="id20.htm" TARGET="_top" TITLE="HEART FAILURE"><U>HEART FAILURE</U></A>   |   <A HREF="id23.htm" TARGET="_top" TITLE="PICTURES"><U>PICTURES</U></A>   |   <A HREF="id24.htm" TARGET="_top" TITLE="AORTA"><U>AORTA</U></A>   |   <A HREF="id17.htm" TARGET="_top" TITLE="Contact Me"><U>Contact Me</U></A></div> <div> <IMG SRC="04207040.png" border=0 width="263" height="4" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B>ANATOMY REVIEW</B></div> <div> <I>ANATOMY REVIEW</I></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"><IMG SRC="05cda550.jpg" border=0 width="474" height="341" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"><IMG SRC="05d2fea0.png" border=0 width="303" height="234" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">Atria. The top two chambers that receive blood from the body </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">or lungs. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Ventricles. The bottom two chambers. The right ventricle pumps </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">blood to the lungs to pick up oxygen, The left ventricle pumps blood to the rest of the body and is the strongest chamber. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Valves. There are four valves in the heart that help to direct blood flow. As they open and close, the valves produce sounds that can be heard with a stethoscope. The heart sounds can often tell your doctor about your hearts function. </div> <bR> <bR> <div> <IMG SRC="05eb4d50.png" border=0 width="180" height="213" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"> <A NAME="subsect11"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A><IMG SRC="05f3ce00.jpg" border=0 width="316" height="480" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">normal <IMG SRC="06062780.png" border=0 width="354" height="376" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">anatomical heart<IMG SRC="061edff0.png" border=0 width="237" height="255" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B>Chordae Tendineae</B> </div> <div> <I><B>Definition: </B></I></div> <div> The tendinous cords that connect each cusp of the two atrioventricular valves to appropriate papillary muscles in the heart ventricles, preventing the valves from reversing themselves when the ventricles contract</div> <bR> <bR> <div> <B><U>Location of the Heart Relative to Surrounding Structures </U></B></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The overall shape of the heart is that of a three-sided pyramid located in the middle mediastinum .</B></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> When viewed from its apex, the three sides of the ventricular mass are appreciated readily </B></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Two of the edges are named: </B></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The acute margin lies inferiorly and describes a sharp angle between the sternocostal and diaphragmatic surfaces. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The obtuse margin lies superiorly, and is much more diffuse. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The posterior margin is unnamed, but is also diffuse in its transition. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"><IMG SRC="0621cae0.png" border=0 width="284" height="174" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">One-third of the cardiac mass lies to the right of the midline, and two-thirds to the left. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The long axis of the heart is oriented from the left upper gastrium to the right shoulder. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The short axis, which corresponds to the plane of the atrioventricular groove, is oblique and is oriented closer to the vertical than the horizontal plane </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Anteriorly, the heart is covered by the sternum and the costal cartilages of the third, fourth, and fifth ribs. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The lungs contact the lateral surfaces of the heart, whereas, posteriorly, the heart abuts onto the pulmonary hila. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right lung overlies the right surface of the heart and reaches to the midline.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> In contrast, the left lung retracts from the midline in the area of the cardiac notch.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The heart has an extensive diaphragmatic surface inferiorly. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Posteriorly, the heart lies on the esophagus and the tracheal bifurcation, and bronchi that extend into the lung. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The sternum lies anteriorly and provides rigid protection to the heart during blunt trauma and is aided by the cushioning effects of the lungs. </B></div> <bR> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The Pericardium and Its Reflections </B></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The heart lies within the pericardium, which is attached to the walls of the great vessels and to the diaphragm.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The pericardium can be visualized best as a bag into which the heart has been placed apex first. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The inner layer, in direct contact with the heart, is the visceral epicardium, which encases the heart and extends several centimeters back onto the walls of the great vessels. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The outer layer forms the parietal pericardium, which lines the inner surface of the tough fibrous pericardial sack. A thin film of lubricating fluid lies within the pericardial cavity between the two serous layers.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Two identifiable recesses lie within the pericardium and are lined by the serous layer. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The first is the transverse sinus, which is delineated anteriorly by the posterior surface of the aorta and pulmonary trunk and posteriorly by the anterior surface of the interatrial groove.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The second is the oblique sinus, a cul-de-sac located behind the left atrium, delineated by serous pericardial reflections from the pulmonary veins and the inferior caval vein. </B></div> <div>  <A NAME="subsect13"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><IMG SRC="06406f50.png" border=0 width="262" height="245" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="0667af30.png" border=0 width="378" height="243" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <B><U>Mediastinal Nerves and Their Relationships to the Heart </U></B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The vagus and phrenic nerves descend through the mediastinum in close relationship to the heart . </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">They enter through the thoracic inlet, with the phrenic nerve located anteriorly on the surface of the anterior scalene muscle and lying just posterior to the internal thoracic artery (internal mammary artery) at the thoracic inlet. In this position, it is vulnerable to injury during dissection and preparation of the internal thoracic artery for use in coronary arterial bypass grafting.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> On the right side, the phrenic nerve courses on the lateral surface of the superior caval vein, again in harm's way during dissection for venous cannulation for cardiopulmonary bypass. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The nerve then descends anterior to the pulmonary hilum before reflecting onto the right diaphragm, where it branches to provide its innervation.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> In the presence of a left-sided superior caval vein, the left phrenic nerve is directly applied to its lateral surface. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The nerve passes anterior to the pulmonary hilum and eventually branches on the surface of the diaphragm. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The vagus nerves enter the thorax posterior to the phrenic nerves and course along the carotid arteries.</B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> On the right side, the vagus gives off the recurrent laryngeal nerve that passes around the right subclavian artery before ascending out of the thoracic cavity. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right vagus nerve continues posterior to the pulmonary hilum, gives off branches of the right pulmonary plexus, and exits the thorax along the esophagus. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">On the left, the vagus nerve crosses the aortic arch, where it gives off the recurrent laryngeal branch. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The recurrent nerve passes around the arterial ligament before ascending in the tracheoesophageal groove. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The vagus nerve continues posterior to the pulmonary hilum, gives rise to the left pulmonary plexus, and then continues inferiorly out of the thorax along the esophagus. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">A delicate nerve trunk known as the subclavian loop carries fibers from the stellate ganglion to the eye and head. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This branch is located adjacent to the subclavian arteries bilaterally. </B></div> <bR> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Excessive dissection of the subclavian artery during shunt procedures may injure these nerve roots and cause Horner's syndrome. </B></div> <bR> <div> <IMG SRC="067fe550.jpg" border=0 width="510" height="341" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">Diagram of the heart in relation to the vagus and phrenic nerves as viewed through a median sternotomy.</div> <bR> <bR> <bR> <div> <B><U>RELATIONSHIP OF THE CARDIAC CHAMBERS AND GREAT ARTERIES </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The surgical anatomy of the heart is best understood when the position of the cardiac chambers and great vessels is known in relation to the cardiac silhouette. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The atrioventricular junction is oriented obliquely, lying much closer to the vertical than the horizontal plane. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This plane can be viewed from its atrial aspect <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><U> </U></FONT>if the atrial mass and great arteries are removed by a parallel cut just above the junction. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The tricuspid and pulmonary valves are widely separated by the inner curvature of the heart lined by the transverse sinus.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Conversely, the mitral and aortic valves lie adjacent to one another, with fibrous continuity of their leaflets. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The aortic valve occupies a central position, wedged between the tricuspid and pulmonary valves.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Indeed, there is fibrous continuity between the leaflets of the aortic and tricuspid valves through the central fibrous body.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> With careful study of this short axis, several basic rules of cardiac anatomy become apparent.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> First, the atrial chambers lie to the right of their corresponding ventricles. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Second, the right atrium and ventricle lie anterior to their left-sided counterparts. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The septal structures between them are obliquely oriented. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Third, by virtue of its wedged position, the aortic valve is directly related to all of the cardiac chambers. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Several other significant features of cardiac anatomy can be learned from the short axis section.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The position of the aortic valve minimizes the area of septum where the mitral and tricuspid valves attach opposite each other. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Because the tricuspid valve is attached to the septum further toward the ventricular apex than the mitral valve, a part of the septum is interposed between the right atrium and the left ventricle to produce the muscular atrioventricular septum.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The central fibrous body, where the leaflets of the aortic, mitral, and tricuspid valves all converge, lies cephalad and anterior to the muscular atrioventricular septum.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The central fibrous body is the main component of the fibrous skeleton of the heart and is made up, in part, by the right fibrous trigone, a thickening of the right side of the area of fibrous continuity between the aortic and mitral valves, and in part by the membranous septum, the fibrous partition between the left ventricular outflow tract and the right heart chambers</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. The membranous septum itself is divided into two parts by the septal leaflet of the tricuspid valve, which is directly attached across it <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><U> </U></FONT>. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Thus, the membranous septum has an atrioventricular component between the right atrium and left ventricle, as well as an interventricular component.</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Removal of the noncoronary leaflet of the aortic valve demonstrates the significance of the wedged position of the left ventricular outflow tract in relation to the other cardiac chambers. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The subaortic region separates the mitral orifice from the ventricular septum; this separation influences the position of the atrioventricular conduction tissues and the position of the leaflets and tension apparatus of the mitral valve </div> <bR> <bR> <div> <B><U><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">CARDIAC CHAMBERS AND VALVES </U></B></div> <div>  <A NAME="subsect18"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Morphology of the Right Atrium and Tricuspid Valve </U></B></div> <div>  <A NAME="subsect21"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>APPENDAGE, VESTIBULE, AND VENOUS COMPONENT</U></B> </div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right atrium has three basic parts: the appendage, the vestibule, and the venous component </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Externally, the right atrium is divided into the appendage and the venous component, which receives the systemic venous return. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The junction of the appendage and the venous component is identified by a prominent groove, the terminal groove.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> This corresponds internally to the location of the terminal crest. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right atrial appendage has the shape of a blunt triangle, with a wide junction to the venous component across the terminal groove. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The appendage also has an extensive junction with the vestibule of the right atrium; the latter structure is the smooth-walled atrial myocardium that inserts into the leaflets of the tricuspid valve. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The most characteristic and constant feature of the morphology of the right atrium is that the pectinate muscles within the appendage extend around the entire parietal margin of the atrioventricular junction </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">These muscles originate as parallel fibers that course at right angles from the terminal crest. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The venous component of the right atrium extends between the terminal groove and the interatrial groove. It receives the superior and inferior caval veins and the coronary sinus. </div> <div>  <A NAME="subsect22"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>SINUS NODE </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The sinus node lies at the anterior and superior extent of the terminal groove, where the atrial appendage and the superior caval vein are juxtaposed.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The node is a spindle-shaped structure that usually lies to the right or lateral to the superior cavoatrial junction <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><U> </U></FONT>. In approximately 10 percent of cases, the node is draped across the cavoatrial junction in horseshoe fashion. </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The blood supply to the sinus node is from a prominent nodal artery that is a branch of the right coronary artery in approximately 55 percent of individuals, and a branch of the circumflex artery in the remainder. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Regardless of its artery of origin, the nodal artery usually courses along the anterior interatrial groove toward the superior cavoatrial junction, frequently within the atrial myocardium. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">At the cavoatrial junction, its course becomes variable and may circle either anteriorly or posteriorly, or rarely both anteriorly and posteriorly, around the cavoatrial junction to enter the node. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Uncommonly, the artery arises more distally from the right coronary artery and courses laterally across the atrial appendage. This places it at risk of injury during a standard right atriotomy. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The artery also may arise distally from the circumflex artery to cross the dome of the left atrium, where it is at risk of injury when utilizing a superior approach to the mitral valve. Incisions in either the right or left atrial chambers always should be made with this anatomic variability in mind. In our experience, these vessels can be identified by careful gross inspection and should prompt appropriate modification of surgical incisions. </div> <div>  <A NAME="subsect23"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>ATRIAL SEPTUM </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The most common incision into the right atrium is made into the atrial appendage parallel and anterior to the terminal groove.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Opening the atrium through this incision confirms that the terminal groove is the external marking of the prominent terminal crest. Anteriorly and superiorly, the crest curves in front of the orifice of the superior caval vein to become continuous with the so-called “septum secundum,” which, in reality, is the superior rim of the oval fossa. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">When the right atrium is inspected through this incision, there appears to be an extensive septal surface between the tricuspid valve and the orifices of the caval veins. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This “septal” surface includes the opening of the oval fossa and the orifice of the coronary sinus. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The apparent extent of the septum is spurious, as the true septum between the atrial chambers is virtually confined to the oval fossa </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The superior rim of the fossa, although often referred to as the “septum secundum,” is an extensive infolding between the venous component of the right atrium and the right pulmonary veins.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The inferior rim is directly continuous with the so-called sinus septum that separates the orifices of the inferior caval vein and the coronary sinus </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The region around the coronary sinus is where the right atrial wall overlies the atrioventricular muscular septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Removing the floor of the coronary sinus reveals the anterior extension of the atrioventricular groove in this region</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. Only a small part of the anterior rim of the oval fossa is a septal structure. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The majority is made up of anterior atrial wall overlying the aortic root. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Thus, dissection outside the limited margins of the oval fossa will penetrate the heart to the outside, rather than provide access to the left atrium via the septum. </div> <div>  <A NAME="subsect24"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <bR> <bR> <div> <B><U>ATRIOVENTRICULAR SEPTUM AND NODE: TRIANGLE OF KOCH </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">In addition to the sinus node, another major area of surgical significance is occupied by the atrioventricular node. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This structure lies within the triangle of Koch, which is demarcated by the tendon of Todaro, the septal leaflet of the tricuspid valve, and the orifice of the coronary sinus </div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. The tendon of Todaro is a fibrous structure formed by the junction of the eustachian valve and the thebesian valve (the valves of the inferior caval vein and coronary sinus, respectively).</FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The entire atrial component of the atrioventricular conduction tissues is contained within the triangle of Koch, which must be avoided to prevent surgical damage to atrioventricular conduction. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The atrioventricular bundle (of His) penetrates directly at the apex of the triangle of Koch before it continues to branch on the crest of the ventricular septum </div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. The key to avoiding atrial arrhythmias is careful preservation of the sinus and atrioventricular nodes and their blood supply. </FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">No advantage is gained in attempting to preserve nonexistent tracts of “specialized atrial conduction tissue,” although it makes sense to avoid prominent muscle bundles where parallel orientation of atrial myocardial fibers favors preferential conduction </div> <DIV ALIGN="LEFT"></DIV> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"><IMG SRC="06804750.jpg" border=0 width="260" height="373" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B><U>TRICUSPID VALVE </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The vestibule of the right atrium converges into the tricuspid valve.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The three leaflets reflect their anatomic location, being septal, anterosuperior, and inferior (or “mural”). </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The leaflets join together over three prominent zones of apposition; the peripheral ends of these zones usually are described as commissures. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The leaflets are tethered at the commissures by fan-shaped cords arising from prominent papillary muscles. The antero-septal commissure is supported by the medial papillary muscle.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The major leaflets of the valve extend from this position in anterosuperior and septal directions. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The third leaflet is less well defined. The antero-inferior commissure is usually supported by the prominent anterior papillary muscle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Often, however, it is not possible to identify a specific inferior papillary muscle supporting the infero-septal commissure.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Thus, the inferior leaflet may seem duplicated. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">There is no well-formed collagenous annulus for the tricuspid valve. Instead, the atrioventricular groove more or less folds directly into the tricuspid valvar leaflets at the vestibule, and the atrial and ventricular myocardial masses are separated almost exclusively by the fibro-fatty tissue of the groove. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The entire parietal attachment of the tricuspid valve usually is encircled by the right coronary artery running within the atrioventricular groove. </div> <div>  <A NAME="subsect19"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Morphology of the Left Atrium and Mitral Valve </U></B></div> <div>  <A NAME="subsect26"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>APPENDAGE, VESTIBULE, AND VENOUS COMPONENT </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Like the right atrium, the left atrium has three basic components: the appendage, vestibule, and venous component <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><U> </U></FONT>. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Unlike the right atrium, the venous component is considerably larger than the appendage and has a narrow junction with it that is not marked by a terminal groove or crest. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">There also is an important difference between the relationship of the appendage and vestibule between the left and right atria. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">As shown, the pectinate muscles within the right atrial appendage extend all around the parietal margin of the vestibule. In contrast, the left atrial appendage has a limited junction with the vestibule, and the pectinate muscles are located almost exclusively within the appendage </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The larger part of the vestibule that supports and inserts directly into the mural leaflet of the mitral valve is directly continuous with the smooth atrial wall of the pulmonary venous component. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Because the left atrium is posterior and tethered by the four pulmonary veins, the chamber is relatively inaccessible.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Several approaches are used by surgeons to gain access. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The most common is an incision just to the right of and parallel to the interatrial groove, anterior to the right pulmonary veins. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This incision can be carried beneath both the superior and inferior caval veins parallel to the interatrial groove, to provide wide access to the left atrium.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> A second approach is through the dome of the left atrium. If the aorta is pulled anteriorly and to the left, an extensive trough may be seen between the right and left atrial appendages. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">An incision through this trough, between the pulmonary veins of the upper lobes, provides direct access to the left atrium. When this incision is made, it is important to remember the location of the sinus node artery, which may course along the roof of the left atrium if it arises from the circumflex artery. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The left atrium also can be reached via a right atrial incision and an opening in the atrial septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">When the interior of the left atrium is visualized, the small size of the mouth of the left atrial appendage is apparent. It lies to the left of the mitral orifice as viewed by the surgeon. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The majority of the pulmonary venous atrium usually is located inferiorly away from the operative field. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The vestibule of the mitral orifice dominates the operative view.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The septal surface is located anteriorly, with the true septum relatively inferior </div> <div>  <A NAME="subsect27"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>MITRAL VALVE </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The mitral valve is supported by two prominent papillary muscles located in anterolateral and posteromedial positions. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The two leaflets of the mitral valve have markedly different appearances </div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. The aortic (or anterior) leaflet is short, relatively square, and guards approximately one-third of the circumference of the valvar orifice. </FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This leaflet is in fibrous continuity with the aortic valve and, because of this, is best referred to as the “aortic leaflet,” since it is neither strictly anterior nor superior in position. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The other leaflet is much shallower but guards approximately two-thirds of the circumference of the mitral orifice.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> As it is connected to the parietal part of the atrioventricular junction, it is most accurately termed the mural leaflet, but is often termed the posterior leaflet. It is divided into a number of subunits that fold against the aortic leaflet when the valve is closed. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Although generally there are three, there may be as many as five or six scallops in the mural leaflet. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Unlike the tricuspid valve, the mitral valve leaflets are supported by a rather dense collagenous annulus, although it may take the form of a sheet rather than a cord. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This annulus usually extends parietally from the fibrous trigones, the greatly thickened areas at either end of the area of fibrous continuity between the leaflets of the aortic and mitral valves </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. The area of the valvar orifice related to the right fibrous trigone and central fibrous body is most vulnerable with respect to the atrioventricular node and penetrating bundle </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The mid-portion of the aortic leaflet of the mitral valve is related to the commissure between the noncoronary and left coronary cusps of the aortic valve. An incision through the atrial wall in this area may be extended into the subaortic outflow tract, and may be useful for enlarging the aortic annulus during replacement of the aortic valve</div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. The circumflex coronary artery is adjacent to the left half of the mural leaflet, whereas the coronary sinus is adjacent to the right half of the mural leaflet </FONT></div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. These structures can be damaged during excessive dissection, or by excessively deep placement of sutures during replacement or repair of the mitral valve. When the circumflex artery is dominant, the entire attachment of the mural leaflet may be intimately related to this artery </FONT></div> <div>  <A NAME="subsect110"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Morphology of the Right Ventricle and Pulmonary Valve </U></B></div> <div>  <A NAME="subsect28"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>INLET AND APICAL TRABECULAR PORTIONS </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The morphology of both the right and left ventricles can be understood best by subdividing the ventricles into three anatomically distinct components: the inlet, apical trabecular, and outlet portions</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This classification is more helpful than the traditional division of the right ventricle into the “sinus” and “conus” parts. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The inlet portion of the right ventricle surrounds the tricuspid valve and its tension apparatus. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">A distinguishing feature of the tricuspid valve is the direct attachment of its septal leaflet. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The apical trabecular portion of the right ventricle extends out to the apex. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Here, the wall of the ventricle is quite thin and vulnerable to perforation by cardiac catheters and pacemaker electrodes. </div> <div>  <A NAME="subsect29"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>OUTLET PORTION AND PULMONARY VALVE </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The outlet portion of the right ventricle consists of the infundibulum, a circumferential muscular structure that supports the leaflets of the pulmonary valve.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Because of the semilunar shape of the pulmonary valvar leaflets, this valve does not have an annulus in the traditional sense of a ring-like attachment. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The leaflets have semilunar attachments that cross the musculo-arterial junction in a corresponding semi-lunar fashion </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Therefore, instead of a single annulus, three rings can be distinguished anatomically in relation to the pulmonary valve. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Superiorly, the sinotubular ridge of the pulmonary trunk marks the level of peripheral apposition of the leaflets (the commissures). A second ring exists at the ventriculo-arterial junction.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> A third ring can be constructed by joining together the basal attachments of the three leaflets to the infundibular muscle</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. None of these rings, however, corresponds to the attachments of the leaflets, which must be semilunar to permit the valve to competently open and close. In fact, these semilunar attachments, which mark the hemodynamic ventriculo-arterial junction, extend from the first ring, across the second, down to the third, and back in each cusp</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"><IMG SRC="06a791b0.png" border=0 width="377" height="283" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="06b40f00.png" border=0 width="320" height="240" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="06c40f00.png" border=0 width="320" height="240" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <B><U>SUPRAVENTRICULAR CREST AND PULMONARY INFUNDIBULUM </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">A distinguishing feature of the right ventricle is a prominent muscular shelf, the supraventricular crest, which separates the tricuspid and pulmonary valves </div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. In reality, this muscular ridge is the posterior part of the subpulmonary muscular infundibulum that supports the leaflets of the pulmonary valve. In other words, it is part of the inner curve of the heart. Incisions through the supraventricular crest run into the transverse septum and may jeopardize the right coronary artery. </FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Although this area is often considered the “outlet” component of the interventricular septum, in fact the entire subpulmonary infundibulum, including the ventriculoinfundibular fold, can be removed without entering the left ventricular cavity. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This is possible because the leaflets of the pulmonary and aortic valves are supported on separate sleeves of right and left ventricular outlet muscle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">There is an extensive external tissue plane between the walls of the aorta and the pulmonary trunk and the leaflets of the pulmonary and aortic valves have markedly different levels of attachments within their respective ventricles.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> This feature enables enucleation of the pulmonary valve, including its basal attachments within the infundibulum, during the Ross procedure without creating a ventricular septal defect. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">When the infundibulum is removed from the right ventricle, the insertion of the supraventricular crest between the limbs of the septomarginal trabeculation is visible</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> This trabeculation is a prominent muscle column that divides superiorly into anterior and posterior limbs. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The anterior limb runs superiorly into the infundibulum and supports the leaflets of the pulmonary valve. The posterior limb extends backwards beneath the ventricular septum and runs into the inlet portion of the ventricle. The medial papillary muscle arises from this posterior limb. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The body of the septomarginal trabeculation runs to the apex of the ventricle, where it divides into smaller trabeculations. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Two of these trabeculations may be particularly prominent.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> One becomes the anterior papillary muscle and the other crosses the ventricular cavity as the moderator band</div> <div>  <A NAME="subsect111"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Morphology of the Left Ventricle and Aortic Valve </U></B></div> <div>  <A NAME="subsect211"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>INLET AND APICAL TRABECULAR PORTIONS </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The left ventricle can be subdivided into three components, as was the right ventricle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The inlet component surrounds, and is limited by, the mitral valve and its tension apparatus.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The two papillary muscles occupy anterolateral and posteromedial positions and are positioned rather close to each other. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The leaflets of the mitral valve have no direct septal attachments because the deep posterior diverticulum of the left ventricular outflow tract displaces the aortic leaflet away from the inlet septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The apical trabecular component of the left ventricle extends to the apex, where the myocardium is surprisingly thin.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The trabeculations of the left ventricle are quite fine compared with those of the right ventricle </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. This characteristic is useful for defining ventricular morphology on diagnostic ventriculograms. </div> <div>  <A NAME="subsect212"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A><IMG SRC="06d16ca0.png" border=0 width="278" height="202" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="06f40e40.jpg" border=0 width="320" height="228" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B><U>OUTLET PORTION </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The outlet component supports the aortic valve and consists of both muscular and fibrous portions. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">This is in contrast to the infundibulum of the right ventricle, which is composed entirely of muscle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The septal portion of the left ventricular outflow tract, although primarily muscular, also includes the membranous portion of the ventricular septum. T</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">he posterior quadrant of the outflow tract consists of an extensive fibrous curtain that extends from the fibrous skeleton of the heart across the aortic leaflet of the mitral valve, and supports the leaflets of the aortic valve in the area of aortomitral continuity </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. The lateral quadrant of the outflow tract is again muscular and consists of the lateral margin of the inner curvature of the heart, delineated externally by the transverse sinus.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The left bundle of the cardiac conduction system enters the left ventricular outflow tract posterior to the membranous septum and immediately beneath the commissure between the right and non-coronary leaflets of the aortic valve.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> After traveling a short distance down the septum, the left bundle divides into anterior, septal, and posterior divisions. </div> <div>  <A NAME="subsect213"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A><IMG SRC="071a12a0.jpg" border=0 width="417" height="298" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="0737c290.png" border=0 width="380" height="297" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B><U>AORTIC VALVE </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The aortic valve is a semilunar valve, morphologically quite similar to the pulmonary valve.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Likewise, it does not have a discrete annulus. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Because of its central location, the aortic valve is related to each of the cardiac chambers and valves. A thorough knowledge of these relationships is essential to understanding aortic valve pathology and many congenital cardiac malformations. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The aortic valve consists primarily of three semilunar leaflets.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> As with the pulmonary valve, attachments of the leaflets extend across the ventriculo-arterial junction in a curvilinear fashion. Each leaflet, therefore, has attachments to the aorta and within the left ventricleBehind each leaflet, the aortic wall bulges outward to form the sinuses of Valsalva. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The leaflets themselves meet centrally along a line of coaptation, at the center of which is a thickened nodule, the nodule of Arantius. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Peripherally, adjacent to the commissures, the line of coaptation is thinner and normally may contain small perforations. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">During systole, the leaflets are thrust upward and away from the center of the aortic lumen, whereas, during diastole, they fall passively into the center of the aorta. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">With normal valvar morphology, all three leaflets meet along lines of coaptation and support the column of blood within the aorta to prevent regurgitation into the ventricle.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Two of the three aortic sinuses give rise to coronary arteries, from which arise their designations as right, left, and non-coronary sinuses. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">By sequentially following the line of attachment of each leaflet, the relationship of the aortic valve to its surrounding structures can be clearly understood.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Beginning posteriorly, the commissure between the non-coronary and left coronary leaflets is positioned along the area of aorto-mitral valvar continuity.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The fibrous sub-aortic curtain is beneath this commissure</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> To the right of this commissure, the non-coronary leaflet is attached above the posterior diverticulum of the left ventricular outflow tract. Here the valve is related to the right atrial wall. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">As the attachment of the non-coronary leaflet ascends from its nadir toward the commissure between the non-coronary and right coronary leaflets, the line of attachment is directly above the portion of the atrial septum containing the atrioventricular node. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The commissure between the non-coronary and right coronary leaflets is located directly above the penetrating atrioventricular bundle and the membranous ventricular septum </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. The attachment of the right coronary leaflet then descends across the central fibrous body before ascending to the commissure between the right and left coronary leaflets. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Immediately beneath this commissure, the uppermost part of the subaortic outflow tract is formed by the wall of the aorta.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> An incision through this area passes into the space between the facing surfaces of the aorta and pulmonary trunk</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> As the facing left and right leaflets descend from this commissure, they are attached to the outlet muscular component of the left ventricle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Only a small part of this area in the normal heart is a true outlet septum, since both pulmonary and aortic valves are supported on their own sleeves of myocardium.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Thus, although the outlet components of the right and left ventricle face each other, an incision below the aortic valve enters low into the infundibulum of the right ventricle.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> As the lateral part of the left coronary leaflet descends from the facing commissure to the base of the sinus, it becomes the only part of the aortic valve that is not intimately related to another cardiac chamber. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The anatomy of the aortic valve and its relationship to surrounding structures is important to successful replacement of the aortic valve, particularly when elargement of the aortic root is required. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The Konno-Rastan aortoventriculoplasty involves opening and enlarging the anterior portion of the sub-aortic region. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The incisions for this procedure begin with an anterior longitudinal aortotomy that extends through the commissure between the right and left coronary leaflets. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Anteriorly, the incision is extended across the base of the infundibulum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The differential level of attachment of the aortic and pulmonary valve leaflets permits this incision without damage to the pulmonary valve</div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. Posteriorly, the incision extends through the most medial portion of the supraventricular crest into the left ventricular outflow tract. </FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">By closing the resulting ventricular septal defect with a patch, the aortic outflow tract is widened to allow implantation of a larger valvar prosthesis. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">A second patch is used to close the defect in the right ventricular outflow tract. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Alternative methods to enlarge the aortic outflow tract involve incisions in the region of aortomitral continuity.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> In the Manouguian procedure , a curvilinear aortotomy is extended posteriorly through the commissure between the left and non-coronary leaflets down to, and occasionally into, the aortic leaflet of the mitral valve. <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><U> </U></FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> A patch is used to augment the incision posteriorly.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> When the posterior diverticulum of the outflow tract is fully developed, this incision can be made without entering other cardiac chambers, although not uncommonly the roof of the left atrium is opened. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The Nicks procedure for enlargement of the aortic root involves an aortotomy that passes through the middle of the non-coronary leaflet into the fibrous sub-aortic curtain and may be extended into the aortic leaflet of the mitral valve.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> This incision also may open the roof of the left atrium. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">When these techniques are used, any resultant defect in the left atrium must be closed carefully. </div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">As discussed previously, the differential level of attachment of aortic and pulmonary valves, as well as the muscular nature of their support, allows the pulmonary valve to be harvested and used as a replacement for the aortic valve in the Ross procedure.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> This procedure can be combined with the incisions of the Konno-Rastan aortoventriculoplasty to repair left ventricular outflow tract obstructions in young children with a viable autograft that has potential for growth and avoids the need for anticoagulation. </div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Accurate understanding of left ventricular outflow tract anatomy is also important in the treatment of aortic valvar endocarditis</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">] Because of the central position of the aortic valve relative to the other valves and cardiac chambers abscess formation can produce fistulas between the aorta and any of the four chambers of the heart.</div> <div> <B><U><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Patients may, therefore, present with findings of left heart failure, left-to-right shunting, and/or complete heart block in addition to the usual signs of sepsis and systemic embolization. </U></B></div> <div> <B><U><IMG SRC="075cd4d0.jpg" border=0 width="461" height="333" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="077d14e0.jpg" border=0 width="465" height="334" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></B></div> <div> <B><U>THE CORONARY ARTERIES </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right and left coronary arteries originate behind their respective aortic valvar leaflets </div> <div> <U><IMG BORDER="0" SRC="Symb075c00b700c8ff000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> </U><FONT SIZE="2" COLOR="#000000" FACE="Arial" >. The orifices usually are located in the upper third of the sinuses of Valsalva, although individual hearts may vary markedly.</FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Because of the oblique plane of the aortic valve, the orifice of the left coronary artery is superior and posterior to that of the right coronary artery. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The coronary arterial tree is divided into three segments; two (the left anterior descending artery and the circumflex artery) arise from a common stem.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The third segment is the right coronary artery. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The “dominance” of the coronary circulation (right vs. left) usually refers to the artery from which the posterior descending artery originates, not the absolute mass of myocardium perfused by the left or right coronary artery. Right dominance occurs in 85–90 percent of normal individuals. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Left dominance occurs slightly more frequently in males than females. </div> <div>  <A NAME="subsect112"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Main Stem of the Left Coronary Artery </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The main stem of the left coronary artery courses from the left sinus of Valsalva anteriorly, inferiorly, and to the left between the pulmonary trunk and the left atrial appendage</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. Typically it is 10–20 millimeters in length but can extend to a length of 40 millimeters. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The left main stem can be absent, with separate orifices in the sinus of Valsalva for its two primary branches (1 percent of patients). </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The main stem divides into two major arteries of nearly equal diameter: the left anterior descending artery and the circumflex artery. </div> <div>  <A NAME="subsect113"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <DIV ALIGN="LEFT"></DIV> <div> <IMG SRC="078f5590.jpg" border=0 width="245" height="345" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="07aa2d70.png" border=0 width="162" height="215" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <B><U>Left Anterior Descending Artery </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The left anterior descending (or interventricular) coronary artery continues directly from the bifurcation of the left main stem, coursing anteriorly and inferiorly in the anterior interventricular groove to the apex of the heart Its branches include the diagonals, the septal perforators, and the right ventricular branches. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The diagonals, which may be two to six in number, course along the anterolateral wall of the left ventricle and supply this portion of the myocardium. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The first diagonal generally is the largest and may arise from the bifurcation of the left main stem (formerly known as the intermediate artery). </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The septal perforators branch perpendicularly into the ventricular septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Typically there are three to five septal perforators; the initial one is the largest and commonly originates just beyond the take-off of the first diagonal.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> This perpendicular orientation is a useful marker for identification of the left anterior descending artery on coronary angiograms.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The septal perforators supply blood to the anterior two-thirds of the ventricular septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Right ventricular branches, which may not always be present, supply blood to the anterior surface of the right ventricle.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> In approximately 4 percent of hearts, the left anterior descending artery bifurcates proximally and continues as two parallel vessels of approximately equal size down the anterior interventricular groove. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Occasionally, the artery wraps around the apex of the left ventricle to feed the distal portion of the posterior interventricular groove.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Rarely, it extends along the entire length of the posterior groove to replace the posterior descending artery. </div> <div>  <A NAME="subsect214"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A><IMG SRC="07c62330.png" border=0 width="354" height="307" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="07e82180.jpg" border=0 width="386" height="280" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08040e40.jpg" border=0 width="320" height="228" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08240e60.jpg" border=0 width="320" height="230" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <B><U>Circumflex Artery </U></B></div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The left circumflex coronary artery arises from the left main coronary artery roughly at a right angle to the anterior interventricular branch.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> It courses along the left atrioventricular groove and, in 85–95 percent of patients, terminates near the obtuse margin of the left ventricle . In 10–15 percent of patients, it continues around the atrioventricular groove to the crux of the heart to give rise to the posterior descending artery (left dominance, </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The primary branches of the left circumflex coronary artery are the obtuse marginals.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> They supply blood to the lateral aspect of the left ventricular myocardium, including the posteromedial papillary muscle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Additional branches supply blood to the left atrium and, in 40–50 percent of hearts, the sinus node. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">When the circumflex coronary artery supplies the posterior descending artery, it also supplies the atrioventricular node. </div> <div>  <A NAME="subsect215"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <I><B><U>Right Coronary Artery </U></B></I></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right coronary artery courses from the aorta anteriorly and laterally before descending in the right atrioventricular groove and curving posteriorly at the acute margin of the right ventricle </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. In 85–90 percent of hearts, the right coronary artery crosses the crux, where it makes a characteristic U-turn before bifurcating into the posterior descending artery and the right posterolateral artery. In 50–60 percent of hearts, the artery to the sinus node arises from the proximal portion of the right coronary artery.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The blood supply to the atrioventricular node (in patients with right dominant circulation) arises from the mid-portion of the U-shaped segment. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The posterior descending artery runs along the posterior interventricular groove, extending for a variable distance toward the apex of the heart. It gives off perpendicular branches, the posterior septal perforators, that course anteriorly in the ventricular septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Typically, these perforators supply the posterior one-third of the ventricular septal myocardium. </div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right posterolateral artery gives rise to a variable number of branches that supply the posterior surface of the left ventricle. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The circulation of the posteoinferior portion of the left ventricular myocardium is quite variable.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> It may consist of branches of the right coronary artery, the circumflex artery, or both. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The acute marginal arteries branch from the right coronary artery along the acute margin of the heart, before its bifurcation at the crux.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> These marginals supply the anterior free wall of the right ventricle. In 10–20 percent of hearts, one of these acute marginal arteries courses across the diaphragmatic surface of the right ventricle to reach the distal ventricular septum. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The right coronary artery supplies important collaterals to the left anterior descending artery through its septal perforators.</div> <div> <I><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> In addition, its infundibular (or conus) branch, which arises from the proximal portion of the right coronary artery, courses anteriorly over the base of the ventricular infundibulum and may serve as a collateral to the anterior descending artery. Kugel's artery is an anastomotic vessel between the proximal right coronary and the circumflex coronary artery that can also provide a branch that runs through the base of the atrial septum to the crux of the heart, where it supplies collateral circulation to the atrioventricular node. </I></div> <bR> <div> <I><B><U><IMG SRC="0830ccf0.png" border=0 width="268" height="207" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08540e80.jpg" border=0 width="320" height="232" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08740e20.jpg" border=0 width="320" height="226" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></B></I></div> <div> <I><B><U>THE CORONARY VEINS</U></B></I></div> <bR> <bR> <div> <I><B><IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">A complex network of veins drains the coronary circulation. An extensive degree of collateralization amongst these veins and the coronary arteries, and the paucity of valves within coronary veins, enables the use of retrograde coronary sinus cardioplegia for intraoperative myocardial protection. </B></I></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The venous circulation can be divided into three systems: the coronary sinus and its tributaries, the anterior right ventricular veins, and the thebesian veins. </div> <div>  <A NAME="subsect114"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Coronary Sinus and Its Tributaries </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The coronary sinus predominantly drains the left ventricle and receives approximately 85 percent of coronary venous blood. It lies within the posterior atrioventricular groove and empties into the right atrium at the lateral border of the<FONT SIZE="2" COLOR="#FF0000" FACE="Arial" ><B><U> triangle of Koch </U></B></FONT></div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">. The orifice of the coronary sinus is guarded by the crescent-shaped thebesian valve.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> The named tributaries of the coronary sinus include the anterior interventricular vein, which courses parallel to the left anterior descending coronary artery. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Adjacent to the bifurcation of the left main stem, the anterior interventricular vein courses leftward in the atrioventricular groove, where it is referred to as the great cardiac vein.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> It receives blood from the marginal and posterior left ventricular branches before becoming the coronary sinus at the origin of the oblique vein (of Marshall) at the posterior margin of the left atrium. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The posterior interventricular vein, or middle cardiac vein, arises at the apex, courses parallel to the posterior descending coronary artery, and extends proximally to the crux.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0"> Here, this vein drains either directly into the right atrium or into the coronary sinus just prior to its orifice. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The small cardiac vein runs posteriorly through the right atrioventricular groove. </div> <div>  <A NAME="subsect115"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Anterior Right Ventricular Veins</U></B> </div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The anterior right ventricular veins travel across the right ventricular surface to the right atrioventricular groove, where they either enter directly into the right atrium or coalesce to form the small cardiac vein. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">As indicated, this vein travels down the right atrioventricular groove, around the acute margin, and enters into the right atrium directly or joins the coronary sinus just proximal to its orifice. </div> <div>  <A NAME="subsect116"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> <B><U>Thebesian Veins </U></B></div> <bR> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">The thebesian veins are small venous tributaries that drain directly into the cardiac chambers. </div> <div> <IMG BORDER="0" SRC="Symb075c00b700c800000000.png" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">They exist primarily in the right atrium and right ventricle. </div> <div> <I><B><U><IMG SRC="08872c30.jpg" border=0 width="370" height="451" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="089672d0.jpg" border=0 width="359" height="301" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08af4550.jpg" border=0 width="500" height="341" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08bf43e0.png" border=0 width="500" height="318" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></B></I></div> <div> <I><B><U>to resume</U></B></I></div> <div>  <A NAME="coronary_arteries"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Coronary Arteries</div> <div> Because the heart is composed primarily of cardiac muscle tissue that continuously contracts and relaxes, it must have a constant supply of oxygen and nutrients. The coronary arteries are the network of blood vessels that carry oxygen- and nutrient-rich blood to the cardiac muscle tissue.</div> <div> The blood leaving the left ventricle exits through the aorta, the body’s main artery. Two coronary arteries, referred to as the "left" and "right" coronary arteries, emerge from the beginning of the aorta, near the top of the heart.</div> <div> The initial segment of the left coronary artery is called the left main coronary. This blood vessel is approximately the width of a soda straw and is less than an inch long. It branches into two slightly smaller arteries: the left anterior descending coronary artery and the left circumflex coronary artery. The left anterior descending coronary artery is embedded in the surface of the front side of the heart. The left circumflex coronary artery circles around the left side of the heart and is embedded in the surface of the back of the heart.</div> <div> Just like branches on a tree, the coronary arteries branch into progressively smaller vessels. The larger vessels travel along the surface of the heart; however, the smaller branches penetrate the heart muscle. The smallest branches, called capillaries, are so narrow that the red blood cells must travel in single file. In the capillaries, the red blood cells provide oxygen and nutrients to the cardiac muscle tissue and bond with carbon dioxide and other metabolic waste products, taking them away from the heart for disposal through the lungs, kidneys and liver.</div> <div> When cholesterol plaque accumulates to the point of blocking the flow of blood through a coronary artery, the cardiac muscle tissue fed by the coronary artery beyond the point of the blockage is deprived of oxygen and nutrients. This area of cardiac muscle tissue ceases to function properly. The condition when a coronary artery becomes blocked causing damage to the cardiac muscle tissue it serves is called a myocardial infarction or heart attack.</div> <div>  <A NAME="superior_vena_cava"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Superior Vena Cava</div> <div> The superior vena cava is one of the two main veins bringing de-oxygenated blood from the body to the heart. Veins from the head and upper body feed into the superior vena cava, which empties into the right atrium of the heart.</div> <div>  <A NAME="inferior_vena_cava"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Inferior Vena Cava</div> <div> The inferior vena cava is one of the two main veins bringing de-oxygenated blood from the body to the heart. Veins from the legs and lower torso feed into the inferior vena cava, which empties into the right atrium of the heart.</div> <div>  <A NAME="aorta"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Aorta</div> <div> The aorta is the largest single blood vessel in the body. It is approximately the diameter of your thumb. This vessel carries oxygen-rich blood from the left ventricle to the various parts of the body.</div> <div>  <A NAME="pulmonary_artery"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Pulmonary Artery</div> <div> The pulmonary artery is the vessel transporting de-oxygenated blood from the right ventricle to the lungs. A common misconception is that all arteries carry oxygen-rich blood. It is more appropriate to classify arteries as vessels carrying blood away from the heart.</div> <div>  <A NAME="pulmonary_vein"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Pulmonary Vein</div> <div> The pulmonary vein is the vessel transporting oxygen-rich blood from the lungs to the left atrium. A common misconception is that all veins carry de-oxygenated blood. It is more appropriate to classify veins as vessels carrying blood to the heart.</div> <div>  <A NAME="right_atrium"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Right Atrium</div> <div> The right atrium receives de-oxygenated blood from the body through the superior vena cava (head and upper body) and inferior vena cava (legs and lower torso). The sinoatrial node sends an impulse that causes the cardiac muscle tissue of the atrium to contract in a coordinated, wave-like manner. The tricuspid valve, which separates the right atrium from the right ventricle, opens to allow the de-oxygenated blood collected in the right atrium to flow into the right ventricle.</div> <div>  <A NAME="right_ventricle"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Right Ventricle</div> <div> The right ventricle receives de-oxygenated blood as the right atrium contracts. The pulmonary valve leading into the pulmonary artery is closed, allowing the ventricle to fill with blood. Once the ventricles are full, they contract. As the right ventricle contracts, the tricuspid valve closes and the pulmonary valve opens. The closure of the tricuspid valve prevents blood from backing into the right atrium and the opening of the pulmonary valve allows the blood to flow into the pulmonary artery toward the lungs.</div> <div>  <A NAME="left_atrium"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Left Atrium</div> <div> The left atrium receives oxygenated blood from the lungs through the pulmonary vein. As the contraction triggered by the sinoatrial node progresses through the atria, the blood passes through the mitral valve into the left ventricle.</div> <div>  <A NAME="left_ventricle"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Left Ventricle</div> <div> The left ventricle receives oxygenated blood as the left atrium contracts. The blood passes through the mitral valve into the right ventricle. The aortic valve leading into the aorta is closed, allowing the ventricle to fill with blood. Once the ventricles are full, they contract. As the left ventricle contracts, the mitral valve closes and the aortic valve opens. The closure of the mitral valve prevents blood from backing into the left atrium and the opening of the aortic valve allows the blood to flow into the aorta and flow throughout the body.</div> <div>  <A NAME="papillary_muscles"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Papillary Muscles</div> <div> The papillary muscles attach to the lower portion of the interior wall of the ventricles. They connect to the chordae tendineae, which attach to the tricuspid valve in the right ventricle and the mitral valve in the left ventricle. The contraction of the papillary muscles opens these valves. When the papillary muscles relax, the valves close.</div> <div>  <A NAME="chordae_tendineae"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Chordae Tendineae</div> <div> The chordae tendineae are tendons linking the papillary muscles to the tricuspid valve in the right ventricle and the mitral valve in the left ventricle. As the papillary muscles contract and relax, the chordae tendineae transmit the resulting increase and decrease in tension to the respective valves, causing them to open and close. The chordae tendineae are string-like in appearance and are sometimes referred to as "heart strings."</div> <div>  <A NAME="tricuspid_valve"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Tricuspid Valve</div> <div> The tricuspid valve separates the right atrium from the right ventricle. It opens to allow the de-oxygenated blood collected in the right atrium to flow into the right ventricle. It closes as the right ventricle contracts, preventing blood from returning to the right atrium; thereby, forcing it to exit through the pulmonary valve into the pulmonary artery.</div> <div>  <A NAME="mitral_value"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Mitral Value</div> <div> The mitral valve separates the left atrium from the left ventricle. It opens to allow the oxygenated blood collected in the left atrium to flow into the left ventricle. It closes as the left ventricle contracts, preventing blood from returning to the left atrium; thereby, forcing it to exit through the aortic valve into the aorta.</div> <div>  <A NAME="pulmonary_valve"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Pulmonary Valve</div> <div> The pulmonary valve separates the right ventricle from the pulmonary artery. As the ventricles contract, it opens to allow the de-oxygenated blood collected in the right ventricle to flow to the lungs. It closes as the ventricles relax, preventing blood from returning to the heart.</div> <div>  <A NAME="aortic_valve"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>Aortic Valve</div> <div> The aortic valve separates the left ventricle from the aorta. As the ventricles contract, it opens to allow the oxygenated blood collected in the left ventricle to flow throughout the body. It closes as the ventricles relax, preventing blood from returning to the heart.</div> <div> <I><B><U><IMG SRC="08cc0250.png" border=0 width="192" height="293" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">1</U></B></I><FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><U>Right Coronary</U></FONT><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>2Left Anterior Descending</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>3Left Circumflex</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>4Superior Vena Cava</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>5Inferior Vena Cava</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>6Aorta</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>7Pulmonary Artery</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <U>8Pulmonary Vein</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <bR> <div> <U><IMG SRC="08dc0250.png" border=0 width="192" height="293" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">9Right Atrium</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT><U>Right Ventricle</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > 10</FONT><U>Left Atrium</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > 11</FONT><U>Left Ventricle</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > 12</FONT><U>Papillary Muscles</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > 13</FONT><U>Chordae Tendineae</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > 14</FONT><U>Tricuspid Valve</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT><U>Mitral Valve</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > 15</FONT><U>Pulmonary Valve</U></div> <div> <U>Aortic Valve (Not pictured)</U><FONT SIZE="2" COLOR="#000000" FACE="Arial" > </FONT></div> <div> <IMG SRC="08e23650.png" border=0 width="291" height="357" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="08fc3250.png" border=0 width="195" height="293" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">1Sinoatrial node (SA node) 2Atrioventricular node (AV node) 3Common AV Bundle  4Right & Left Bundle Branches </div> <bR> <div> <U><IMG SRC="0901cdc0.png" border=0 width="284" height="220" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="09240e20.jpg" border=0 width="320" height="226" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"><IMG SRC="09440e20.jpg" border=0 width="320" height="226" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></div> </td> </tr></table></body>