cardio
reduced cardiac output:
Hypertrophic cardiomyopathy
There are 4 major types of HCM.
Type 1. In type 1 HCM the hypertrophy is localized to the anterior segment of the ventricular septum.
Type 2. In the case of type 2 HCM the hypertrophy affects both the anterior and posterior segments of the ventricular septum.
Type 3. In type 3 HCM the hypertrophy affects the ventricular septum and the free wall of the left ventricle.
Type 4. In type 4 HCM thickening of the posterior segment of the septum and the anterolateral free wall of the heart is seen.
The left ventricle is almost always affected and in some patients the muscle of the right ventricle also thickened. In each type of HCM there can be different degrees of heart muscle thickening resulting in a variety of symptoms that characterize the disease.
Similar symptoms to HCM exist and are linked to non-genetic causes such as high blood pressure or excessive athlete training. The disease is diagnosed with the use of an echocardiogram (EKG), and is detected by a presystolic gallop (heart murmur).
![](Symb075c00b700f000000000.png) The cardiac output equals stroke volume times heart rate.
![](Symb075c00b700f000000000.png) Stroke volume is determined by afterload (resistance that the heart must overcome),
![](Symb075c00b700f000000000.png) preload (stretch on the ventricles),
![](Symb075c00b700f000000000.png) state of inotropy (contractility) of the heart,
![](Symb075c00b700f000000000.png) and synchronous contraction of the ventricles.
![](Symb075c00b700f000000000.png) In hypertrophic cardiomyopathy, there is usually an asymmetric hypertrophy of the ventricular septum,
![](Symb075c00b700f000000000.png) with increased thickness of the free left ventricular wall.
This condition decreases the left ventricular volume.
![](Symb075c00b700f000000000.png) The anterior leaflet of the mitral valve is closely approximated to the asymmetric interventricular septum and is drawn against that structure by the negative pressures created behind the ejected stream of blood,
![](Symb075c00b700f000000000.png) thereby obstructing blood flow and decreasing the cardiac output.
![](Symb075c00b700f000000000.png) Positive inotropic agents (e.g., digitalis) or b agonists are contraindicated, because the increased force of contraction causes the anterior leaflet to obstruct the opening even earlier.
![](Symb075c00b700f000000000.png) Negative inotropic agents (e.g., propranolol) decrease the force of contraction and also increase preload, thereby enhancing the cardiac output.
Obstruction to flow of blood out of the left ventricle to the aorta. This is an unusual type of obstruction in that it occurs only while the left ventricle is contracting and only when the portion of the septum near the aortic valve is thickened. To understand why obstruction occurs, it is important to understand that one of the leaflets that make up the mitral valve lies close to the septum when the mitral valve is open. When the left ventricle begins to contract, blood starts to flow between the opened mitral leaflet and the septum into the aortic valve, which lies between them. This flow of blood draws the mitral valve leaflet closer to the septum, which makes it harder for the blood to flow.
![](Symb075c00b700f000000000.png) This is called dynamic obstruction.
Diagnosis of obstructive hypertropic cardiomyopathy can be made by echocardiography and by left heart catheterization.
Treatments for obstructive hypertrophic cardiomyopathy include medications that are negative inotropic agents, such as beta-blockers and verapamil, avoidance of positive inotropes such as digitalis compounds, implantation of a dual chamber pacemaker, replacement of the mitral valve (to eliminate the leaflet that obstructs the passage of blood flow), and surgical or chemical resection of the thickened part of the septum. Each of these options has advantages and disadvantages, and should be discussed with your doctor.
Heart failure "Heart failure" in this setting refers to shortness of breath and/or weakness due to inability of the heart to pump enough blood to empty the lungs and supply the body with oxygenated blood. Unlike congestive heart failure, heart failure in hypertrophic cardiomyopathy is due to "diastolic dysfunction", which means that the heart muscle does relax fast enough and completely enough to allow blood to flow in before the heart begins to contract again.
If obstruction to flow is present, the treatments are as above. If there is no obstruction, only the medications described above are used.
Fast heart rhythms such as ventricular tachycardia. Unfortunately, the cellular structure of the heart muscle in hypertrophic cardiomyopathy is not normal. Perhaps for this reason, people with this condition are at risk for sudden death due to ventricular tachcardia and ventricular fibrillation.
There are no good diagnostic tests for identifying the few people with this condition who will die suddenly. Electrophysiological study has been reported to be helpful by some physicians but not all. For this reason, electrophysiologists look for clues in a person's history that suggest a higher risk: family history of sudden death with hypertrophic cardiomyopathy, syncope (passing out spells) or near-syncope, and the finding of ventricular tachycardia on ambulatory ("Holter") electrocardiography recordings.
Until relatively recently, there were no good treatments for patients with hypertrophic cardiomyopathy who were at high risk for sudden death. At this time, most such patients are treated with implantable cardioverter-defibrillators (ICDs), which are quite safe and very effective.
Sarcomere Genes
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# of Known Mutations
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Gene Chromosome Location
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Code for Thick or Thin Filament
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Expressed in Cardiac or Skeletal Muscle
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Beta-cardiac myosin heavy chain
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>50
|
14q11.2-q13
|
Thick
|
cardiac
&
skeletal
|
Cardiac myosin essential light chain
|
2
|
3p21.2-p21.3
|
Thick
|
cardiac
&
skeletal
|
Cardiac myosin regulatory light chain
|
4
|
12q23-q24.3
|
Thick
|
cardiac
&
skeletal
|
Alpha-tropomyosin
|
4
|
15q22
|
Thin
|
cardiac
&
skeletal
|
Cardiac troponin T
|
11
|
1q32
|
Thin
|
cardiac
&
skeletal
|
Cardiac troponin I
|
6
|
19p13.2-q13.2
|
Thin
|
cardiac
|
Cardiac myosin binding protein C
|
21
|
11p11.2
|
Thick
|
cardiac
|
Cardiac alpha-actin
|
?
|
15q14
|
Thin
|
cardiac
&
skeletal
|
There is further inconsistency in the age at which carriers become symptomatic. Some
Cardiomyopathy is a condition in which the muscle of the heart is abnormal in the absence of an apparent cause.
This terminology is purely descriptive and is based on the Latin deviation.
There are three types of cardiomyopathy:
![](Symb075c00b700f000000000.png) " hypertrophic",
![](Symb075c00b700f000000000.png) "dilated"
![](Symb075c00b700f000000000.png) and "restrictive".
The main feature of Hypertrophic Cardiomyopathy is an excessive thickening of the heart muscle (hypertrophy literally means to thicken).
Heart muscle may thicken in normal individuals as a result of high blood pressure or prolonged athletic training.
In Hypertrophic Cardiomyopathy (HCM), however the muscle thickening occurs without an obvious cause.
In addition, microscopic examination of the heart muscle in HCM shows abnormal.
The normal alignment of muscle cells is absent and this abnormality is called "myocardial disarray"
Microscopic examination of the heart muscle in HCM is abnormal. The normal alignment of muscle cells is absent and this abnormality is called " myocardial disarray".
It is thought that HCM is due to genetic mutations of one or several genes encoding proteins of the cardiac sacomere (heart muscle).
Since HCM is often inherited it has been observed to show a pattern of autosomal dominance.
The prevalence of HCM in the general population is estimated at 0.1-0.2%. Worldwide approximately 1 in 5000 individuals have HCM. HCM is the most common cause of sudden cardiac deaths in young. It is also responsible for approximately 35% of sudden deaths among athletes.
Although hypertrophy may be present at birth or in childhood,
it is much more common for the heart to appear normal at this time.
Occasionally, Hypertrophic Cardiomyopathy is the cause of a stillbirth or develops during infancy, with heart failure which may be fatal.
However, hypertrophy more commonly develops in association with growth and is usually apparent by the late teens or early twenties.
After this time it appears that there is no significant change in muscle thickness in the years of adult life.
Children and adolescents with the condition usually come to attention when a family screening is performed after an adult in the family is found to be affected.
Approximately 50% of adults with the condition present with symptoms.
In the remainder the diagnosis is made during family screening or following the detection of a murmur or abnormality on routine electrocardiogram (ECG).
![](Symb075c00b700f000008000.png) Hypertrophic cardiomyopathy (HCM) is a complex cardiac disease marked by thickening of the heart muscle. In HCM patients this thickening occurs for no apparent clinical cause like significant high blood pressure.
![](Symb075c00b700f000000000.png) The disease doesn't affect everyone the same way, with different degrees of muscular wall thickening and a variety of symptoms
![](Symb075c00b700f000000000.png) Patients may have shortness of breath, exercise intolerance, chest pressure or pain, fainting, or no symptoms at all. In unusual cases HCM can cause sudden cardiac death.
![](Symb075c00b700f000000000.png) The diagnosis of HCM is usually made with echocardiography, a cardiac ultrasound examination. Among the many variations that can occur in HCM, some patients are found to have obstruction while others are non-obstructed.
![](Symb075c00b700f000000000.png) Patients in both groups have heart thickening and both can have troubling symptoms.
![](Symb075c00b700f000000000.png) Patients with obstruction have a blockage inside the heart that results in the heart overworking as it pumps blood to the body
![](Symb075c00b700f000000000.png) Obstructive HCM used to be called idiopathic hypertrophic subaortic stenosis (IHSS).
![](Symb075c00b700f000000000.png) In patients without obstruction the thickening of the heart itself results in the symptoms.
![](Symb075c00b700f000000000.png) Why do patients seek evaluation and treatment for HCM? Some patients seek relief of symptoms.
![](Symb075c00b700f000000000.png) Others come because they have risk factors for sudden cardiac death such as blackouts or sudden deaths in the family.
![](Symb075c00b700f000000000.png) Occasionally patients seek confirmation of a diagnosis of HCM.
![](Symb075c00b700f000000000.png) For example, it is sometimes difficult to differentiate HCM from the athlete's heart syndrome, a mild thickening of the heart due to exercise conditioning. Because HCM is often inherited, family members may carry a gene for the disease even if they have no symptoms.
![](Symb075c00b700f000000000.png) All parents, children, brothers and sisters of anyone with HCM should be screened.
![](Symb075c00b700f000000000.png) In HCM patients, it is thought that the walls of the heart thicken because of a genetic abnormality of the heart muscle.
Diagnosis and Echocardiography in HCM
![](Symb075c00b700f000000000.png) Hypertrophic cardiomyopathy is cardiology's great masquerader. Sometimes, it simulates coronary artery disease when patients have chest pains or abnormal electrocardiograms. Sometimes, it resembles valvular heart disease with heart murmurs. Sometimes, it resembles dilated cardiomyopathy with heart failure. Sometimes, it has no symptoms at all and resembles normal.
![](Symb075c00b700f000000000.png) In rare cases adolescents and young adults with no prior symptoms at all can die suddenly without knowing that they have the disease. HCM is the most common cause of sudden cardiac death in young athletes and in people under 30 years of age. We suspect that ventricular fibrillation, a chaotic heart rhythm, is the cause of death.
![](Symb075c00b700f000000000.png) Proper therapy depends on accurate diagnosis of HCM. We make the initial diagnosis with an echocardiogram. Echocardiography is a non-invasive, non-Xray, imaging technique that uses sound waves to picture the heart.
![](Symb075c00b700f000000000.png) HCM is marked by thickening of the heart that occurs in the absence of significant high blood pressure or heart valve disease. Normally, heart walls are 11 mm or less in thickness. Patients with HCM have a characteristic thickening of the heart walls that can range from 14 to 60 mm, visible though echocardiography. By bouncing ultrasound off the heart, an image is produced which is recorded on videotape for analysis. Below are examples of cross-sectional images of a normal patient.
There is no particular symptom or complaint which is unique Hypertrophic Cardiomyopathy. Symptoms may occur at any stage in a person's life even though the condition may have been present for some time. The reason for the onset of symptoms is often not clear.
Shortness of Breath
Exercise capacity may be limited by breathlessness and fatigue. Most individuals experience only mild exercise limitations, but occasionally limitation is severe and a minority may have shortness of breath at rest.
Chest Pain
Chest pain is a common symptom. It is usually brought on by exertion and relieved by rest, but pain may occur at rest or during sleep and may persist. The cause of the pain is thought to be insufficient oxygen supply to the myocardium. In Hypertrophic Cardiomyopathy the main coronary arteries are usually normal, but the greatly thickened muscle demands and increased oxygen supply which cannot be met in some circumstances.
Palpitation
Palpitation is an uncomfortable awareness of the heart beat. People may occasionally feel an extra beat or a skipped beat and this is usually normal. Sometimes an awareness of the heart beating does suggest and irregular heart rhythm. In this case, palpitation may start suddenly, appear to be very fast and may be associated with sweating or light-headedness. The cause of such episodes should be determined and treated.
Light-Headedness and Blackouts
Persons with the condition may experience light-headedness, dizziness and more seriously, blackouts. Episodes may occur in association with exercise, with palpitations or without any apparent provocation. The reasons for these episodes are not always clear. They may be due to an irregularity if the heart beat, or fall in blood pressure. Episodes of light-headedness and certainly a blackout should be reported to one's doctor and investigated.
clinic
Some individuals will have no symptoms and others can exhibit mild or severe symptoms or even sudden cardiac death. Shortness of breath and the inability to exercise or fainting can be due to an irregularity of the heartbeat or fall in blood pressure. Chest pain may result from insufficient oxygen supply to the myocardium. Palpitation is an uncomfortable awareness of the heartbeat, when an individual feels an extra beat or a skipped beat. HCM can result in stillbirth or develop during infancy but hypertrophy develops more commonly with growth and is usually evident by late teens or early twenties. Proper therapy depends on accurate diagnosis of HCM.
Other symptoms include:
![](1x1.gif) |
heart murmur
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![](1x1.gif) |
light-headedness & blackouts
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![](1x1.gif) |
ventricular & atrial arrhythmias
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![](1x1.gif) |
heart muscle is abnormally aligned
|
![](1x1.gif) |
heart muscle is stiff and therefore relaxes poorly requiring higher pressures than normal to expand with inflow of blood
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Physical Examination
In the majority of patients with Hypertrophic Cardiomyopathy, the physical examination is unremarkable and the abnormalities may be subtle.
Most patients have forceful or jerky pulse and a forceful heart beat, which can be felt on the left side of the chest.
Both of these reflect the thickened, strongly contracting heart.
However the most obvious abnormality on physical examination is a heart murmur, which is present in 30 - 40% of patients.
Complications of Hypertrophic Cardiomyopathy
In a minority of cases a number of specific complications can occur:
Arrhythmias:
Arrhythmias are a common complication.
Symptoms such as palpitation may occur, but not often.
Exercise testing or Holter monitoring may detect them.
The arrhthymias ventricular tachycardia (arising from the ventricles) or atrial fibrillation (described below) are particularly important and may require treatment.
Atrial Fibrillation The normal regular rhythm of the heart beat is lost and replaced by an irregular rhythm which may be episodic or persistent.
The loss of normal atrial contraction produces a risk of clot formation in the atria. Anticoagulants and drugs to slow the heart rate are required.
Endocarditis:
This is an infection of the heart which occurs rarely in Hypertrophic Cardiomyopathy.
Bacteria in the bloodstream can stick to the inside of the heart where it has been roughened by turbulent blood flow.
**As uncommon as this is I myself fell victim to this. I was MISINFORMED by a dentist who told me
"Genetic disorders do not need to be premedicated". I personally advise extreme caution when undergoing any "invasive" medical procedure**
Heart Block:
The normal electrical signal may travel down to the ventricles slowly or may even be completely blocked,
"heart block". If this occurs, a pacemaker is implanted
Sudden Death:
Overall, in patients with Hypertrophic Cardiomyopathy there is an increased risk of premature death,
which can occur with little or no warning.
Sudden death can strike at any age.
At present there is no cure for hypertrophic Cardiomyopathy.
There is a slight possibility that some drugs may decrease the degree of muscle thickening.
And more recently studies are being performed on the use of pacemakers to reduce the effects of "obstruction".
However, no treatment has been shown to return the heart to normal.
Developments are most likely to come from the early detection of persons carrying the gene for Hypertrophic Cardiomyopathy and treating them to prevent the development of hypertrophy
![](Symb075c00b700f000000000.png) Early endotoxic shock, severe anemia , and thyrotoxicosis are associated with a high-output failure.
![](Symb075c00b700f000000000.png) High-output failure is the outcome of any condition that increases blood volume,
![](Symb075c00b700f000000000.png) increases positive inotropism ( thyrotoxicosis), increases blood flow (decreased blood viscosity as in anemia), or decreases peripheral vascular resistance, with subsequent increase in venous return to the heart (early endotoxic shock with arteriolar vasodilation).
![](Symb075c00b700f000000000.png) Aortic regurgitation increases preload in the left ventricle, because blood drips back into the left ventricle in diastole, thereby increasing the left ventricular end-diastolic pressure and stroke volume.
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