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Hypertrophic cardiomyopathy includes a group of heart disorders in which the walls of the ventricles thicken (hypertrophy) and become stiff, even though the workload of the heart is not increased.
Generally, hypertrophic cardiomyopathy affects men and women equally. But among older people, it is more common among women than among men, mainly because women live longer than men. It occurs in about 4% of older people.
Causes
Hypertrophic cardiomyopathy may be present at birth (congenital) or acquired later in life. Hypertrophic cardiomyopathy that is congenital and most cases that develop later are caused by an inherited genetic defect. Acquired hypertrophic cardiomyopathy may be caused by such disorders as acromegaly (excessive growth due to overproduction of growth hormone, usually by a benign pituitary tumor) and a pheochromocytoma (a tumor that overproduces the hormone epinephrine). Neurofibromatosis, a hereditary disorder, may also cause hypertrophic cardiomyopathy.
Symptoms
Symptoms include fainting (syncope), chest pain, shortness of breath, and awareness of irregular heartbeats (palpitations) produced by an abnormal heart rhythm (arrhythmia). Fainting usually occurs during exertion.
Shortness of breath develops because fluid accumulates in the lungs. Fluid accumulates because the thickened, stiff heart resists filling with blood from the lungs and blood consequently pools in the lungs.
Because the ventricle walls thicken, the mitral valve (the valve that opens between the left atrium and the left ventricle) may be unable to close normally, resulting in leakage of a small amount of blood back into the left atrium. In some people, the thickened muscle obstructs the flow of blood out of the heart below the aortic valve. This variation is called hypertrophic obstructive cardiomyopathy.
Diagnosis
Doctors can usually make a preliminary diagnosis of hypertrophic cardiomyopathy based on the results of a physical examination. For example, the heart sounds heard through a stethoscope are usually characteristic. Echocardiography is the best way to confirm the diagnosis. Electrocardiography (ECG) and a chest x-ray are also helpful. Cardiac catheterization, an invasive procedure, is performed to measure pressures in the heart chambers only if surgery is being considered.
Prognosis
About 4% of people with hypertrophic cardiomyopathy die each year. Death is usually sudden, presumably due to an abnormal heart rhythm. Death due to chronic heart failure is less common. People who learn that they have inherited this disorder may wish to obtain genetic counseling when they plan a family. Family members of people who have this inherited disorder may wish to consider genetic testing. Hypertrophic cardiomyopathy increases the risk of sudden death in young athletes.
Treatment
If possible, doctors treat the underlying cause.
Treatment of hypertrophic cardiomyopathy is aimed primarily at reducing the heart's resistance to filling with blood between heartbeats. Beta-blockers and the calcium channel blocker verapamil—taken separately or together—are the main treatment. Both reduce the extent to which heart muscle contracts, so that the heart contracts less forcefully. As a result, the heart can fill better and, if the thickened muscle was blocking blood flow, blood can flow out of the heart more easily. Also, beta-blockers and verapamil slow the heart rate, so that the heart has more time to fill. Sometimes, disopyramide, a drug that decreases the strength of heart contractions, is also used.
In people who are thought to have an increased risk of sudden death, doctors may recommend an implantable cardioverter-defibrillator.
Surgery to remove some of the thickened heart muscle (myectomy) can improve the flow of blood from the heart, but it is done only when symptoms are incapacitating despite drug therapy. Surgery can relieve symptoms, but it does not reduce the risk of death. Alcohol ablation (controlled destruction of a small area of heart muscle) is increasingly being used in certain people to improve blood flow from the heart because it can be done by using cardiac catheterization. Although cardiac catheterization is an invasive procedure in which a catheter is threaded into the heart, it has fewer risks than surgery.
Last full review/revision January 2008 by J. Malcolm O. Arnold, MD
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