Hypertrophic cardiomyopathy includes a group of heart disorders in which the walls of the ventricles (the two lower chambers of the heart) thicken (hypertrophy) and become stiff.
- Most cases of hypertrophic cardiomyopathy are caused by an inherited genetic defect.
- People experience fainting, chest pain, shortness of breath, and palpitations (awareness of irregular heartbeats).
- Doctors suspect the diagnosis based on physical examination findings, but they use echocardiography or magnetic resonance imaging to confirm the diagnosis.
- Drugs that reduce the force of the heart’s contractions are given.
Cardiomyopathy refers to progressive impairment of the structure and function of the muscular walls of the heart chambers. There are three main types of cardiomyopathy. In addition to hypertrophic cardiomyopathy, there are dilated cardiomyopathy and restrictive cardiomyopathy (see also Overview of Cardiomyopathy).
The term cardiomyopathy is used only when a disorder directly affects the heart muscle. Other disorders, such as high blood pressure and abnormal heart valves (such as aortic stenosis), also can eventually cause thickened heart muscle and heart failure. However, doctors do not classify the heart muscle problems caused by those disorders as cardiomyopathies.
Hypertrophic cardiomyopathy is a common cause of sudden death in young athletes. At least 1 in 500 people is affected.
Hypertrophic cardiomyopathy is nearly always caused by a
- Spontaneous genetic mutation or an inherited genetic defect
Very rarely, people acquire hypertrophic cardiomyopathy when they have disorders such as acromegaly (excessive growth due to overproduction of growth hormone, usually by a benign pituitary tumor), a pheochromocytoma (a tumor that overproduces the hormone epinephrine), or neurofibromatosis (a genetic disorder in which many soft, fleshy growths of nerve tissue grow under the skin and in other parts of the body).
The thick, stiff walls of the ventricles do not relax appropriately to allow the heart chambers to fill with blood. This difficulty becomes more severe when the heart beats quickly (as during exercise) because there is then even less time for the heart to fill. Because the heart does not fill properly, it pumps less blood with each beat. Sometimes the thickened heart walls also interfere with blood flow out of the heart. This variation is called hypertrophic obstructive cardiomyopathy.
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 blood back into the left atrium (mitral regurgitation). This valve leakage and the enlarged ventricular walls typically cause abnormal heart sounds (heart murmurs).
Abnormal heart rhythms can occur, which can cause sudden death.
Symptoms are highly variable, but when they occur, they usually develop when people are between ages 20 and 40. Symptoms first occur during exercise and include
- Fainting (syncope)
- Chest pain
- Shortness of breath
- Sensation of irregular heartbeats (palpitations)
Fainting usually occurs suddenly without any warning symptoms. Fainting or even sudden death may be the first sign that a person has this condition.
- Echocardiography and/or magnetic resonance imaging (MRI) of the heart
Doctors usually suspect the diagnosis of hypertrophic cardiomyopathy based on the person's symptoms, the results of a physical examination, electrocardiography (ECG), and a chest x-ray. The heart sounds and any murmurs heard through a stethoscope may be helpful.
Cardiac catheterization, an invasive procedure in which a catheter is threaded from a blood vessel in the arm, neck, or leg into the heart, is done to measure pressures in the heart chambers and the degree to which blood flow from the left ventricle is blocked due to the thickened walls.
Because hypertrophic cardiomyopathy is usually caused by a gene mutation, genetic testing may also be done.
About 1% of adults with hypertrophic cardiomyopathy die each year. Children with hypertrophic cardiomyopathy are more likely to die than adults.
Other factors that suggest a greater risk of death include the following:
- Family history of sudden death
- Unexplained fainting
- Occurrence of rapid and abnormal heart rhythms
- Abnormal blood pressure response during exercise
- Severity of thickening in the heart muscle
- Characteristic MRI appearance
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 should have genetic counseling when they plan a family because they have a 50% chance of passing this disorder on to their offspring. First-degree family members (siblings or children) of people who have this inherited disorder should have their heart evaluated (with either genetic testing and/or routine echocardiography).
- Drugs such as a beta-blocker and/or a calcium channel blocker
- Sometimes a procedure to improve blood flow
- Sometimes an implantable cardioverter-defibrillator
If possible, doctors treat the condition causing hypertrophic cardiomyopathy.
Treatment of hypertrophic cardiomyopathy is aimed primarily at reducing the heart’s resistance to filling with blood between heartbeats.
Drugs for hypertrophic cardiomyopathy
Beta-blockers and the calcium channel blocker verapamil—taken separately or together—are the main treatment. Both reduce the force of heart muscle contraction. 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.
Amiodarone is sometimes used to treat abnormal heart rhythms.
Surgery to remove some of the thickened heart muscle (myectomy) can improve the flow of blood from the heart, but surgery is done only when symptoms are incapacitating despite drug therapy. Myectomy can relieve symptoms, but it does not reduce the risk of death. When myectomy is done in hospitals that have extensive experience doing the procedure, long-term results are excellent.
Alcohol ablation (controlled destruction of a small area of heart muscle by injecting it with alcohol) is increasingly being used in certain people to improve blood flow from the heart because it can be done during cardiac catheterization. Although cardiac catheterization is an invasive procedure in which a catheter is threaded into the heart, it has fewer risks in people who are at high risk of complications if they have heart surgery.
People who have severe heart muscle thickening, especially thickening of the wall that separates the heart chambers (cardiac septum), have a high risk of developing deadly abnormal heart rhythms which cause sudden death. Doctors may recommend an implantable cardioverter-defibrillator for these people.
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