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 Dilated Cardiomyopathy Dilated cardiomyopathy is a group of heart muscle disorders in which the ventricles (the two lower chambers of the heart) enlarge (dilate) but are not able to pump enough blood for the body’s... read more and restrictive cardiomyopathy Restrictive Cardiomyopathy Restrictive cardiomyopathy includes a group of heart disorders in which the walls of the ventricles (the two lower chambers of the heart) become stiff, but not necessarily thickened, and resist... read more (see also Overview of Cardiomyopathy Overview of Cardiomyopathy 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: Dilated cardiomyopathy... read more ).
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.
Hypertrophic cardiomyopathy is a common cause of sudden death in young athletes Sudden Cardiac Death in Athletes An estimated 1 to 3 per 100,000 apparently healthy young athletes develop an abrupt-onset heart rhythm abnormality and die suddenly during exercise. Males are affected up to 10 times more often... read more . At least 1 in 500 people is affected.
Causes of Hypertrophic Cardiomyopathy
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 Gigantism and Acromegaly Overproduction of growth hormone causes excessive growth. In children, the condition is called gigantism. In adults, it is called acromegaly. Excessive growth hormone is almost always caused... read more (excessive growth due to overproduction of growth hormone, usually by a benign pituitary tumor), a pheochromocytoma Pheochromocytoma A pheochromocytoma is a tumor that usually originates from the adrenal glands’ chromaffin cells, causing overproduction of catecholamines, powerful hormones that induce high blood pressure and... read more (a tumor that overproduces the hormone epinephrine), or neurofibromatosis Neurofibromatosis Neurofibromatosis is a group of genetic disorders in which many soft, fleshy growths of nerve tissue (neurofibromas) form under the skin and in other parts of the body, and flat spots that are... read more (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 Mitral Regurgitation Mitral regurgitation is leakage of blood backward through the mitral valve each time the left ventricle contracts. Genetic weakness of the mitral valve tissue (myxomatous degeneration) and heart... read more ). This valve leakage and the enlarged ventricular walls typically cause abnormal heart sounds (heart murmurs).
Abnormal heart rhythms Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more can occur, which can cause sudden death.
Symptoms of Hypertrophic Cardiomyopathy
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
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.
Diagnosis of Hypertrophic Cardiomyopathy
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. Although ECG and echocardiography are not recommended for all young competitive athletes, all such athletes should be evaluated for risk factors that indicate the need for further testing.
Echocardiography Echocardiography and Other Ultrasound Procedures Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of... read more is the best way to confirm the diagnosis, but MRI of the heart Magnetic Resonance Imaging (MRI) of the Heart With magnetic resonance imaging (MRI), a powerful magnetic field and radio waves are used to produce detailed images of the heart and chest. This expensive and sophisticated procedure is used... read more may also be used because it may provide more detailed information.
Cardiac catheterization Cardiac Catheterization and Coronary Angiography Cardiac catheterization and coronary angiography are minimally invasive methods of studying the heart and the blood vessels that supply the heart (coronary arteries) without doing surgery. These... read more , 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.
Prognosis of Hypertrophic Cardiomyopathy
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, particularly premature sudden death
Unexplained fainting, cardiac arrest, or ventricular tachycardia
Occurrence of rapid and abnormal heart rhythms
Severity of thickening in the heart muscle
Inability of the heart to pump enough blood
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).
Treatment of Hypertrophic Cardiomyopathy
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.
Mavacamtem, a new drug, seems to relieve symptoms and increase exercise tolerance.
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 Cardiac Catheterization and Coronary Angiography Cardiac catheterization and coronary angiography are minimally invasive methods of studying the heart and the blood vessels that supply the heart (coronary arteries) without doing surgery. These... read more . 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 Restoring normal rhythm Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more for these people.
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
American Heart Association: Hypertrophic cardiomyopathy: Provides comprehensive information on symptoms, diagnosis, and treatment of hypertrophic cardiomyopathy