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Author: William J McKenna, MD
Editors: Bernard J Gersh, MB, ChB, DPhil, FRCP; Leah K Moynihan, RNC, MSN; Susan B Yeon, MD, JD, FACC
 HYPERTROPHIC CARDIOMYOPATHY OVERVIEW — Hypertrophic cardiomyopathy (HCM) is a genetic disease that causes the heart muscle to become thickened, or hypertrophied. This can impair blood flow into and out from the main pumping chamber of the heart, the left ventricle. In addition, the mitral valve can be affected and may not function properly.
Approximately 1 in 500 adults have HCM. It usually causes no symptoms or major problems. In some patients it causes chest pain and shortness of breath, particularly with exercise. In a minority, however, it may cause major limitations and it is the most common cause of sudden cardiac death in people under age 30.
Normal heart function — The heart is a pump that contains four chambers: the right atrium, right ventricle, left atrium, and left ventricle (figure 1). Blood returning to the heart from the body flows into the right atrium, and then into the right ventricle. Blood is pumped out of the right ventricle to the lungs, where oxygen is added. Blood then returns to the heart through the left atrium. Blood in the left atrium flows into the left ventricle, which pumps the blood into the aorta to deliver oxygen to the organs and tissues of the body.
HOW DOES HYPERTROPHIC CARDIOMYOPATHY DEVELOP? — Hypertrophic cardiomyopathy is a disorder caused by a "spelling mistake" (mutation) in one of a number of different genes, some of which have not yet been identified. The disorder is transmitted as an autosomal dominant trait. This means that there is a 50 percent chance that a parent with HCM will pass the abnormal gene to his or her child. Men and women are equally likely to inherit HCM. However, even if a child is known to have the mutation, the severity of heart disease that will develop cannot be accurately predicted.
In hypertrophic cardiomyopathy, the muscular walls of the left ventricle become thickened (figure 2). As the left ventricular walls thicken, their ability to relax is impaired, causing blood flow into the ventricle to be reduced, like a weight lifter whose muscles may be strong, but stiff.
The thickened septum may also cause obstruction of blood from the left ventricle to the aorta by reducing the size of outflow tract so that the mitral valve leaflets contact the septum. This involvement of the mitral valve may prevent the valve from closing completely and allow blood to leak backwards through the opening (known as mitral regurgitation). Other heart-related complications can also develop. (See 'Hypertrophic cardiomyopathy complications' below.)
HYPERTROPHIC CARDIOMYOPATHY SYMPTOMS — Most patients with hypertrophic cardiomyopathy have no or few symptoms. In some cases, symptoms are only seen with exercise or exertion. Symptoms may first appear during infancy or childhood, although they begin more commonly during puberty, when hypertrophy develops. In a smaller percentage of cases, symptoms may not occur until later in life. If symptoms develop, they may vary in severity from one day to another.
The age when symptoms develop, the severity of symptoms, and the long-term prognosis of a person with hypertrophic cardiomyopathy varies. With some mutations there is marked variation between families, but members of the same family are affected more similarly. Some mutations, however, may cause disease within a family that is severe in some people and mild or even absent in others. (See 'Prognosis' below.)
The most common symptoms include:
* Breathlessness (dyspnea) on exertion
* Breathlessness when lying down that is relieved when sitting or standing (orthopnea)
* Breathlessness at night that occurs suddenly, often waking the patient (nocturnal dyspnea)
* Chest pain, which may be caused or worsened by exertion.
* Fainting (syncope) and near-fainting (presyncope)
* Palpitations, awareness of the heart beat
* Lightheadedness when sitting or standing up
* Fatigue or lack of energy
* Swelling of the legs and feet (edema)
Patients with no or only minor symptoms generally have a better prognosis than those with more severe symptoms. However the severity of symptoms does not necessarily correlate with the extent of cardiac involvement or the risk of sudden death.
HYPERTROPHIC CARDIOMYOPATHY DIAGNOSIS — Testing for hypertrophic cardiomyopathy may be performed because a person has a family history of the disease or because of a heart murmur, abnormal electrocardiogram (ECG or EKG), or new symptoms. The best first test for HCM is an ECG. However, an echocardiogram is required to confirm the diagnosis. Other tests may also be recommended after the echocardiogram, depending upon the person's symptoms, family history, and echocardiographic findings.
Electrocardiography — An electrocardiogram (ECG or EKG) is a recording of the electrical activity of the heart. It can help determine if there are abnormalities in electrical conduction or thickening or damage to the heart muscle.
Echocardiography — An echocardiogram uses ultrasound (high frequency sound waves) to measure the thickness and motion of the ventricular walls, the size of the heart's chambers, the function of the heart valves (including the mitral valve), and flow of blood within the heart. Blood flow measurements help to diagnose any left ventricular outflow tract obstruction.
Echocardiography is usually performed during rest and may also be performed during or immediately after exercise.
Exercise testing — Exercise testing determines how the heart performs during activity. The response to exercise is measured by observing symptoms, the heart rhythm, blood pressure, and heart rate as the person walks on a treadmill. The blood pressure and heart rate normally increase during exercise. People with HCM whose blood pressure does not rise with exercise may be at increased risk for sudden cardiac death.
 Exercise testing may be combined with echocardiography to determine whether left ventricular outflow obstruction develops or worsens during exercise.
Arrhythmia evaluation — Continuous portable (also called ambulatory) monitoring of the ECG can be helpful in identifying rhythm disorders (arrhythmias) in people with hypertrophic cardiomyopathy. One common type of ambulatory monitor is the Holter monitor. This is a small, lightweight, battery operated device that can record a person's ECG for 24 to 48 hours (figure 3). It is worn at home or at work during routine activities to detect rhythm disorders that may occur sometime during the course of the day.
Ambulatory monitoring may identify the cause of symptoms of an irregular heart rhythm, such as heart palpitations, passing out, or feeling lightheaded. Ambulatory monitoring is recommended for all people with HCM to identify abnormal heart rhythms, which may not cause symptoms. (See 'Arrhythmias' below.)
Arrhythmia evaluation is an important part of the assessment for risk of sudden cardiac death.
Other tests — Other tests may be recommended during an evaluation for hypertrophic cardiomyopathy, including monitoring for irregular heart rhythms, imaging tests (such as MRI) of the heart, and cardiac catheterization. Testing of family members is recommended in certain situations.
Cardiovascular magnetic resonance — Magnetic resonance imaging (MRI) of the heart (also known as cardiovascular magnetic resonance, CMR) can detect thickening of the left ventricular wall, including portions of the wall than can be difficult to assess by echocardiography. This test may also be helpful in detecting other abnormalities in people with HCM such as leaking of the mitral valve (mitral regurgitation) and scar in the ventricular walls.
Cardiac catheterization — Although echocardiography provides adequate information to assess cardiac function, obstruction and valvular regurgitation in most patients, cardiac catheterization may be indicated in certain patients.
In this procedure, catheters (long tubes) are passed through the large blood vessels into the heart to measure pressures and obtain images of the left ventricular chamber. If there is concern that blood vessels of the heart could also be diseased (coronary artery disease), imaging of the coronary arteries (coronary angiography) may also be performed.
Evaluation of first-degree relatives — Because hypertrophic cardiomyopathy can be passed from parents to children, evaluation is recommended for all first degree relatives of anyone who is diagnosed with the disease. First degree relatives include siblings and parents.
The following are recommendations for evaluation:
* A medical history, physical examination, electrocardiography, and echocardiography.
* Evaluation is not recommended in children younger than 12 years unless the child has symptoms, has a high-risk family history, or the child is participating in intense competitive sports. Thickening of the heart wall often does not appear until adolescence.
* Evaluation should be repeated once per year from 12 to 18 years of age.
* Adults (>18 years) with a normal echocardiogram should have screening approximately every five years.
* Genetic testing for HCM is available, but it is expensive and the results do not always help to determine if and when a person will develop the disease. As a result, genetic testing is not currently recommended in most cases.
 HYPERTROPHIC CARDIOMYOPATHY COMPLICATIONS — Depending in part upon the severity of disease, some patients with hypertrophic cardiomyopathy develop the following complications:
* Heart failure (see "Patient information: Heart failure causes, symptoms, and diagnosis".
* Stroke (see "Patient information: Stroke symptoms and diagnosis")
* Rhythm disorder (arrhythmias)
* Heart block
* Infection of the heart valve (infective endocarditis)
* Increased risk of death due to sudden cardiac death, heart failure, or stroke
HCM and sudden cardiac death — Some people with hypertrophic cardiomyopathy have an increased risk of developing a dangerous heart rhythm (arrhythmia), which can lead to sudden cardiac death (SCD). (See 'Arrhythmia evaluation' above.)
In individuals at high risk for sudden cardiac death, an implantable cardioverter-defibrillator (ICD) is recommended to reduce this risk. (See 'Arrhythmias' below.)
HYPERTROPHIC CARDIOMYOPATHY TREATMENT — There is no cure for hypertrophic cardiomyopathy. However, several treatments are available to relieve the symptoms and decrease the risks associated with HCM.
Treatment may be recommended to:
* Reduce the symptoms of heart failure and chest pain
* Remove excess muscle from the interventricular septum to improve blood flow
* Treat abnormal heart rhythms and/or reduce the risk of sudden death
The optimal treatment depends upon the individual situation. Most people do not have symptoms and do not require any treatment.
Avoidance of dehydration — People with hypertrophic cardiomyopathy should try to maintain a steady fluid balance and avoid situations in which fluid is lost from the body and not adequately replaced. (eg, having diarrhea and not drinking adequate fluids).
Activity restriction — Anyone with hypertrophic cardiomyopathy should talk to his/her healthcare provider about the safety of exercise. Most people with HCM are advised to avoid playing competitive sports, with the possible exception of some low-intensity sports (eg, golf, billiards). Certain recreational sports are also not advised. These recommendations generally apply to all people with HCM.
Medications
Shortness of breath and chest pain — One or more medications may be used to treat the symptoms of shortness of breath and/or chest pain. Options include a beta blocker, verapamil, and/or disopyramide. These medications work to decrease the heart's need for oxygen, improve the heart's ability to fill with blood, and improve blood flow to the heart.
If these treatments do not adequately relieve symptoms and there is significant obstruction to the flow of blood out of the left ventricle (left ventricular outflow tract obstruction), a procedure to reduce the obstruction may be recommended.
Arrhythmias — People with hypertrophic cardiomyopathy are at risk for irregular hearth rhythms (arrhythmias). Although most arrhythmias do not cause symptoms, some can have serious consequences or even lead to sudden cardiac death. Therefore, testing for arrhythmias is important. (See 'Arrhythmia evaluation' above.)
There are two main types of arrhythmias: atrial and ventricular.
* Atrial arrhythmias — The most common atrial arrhythmia is atrial fibrillation (AF). Because AF may cause palpitations, shortness of breath, chest pain, low blood pressure, passing out and risk of stroke, treatment of AF is important. The treatment of AF is discussed separately. (See "Patient information: Atrial fibrillation".)
* Ventricular arrhythmias — There are several types of ventricular arrhythmias, including ventricular premature beats (VPBs), nonsustained ventricular tachycardia (NSVT), sustained ventricular tachycardia (VT), and ventricular fibrillation (VF).
* - Ventricular premature beats, also known as premature ventricular contractions (PVCs), are not associated with increased risk of sudden cardiac death and do not usually require treatment. (See "Patient information: Palpitations and extra heartbeats".)
* - NSVT does not itself require treatment, although it is a marker for increased risk of sudden cardiac death.
* - Sustained VT and VF are dangerous arrhythmias that can lead to sudden cardiac death (SCD). People with HCM who have experienced sustained VT or VF, or who are at risk of these rhythms, are advised to have an implantable cardioverter-defibrillator (ICD) to decrease their risk of sudden cardiac death (reasons for ICD placement in people with HCM described here, (table 1). This therapy is discussed in detail in a separate topic. (See "Patient information: Implantable cardioverter-defibrillators".)
Procedures to relieve left ventricular outflow tract obstruction — Patients with hypertrophic cardiomyopathy who are severely symptomatic and who do not improve with medications may be advised to consider septal ablation or surgical treatment, such as myectomy.
These procedures are most likely to be successful when performed in a medical center with significant experience in treating people with hypertrophic cardiomyopathy. Assistance in findings such centers can be obtained online at websites for the Hypertrophic Cardiomyopathy Association (www.4HCM.org) and the Cardiomyopathy Association (www.cardiomyopathy.org).
Septal myectomy — Septal myectomy is the surgical removal of excess muscle from the thickened ventricular septum, the muscular wall between the left and right ventricles. The surgery is performed by opening the chest, placing the person on cardiopulmonary bypass (a heart lung machine), and removing excess tissue in the region of obstruction. Myectomy eliminates or improves symptoms in over 90 percent of patients.
When myectomy is performed by an experienced surgeon, the complication rate is low (1 to 2 percent). The most common complication is development of heart block, which sometimes requires treatment with a pacemaker. (See "Patient information: Pacemakers".)
The mitral valve may be repaired at the time of myectomy if significant mitral regurgitation (leaking of the mitral valve) is present. (See "Patient information: Mitral regurgitation".)
Nonsurgical septal reduction therapy — Ethanol ablation of the septum, also known as nonsurgical septal reduction therapy (NSRT), or transcoronary ablation of septal hypertrophy (TASH) involves injecting ethanol (alcohol) into the blood vessel supplying the upper part of the thickened septum.
In this procedure, a cardiologist inserts an angioplasty catheter into an artery in the groin and threads it up to the base of the aorta (figure 1). The catheter is passed into the left coronary artery to the branch that supplies the upper part of the septum. A small amount of ethanol is injected into this arterial branch.
The ethanol causes death of muscle tissue supplied by the arterial branch, causing the upper part of the septum to become thinner. Thinning of the upper septum reduces obstruction of blood flow from the left ventricle (left ventricular outflow obstruction). The procedure is successful in reducing blockage in 80 to 90 percent of cases.
Ethanol ablation should only be performed by an experienced interventional cardiologist in a hospital that has experience caring for people with HCM. Complications are somewhat more common in people who undergo ablation compared to myectomy, with approximately 5 to 25 percent of people developing complete heart block requiring a pacemaker.
Myectomy versus ethanol ablation — Although the outcomes with myectomy and ablation are similar, each procedure has its own advantages and disadvantages. Patients should discuss the risks and benefits of each procedure with their healthcare providers.
Pregnancy — Women with hypertrophic cardiomyopathy are generally able to become pregnant and carry the pregnancy without any difficulty. Before becoming pregnant, the woman should speak with her healthcare provider to discuss any potential risks, any medication changes that may be needed, and care during pregnancy.
Management of surgical procedures — Because people with hypertrophic cardiomyopathy have alterations in the heart function, special care may be needed before, during and after surgical procedures to reduce the risk of complications such as heart failure or low blood pressure (hypotension).
PROGNOSIS — The long-term outcome for people with hypertrophic cardiomyopathy is generally good, especially in those who have few or no symptoms and those who are diagnosed later in life. Most people with HCM can live a long life.
However some patients with hypertrophic cardiomyopathy are at risk for severe cardiac complications, including heart failure and sudden death. The risk of cardiac complications varies among different families as well as among members within a given family. A major goal of the diagnosis and evaluation process is to identify those patients most likely to develop complications so that appropriate treatment can be provided.
Reference:
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