Patient education: Hypertrophic cardiomyopathy (Beyond the Basics)

HYPERTROPHIC CARDIOMYOPATHY OVERVIEW — 

Hypertrophic cardiomyopathy (HCM) is a genetic disease that causes the heart muscle to become thickened, or hypertrophied. The heart cells in HCM are also abnormal, arranged in a disorganized pattern with fibrosis/scarring often present between the cells. In addition, the mitral valve can be affected and, in some people, may briefly obstruct blood flow out from the main pumping chamber of the heart, which can result in regurgitation of blood back to the left atrium and higher pressures than normal in the heart.

The prevalence of HCM in the general population is 1 in 500 adults, although the majority of these cases remain undiagnosed. The vast majority of people diagnosed with HCM have a normal lifespan. In addition, most people with HCM do not have any symptoms and are not at risk of developing complications related to HCM. Among people who do develop symptoms, the most common complaints include chest pain, shortness of breath with exertion, fatigue, palpitations, and lightheadedness. A very small minority of people are at risk of sudden death, which occurs most commonly in young people.

Normal heart function — The heart is essentially a pump that contains four chambers: two upper chambers (right and left atrium), and two bottom chambers (right and left ventricle) (figure 1). Blood without oxygen returns to the heart from the body and 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 (HCM) is a disorder caused by a "spelling mistake" (mutation) in one of a number of different genes which encode for the structure of the heart. Not all the genes responsible for HCM have 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. However, not all family members who inherit an HCM mutation will develop disease and can remain only a carrier of the mutation. Men and women are equally likely to inherit HCM. If a child does inherit the mutation, the most likely period in which the disease will develop (ie, the heart wall muscle thickening) is during puberty, although the severity of heart disease that will develop cannot be accurately predicted. In addition, the thickness of the muscle that people have at the end of adolescence is usually the thickness that they will have the rest of their life. In this regard, for the vast majority of people, the heart muscle does not continue to grow and get bigger throughout life. For this reason, other factors related to HCM, including the function of the muscle and the obstruction to blood flow out of the heart, can cause symptoms to develop at any time during a person's life.

In HCM, the muscular walls of the left ventricle become thickened (figure 2). The location and pattern of wall thickening is diverse, but the majority of people have increased wall thickening of the basal (upper) portion of the ventricular septum (muscle dividing the two bottom chambers). However, occasionally a person may have thickening confined to only other areas such as the apex (tip of the heart). As the left ventricular wall thickens, its ability to relax properly is impaired, causing blood flow into the ventricle to be reduced, like a weightlifter whose muscles may be strong, but stiff.

The mitral valve may also make an abnormal motion and contact the thickened septum during the ejection phase of blood out of the heart, which can cause obstruction of blood flowing out of the left ventricle (obstructive HCM). This can result in higher pressures than normal in the left ventricle, and the involvement of the mitral valve may also prevent the valve from closing completely and allow blood to leak through the opening and back into the left atrium (known as mitral regurgitation). Other heart-related complications can also develop. The majority of people with HCM have obstruction to blood flow out of the heart either at rest or with exertion, while the minority of people with HCM do not have obstruction to blood flow out of the heart ("nonobstructive" HCM). (See 'Hypertrophic cardiomyopathy complications' below.)

HYPERTROPHIC CARDIOMYOPATHY SYMPTOMS — 

The majority of people with hypertrophic cardiomyopathy (HCM) have no or few symptoms. In some cases, symptoms are only seen with exercise or exertion. Symptoms may occur during puberty, when hypertrophy develops, but they most commonly start in mid-life. In a smaller percentage of cases, symptoms may not occur until late in life. If symptoms develop, they can vary in severity from one day to another. People with the obstructive form of HCM are much more likely to develop symptoms.

The age when symptoms develop and the severity of symptoms vary significantly from person to person. In addition, it is common for symptoms to come and go, with people often reporting "good" (no or little symptoms) days and weeks often separated by "bad" (symptomatic) days and weeks. There is no relationship between a specific gene mutation and the likelihood of developing symptoms or risk for future adverse events (See 'Prognosis' below.)

The most common symptoms include:

●Breathlessness (dyspnea) on exertion

●Chest pain may occur at rest or associated with exertion

●Fainting (syncope) and near-fainting (presyncope)

●Palpitations, awareness of the heart beat or feeling a "forceful" heart beat

●Lightheadedness when sitting or standing up

●Exertional fatigue or lack of energy (ie, not having the appropriate exertional stamina for certain activities)

People with no or only minor symptoms generally have a better prognosis than those with more severe symptoms, although people with symptoms due to obstruction who have septal reduction therapy typically have significant improvement in symptoms and normal longevity (see 'Nonsurgical septal reduction therapy' below). 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 (HCM) may be performed because a person has a family history of the disease or because of a heart murmur, abnormal electrocardiogram (ECG or EKG), new symptoms, or an acute event such as syncope (loss of consciousness). An ECG is often abnormal in people with HCM, but there is no specific abnormal pattern diagnostic of HCM, and therefore an echocardiogram and/or cardiac magnetic resonance imaging (CMR) test must be done 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. The ECG pattern is abnormal in 90 percent of people with HCM. Of note, a small minority of people with HCM can have a normal ECG.

Echocardiography — An echocardiogram uses ultrasound (high-frequency sound waves) to measure the muscle thickness of the left ventricle 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 identify left ventricular outflow tract obstruction and determine the magnitude of extra pressure in the heart generated by this obstruction, as well as the presence and severity of mitral regurgitation.

Some people may develop obstruction to blood flow only with exertion, and therefore echocardiography may also be performed during or immediately after exercise in order to detect this issue.

Testing family members with an echocardiogram and ECG is recommended in many situations.

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.

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 HCM. 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). Newer "wireless" monitors are also now being used more frequently and can monitor a person's rhythm over several weeks. 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. Occasionally, a person may be monitored for periods greater than 48 hours depending on their situation.

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 scarring of the heart muscle.

Cardiac catheterization — Although echocardiography provides adequate information to assess cardiac function, obstruction, and valvular regurgitation in most people, cardiac catheterization may be indicated in some cases. In addition, for some people, cardiac catheterization may be performed prior to cardiac surgery to evaluate for coronary artery disease.

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.

Computed tomography angiography (CTA) can also evaluate the coronary arteries and may be recommended as an alternative to cardiac catheterization in some situations.

Evaluation of first-degree relatives — Because HCM 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.

●After a family member is diagnosed, any related children or adolescents should be screened before puberty. In most people, thickening of the heart wall often does not appear until adolescence, although it is reasonable for children younger than 12 years to be evaluated, particularly if they have symptoms, have a high-risk family history, or are participating in intense competitive sports.

●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 three to five years. If there are no signs of abnormal heart function by the early 40s, screening can stop.

●Genetic testing for HCM is available, but the results do not always help to determine if a family member is at risk of developing disease in the future. Before pursuing genetic testing, the advantages and disadvantages of this test should be thoroughly discussed with your physician.

HYPERTROPHIC CARDIOMYOPATHY COMPLICATIONS — 

Depending in part upon the severity of disease, some people with hypertrophic cardiomyopathy (HCM) develop the following complications:

●"Limiting" symptoms (eg, shortness of breath, chest discomfort) with routine daily activities that may impact quality of life.

●End-stage heart failure. (See "Patient education: Heart failure (Beyond the Basics)".)

●Stroke as a consequence of atrial fibrillation (AF). (See "Patient education: Stroke symptoms and diagnosis (Beyond the Basics)".)

●Rhythm disorder (atrial and ventricular arrhythmias).

●Sudden cardiac death due to ventricular tachyarrhythmias.

Hypertrophic cardiomyopathy and sudden cardiac death — A very small minority of people with HCM have an increased risk of developing a dangerous heart rhythm (arrhythmia), which can lead to sudden cardiac death (SCD). Your doctor will assess your future risk for developing this dangerous arrhythmia by assessing the results of a number of noninvasive tests to determine if you are at increased risk. (See 'Arrhythmia evaluation' above.)

In individuals at high risk for sudden cardiac death, an implantable cardioverter-defibrillator (ICD) is recommended to protect against sudden death by providing a life-saving shock to convert the heart back to a normal rhythm. ICDs can be associated with some side effects such as inappropriate shocks and low risk of infection. Also, a person cannot undergo an MRI of any part of the body if they have an ICD that is not MRI-compatible. (See 'Arrhythmias' below.)

HYPERTROPHIC CARDIOMYOPATHY TREATMENT — 

There is no cure for hypertrophic cardiomyopathy (HCM). However, several medical and invasive treatments are available to relieve or eliminate symptoms, providing the vast majority of people with HCM the opportunity to achieve normal longevity with an excellent quality of life.

Treatment may be recommended to:

●Reduce or eliminate the burden of limiting symptoms, such as shortness of breath (commonly experienced with inclines such as stairs or hills and less commonly walking on level ground), exertional fatigue, strong heart beats (palpitations), and chest discomfort.

●Protect against future stroke risk.

●Treat abnormal heart rhythms and/or reduce the risk of sudden death.

The optimal treatment depends upon the individual situation. Most people with HCM have normal longevity and do not develop symptoms or require any treatment.

Avoidance of dehydration — People with HCM 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 — Most people with HCM can participate in mild to moderate physical activity, but are advised to avoid engaging in most 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. Anyone with HCM should talk to their health care provider about the safety of exercise.

Medications

Shortness of breath and chest pain — One or more medications may be used to treat limiting symptoms. Options include a beta blocker, verapamil, disopyramide, and the myosin inhibitor mavacamten. These medications work to decrease the heart's need for oxygen, improve the heart's ability to fill with blood, improve blood flow to the heart, and decrease the obstruction of blood flow out of the heart. In general, the first-line medical therapy is either a beta blocker or verapamil and second line is disopyramide or a myosin inhibitor. All of these drugs have certain strengths and limitations, which should be thoroughly discussed with your HCM provider to best determine which drug options may be best.

If these treatments do not adequately relieve symptoms or a person prefers not to escalate drug therapy, an invasive procedure to reduce the obstruction of blood out of the heart may be recommended.

Arrhythmias — People with HCM are at risk for irregular heart 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 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 education: Atrial fibrillation (Beyond the Basics)".)

●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.

•NSVT most often does not require treatment, although it is a marker for increased risk of sudden cardiac death and may justify recommendation for an implantable cardioverter-defibrillator (ICD).

•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 felt to be at high risk of developing these rhythms, are advised to have an ICD to decrease their risk of sudden cardiac death. This therapy and the strengths and limitations of various ICD devices are discussed in detail in a separate topic. (See "Patient education: Implantable cardioverter-defibrillators (Beyond the Basics)".)

Procedures to relieve left ventricular outflow tract obstruction — People with HCM who are severely symptomatic and who do not improve with medications, or who choose not to pursue escalating drug therapy, may be advised to consider invasive septal reduction therapies such as alcohol septal ablation or heart surgery such as myectomy.

These procedures are most likely to be successful when performed in a medical center with significant experience in treating people with HCM. Assistance in findings such centers can be obtained online at websites for the Hypertrophic Cardiomyopathy Association (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 muscle from the ventricular septum, which will then prevent the mitral valve from making contact with the septum, allowing the blood to flow out of the heart unimpeded. By removing the obstruction, the pressures in the heart will be restored to normal and limiting symptoms due to HCM significantly improved or abolished. In addition, this operation will also cause the mitral valve to close more normally, significantly decreasing or eliminating mitral regurgitation.

Surgical myectomy eliminates or improves symptoms in over 90 percent of people with very low operative risk, and when 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 education: Pacemakers (Beyond the Basics)".)

In a small number of people, the mitral valve may need to be repaired (or even more uncommon, replaced) at the time of myectomy if significant mitral regurgitation (leaking of the mitral valve) is present. (See "Patient education: Mitral regurgitation (Beyond the Basics)".)

Nonsurgical septal reduction therapy — Alcohol 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 a catheter into an artery and threads it up to the base of the aorta (figure 1). Another 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 a "controlled heart attack," resulting in death of muscle tissue supplied by the arterial branch. Over time, this damage will result in the upper part of the septum becoming thinner, reducing obstruction of blood flow from the left ventricle (left ventricular outflow obstruction). The procedure is successful in reducing obstruction of blood flow in 80 percent of cases.

Alcohol 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 with myectomy, with approximately 10 percent of people developing complete heart block requiring a pacemaker and 10 percent of people who will not achieve successful reduction in the obstruction with the initial procedure.

Myectomy versus ethanol ablation — Following either of these procedures, heart muscle does not grow back, which is the reason that these procedures can successfully relieve obstruction to blood flow over the person's lifetime. Although the outcomes with myectomy and ablation are similar, each procedure has its own advantages and disadvantages. People should discuss the risks and benefits of each procedure with their health care providers.

Pregnancy — Women with HCM are generally able to become pregnant with normal vaginal birth in the majority of cases without any increased risk of adverse events. Before becoming pregnant, the woman should speak with her health care provider to discuss any potential risks, any medication changes that may be needed, and care during pregnancy. Women with HCM who get pregnant are often followed by a high-risk OB/GYN physician.

Management of surgical procedures — Because people with HCM 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 HCM is generally excellent, especially in those diagnosed later in life. With the contemporary cardiovascular treatments available today, mortality due to the disease is very low. Indeed, the vast majority of people with HCM have normal life expectancy without incurring any significant limiting symptoms or adverse disease complications.

However, a small number of people with HCM are at risk for adverse disease-related events, 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 people most likely to develop complications so that appropriate treatment can be provided.

Comprehensive hypertrophic cardiomyopathy centers — HCM is a relatively uncommon disease, and centers that have more experience with the management of HCM may offer the broadest range of therapies and have the lowest risk of adverse outcomes with invasive procedures such as cardiac surgery or catheter procedures. Centers certified by the Hypertrophic Cardiomyopathy Association can be found on the internet at https://4hcm.org/center-of-excellence/.

WHERE TO GET MORE INFORMATION — 

Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/contents/table-of-contents/patient-education). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Hypertrophic cardiomyopathy in adults (The Basics)
Patient education: Hypertrophic cardiomyopathy in children (The Basics)
Patient education: Shortness of breath (The Basics)
Patient education: ECG and stress test (The Basics)
Patient education: Echocardiogram (The Basics)
Patient education: Ventricular premature beats (The Basics)
Patient education: Friedreich ataxia (The Basics)
Patient education: Ambulatory heart monitoring (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Heart failure (Beyond the Basics)
Patient education: Stroke symptoms and diagnosis (Beyond the Basics)
Patient education: Atrial fibrillation (Beyond the Basics)
Patient education: Implantable cardioverter-defibrillators (Beyond the Basics)
Patient education: Pacemakers (Beyond the Basics)
Patient education: Mitral regurgitation (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Acquired heart disease and pregnancy
Hypertrophic cardiomyopathy in adults: Supraventricular tachycardias including atrial fibrillation
Auscultation of cardiac murmurs in adults
Definition and classification of the cardiomyopathies
Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation
Echocardiographic recognition of cardiomyopathies
Hypertrophic cardiomyopathy: Gene mutations and clinical genetic testing
Hemodynamics of valvular disorders as measured by cardiac catheterization
Hypertrophic cardiomyopathy: Management of patients without outflow tract obstruction
Hypertrophic cardiomyopathy: Natural history and prognosis
Hypertrophic cardiomyopathy: Management of patients with outflow tract obstruction
Hypertrophic cardiomyopathy in children: Clinical manifestations and diagnosis
Athletes: Overview of sudden cardiac death risk and sport participation
Hypertrophic cardiomyopathy: Morphologic variants and the pathophysiology of left ventricular outflow tract obstruction

The following organizations also provide reliable health information.

●National Library of Medicine

(medlineplus.gov/ency/article/000192.htm)

●Hypertrophic Cardiomyopathy Association

(4HCM.org)

●The Cardiomyopathy Association

(www.cardiomyopathy.org/?id=49)