What Is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a relatively common condition in which the heart muscle becomes thick and unable to pump blood normally. Most people with HCM do not have symptoms or find the condition interferes with daily life.

People with symptomatic HCM typically experience shortness of breath, chest pain, and abnormal heart rhythms. Imaging tests are required to detect hypertrophic cardiomyopathy. Once diagnosed, HCM can be managed (but not cured) with lifestyle measures and medication.

This article provides an overview of HCM symptoms, causes, diagnosis, and treatment.

Symptoms

The majority of people who have hypertrophic cardiomyopathy do not experience symptoms. Those who do are likely to experience them as they get older.

Potential symptoms of HCM include:

• Shortness of breath during exercise, while lying down (orthopnea), or suddenly during sleep (paroxysmal nocturnal dyspnea)
• Angina (chest pain)
• Heart palpitations
• Lightheadedness
• Fatigue
• Edema (swelling) of the ankles
• Fainting (syncope)

Complications

In HCM, the muscular walls of the ventricles (the lower chambers of the heart) become abnormally thick—a condition called hypertrophy. This causes the heart muscle to function abnormally. If severe, the hypertrophy can lead to heart failure and cardiac arrhythmias. 

If hypertrophy becomes extreme, it can distort the ventricles, which can interfere with the function of the mitral valve and can cause an obstruction below the aortic valve, disrupting the flow of blood through the heart. Hypertrophic cardiomyopathy is linked to a number of cardiac health issues, most of which can lead to heart failure.

Diastolic Dysfunction

Diastolic dysfunction refers to an abnormal stiffness of the ventricular muscle, which makes it more difficult for the ventricles to fill with blood in between each beat. In HCM, the hypertrophy itself produces at least some diastolic dysfunction. If severe, diastolic dysfunction can lead to heart failure, fatigue, and severe shortness of breath. Even relatively mild diastolic dysfunction makes it more difficult for patients with HCM to tolerate cardiac arrhythmias, especially atrial fibrillation.

Left Ventricular Outflow Obstruction (LVOT)

In LVOT, thickening of the heart muscle just below the aortic valve creates a partial obstruction known as subvalvular stenosis that interferes with the ability of the left ventricle to eject blood with each heartbeat.

Mitral Regurgitation

In mitral regurgitation, the mitral valve fails to close normally when the left ventricle beats, allowing blood to flow backward (“regurgitate”) into the left atrium. In HCM this occurs due to a distortion in the way the ventricle contracts.

Ischemia of the Heart Muscle

With ischemia (oxygen deprivation) that occurs as a result of hypertrophic cardiomyopathy, the heart becomes so thick that some portions of the muscle do not receive enough blood, even when the coronary arteries themselves are completely normal. When this happens, angina can occur (especially with exertion) and a myocardial infarction (death of heart muscle) is even possible.

Causes

This condition is caused by one of several genetic mutations that causes the heart muscle to become thick and stiff.

HCM can be either obstructive or nonobstructive. In obstructive HCM, the wall (septum) between the two bottom chambers of the heart thickens. The walls of the pumping chamber can also become stiff, blocking or reducing blood flow from the left ventricle to the aorta. Most people with HCM have this type.

In nonobstructive HCM, the heart’s main pumping chamber stiffens. This limits how much blood the ventricle can take in and pump out, but blood flow is not blocked. 

In almost half of patients with HCM, the genetic disorder is not inherited at all but occurs as a spontaneous gene mutation—in which case, the parents and siblings of the patient will not be at elevated risk for HCM. However, this “new” mutation can be passed on to the next generation. 

Diagnosis

There are several ways this condition can be diagnosed:

• Magnetic resonance imaging (MRI) of the heart is considered the best method of diagnosing HCM. Using powerful magnets and radio waves, the MRI scanner creates images of the heart muscle, allowing healthcare providers to see how well it functions.
• Echocardiogram testing uses sound waves (ultrasound) to detect abnormalities in the thickness of the heart and to check whether the chambers and valves are pumping blood. Echocardiograms are sometimes performed during exercise—what is known as a "stress test."
• Electrocardiogram (ECG) can reveal left ventricular hypertrophy. An ECG can show abnormal heart rhythms and signs of heart thickening. In some cases, a portable ECG, called a Holter monitor, is needed. This device records the heart's activity continuously over one to two days. This test is sometimes used as a screening tool to look for HCM in young athletes.

Treatment

Although HCM cannot be cured, in most cases it can be controlled. However, the management of HCM can become quite complex, and anyone who has symptoms due to HCM should be followed by a cardiologist.

Among the treatments used to manage hypertrophic cardiomyopathy are:

• Beta blockers—medications that decrease heart rate and reduce the heart's workload
• Calcium blockers—medications shown to reduce symptoms and improve exercise tolerance in people with HCM
• Anti-arrhythmic medicines—such as amiodarone, used to control the heart's rhythm
• Alcohol septal ablation—a procedure in which ethanol (a type of alcohol) is injected through a tube into the small artery that supplies blood to the thickened area of heart muscle, causing cells there to die and the tissue to shrink
• Septal myectomy—an open-heart surgery that removes part of the thickened septum that’s bulging into the left ventricle; it’s generally considered only for younger people with obstructive HCM and severe symptoms whose medications are not working well
• An implantable cardioverter defibrillator (ICD) if the risk of sudden death is thought to be elevated.
• A heart transplant—in advanced, end-stage HCM disease this procedure replaces a diseased heart with a healthy donor heart

Living with HCM

If you've been diagnosed with HCM, you may have to make a few lifestyle adjustments, depending on the severity of the disease.

• Avoid strenuous exercise, especially intense, competitive sports and heavy weight lifting.
• Stay well-hydrated, as dehydration can exacerbate HCM.
• Reduce your alcohol consumption, as drinking more than the recommended amount can damage your heart and lead to high blood pressure.
• Monitor your weight changes: A sudden weight gain could be caused by fluid retention related to medications you may be taking.
• Get regular check-ups to monitor your condition.
• Avoid having sex after a heavy meal, to reduce the chance of angina. You should also try not to be too energetic at the start of your sexual activity. 
• Give up smoking, which increases your likelihood of developing coronary artery disease.

A Word from Verywell

A diagnosis of HCM does not have to stop you from living your life. In most cases, HCM is a relatively benign disease, with approximately two-thirds of patients experiencing a normal life span without significant problems. If you are aware of the disease and manage it carefully with the help of your healthcare provider, there's nothing to prevent you from living a full and active life.