Content independently created by WebMD and supported by our partners. Learn More

Hypertrophic cardiomyopathy (HCM) means "thickened heart muscle disease." It's the most common genetic (inherited) heart disease in the U.S.

When you have it, the walls of your heart's left lower chamber are thicker than they should be. They can get stiff and sometimes scarred. This makes it harder for your heart to pump blood to your body.

HCM is usually caused by mutations in some of the genes you inherit from your parents. Many different mutations can cause it. But even if you have a gene for HCM, you might never develop it.

For some people with HCM, the cause is unknown.

Know the Numbers


Some people with HCM don't have any symptoms. For those who do, the symptoms can be different for different people, even those in the same family.

Your thicker heart muscle walls may reduce or block the flow of blood out of your heart. This can cause an abnormal-sounding heartbeat and blood flow. If your heart can't pump blood efficiently, this can cause other symptoms.

Some of the more common symptoms include:

Doctors might misdiagnose HCM because it can mimic other conditions like mitral valve prolapse, aortic stenosis, and coronary artery disease.

Some conditions not related to the heart, such as exercise-induced asthma and panic attacks, can cause shortness of breath and a pounding heartbeat like HCM does.

For most people, HCM doesn't cause major health problems. But for some, it can lead to complications such as:

  • Atrial fibrillation, an irregular and/or fast heart rhythm that can cause blood clots.
  • Reduced blood flow out of the heart.
  • Mitral valve disease. This is a problem with the valve between the two left chambers of your heart that causes blood to flow backward and makes symptoms worse.
  • Dilated cardiomyopathy, which happens when a weak heart muscle results in an enlarged ventricle that can't pump blood as forcefully as it should.
  • Heart failure. Your thickened heart muscle can eventually become too stiff to fill your heart with blood. As a result, your heart can't pump enough blood to meet your body's needs.
  • Autonomic dysfunction. This is a nervous system issue that can cause heart rate problems.
  • Sudden cardiac death. It's rare, but it can be the first sign of HCM in some people.

Kids with HCM often have no symptoms, but their condition can get worse as they get older. If they're also athletes, they may be at risk of sudden death. High-intensity training can trigger a life-threatening arrhythmia, or abnormal heart rhythm. But preventive measures like defibrillators can reduce this risk.

If your doctor suspects you have HCM, they'll use several tests and ask you questions to gather more information.

These tests may include:


This uses sound waves called ultrasound to create images of your heart walls so your doctor can measure their thickness. Your doctor uses it to see how well your heart pumps blood or if there's any obstruction to blood flow. They'll also look at the valves of your heart. They might do this test using a handheld device pressed to your chest. Or they may insert a probe into your esophagus. Views from the esophagus give a clearer view of any obstructions you might have.

Cardiac MRI

MRI stands for magnetic resonance imaging. It uses a magnetic field and radio waves to make images of your heart. It can show your doctor how thick your heart walls are and if there's any scarring.

Electrocardiogram (ECG or EKG)

Your doctor attaches electrodes to your chest, wrists, or legs to measure the electrical signal coming from your heart. This can show them whether this signal is irregular. Your doctor may ask you to get additional readings at home using a portable device called a Holter monitor that you wear for a day.

Stress test

In this test, your doctor has you walk on a treadmill or ride a stationary bike while wearing a heart monitor. That lets them measure how your heart responds to exercise.


If you have a parent with HCM, you have a 50% chance of having the genetic mutation for the disease. Your doctor may recommend screening with genetic testing to see if you have this mutation. If you already know you have HCM, they may suggest your relatives have genetic screening for it.

A DNA analysis may involve a blood test, or in some cases, a sputum sample from mucus you cough up. The sample goes to a lab where technicians analyze it. This helps doctors determine whether you have a genetic mutation that increases your risk for HCM.

Some people turn to genetic testing as part of their family planning. In some cases, people with HCM may not be able to carry a baby because of the heart risks. And even if only one parent has the genetic mutation for HCM, it can be passed to your children.

Others use genetic testing after a sudden cardiac death in the family to help find out whether HCM may have been the cause.

There's no cure for HCM. But doctors have several treatment options to ease symptoms and prevent complications. You may take meds such as:


These slow down your heart rate and reduce some of its workload by blocking adrenaline, the hormone your body releases as part of your "fight or flight" response.


This medication helps your heart beat regularly.

Calcium channel blockers

These slow the rate at which calcium passes into your heart muscle. That slows and regulates your heart rate.

Antiarrhythmic medications

These drugs block irregular electrical activity in your heart. That helps it beat normally.

Blood thinners

Abnormal heart rhythms can increase your risk of blood clots. Blood thinners (anticoagulants) help prevent these clots, which can lead to stroke, heart attack, or even sudden death.


This new drug reduces the obstruction of blood flow in your heart and improves its function.

When medications don't work well enough, doctors can treat HCM with procedures such as:

Septal myectomy

This is an open-heart surgery where your surgeon removes part of the thickened wall between your heart chambers. The goal is to improve blood flow out of your heart and help prevent backward blood flow.

Septal ablation

During this procedure, your doctor injects alcohol into the artery that supplies blood to your heart to destroy part of the thickened wall.

Implantable cardioverter-defibrillator (ICD)

Your doctor implants this small device into your chest. It monitors your heartbeat and sends an electrical shock to restore your heart rhythm if HCM causes a life-threatening disruption to your heartbeat.


This battery-operated device is implanted inside your chest. It sends electrical signals to your heart through two wires called leads. Pacemakers help correct slow heart rhythms.

How Lifestyle Choices Affect HCM