Understanding Hypertrophic Cardiomyopathy (HCM)

Hypertrophic cardiomyopathy (HCM) is a disease that causes the muscles in your heart to thicken. Often inherited, it makes it difficult for your heart to function properly.

In some people, HCM doesn’t cause any symptoms. People with HCM are generally able to lead typical lives. But HCM can become very serious in some people. Serious HCM may develop either slowly or suddenly.

HCM affects about 0.2% of the population in the United States.

HCM is a condition in which your heart muscle, or myocardium, becomes thicker than usual. This interferes with your heart’s ability to pump blood and to relax.

While an older person with heart disease can experience these symptoms, those with HCM experience them unexpectedly and sometimes at a young age.

Many people with HCM don’t experience any symptoms. Some symptoms you can experience include:

• fatigue
• shortness of breath
• heart palpitations, which is a pounding or fluttering heart rate
• high blood pressure
• chest pain
• shortness of breath
• fainting
• dizziness

Treatment for HCM focuses on relieving symptoms and preventing complications, especially sudden cardiac death. The methods used depend on your:

• symptoms
• age
• activity level
• heart function
• outflow obstruction

Medications

If you have HCM symptoms, a doctor or healthcare professional will usually prescribe beta-blockers and calcium channel blockers. These medications relax your heart muscle. Relaxation helps it work better.

If you have an irregular heart rhythm, a doctor might prescribe antiarrhythmic medications such as:

• amiodarone
• sotalol
• disopyramide

More recently, researchers have investigated a drug called mavacamten (MyoKardia) for its use in treating people who have symptomatic cardiomyopathy. Researchers in human trials found that the medication reduces symptoms and improves physical functioning.

The medication works by inhibiting cardiac myosin, a protein in your heart that is involved in contraction (squeezing).

Septal myectomy

A septal myectomy is an open-heart surgery that’s done to remove part of your thickened septum. The septum is the heart muscle wall between your two lower heart chambers (ventricles). It helps improve blood flow through your heart.

A septal myectomy is done only if medications don’t reduce your symptoms.

Septal ablation

Septal ablation involves the use of alcohol to destroy part of your thickened heart muscle. The alcohol is injected through a catheter placed in the artery that supplies it to the part of your heart that’s being treated.

A septal ablation is often done in people who can’t have a septal myectomy.

Pacemaker implantation

If you have an irregular heart rate and rhythm, a tiny electronic device called a pacemaker can be placed under the skin on your chest. The pacemaker helps regulate your heart rate by sending regulated electrical signals to it.

Implantable cardioverter defibrillator

An implantable cardioverter defibrillator (ICD) is a small device that uses electric shocks to track your heart rate and fix dangerous, atypical heart rhythms. It’s placed inside your chest.

An ICD is often used in people who have a high risk of sudden heart failure.

Lifestyle changes

If you have HCM, a doctor may recommend lifestyle changes to reduce your risk of complications. These include:

• eating a healthy diet
• keeping your weight at a healthy level
• doing low-intensity physical activities
• limiting alcohol intake, as alcohol can cause atypical heart rhythms
• restricting high-impact exercise and focusing on low-impact activities, such as walking, golfing, or bowling

HCM is typically an inherited condition, but in some people, the cause of their HCM is never identified.

Genetics

Mutated genes can cause your heart muscle to thicken. Doctors have identified mutations in more than 15 different genes that may cause HCM.

HCM follows a dominant pattern of inheritance. This means if you inherit one gene associated with the condition, you could have symptoms. But inheriting the gene doesn’t necessarily mean you’ll have symptomatic disease.

If you have a family history of HCM or have the condition yourself, you can talk with a genetic counselor about testing. Genetic testing can help you identify if you’re a carrier for the HCM mutation (even if you don’t have symptoms) or your likelihood of passing the condition on to another generation.

Other causes

Other possible causes of HCM include aging and high blood pressure. Some increase in blood pressure can be expected as you get older, but this can also lead to more serious conditions, such as HCM.

The condition can cause different effects in people. Some of the changes to your heart that doctors may identify include:

• Septal hypertrophy: This is the thickening of your heart’s walls, which means your heart needs more force to pump. Hypertrophy can also happen in other parts of your heart.
• Mitral leaflet abnormalities: These are changes to the four flaps that come together to close your mitral valve so blood keeps moving forward in your heart.
• Mitral regurgitation: This generally occurs as a result of a suction effect (known as the Venturi effect) that can cause blood to backflow in your heart. As a result, you can feel short of breath and fatigued.
• Problems with blood leaving your heart: This is also known as left ventricular outflow tract obstruction. These are changes to your heart that keep blood from leaving and going to the rest of your body.
• Arrhythmia: An irregular or fluttering heart rate is a common side effect of HCM.
• Relaxation abnormalities: Thickening of your heart muscle that occurs along with HCM can cause a sluggish or irregular heart rate.

Some people receive a diagnosis when they’re having imaging studies done for something else and a doctor notices an atypical characteristic.

Doctors can use different tests to diagnose HCM:

• Physical exam: During this exam, a doctor will listen for a heart murmur or unusual heart rate. Heart murmurs may occur if a thickened heart muscle disrupts blood flow to your heart.
• Echocardiogram: An echocardiogram creates images of your heart using sound waves. A doctor will look for any unusual movements.
• Electrocardiogram: An electrocardiogram measures the electrical activity in your heart. HCM can cause atypical results.
• Holter monitor: A Holter monitor is a portable electrocardiogram that you can wear throughout the day. You may wear it for 24 to 48 hours or up to 1 month. This allows a doctor to see how your heart rate changes during different activities and if you’re at risk of sudden cardiac death.
• Cardiac MRI: A cardiac MRI uses a magnetic field to produce detailed images of your heart.
• Cardiac catheterization: This test measures the pressure of blood flow in your heart and looks for blockages. A doctor will place a catheter in one of the arteries in your arm or near your groin. The catheter is carefully threaded up through your artery to your heart. Once it reaches your heart, dye is injected so a doctor can take detailed X-ray images.

Many people with HCM may never have any serious health problems caused by it. But HCM can cause severe complications in some people. The most common complications of HCM are:

Sudden cardiac arrest

Sudden cardiac arrest occurs when your heart suddenly stops working. This condition is also called “sudden cardiac death.”

This is typically caused by a rapid heart rhythm known as ventricular tachycardia. Without emergency treatment, sudden cardiac arrest can be fatal.

HCM is the leading cause of sudden cardiac death in young athletes. This could manifest in an athlete with undiagnosed HCM who experiences sudden cardiac death on the playing field.

You might be at a higher risk of sudden cardiac death if you have one or more of the following:

• a family history of sudden cardiac death
• inadequate heart function
• severe symptoms
• a history of irregular heart rhythms with a fast heart rate
• a history of fainting on several occasions when you’re young
• an unusual blood pressure response to physical activity

The longer you live with HCM, the less likely you are to die from sudden cardiac death.

Heart failure

When your heart doesn’t pump the amount of blood your body needs, this is known as heart failure. Medications may help to reduce heart failure symptoms and the chest pain that can commonly occur with this condition.

HCM is a genetic, lifelong disease. In some people, it can contribute to early death and disability.

New treatments and medications may potentially extend the life and daily functioning of those with symptomatic HCM.