What is cardiomyopathy?

Cardiomyopathy is an abnormality of the heart muscle that can cause heart failure. There are three main types of cardiomyopathy: dilated, hypertrophic, and restrictive.

In dilated cardiomyopathy, the heart muscle becomes weak. As the heart muscle weakens, it is less able to pump enough blood. This raises the pressure of blood in the main pumping chamber of the heart (the left ventricle). The higher pressure in the left ventricle causes the heart to expand, just like a balloon expands when you put air into it. Dilated cardiomyopathy is one cause of an enlarged heart. This occurs slowly, over several weeks to months. Unlike a balloon, the pressure in the heart never rises high enough to cause the heart to rupture or pop.

In hypertrophic cardiomyopathy (HCM), the individual heart muscle cells get bigger. This causes the walls of the heart muscle to thicken. When the walls of the heart become thick enough, it cannot pump properly. Thick walls are usually very stiff, making it difficult for the heart to fill within enough blood to pump. In addition, the overgrown heart muscle can distort the shape of the heart. HCM is another cause of an enlarged heart. For reasons we don't understand very well, some people with HCM develop a weakened heart muscle over time. They gradually change to have dilated cardiomyopathy.

In restrictive cardiomyopathy, abnormal substances get deposited throughout the heart between heart muscle cells, or the inner surface of the heart gets coated with a layer of scar tissue. This causes the heart muscle to become very stiff. Of the three main types of cardiomyopathy, restrictive cardiomyopathy is the least common.

How does cardiomyopathy occur?

Coronary artery disease causes poor blood supply to the heart, and may injure the heart. This is the most common cause of dilated cardiomyopathy. When some of the heart muscle cells are injured or destroyed, the remaining cells have to work harder and eventually weaken.

Substances such as cocaine or heavy alcohol use weaken the heart muscle cells. Some medicines, such as cancer chemotherapy drugs like adriamycin, are toxic to heart muscle cells and can weaken the heart.

Weakening and dilatation may occur for no apparent reason. When this happens, it is called idiopathic dilated cardiomyopathy.

High blood pressure causes the heart to pump against a heavy workload. The walls of the heart enlarge just like the muscles of a weight lifter or body builder enlarge. When high blood pressure goes untreated for many years, you may develop hypertrophic cardiomyopathy.

HCM often runs in families. It may be caused by certain abnormal proteins that control heart muscle growth. The heart tries to make up for this by enlarging, becoming thick and deformed.

Many diseases can cause scar tissue to form on the inner surface of the heart, including some cancers and infections. Amyloidosis can cause scar tissue to form on the walls of the heart (myocardium). This scar tissue may lead to restrictive cardiomyopathy.

What are the symptoms?

Cardiomyopathy may not cause symptoms. If it does, the symptoms may include chest pain, shortness of breath with physical activity, waking from sleep at night short of breath, swelling of the legs or ankles, dizziness, and fainting.

How is it diagnosed?

Your health care provider will examine you and ask about your symptoms. You may have a chest x-ray. An electrocardiogram, a test that measures the electrical activity of the heart, may show abnormalities of the heart muscle. A 24-hour recording of your electrocardiogram made by a portable recorder may show heart rhythm problems. An echocardiogram uses ultrasound pictures of the heart to show the degree and location of heart muscle thickening. Ultrasound may show possible blockage to outflow of blood from the heart.

Because the disease may run in families, your health care provider may suggest that the other members of your family be tested.

How is it treated?

Treatment depends on the type of cardiomyopathy you have and on what caused it.

Medicines such as beta blockers and calcium channel blockers may be used to relax the heart muscle and reduce the amount of blockage. Your health care provider may prescribe a drug called a vasodilator. These drugs make the blood vessels open up. The increased size of the blood vessels allows more blood to flow through them. This lowers blood pressure slightly and lessens the workload of the heart. ACE inhibitors are another type of medicine that can relax blood vessels and lower blood pressure. This enables the heart to pump more blood out to the body.

Your health care provider may also prescribe a blood-thinner (anticoagulant). Anticoagulants help to keep the blood from clotting and prevent artery blockages and strokes.

You may need an operation called myectomy (muscle removal). In some case, this can be done with a heart catheter and surgery is not required. In some people, inserting an electronic cardiac pacemaker helps by slightly changing the pattern of the heartbeat. Sometimes a device called an implantable cardioverter-defibrillator (ICD) is needed to treat abnormal heart rhythms.

Published by McKesson Health Solutions LLC.

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.

Written by Edward Havranek, MD, for McKesson Health Solutions LLC.