Cardiomyopathy Overview

What is cardiomyopathy?

Cardiomyopathy is a problem with the heart muscle that can cause heart failure. There are 3 main types of cardiomyopathy:

Dilated cardiomyopathy, which causes the heart muscle to get weak. As the heart muscle weakens, it is less able to pump enough blood. Because the heart can't pump as well, the main pumping chamber of the heart (the left ventricle) fills with blood and cannot empty. The extra blood in the left ventricle causes the heart muscle to stretch, just like a balloon expands when you put air into it. This happens slowly, over several weeks to months. The pressure in the heart never gets high enough to cause the heart to rupture or pop.
Hypertrophic cardiomyopathy (HCM), which causes the heart muscle cells to get bigger. This makes the walls of the heart muscle thick. When the walls of the heart get too thick, it cannot pump well. Thick walls are usually very stiff, making it hard for the heart to fill with enough blood to pump. For reasons we don't understand, some people with HCM develop a weak heart muscle over time. The weak heart muscle can slowly change to be dilated cardiomyopathy.
Restrictive cardiomyopathy causes the heart muscle to get very stiff. This may be caused by deposits (like iron) that build up in the heart muscle, or scars that form on the inside of the heart. The stiffness makes it hard for the heart to fill with blood and pump properly. This is the least common kind of cardiomyopathy.

How does cardiomyopathy occur?

The heart muscle may be weakened by many things. Coronary artery disease (CAD) can make the heart muscle weak. CAD causes poor blood supply to the heart, and may hurt the heart muscle, making it weak. This is the most common cause of dilated cardiomyopathy. Cocaine or heavy alcohol use weaken the heart muscle. Some medicines used to treat cancer are deadly to heart muscle cells and can weaken the heart.

What causes the heart to enlarge and weaken may not be known. When the cause is not known, it is called idiopathic dilated cardiomyopathy.

HCM may be caused by high blood pressure. High blood pressure makes the heart pump harder. The walls of the heart enlarge just like the muscles of a weight lifter enlarge. When high blood pressure goes untreated for many years, the heart muscle will get thicker and 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 scarring on the inside of the heart. This is because protein gets left in the heart muscle, and the protein can cause scars on the walls of the heart. Some cancers and infections can also cause scar tissue. This scarring keeps the heart muscle from pumping properly and 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 up short of breath
swelling of the legs or ankles
dizziness
fainting.

How is it diagnosed?

Your health care provider will examine you and ask about your symptoms. You may have:

chest x-rays
electrocardiogram (ECG), a recording of your heart's rhythm
echocardiogram (an ultrasound scan of the heart), which can show the areas of heart muscle that are thick).

You may also need to wear a Holter monitor. A Holter monitor is a recorder you wear for at least 24 hours. It makes a constant recording of your heart rhythm.

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 or calcium channel blockers may be used to relax the heart muscle. 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 helps 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.

Procedures that may be used to treat cardiomyopathy include:

myectomy to take out a piece of the heart muscle. (In some case, this can be done with a heart catheter and surgery is not needed.)
putting in an artificial pacemaker or an implantable cardioverter-defibrillator (ICD) to treat abnormal heart rhythms.

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

HIA File CRD3611F.HTM Release 9.0/2006