How Is Cardiomyopathy Diagnosed?

If cardiomyopathy is suspected, the diagnosis is based on a person's:

• Symptoms and medical history
• Family history of cardiomyopathy, heart failure, or sudden cardiac arrest
• Physical exam
• Results on diagnostic tests and procedures

The physical exam will identify a number of findings in patients with cardiomyopathy. The doctor will use a stethoscope to listen to the person's heart and lungs for sounds that may suggest the presence of cardiomyopathy. These sounds may even indicate a certain type of cardiomyopathy. For example, the loudness, timing, and location of a heart murmur may suggest that a person has hypertrophic obstructive cardiomyopathy. A "crackling" sound in the lungs may be a sign of heart failure, which often develops in the later stages of cardiomyopathy.

Physical signs also help the doctor diagnose cardiomyopathy. Swelling of the abdomen, legs, or feet may indicate excess fluid, which is a sign of heart failure.

Sometimes, doctors discover cardiomyopathy during a routine exam if they hear a heart murmur or if the patient has an abnormal electrocardiogram (see Diagnostic Tests and Procedures below).

Specialists Involved

Often a cardiologist or pediatric cardiologist is involved in the care of a patient with cardiomyopathy. A cardiologist is a doctor who specializes in heart diseases. A pediatric cardiologist specializes in children's heart diseases.

Diagnostic Tests and Procedures

Doctors may order one or more tests to diagnose cardiomyopathy, including:

• EKG (electrocardiogram). This test measures the rate and regularity of the heartbeat and can detect arrhythmias.
• Holter monitor (ambulatory EKG/ECG). This test records the EKG readings for a continuous 24-hour period. It can detect arrhythmias that occur only rarely throughout the day. A small monitoring device is attached to patches (electrodes) that are placed on the patient's chest. The device is carried in a pouch around the neck or attached to a belt.
• Echocardiogram. This test uses sound waves to create a moving picture of your heart. Echocardiogram provides information about the size and shape of your heart and how well your heart chambers and valves are functioning. The test also can identify areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow.
• There are several different types of echocardiograms, including a stress echocardiogram. During this test, an echocardiogram is done both before and after your heart is stressed either by having you exercise or by injecting a medicine into your bloodstream that makes your heart beat faster and work harder. A stress echocardiogram is usually done to find out if you have decreased blood flow to your heart (coronary artery disease). Echocardiogram is a good way to diagnose hypertrophic cardiomyopathy because it shows the thickened walls of the heart.
• Transesophageal (tranz-ih-sof-uh-JEE-ul) echocardiography (TEE). In this test, the doctor inserts an ultrasound probe into the throat after the patient is sedated. TEE provides a view of the back of the heart.
• Stress Test. Some heart problems are easier to diagnose when your heart is working harder and beating faster than when it’s at rest. During stress testing, you exercise (or are given medicine if you are unable to exercise) to make your heart work harder and beat faster while heart tests are performed.
• During exercise stress testing, your blood pressure and EKG readings are monitored while you walk or run on a treadmill or pedal a bicycle. Other heart tests, such as nuclear heart scanning or echocardiography, also can be done at the same time. These would be ordered if your doctor needs more information than the exercise stress test can provide about how well your heart is working.
• If you are unable to exercise, a medicine can be injected through an intravenous line (IV) into your bloodstream to make your heart work harder and beat faster, as if you are exercising on a treadmill or bicycle. Nuclear heart scanning or echocardiography is then usually done.
• During nuclear heart scanning, radioactive tracer is injected into your bloodstream, and a special camera shows the flow of blood through your heart and arteries. Echocardiography uses sound waves to show blood flow through the chambers and valves of your heart and to show the strength of your heart muscle.
• Your doctor also may order two newer tests along with stress testing if more information is needed about how well your heart works. These new tests are magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning of the heart. MRI shows detailed images of the structures and beating of your heart, which may help your doctor better assess if parts of your heart are weak or damaged. PET scanning shows the level of chemical activity in different areas of your heart. This can help your doctor determine if enough blood is flowing to the areas of your heart. A PET scan can show decreased blood flow caused by disease or damaged muscles that may not be detected by other scanning methods.
• Chest x ray. A chest x ray takes a picture of the organs and structures inside the chest, including the heart, lungs, and blood vessels. This test can show whether the heart is enlarged or whether fluid is building up in the lungs.
• Blood tests, such as complete blood count, blood chemistries, and cardiac enzymes. These tests are done to provide information on the condition of the heart and to rule out other conditions.

The doctor may order additional tests to confirm the diagnosis or if surgery is planned. These tests may include:

• Cardiac catheterization. With this test doctors can check the pressure and blood flow in the heart's chambers, collect blood samples from the heart, and examine the arteries of the heart using x ray. A thin, flexible tube (catheter) is passed through an artery in the upper thigh (groin) or in the arm to reach the coronary arteries. This allows the doctor to study the inside of the arteries to look for blockages.
• Coronary angiography. This test is usually performed along with cardiac catheterization. Angiography enables the doctor to see the flow of blood to the heart muscle. A dye that can be seen on an x ray image is injected into the coronary arteries. Dye also can be injected into the chambers to evaluate the pumping function of the heart.
• Myocardial biopsy. In this test, the doctor removes a piece of heart muscle to look at under a microscope. The biopsy can be done during a cardiac catheterization and is useful in diagnosing some types of cardiomyopathy.

Because some types of cardiomyopathy run in families, the doctor may recommend looking for the disease in the parents, brothers and sisters, and children of people with cardiomyopathy.

Genetic counseling may be recommended. Genetic counseling is useful to help define and explain how the disease runs in families and to determine the chances of parents passing it on to their children.

Author/Source: National Heart, Lung & Blood Institute, Division of the National Institutes of Health [NIH]

Retrieved: June 2008