CARDIAC PROBLEMS ARE COMMON

The heart is almost always affected in Duchenne and Becker muscular dystrophies, although the degree to which it's affected and the age at which it becomes a problem vary.

The main problem in both conditions is degeneration of the heart, which is, of course, a muscle. The medical term for this condition is cardiomyopathy. The problem caused by cardiomyopathy is heart failure, which means the heart isn't effective enough at pumping blood through the body. (In BMD, boys with mild skeletal muscle involvement can have severe cardiac involvement. The mildness of the skeletal muscle effects may give parents and doctors a false sense of security regarding the health of the heart.)

Recognizing Heart Problems

A common early sign of heart failure is shortness of breath with exercise, along with general fatigue and inability to do much activity. If fluid accumulates in the lungs, as may occur when the heart isn't working effectively, there may be wheezing and coughing.

In boys who are already using a wheelchair most of the time, shortness of breath with exercise doesn't usually alert parents or physicians to the presence of a heart problem, since the boys aren't getting much exercise. In boys who are still walking as their heart failure is progressing, shortness of breath may occur as it would in other children with heart disease. Coughing may occur if the lungs fill with fluid.

Experts recommend that children with DMD and BMD be referred for evaluation of their cardiac function at an early age (some say even by 4 years old) and then have a yearly re-evaluation.

Many neurologists order regular electrocardiograms (ECGs) on boys with DMD or BMD, starting at a young age, so that they can watch for changes. The ECG, however, doesn't tell the doctor very much. It only gives the most general idea of how the heart is functioning.

These days, you'll likely be referred for another test of heart function, the echocardiogram. The echocardiogram is a more modern and much more specific tool to assess cardiac function. It uses ultrasound to view the heart and tells the doctor quite a lot about how the heart is working. It's painless and is usually covered by insurance. Some doctors recommend yearly echocardiograms for boys with DMD or BMD, starting at about age 4, or as soon as the condition is diagnosed.

Occasionally more elaborate and invasive tests, such as cardiac catheterization, may be ordered later if serious cardiac involvement is suspected. Cardiac catheterization involves going into the heart with a catheter (tube).

Treating Heart Problems

Fortunately, treatment of cardiomyopathy and heart failure has come a long way in recent years.

There are several types of drugs that are used. Among them are an old class of drugs known as cardiac glycosides. The main drug in this group in use today is digoxin (Lanoxin). In general, the cardiac glycosides increase the force of the heart's contractions. Digoxin and related drugs can increase the efficiency of muscle cells in the heart that haven't yet undergone degeneration and scarring.

Another type of drug that's sometimes prescribed in heart failure is a diuretic. Diuretics, sometimes called water pills, increase the elimination of water from the body through the kidneys. This fluid reduction seems to help the heart work more efficiently with reduced muscle power. There are many types of diuretics. Among the names you may encounter are furosemide (Lasix), bumetanide (Bumex) and spironolactone (Aldactone).

A recent addition to the array of drugs used to treat heart failure are the ACE (angiotensin converting enzyme) inhibitors. They reduce production of the chemical angiotensin. Reduced angiotensin causes blood vessels to dilate and improves the efficiency of the failing heart. Enalapril (Vasotec) and captopril (Capoten) are examples of this type of drug.

Still another new addition to the treatment of heart failure is the class of drugs known as beta blockers. Many people have heard of these drugs in the treatment of high blood pressure, where their benefit derives from slowing the heart rate and decreasing the force of the heart's contractions. It may seem confusing to use such drugs in heart failure, where the heart doesn't seem to be contracting hard enough, but studies have shown that, at least at certain points in the progression of heart failure, they are helpful. Metoprolol (Lopressor) is an example of a beta blocker used in this condition.

Other drugs, as well as a diet low in sodium, may also be prescribed by a cardiologist. A low-sodium diet helps the body rid itself of excess fluid.

If drugs and diet are no longer effective and death from heart failure is imminent, the only recourse may be a heart transplant. Heart transplants have been performed in several young men with BMD. In these patients, the general prognosis was considered good enough to warrant this drastic step. Boys with Duchenne are not considered candidates for heart transplantation, because their overall prognosis, especially with regard to their respiratory status, is poor.

A new type of surgery for some types of heart failure is a procedure that reduces the size of the heart. This type of operation is considered experimental but may someday replace heart transplantation as a treatment for heart failure.

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