Early Diagnosis, Treatment Improve
Cardiac Outlook In DMD, BMD

A research group led by Jeffrey Towbin, consulting cardiologist to the MDA clinic at Texas Children’s Hospital and a professor at Baylor College of Medicine (both in Houston), has found that early diagnosis and treatment of the most common type of heart problem found in Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) can markedly improve the course of this disorder, dilated cardiomyopathy.

The study, published in the Nov. 1 issue of Circulation (see PubMed summary), included 62 boys with DMD and seven with BMD who were referred to the Cardiovascular Genetics Clinic at Texas Children’s Hospital from the local MDA clinic, regardless of whether they had any indications of cardiac impairment.

Evidence of cardiac damage was eventually detected in 31 of the boys. Average age at onset was 15, although evidence of cardiomyopathy was found in some children as young as 10.

After the first abnormalities were found on an echocardiogram (imaging study of the heart), the patients were given an angiotensin-converting enzyme (ACE) inhibitor medication. In those who didn’t show improvement in three months, another type of drug, a beta blocker, was added. ACE inhibitors reduce the pressure against which the heart has to pump, and beta blockers slow the heart rate.

“We think that the combination of our study plus Duboc’s study [recently published data from France advocating early use of an ACE inhibitor] is strong support for the fact that early treatment, either predating the onset by echocardiogram of disease or as early as you can get the onset of disease, is a good thing,” Towbin said. “And it suggests testing the hypothesis, in a large study, that preclinical therapy is a good idea. You might want to treat patients at age 8 or 10, before they have problems from a cardiovascular standpoint, and see how late you could push the age of onset.”

Heart Damage Varies With Dystrophin Mutation

The team also found that certain mutations (DNA coding errors) in the gene for dystrophin, the skeletal and heart muscle protein entirely missing in DMD muscle cells and partly deficient in BMD cells, are more likely than others to lead to serious heart disease.

The researchers found that mutations affecting the area of the dystrophin gene known as exons 12 and exons 14 to 17, as well as mutations in exons 31 to 42, seem to be particularly associated with heart disease. Boys with mutations in exons 51 or 52 had a lower risk of cardiac involvement. They caution that these findings should be considered preliminary because of the small sample size.