Cardiac disease, particularly dilated cardiomyopathy and heart failure, is the major cause of mortality in patients with muscular dystrophy and is present in most boys with Duchenne muscular dystrophy and approximately 70 percent of those with Becker muscular dystrophy. These are the two common forms of muscular dystrophy caused by defects in a gene called dystrophin.
"It should be the standard of care for all newly diagnosed Duchenne and Becker muscular dystrophy patients to be referred to a cardiologist for screening, probably by 10 years of age or earlier," says Dr. Jeffrey A. Towbin, professor of pediatrics at BCM and chief of pediatric cardiology at Texas Children's Hospital.
Towbin and his group studied 69 boys with DMD and BMD. After the first abnormal echocardiogram, which occurred at 14-15 years, 31 boys were started on ACE inhibitor or beta blocker therapy. During the follow-up two patients remained stable with their dilated cardiomyopathy, eight showed improvement and 19 normalized both heart size and function.
"This study also helped us realize that while some dystrophin-gene mutations are predictors of early onset cardiac abnormalities, others may actually protect against early development of these abnormalities," says Towbin.
Cardiac symptoms typically appear late in the course of cardiomyopathy, in part because affected individuals are usually wheelchairchair bound and often physically inactive. Heart disease progresses quickly, leading to premature death, often before 25 years of age.
The work by Towbin and his colleagues suggests longer heart health and longer lives based on this treatment approach. Other contributors to this study include Drs. John L. Jefferies, Benjamin W. Eidem, John W. Belmont, William J. Craigen, E. O'Brian Smith, Steven R. Neish and Susan Fernbach, R.N. of BCM and Stephanie M. Ware of Texas Children's Hospital.