Guidance for primary care clinicians evaluating and managing cardiomyopathy in children with Duchenne muscular dystrophy

Cardiac abnormalities are a significant cause of death and morbidity in patients with Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), especially as boys with DMD are now living through their twenties. The clinical course of cardiomyopathy – progressive decline in left ventricular function resulting in cardiac failure – is usually prolonged, though sudden death from arrhythmia may occur. Many patients do not show symptoms of cardiomyopathy due to their lack of physical activity, but early changes in cardiac function are usually apparent on cardiac imaging studies, e.g., echocardiogram or cardiac magnetic resonance imaging (MRI).

Because changes in cardiac function are uncommon before the second decade of life, the Treat-NMD standards, [Birnkrant: 2018], recommend a cardiology evaluation with an echocardiogram and electrocardiogram (ECG) at the time of diagnosis every 2 years until age 10 and then annually unless progressive problems suggest the need for more frequent exams. [Feingold: 2017] Cardiology referral is also recommended before any major surgery. When present, clinical symptoms may include those associated with congestive heart failure (edema, shortness of breath, orthopnea), reduced cardiac output (especially fatigue), and/or arrhythmias. However, symptoms might be absent due to decreased skeletal muscle strength and decreased physical activity until very late in the course of the disease. With severe cardiomyopathy, thromboembolic events have been observed.

Some cardiologists may order a cardiac MRI instead of or in addition to ECG/echocardiogram for better anatomical visualization. Cardiac MRI may show evidence of heart muscle scarring that cannot be seen via echocardiogram. Decreased left ventricular ejection fraction on echocardiogram is the most common early finding of dilated cardiomyopathy.

Early diagnosis and treatment of dilated cardiomyopathy, based on echocardiographic findings and not clinical deterioration, are advised. Initial medication options include angiotensin converting enzyme (ACE) inhibitors, such as enalapril or lisinopril, and angiotensin receptor blockers (ARBs), such as losartan. Some clinicians will start these medications at age 10, even before detection of reduced ejection fraction. The 2017 American Heart Association guidelines for the treatment of cardiac problems in children with neuromuscular disease include this approach as “may be considered.” [Feingold: 2017]

These medications are also commonly used to treat high blood pressure, which may be related to prolonged steroid exposure in boys with DMD. Other agents, such as beta-blockers, may be added in the setting of advanced dilated cardiomyopathy, depending on cardiology preference and disease manifestations. Other medications, such as diuretics, may be added when a patient has signs or symptoms of congestive heart failure.

Anti-arrhythmic therapy is sometimes needed as well. Left ventricular assist devices (LVADs) may be increasingly offered to boys in heart failure. In some cases, cardiac transplantation may be possible, although this varies with the site where the child is receiving care. Recent evidence suggests that prolonged steroid therapy may help delay the onset of cardiomyopathy. [Schram: 2013]

The mothers of boys with DMD/BMD may also be at risk for cardiac problems. They should be evaluated by genetic testing to confirm carrier status and, if positive, evaluation and monitoring by a cardiologist.

Pediatric Cardiology (see NW providers [0])
Boys with DMD and BMD should receive cardiac evaluation with an echocardiogram (or MRI) and EKG at diagnosis and then yearly unless clinical circumstances mandate more frequent visits. Subsequent visits to pediatric cardiologists familiar with DMD are recommended for treatment of cardiac complications.