Exercise Cardiac Magnetic Resonance Imaging in Boys With Duchenne Muscular Dystrophy Without Cardiac Disease

Duchenne muscular dystrophy is caused by mutations in the DMD gene, resulting in cardiomyopathy in all affected children by 18 years. Although cardiomyopathy is now the leading cause of mortality in these children, there is ongoing debate regarding timely diagnosis, secondary prevention, and treatment of this condition. The purpose of this study was to use exercise cardiac magnetic resonance imaging in asymptomatic young boys with Duchenne muscular dystrophy to describe their heart function and compare this with healthy controls.

We studied 11 boys with Duchenne muscular dystrophy aged 8.6 to 13.9 years and 11 healthy age- and sex-matched controls.

Compared with the controls, boys with Duchenne muscular dystrophy had lower ejection fraction at rest (57% versus 63%; P = 0.004). During submaximal exercise, they reached similar peak tachycardia but increased their heart rate and cardiac output only half as much as controls (P = 0.003 and P = 0.014, respectively). End-systolic volume remained higher in boys with Duchenne muscular dystrophy both at rest and during exercise. When transthoracic echocardiography was compared with cardiac magnetic resonance imaging, 45% of the echocardiograms had suboptimal or poor views in the Duchenne muscular dystrophy group.

Boys with Duchenne muscular dystrophy had abnormalities in left ventricular systolic function that were exaggerated by exercise stress. Exercise cardiac magnetic resonance imaging is feasible in a select population of children with Duchenne muscular dystrophy, and it has the potential to unmask early signs of cardiomyopathy.