DMD & BMD – CLINICAL: P.52 The natural history of the cardiomyopathy of Duchenne and Becker muscular dystrophy

Abstract

Duchenne/Becker muscular dystrophy (DMD/BMD) is a progressive skeletal myopathy as well as a cardiomyopathy. Historically, it is reported that patients with DMD/BMD experience significant morbidity/mortality as a result of rhythm abnormalities. However, natural history data is limited regarding the specific mode of death, e.g. heart failure vs. sudden cardiac death vs. non-cardiac death. We identified 82 patients at our institution to analyze retrospectively (67 DMD/15 BMD). Average age was 21 (range 10-38) years. We obtained demographics, Holter monitors, electrocardiograms, and mortality on all patients. We classified cardiac function based on left ventricular ejection fraction (LVEF), defined as normal (>/= 55%), mild-to-moderately depressed (35-54%), or severely depressed (<35%). Cardiac arrhythmias occurred in 22 patients (27%), with rates of 19%, 18%, and 59% in patients with normal, mild-to-moderately depressed, and severely depressed LV EF, respectively. Abnormalities included non-sustained ventricular tachycardia (10 patients, 12%), ventricular fibrillation (10 patients, 12%), and supraventricular tachycardia (5 patients, 6%). There were 5 patients (6%) with multiple arrhythmia types. The mortality rate was 10% with only 2 of the 8 deaths being cardiogenic (1 cardiac arrest, 1 heart failure). The majority of patients had a non-cardiac cause of death, including sepsis, renal failure, and respiratory failure. Both patients with cardiac deaths had severely depressed LVEF and 1 had a history of arrhythmia. Consistent with previous studies, cardiac arrhythmias occurred more frequently in patients with severe left ventricular dysfunction. However, mortality was rarely due to a cardiac etiology, with sudden death representing only a subset of these. This data informs us that surveillance for cardiac rhythm abnormalities and treatment of arrhythmias should be targeted to individuals with severely depressed ventricular function.