Cardiac involvement in patients with Becker muscular dystrophy: new diagnostic and pathophysiological insights by a CMR approach

Background : Becker-Kiener muscular dystrophy (BMD) represents an X-linked genetic disease associated with myocardial involvement potentially resulting in dilated cardiomyopathy (DCM). Early diagnosis of cardiac involvement may permit earlier institution of heart failure treatment and extend life span in these patients. Both echocardiography and nuclear imaging methods are capable of detecting later stages of cardiac involvement characterised by wall motion abnormalities. Cardiovascular magnetic resonance (CMR) has the potential to detect cardiac involvement by depicting early scar formation that may appear before onset of wall motion abnormalities. Methods : In a prospective two-center-study, 15 male patients with BMD (median age 37 years; range 11 years to 56 years) underwent comprehensive neurological and cardiac evaluations including physical examination, echocardiography and CMR. A 16-segment model was applied for evaluation of regional wall motion abnormalities (rWMA). The CMR study included late gadolinium enhancement (LGE) imaging with quantification of myocardial damage. Results : Abnormal echocardiographic results were found in eight of 15 (53.3%) patients with all of them demonstrating reduced left ventricular ejection fraction (LVEF) and rWMA. CMR revealed abnormal findings in 12 of 15 (80.0%) patients (p = 0.04) with 10 (66.6%) having reduced LVEF (p = 0.16) and 9 (64.3%) demonstrating rWMA (p = 0.38). Myocardial damage as assessed by LGE-imaging was detected in 11 of 15 (73.3%) patients with a median myocardial damage extent of 13.0% (range 0 to 38.0%), an age-related increase and a typical subepicardial distribution pattern in the inferolateral wall. Ten patients (66.7%) were in need of medical heart failure therapy based on CMR results. However, only 4 patients (26.7%) were already taking medication based on clinical criteria (p = 0.009). Conclusion : Cardiac involvement in patients with BMD is underdiagnosed by echocardiographic methods resulting in undertreatment of heart failure. The degree and severity of cardiac involvement in this population is best characterised when state-of-the-art CMR methods are applied. Further studies need to demonstrate whether earlier diagnosis and institution of heart failure therapy will extend the life span of these patients.