Abnormal Circumferential Strain is Present in Young Duchenne Muscular Dystrophy Patients

Advances in management of non-cardiac issues in Duchenne muscular dystrophy (DMD) have improved such that DMD-associated cardiac disease has become the leading cause of death for such patients. Cardiac dysfunction measured by standard transthoracic echocardiographic methods, e.g., fractional shortening (FS) and ejection fraction (EF), is rarely present during the first decade of life. The current study used transthoracic echocardiogram (TTE) to assess strain (ε), an indicator of regional ventricular function, in young DMD patients. A retrospective review of the TTE database was performed. TTE results from DMD patients <8 years (n = 63) performed during 2009 to 2010 were compared with TTE results from an unaffected control group (n = 61). Feature tracking analysis software was used to measure total circumferential strain (ε _cc) as well as segmental ε _cc based on the American Society of Echocardiography 16-segment model. Although there were no differences in FS, the absolute value for left-ventricular (LV) ε _cc at the mid-chamber level was decreased in DMD (−21.7 % ± 3.8 % vs. −19.8 % ± 4.2 %, p < 0.01; unaffected vs. DMD). Segmental ε _cc was similarly affected in the anteroseptal segment (−23.0 % ± 6.1 % vs. −18.9 % ± 7.0 %, p = 0.001; controls vs. DMD), the inferior segment (−20.7 % ± 5.16 % vs. −17.7 % ± 6.1 %, p = 0.003; controls vs. DMD), and the inferolateral segment (−18.3 % ± 6.2 % vs. −15.9 % ± 6.7 %, p = 0.04; controls vs. DMD). In the present study we demonstrate both total and segmental LV ε _cc (anteroseptal, inferior, and inferolateral segments) abnormalities at the mid-chamber level in a large group of young DMD patients with normal FS. These novel findings substantiate that the disease process is present and results in abnormal myocardial function before standard measures detect global dysfunction.