Cardiac Autonomic Function and Heart Rate Variability in Patients with Duchenne Muscular Dystrophy

The effects of autonomic nervous dysfunction on the cardiopulmonary system are not fully understood in patients with Duchenne muscular dystrophy (DMD). We evaluated cardiac autonomic function by time and frequency domain heart rate variability (HRV) analysis, as determined by 24-hour Holter recordings, in 31 patients with DMD and 23 healthy controls. The 5 times domain parameters measured were Standard deviation of all R-R intervals (SDNN), standard deviation of mean R-R interval of 5-minute segments (SDANN), sguare root of mean sguared differences of successive R-R intervals (rMSSD) and percentage of differences between adjacent R-R intervals>50ms (pNN50), and the 4 frequency domain parameters were low frequency (LF), high frequency (HF), LF/HF ratio, and very LF (VLF). In DMD patients, left ventricular ejection fraction (LVEF) was measured by 2D echocardiography and comparisons were made between low cardiac function (DMD-L) and normal (DMD-N). Compared to controls, total heart rate was significantly increased in DMD (p<0.0001) while all time domain parameters were significantly decreased. LF/HF ratio did not differ between the two groups. HF and VLF was significantly lower in DMD (p<0.001, p