ASSESSMENT OF AUTONOMIC FUNCTION IN MYOTONIC-DYSTROPHY BY SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY

We analyzed by means of autoregressive spectral analysis the spontaneo us beat-to-beat heart-rate variability (HRV) of 10 myotonic dystrophy (MD) patients (4 men and 6 women, aged 37-53 years) and 10 age- and se x-matched healthy, sedentary humans (central) at rest in the supine po sition. All MD patients had no cardiac conduction disturbances (i.e., atrioventricular or intraventricular conduction defects) on 12-lead el ectrocardiogram and were able to walk and perform daily activities. In the MD group, the total power, the power of the low-frequency compone nt (a marker of sympathetic and vagal modulation of heart rate) and th at of the high-frequency component (a marker of vagal modulation of he art rate) were smaller than those in the control group (P < 0.01, P < 0.05 and P < 0.05, respectively). The results of this study suggest th at the cardiovascular autonomic nervous system contributing to the HRV may be disturbed even in the MD patients who can walk and perform dai ly activities. Therefore, one must give careful consideration to the c ardiovascular autonomic dysfunction, as well as the cardiac conduction disturbance in the MD patients.