9-YEAR FOLLOW-UP-STUDY OF HEART-RATE-VARIABILITY IN PATIENTS WITH DUCHENNE-TYPE PROGRESSIVE MUSCULAR-DYSTROPHY

Objectives The purpose of this study was to investigate the progressio n of autonomic dysfunction in patients with Duchenne-type progressive muscular dystrophy (DMD) over time by using heart rate variability. Ba ckground Although previous studies suggest the presence of autonomic d ysfunction in patients with DMD, the precise cause is not known. On th e other hand, it is well known that analysis of heart rate variability provides a useful, noninvasive means of quantifying autonomic activit y. High frequency power is determined predominantly by the parasympath etic nervous system, whereas low frequency power is determined by both the parasympathetic and sympathetic nervous systems. Methods and Resu lts Frequency and time domain analyses of heart rate variability durin g ambulatory electrocardiographic monitoring were performed in 17 pati ents with DMD over a 9-year period. At the time of entry, the mean pat ient age was 11 years and the mean Swinyard-Deaver stage was 4. In the first year, high frequency power was significantly lower and the rati o of low frequency to high frequency was significantly higher in patie nts with DMD than in the normal control subjects. These differences be came significantly greater as the disease progressed. At the time of e ntry, low and high frequency powers increased at night in both groups. However, over time, high and low frequency powers at night tended to decrease. All of the time domain parameters were significantly lower i n the patients with DMD at all time points compared with the normal co ntrol subjects. Conclusions We concluded that DMD patients have either a decrease in parasympathetic activity, an increase in sym pathetic a ctivity, or both as their disease progresses.