Circadian rhythm and variability of heart rate in Duchenne-type progressive muscular dystrophy

Abstract Using 24-hour Holter monitoring and time domain and power spectral measurements, we evaluated the variability or the heart rate and its circadian rhythm in 55 male patients with Duchenne-type progressive muscular dystrophy (DMD) to characterize their autonomic function versus findings in 20 normal controls. Comparisons were also made in patients with mild, moderate, and severe stages of DMD. The percent difference between successive RR intervals that exceeded 50 ms, a measure of parasympathetic tone, was significantly lower even in patients with early stage of DMD than in controls (p LF HF ratio), a measure of sympathetic tone, was higher in DMD patients versus controls (p LF HF ratio. Patients with severe disease had virtually no circadian rhythm in HF. Their LF HF ratio was higher at night (p