AUTONOMIC NERVOUS-SYSTEM ACTIVITY IN IDIOPATHIC DILATED CARDIOMYOPATHY AND IN HYPERTROPHIC CARDIOMYOPATHY

To assess autonomic nervous activity in patients with cardiomyopathies , analysis of heart rate variability was performed using 24-hour ambul atory electrocardiograms in 14 patients with idiopathic dilated cardio myopathy (IDC), 15 with hypertrophic cardiomyopathy (HC) and 18 health y subjects. Heart rate variability during the night and daytime was ca lculated using fast-Fourier transform, and power spectra were quantifi ed in 2 frequency bandwidths: 0.00 to 0.15 Hz (low-frequency power [LF ]) and 0.15 to 0.50 Hz (high-frequency power [HF]. Log(HF) was used as an index of parasympathetic nervous activity. Log (HF) was significan tly lower and log(LF/HF) was significantly higher IDC. These changes w ere related to ejection fraction. In HC, lower log(HF) and higher log( LF/HF) were recognized only during the night, and these changes were i ndependent of the degree of myocardial hypertrophy. Our results indica ted attenuation of parasympathetic activity and enhanced sympathetic a ctivity in HC during the night, and also in IDC. Assessment of autonom ic imbalance by analysis of heart rate variability may be useful for u nderstanding the pathophysiology of cardiomyopathies.