HEART-RATE-VARIABILITY AND ITS RELATION TO VENTRICULAR ARRHYTHMIAS INCONGESTIVE-HEART-FAILURE

Background-It has been shown that heart rate variability is decreased in patients with congestive heart failure and that depressed heart rat e variability is associated with a propensity to ventricular arrhythmi as. Little is known, however, about heart rate variability in patients with both congestive heart failure and ventricular arrhythmias. Metho ds-Spectral heart rate variability was analysed from 24 hour ambulator y electrocardiograms in 15 controls, 15 patients with non-sustained ve ntricular tachycardia associated with clinically normal hearts (NHVT g roup), and 40 patients with congestive heart failure (CHF group) secon dary to either ischaemic heart disease (n = 15) or idiopathic dilated cardiomyopathy (n = 25). Of the 40 patients with congestive heart fail ure 15 had no appreciable ventricular arrhythmias (ventricular extrasy stoles < 10 beats I h and no salves) and formed the CHF-VA group. Anot her 15 patients with congestive heart failure and nonsustained ventric ular tachycardia formed the CHF-NSVT group. Results-Heart rate variabi lity was significantly lower in the CHF group than in controls (mean ( SD) total frequency 23 (12) v 43 (13) ms; low frequency 12 (8) v 28 (9 ) ms; high frequency 8 (5) v 14 (7) ms; p < 0.001). The differences in heart rate variability between controls and the NHVT group, between i schaemic heart disease and dilated cardiomyopathy, and between the CHF -VA and CHF-NSVT groups were not significant. In the CHF group heart r ate variability was significantly related to left ventricular ejection fraction but not associated with ventricular arrhythmias. The frequen cy of ventricular extrasystoles was significantly related to the high frequency component of heart rate variability (r = 0.54, p < 0.05) in the NHVT group. Stepwise multiple regression analysis showed that in t he CHF group, heart rate variability was predominantly related to left ventricular ejection fraction (p < 0.05). There was no significant di fference in heart rate variability between survivors (n = 34) and thos e who died suddenly (n = 6) at one year of follow up in the CHF group. Conclusion-In patients with congestive heart failure, heart rate vari ability is significantly decreased. The depressed heart rate variabili ty is principally related to the degree of left ventricular impairment and is independent of aetiology and the presence of ventricular arrhy thmias. The data suggest that analysis of heart rate variability does not help the identification of patients with congestive heart failure at increased risk of sudden death.