IMPACT OF ATRIOVENTRICULAR DELAY ON HEART-RATE-VARIABILITY OF PACED PATIENTS WITH AND WITHOUT HEART-FAILURE

The aim of the study was to investigate whether the optimisation of at rioventricular (Av) delay in patients with complete AV block, with or without heart failure,paced under VDD mode, has an effect on heart rat e variability and consequently on the autonomic nervous system in thes e patients. We studied 10 patients (Group I: 7 men, aged 68 +/- 9 year s) with normal left ventricular function and 9 patients (Group II: 6 m en, aged 70 +/- 6 years) with systolic left ventricular dysfunction (N YHA heart failure Class II or III). Each patient was paced for 24 h wi th the optimal and 24 h with the worst AV delay in random order and am bulatory electrocardiograms (ECGs) (Marquette) were recorded. Spectral heart rate variability was analysed for each 24-h period on a Holter analysis system (Marquette Series 8000). The optimal and worst AV dela y were determined by echo-Doppler as those which produced the greatest and least cardiac output, respectively. For the patients in Group I, there was no difference between the two AV delays as regards indices o f heart rate variability. In contrast, for Group II the total frequenc y (TF) was significantly higher and the low frequency (LF) and LF/high frequency (HF) ratio were significantly lower when the patients were paced with optimum AV delay. Furthermore, this AV delay resulted in si gnificantly higher mean NN and SD. In conclusion, in patients with nor mal left ventricular function, changes in AV delay do not appear to af fect the activity of the autonomic nervous system in the heart. In pat ients with mild to moderate heart failure, optimisation of the AV dela y causes a significant drop in sympathetic nervous tone.