Arterial blood pressure variability before and after chronic pacing induced heart failure in conscious dogs

To examine the effects of heart failure on beat-to beat arterial blood pressure (ABP) variability, four adult mongrel dogs (20-25 kg) were chronically instrumented for ventricular pacing and continuous measurements of central ABP and cardiac output (CO). Five minutes recordings with the dogs conscious and at rest took place after recovery from surgery (control) and after a 30 days long period of pacing at 240 bpm (heart failure). Autoregressive spectral analysis of the beat-to-beat ABP fluctuations was performed and paired t-test revealed that ABP total, low frequency (LF) and high frequency (HF) power all significantly decreased following chronic pacing induced heart failure. No significant difference was found in the contribution of CO to ABP variability. Our results suggest that heart failure induces changes in autonomic reflexes and hemodynamics that dampen the mechanisms responsible for generating ABP variability.