Aerobic exercise training for 8 weeks significantly reduced the probability of ventricular fibrillation induction to 6.7% compared to 26.1% in sedentary control rats.
Does aerobic exercise training reduce the inducibility of ventricular tachycardia and fibrillation in healthy rats?
Aerobic exercise in healthy rats induces intrinsic cardiac remodeling that reduces susceptibility to ventricular fibrillation and increases the electrical complexity of the heart.
Absolute Event Rate: 6.7% vs 26.1%
p-value: p=<0.05
BACKGROUND: The mechanisms whereby aerobic training reduces the occurrence of sudden cardiac death in humans are not clear. We test the hypothesis that exercise-induced increased resistance to ventricular tachycardia and fibrillation (VT/VF) involve an intrinsic remodeling in healthy hearts. METHODS AND RESULTS: Thirty rats were divided into a sedentary (CTRL, n = 16) and two exercise groups: short- (4 weeks, ST, n = 7) and long-term (8 weeks, LT, n = 7) trained groups. Following the exercise program hearts were isolated and studied in a Langendorff perfusion system. An S1-S2 pacing protocol was applied at the right ventricle to determine inducibility of VT/VF. Fast Fourier transforms were applied on ECG time-series. In-vivo measurements showed training-induced increase in aerobic capacity, heart-to-body weight ratio and a 50% low-to-high frequency ratio reduction in the heart rate variability (p<0.05). In isolated hearts the probability for VF decreased from 26.1±14.4 in CTRL to 13.9±14.1 and 6.7±8.5% in the ST and LT, respectively (p<0.05). Duration of VF also decreased from 19.0±5.7 in CTRL to 8.8±7.1 and 6.0±5.8 sec in ST and LT respectively (p<0.05). Moreover, the pacing current required for VF induction increased following exercise (2.9±1.7 vs. 5.4±2.1 and 8.5±0.9 mA, respectively; p<0.05). Frequency analysis of ECG revealed an exercise-induced VF transition from a narrow single peak spectrum at 17 Hz in CTRL to a broader range of peaks ranging between 8.8 and 22.5 Hz in the LT group (p<0.05). CONCLUSION: Exercise in rats leads to reduced VF propensity associated with an intrinsic cardiac remodeling related to a broader spectral range and faster frequency components in the ECG.
Dor‐Haim et al. (Tue,) conducted a other in Healthy (Normal rats) (n=30). Aerobic exercise training vs. Sedentary control was evaluated on Probability of ventricular fibrillation (VF) induction (p=<0.05). Aerobic exercise training for 8 weeks significantly reduced the probability of ventricular fibrillation induction to 6.7% compared to 26.1% in sedentary control rats.