Key result
Vagal stimulation significantly delayed the time to ventricular fibrillation after acute coronary occlusion in pigs with spontaneous heart rates (1102 vs 925 seconds), but this effect was abolished when heart rate was fixed.
Why the study?
Does vagal stimulation delay the time to ventricular fibrillation after acute coronary occlusion in pigs, and is this effect dependent on heart rate?
Does vagal stimulation delay the time to ventricular fibrillation after acute coronary occlusion in pigs, and is this effect dependent on heart rate?
Absolute Event Rate: 1102% vs 925%
p-value: p=<0.05
The antiarrhythmic effect of vagal stimulation during acute myocardial ischemia in pigs is dependent on its ability to reduce heart rate, as maintaining a constant rapid heart rate abolishes the protective delay in ventricular fibrillation onset.
Heart rate slowing mediates vagal antiarrhythmic protection in porcine ischemia; leaves open translation to clinical acute coronary syndromes.
BACKGROUND: There is a well documented causal link between autonomic imbalance and cardiac elec-trical instability. However, the mechanisms underlying the antiarrhythmic effect of vagal stimulation are poorly understood. The vagal antiarrhythmic effect might be modulated by a decrease in heart rate. METHODS: The proximal anterior interventricular artery was occluded in 16 pigs by clamping under general anaesthesia. Group 1: heart rates remained spontaneous (n = 6; 12 occlusions); Group 2: heart rates were fixed at 190 bpm with atrial electrical stimulation (n = 10; 20 occlusions). Each pig received two occlusions, 30 min apart, one without and one with vagal stimulation (10 Hz, 2 ms, 5-20 mA). The antiarrhythmic effect of vagal activation was defined as the time to the appearance of ventricular fibrillation (VF) after occlusion. RESULTS: In Group 1, vagal stimulation triggered a significant decrease in basal heart rate (132 ± 4 vs. 110 ± 17 bpm, p < 0.05), and delayed the time to VF after coronary occlusion (1102 ± 85 vs. 925 ± ± 41 s, p < 0.05). In Group 2, vagal stimulation did not modify the time to VF (103 ± 39 vs. 91 ± 20 s). Analyses revealed that heart rate and the time to VF were positively linearly related. CONCLUSIONS: Maintaining a constant heart rate with atrial electrical stimulation in pigs prevented vagal stimulation from modifying the time to VF after acute coronary occlusion.
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Manati et al. (2013) studied Acute coronary occlusion (n=16). Vagal stimulation vs. No vagal stimulation was evaluated on Time to the appearance of ventricular fibrillation (TaVF) after occlusion (spontaneous heart rate group) (p=<0.05). Vagal stimulation significantly delayed the time to ventricular fibrillation after acute coronary occlusion in pigs with spontaneous heart rates (1102 vs 925 seconds), but this effect was abolished when heart rate was fixed.
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