Effects of alpha adrenergic blockade during stellate ganglion stimulation on arrhythmias induced by acute myocardial ischemia in pigs

Summary The effects of α-adrenergic receptor blockade during stellate ganglion stimulation on arrhythmias induced by repeated coronary artery occlusion in pigs under spontaneous breathing were studied. Prazosin, α₁-receptor blocker, did not have any effect on the early ischemic dysrhythmia. Yohimbin, which selectively blocks α₂-receptor, significantly increased the number of premature ventricular complexes (19±3→ 32±2 PVC;P<0.01), but produced no effects on the percentage of appearance of ventricular fibrillation (VF) and ventricular tachycardia (VT). However, nonselective α-receptor blocker phentolamine significantly reduced the number of premature ventricular complexes (30.5 ± 4.5→ 11 ±3 PVC;P<0.05), but did not affect the frequency of occurrence of VF and VT. The above results show that α-adrenergic mechanisms do not play any important role in the genesis of arrhythmias during ischemia in the pig model.