The effects of brief ischemia (preconditioning) on early phase arrhythmias induced by coronary artery occlusion were studied in two sets of rat experiments. In the first protocol, the duration of the preconditioning coronary occlusion was varied. We used three different periods, 1 min (group 2, n=8), 3 min (group 3, n=10), and 5 min (group 4, n=10). A 10 min reperfusion period was maintained before the coronary artery was reoccluded for 30 min. The severity of arrhythmia during this 30 min reocclusion period was assessed and was compared with that in control rats (group 1, n=12) in which the coronary artery was also occluded for 30 min, without preconditioning. Total numbers of ventricular ectopics in each group were 1236±262 beats (M±SE), 1230±370 beats (NS), 200±60 beats (p<0.01) and 394±152 beats (p<0.01), respectively. The incidence of VT in groups 1-4 was 100%, 100%, 70%, and 60% (p<0.05), respectively. The 3 min preconditioning occlusion had the most potent protective effects against ventricular arrhythmias induced by coronary artery occlusion. In the second protocol, the duration of reperfusion after the 3 min preconditioning occlusion was varied, the periods being 10 min, 20 min, and 30 min. The longer reperfusion period attenuated the protective effett of the 3 min occlusion preconditioning. In conclusion, preconditioning periods of more than 3 min of myocardial ischemia protected against the ventricular arrhythmias induced by prolonged coronary occlusion. The protective effect of 3 min occlusion preconditioning lasted for 30 min.
<Original Article> Ischemic Preconditioning Reduces the Severity of Ventricular Arrhythmias Induced by Coronary Artery Occlusion in Rats
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