REPEATED 15-MINUTE CORONARY OCCLUSIONS IN PIGS INCREASE OCCLUSION ARRHYTHMIAS BUT DECREASE REPERFUSION ARRHYTHMIAS THAT ARE ASSOCIATED WITHEXTRACELLULAR HYPOKALEMIA

Objectives. We sought to evaluate the effects of repetitive 15-min cor onary occlusions followed by 45-min reperfusions on the incidence of o cclusion and reperfusion arrhythmias in pigs. Background. Brief 2- to 5-min coronary occlusions seem to exert a protective effect on occlusi on and reperfusion arrhythmias. However, because clinical ischemic epi sodes are often longer, it would be appropriate to assess whether such protection also occurs when longer cycles of occlusion-reperfusion ar e produced. Methods. Three to four cycles of 15 min coronary occlusion s with 45-min reperfusions were performed in 34 pigs, and changes in S T segment and incidence of ventricular arrhythmias were assessed. Plas ma potassium ion concentrations in eight pigs and blood gas in six wer e measured from blood from the ischemic area during reperfusion. Resul ts. Repetitive occlusions were associated with a progressively higher ST segment elevation and a higher incidence of ST segment alternans (p < 0.001) and ventricular fibrillation (VF) (p < 0.01). However, durin g repetitive reperfusions, normalization of the ST segment was increas ingly faster, the incidence of VF was progressively reduced (p < 0.03) , and there was progressively less severe regional acidosis ([mean +/- SD] 7.06 +/- 0.12 vs. 7.26 +/- 0.06, p < 0.05) and hypokalemia (1.9 /- 0.7 vs. 2.3 +/- 0.4 mEq/liter, p = NS). Conclusions. The progressiv e electrocardiographic deterioration and increasing incidence of ventr icular arrhythmias during repetitive 15-min occlusions in pigs suggest Increasing metabolic derangement. However, the progressively faster n ormalization of the ST segment and the reduced incidence of ventricula r arrhythmias during reperfusion suggest an increasingly faster restor ation of the metabolic and ionic balance.