Repeated 15-minute coronary occlusions in pigs increase occlusion arrhythmias but decrease reperfusion arrhythmias that are associated with extracellular hypokalemia.

Abstract

We sought to evaluate the effects of repetitive 15-min coronary occlusions followed by 45-min reperfusions on the incidence of occlusion and reperfusion arrhythmias in pigs. Brief 2- to 5-min coronary occlusions seem to exert a protective effect on occlusion and reperfusion arrhythmias. However, because clinical ischemic episodes are often longer, it would be appropriate to assess whether such protection also occurs when longer cycles of occlusion-reperfusion are produced. Three to four cycles of 15-min coronary occlusions with 45-min reperfusions were performed in 34 pigs, and changes in ST segment and incidence of ventricular arrhythmias were assessed. Plasma potassium ion concentrations in eight pigs and blood gas in six were measured from blood from the ischemic area during reperfusion. 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, during repetitive reperfusions, normalization of the ST segment was increasingly 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). The progressive electrocardiographic deterioration and increasing incidence of ventricular arrhythmias during repetitive 15-min occlusions in pigs suggest increasing metabolic derangement. However, the progressively faster normalization of the ST segment and the reduced incidence of ventricular arrhythmias during reperfusion suggest an increasingly faster restoration of the metabolic and ionic balance.