A modified regionally ischemic porcine heart preparation with eligible residual blood flows

Abstract

The left anterior descending coronary artery was occluded in each of 28 thoracotomized pigs around an intracoronary catheter for periods between 30 and 240 min followed by 90 min of reperfusion. The catheter was connected via an external pump with another arterial catheter. The pump rate was set to deliver 1.5 ml (group I), 3 ml (group II), or 6 ml blood/min (group III) respectively during ischemia. The distribution of the residual blood flow during ischemia was determined in group II with non-radioactive microspheres. We delineated the risk region by a fluorescent dye and the infarcted tissue with a tetrazolium stain. The higher residual blood flow in groups II and III reduced the incidence of ventricular fibrillation during ischemia from 70% (group I) to 28%, suggesting that the amount of residual blood flow is one important determinant for this rhythm disturbance. The subendocardial-subepicardial blood flow ratio in the risk region of the anterior wall was 41%. Infarcts started to develop after 30 min of ischemia (groups I and II). In all groups necrosis progressed most rapidly within the first 90 min of ischemia indicating that besides the beneficial effect of a high residual blood flow only early reperfusion is able to salvage a substantial amount of jeopardized myocardium. Compared to conventional regionally ischemic canine and porcine heart preparations the described model offers the following advantages: Accurate delineation of the risk region, eligible residual blood flow, reduction of ventricular fibrillation with higher residual blood flows, and the possibility to selectively test the metabolic influence of drugs on ischemic injury while avoiding systemic effects.