INEFFECTIVE PERFUSION-CONTRACTION MATCHING IN CONSCIOUS, CHRONICALLY INSTRUMENTED PIGS WITH AN EXTENDED PERIOD OF CORONARY STENOSIS

Several models purported to represent hibernating myocardium involve a coronary stenosis (CS) to reduce blood flow (BF) and function without eliciting necrosis in anesthetized pigs. The goal of the present stud y was to determine whether sustained moderate reduction in coronary BF in conscious pigs induced hibernating myocardium, ie, perfusion-contr action matching with no necrosis. These experiments were conducted in conscious pigs chronically instrumented with a coronary artery BF prob e and hydraulic occluder, left ventricular (LV) pressure gauge, and wa ll thickening (WT) crystals in the potentially ischemic and nonischemi c zones. The hydraulic occluder was inflated to induce a stable 41+/-4 % reduction in BF for 24 hours. Ischemic zone systolic WT fell initial ly with CS and then continued to decline during the period of CS even though blood flow did not change further, suggesting the induction of myocardial stunning, At 2 days after release of CS, WT was still depre ssed by 48+/-15%. Assessment of necrosis by histology or triphenyltetr azolium chloride showed 40+/-5% multifocal patchy necrosis intersperse d with normal tissue involving the inner one third to one half of the ventricular wall, Regional myocardial BF (radioactive microsphere tech nique) was assessed by dividing the entire LV into an average of 488+/ -59 pieces and examining the spatial distribution of BF within the are a at risk (AAR). EF in the samples in the area of patchy necrosis was reduced (-66+/-4% from a baseline of 1.55+/-0.27 mL.min(-1).g(-1)), wh ereas BF was maintained in samples in the AAR without necrosis (-2+/-7 % from a baseline of 1.25+/-0.22 mL.min(-1).g(-1)). These findings ind icate that when hypoperfusion induced by CS in conscious pigs is susta ined, the result is necrosis rather than hibernating myocardium. The r emainder of the AAR, which lacked necrosis, might have been mistaken f or hibernating myocardium had only histology been evaluated and BF not been measured and found to be at normal levels.