Effect of early reperfusion on use of triphenyltetrazolium chloride to differentiate viable from non-viable myocardium in area of risk

STUDY OBJECTIVE - The aim of the study was to assess the value of triphenyltetrazolium chloride (TTC) staining as an indicator of non-viable myocardium after early reperfusion of ischaemic myocardium. DESIGN - Left anterior descending artery occlusion was performed in pigs for various lengths of time and at two different sites (proximal and distal). After 120 min reperfusion, TTC was injected distal to the occlusion while the remainder of the myocardium was stained with Evans Blue. Myocardial enzymes were measured in non-ischaemic zone, regions of risk and in necrotic zones and related to staining characteristics. SUBJECTS - 31 male Hampshire pigs, weight 34-39 kg, were studied. Twelve were excluded because of resistant ventricular fibrillation or poorly defined areas of infarction. In the remaining 19 pigs, proximal occlusion was carried out in 15 and distal in four. Occlusion lasted for 15 min in six animals, for 30 min in eight (four of which were the animals with distal occlusions), and for 45 min in five. MEASUREMENTS and RESULTS - Biopsies from non-ischaemic zones, regions of risk and necrotic zones were analysed for creatine kinase and lactate dehydrogenase. In the 15 min group, myocardial creatine kinase in the region of risk (red stained) was similar to the non-ischaemic (blue) zone, but in the 30 min distal occlusion group it was reduced. After 30 and 45 min of proximal occlusion, creatine kinase activity in the necrotic (white) zone was reduced compared to the red zone in the same group, and in the red zone of both groups it was reduced compared to the non-ischaemic area. CONCLUSIONS - The red zone, as defined by TTC staining, may be associated with significant creatine kinase depletion after relatively brief periods of occlusion and subsequent reperfusion. This suggests that the red region may be a heterogeneous area of dead and viable cells.