Impact of resting and ischemic blood flow on infarct probability in ischemic preconditioning - a new approach to infarct size-blood flow data by logistic regression

The linear regression analysis of infarct size (IS) nu ischemic myocardial blood flow (MBF) does not account for the heterogeneity of MBF and infarcte d tissue; moreover, it cannot assess a blood now threshold for infarction ( MBFT) accurately, as with ischemic preconditioning (IP) the close relations hip between ischemic MBF and IS otherwise observed is lost. Finally, the im pact of resting blood flow on myocardial infarction cannot be considered in such analysis. Therefore, in a retrospective data analysis of 32 enflurane -anaesthetized swine undergoing 90 min severe ischemia and 120 min reperfus ion without (CON, n=12) or with IP induced by either 3 (IP3, n=8) or 10 min ischemia (IP10, n=12) and 15 min reperfusion, a MBFT was assessed by logis tic regression (LR) in individual tissue pieces. MBFT was arbitrarily defin ed as that ischemic MBE (microspheres) at which infarct probability was 0.2 , derived from the ratio of infarcted (n=141, TTC) to all tissue samples (n =684). The duration of the preconditioning ischemia and MBF both at rest an d during the sustained ischemia were significant predictors of infarct prob ability. Ischemic MBFT at an infarct probability of 0.2, was 0.089 +/- 0.02 3 ml/min/g in CON. MBFT was decreased to 0.051 +/- 0.03 ml/min/g with IP3 ( P<0.05 v CON) and further to 0.004 +/- 0.03 7 ml/min/g with IP10 (P<0.05 nu CON, IP3). Corresponding to the leftward shift of MBFT, the relationships between infarct probability and MBF were shifted in parallel by IP with no change in their slopes. (C) 1998 Academic Press.