Ischemic preconditioning and myocardial hypothermia in rabbits with prolonged coronary artery occlusion

Ischemic preconditioning and myocardial hypothermia in rabbits with prolong ed coronary artery occlusion. Am. J. Physiol. 276 (Heart Circ. Physiol. 45) : H2029-H2034, 1999.-This study tests whether combining regional hypothermi a and ischemic preconditioning (IP) provides greater myocardial protection during prolonged coronary artery occlusion (CAO) than either intervention a lone, and whether increasing the duration of TP from 5 to 7 min extends the window of protection to include a 2-h CAO. Anesthetized rabbits were rando mized to four groups (n = 8 rabbits/group): control (C), hypothermia alone (H), IP alone for two 7-min episodes (IP7), and IP plus hypothermia (H + IP 7). To compare differences in IP for 5 versus 7 min, additional rabbits (n = 6) received one 5-min episode of ischemia (IP5). All rabbits got 2 h of C AO and 3 h of reperfusion. Tn comparison with the infarct size in the contr ol group (72 +/- 4% of the risk zone), infarct size was significantly reduc ed in H (50 +/- 7%), IP7 (49 +/- 5%), and H + IP7 (42 +/- 6%) (all P < 0.05 vs. control group). IP5 failed to confer protection (67 +/- 5% of the risk zone). Therefore, TP can protect against a 2-h CAO if the TP regimen is in creased from 5 to 7 min. The combination therapy significantly improved reg ional myocardial blood flow in the previously ischemic region to a greater extent than either treatment alone.