Remote Postconditioning is More Potent than Classic Postconditioning in Reducing the Infarct Size in Anesthetized Rabbits

Purpose Postconditioning confers protection to the heart after a potentially lethal episode of prolonged ischemia. There is evidence that it may also be protective when applied at a distal artery. In the present study, we sought to determine whether remote postconditioning within the heart (local) or outside the heart (distal) is effective in salvaging the ischemic heart in vivo and to compare its effect with that of the classic postconditioning. Methods Twenty seven open chest New Zealand white anesthetized male rabbits were divided into four groups and were exposed to 30 min regional myocardial ischemia (isc), after ligation of a prominent coronary artery, followed by 3 h reperfusion (rep) after releasing the snare. Control group (n = 7) was subjected to no additional interventions, postC group (n = 6) was subjected to four cycles of 1 min isc/1 min rep of the same coronary artery at the beginning of reperfusion, remote local postC group (n = 7) to four cycles of 1 min isc/1 min rep of another coronary artery 30 s before the end of index isc and remote distal postC group (n = 7) to four cycles of 1 min isc/1 min rep of another (carotid) artery again 30 s before the end of index isc. Infarct size (I) and area at risk (R) were delineated with the aid of TTC staining and green fluorescent microspheres respectively and their ratio was expressed in percent (%I/R). Results Remote local and remote distal postC reduced the % I/R ratio (17.7 +/- 1.7% and 18.4 +/- 1.6%, respectively vs 47.0 +/- 2.5% in the control group, P<0.01). Classic PostC had an intermediate protective effect (33.1 +/- 1.7%, P<0.05 vs all the other groups). Conclusion Remote postconditioning consisted of 1 min isc/1 min rep protects the ischemic rabbit heart in vivo, independently of the site of the remote artery. This intervention seems to confer a stronger protection than the classic postconditioning.