Abstract 13510: No-reflow in Reperfused Myocardium Does Not Contribute to Final Infarct Size in Pigs
The no-reflow phenomenon is a frequent complication in patients with reperfused acute myocardial infarction and associated with a worse prognosis. It is unclear whether cardioprotection, apart from infarct size (IS) reduction, has also a beneficial impact on the extent of no-reflow.
In an anesthetized pig model of myocardial ischemia/reperfusion, we have now used established conditioning maneuvers as a tool to distinguish damage and protection from it in the myocardium, expressed as final IS, and in the coronary microcirculation, expressed as area of no-reflow (ANR).
Myocardial ischemia was induced by transient occlusion of the left anterior descending coronary artery (LAD). Myocardial blood flow was measured with microspheres. Cardioprotection was induced by local ischemic preconditioning (IPC; n=10; 2 x 3 min LAD occlusion/2 min reperfusion 15 min prior to 60 min LAD occlusion), remote ischemic preconditioning (RIPC; n=10; 4x5 min hindlimb occlusion/reperfusion 90 min prior to 60 min LAD occlusion), or ischemic postconditioning (POCO; n=6; 4x1 min LAD re-occlusion/reperfusion at 1 min reperfusion after 60 min LAD occlusion). Pigs without protection (PLA; n=10) served as controls. After 180 min reperfusion, the ANR (intra-atrial injection of thioflavin S) and the area at risk (AAR; intra-atrial injection of blue dye with re-occluded LAD) were demarcated. IS was determined by post-mortem triphenyl-tretrazolium chloride (TTC) staining.
The AAR and myocardial blood flow during ischemia were not different among groups. IS reduction was similar with IPC, RIPC, and POCO (PLA: 37±3% of AAR; IPC*: 21±3%; RIPC*: 17±2; POCO*: 24±5%; mean±SEM; *p<0.05 vs. PLA). Only IPC and RIPC reduced the ANR (PLA: 28±4% of AAR; IPC*: 4±3%; RIPC* 9±2%), whereas POCO did not (24±5%).
All conditioning maneuvers protected the myocardium, but the microcirculation was only protected by conditioning maneuvers applied prior to LAD occlusion. POCO’s protection of myocardium, but not coronary microcirculation might be related to different time frames or to different underlying mechanisms of injury and/or protection in the two compartments. Nevertheless, the remaining no-reflow observed with POCO did not result in greater infarction.
Author Disclosures: A. Skyschally: None. P. Kleinbongard: None. G. Heusch: None.
- © 2016 by American Heart Association, Inc.