Question: 

Timely reperfusion is mandatory to salvage ischemic myocardium. However, reperfusion per se induces additional damage and contributes to infarct final size. Ischemic postconditioning (PoCo), brief coronary re-occlusions at the onset of reperfusion, reduces infarct size. PoCo is also operative in humans, but has not become common use in clinical practice for fear that repeated mechanical manipulation of the culprit coronary lesion induces coronary microembolization (ME). Whether or not ME indeed interferes with PoCo is currently unclear.

Methods: 

We therefore investigated the consequences of ME at reperfusion using a clinically relevant model. Anesthetized, open chest pigs were subjected to 90 min coronary hypoperfusion followed by 120 min reperfusion, initiated with PoCo (n=8; 6 x 20s/20s reperfusion/re-occlusion) or as immediate full reperfusion (IFR; n=8). In two additional groups, ME was induced by intracoronary injection of microspheres (42m diameter; 3000 spheres/ml coronary inflow, as measured before ischemia) either during PoCo (PoCo+ME; n=8) or during IFR (IFR+ME; n=7). Area at risk, myocardial blood flow (microspheres), and infarct size (TTC) were determined.

Results: 

Area at risk and transmural blood flow during ischemia were similar among groups. ME per se increased infarct size (IFR+ME: 49±3% vs. IFR: 32±3%; % area at risk; mean±SEM; p<0.05; 2-way-ANOVA, LSD post-hoc tests). PoCo reduced infarct size without (PoCo: 21±3%; p<0.05 vs. IFR), but also with ME (PoCo+ME: 26±5%; p<0.05 vs. IFR+ME).

Conclusion: 

Obviously, ME at reperfusion is deleterious and increases infarct size. However, PoCo protects from reperfusion injury and reduces infarct size, even with concomitant ME. Therefore, PoCo is recommended for clinical use.