Staged reperfusion attenuates myocardial stunning in dogs. Role of transient acidosis during early reperfusion.

BACKGROUND Acidosis during early reperfusion is reported to be beneficial for myocardial stunning. We tested in 31 dogs the hypothesis that staged reperfusion is beneficial to myocardial stunning. METHODS AND RESULTS Contractile dysfunction was observed 3 hours after the onset of reperfusion after 15 minutes of occlusion of the coronary artery. In the staged reperfusion, pH of the coronary venous blood was lower for 20 minutes and fractional shortening was significantly improved compared with the control reperfusion group. When we increased pH of the reperfused myocardium by an intracoronary infusion of sodium bicarbonate, beneficial effects of the staged reperfusion were abolished. Furthermore, an intracoronary infusion of hydrogen chloride, which mimicked the changes in pH in coronary venous blood of the staged reperfusion, attenuated myocardial stunning. CONCLUSIONS These results indicate that acidosis during staged reperfusion primarily attenuates myocardial stunning. This procedure is clinically applicable for attenuation of reperfusion injury.