In this study, we used a swine model to study coronary autoregulation in the stunned myocardium. In 18 domestic swine, the left anterior descending coronary artery was cannulated and flow to this artery controlled via an extracorporeal perfusion circuit. Stunning was induced by reducing pump flow to approximately 25% of the baseline value for 15 minutes followed by 1 hour of reperfusion. This ischemia/reperfusion protocol reduced systolic shortening to approximately 50% of control, at 1 hour of reperfusion. Neither the slope of the coronary pressure-flow relation (0.41 +/- 0.19 vs 0.48 +/- 0.26 mL/100 g per min per mmHg) nor an autoregulation index (0.43 +/- 0.16 vs 0.30 +/- 0.32) was significantly changed at 1 hour reperfusion (p > 0.05) compared to baseline. These findings argue against the hypothesis that the mechanical dysfunction of the stunned myocardium is due to suboptimal perfusion caused by poor coronary autoregulation.
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