Mechanically Unloading the Left Ventricle Before Coronary Reperfusion Reduces Left Ventricular Wall Stress and Myocardial Infarct Size
Background—Ischemia-reperfusion injury worsens infarct size, a major determinant of morbidity and mortality after acute myocardial infarction (MI). We tested the hypothesis that reducing left ventricular (LV) wall stress with a percutaneous left atrial-to-femoral artery centrifugal (pLA-FA) bypass system, while delaying coronary reperfusion limits myocardial injury in a model of acute MI.
Methods and Results—MI was induced by balloon occlusion of the left anterior descending artery (LAD) in adult, male swine. In the MI group(n=4), 120 minutes of LAD occlusion was followed by 120 minutes of reperfusion without mechanical support. In the mechanically supported group (MI+Unload)(n=4), pLA-FA bypass was initiated after 120 minutes of ischemia and LAD occlusion prolonged for an additional 30 minutes, followed by 120 minutes of reperfusion with device support. All animals were sacrificed after reperfusion and infarct size quantified by triphenyltetrazolium chloride staining. Compared to baseline, mean LV wall stress and stroke work were not changed at any point in the MI group, but were decreased after reperfusion in the MI+Unload group (mean LV wall stress: 44658 vs 22963 dynes/cm2; stroke work: 2823 vs 655 mmHg x mL, MI vs MI+Unload). Phosphorylation of reperfusion injury salvage kinase (RISK) pathway proteins from non-infarcted LV tissue was unchanged in the MI group, but increased in the MI+Unload group. Compared to MI alone, total infarct size was reduced in the MI+Unload group (49% vs 28%, MI vs MI+Unload).
Conclusions—These data support that first unloading the LV despite delaying coronary reperfusion during an acute MI reduces myocardial injury.
- Received November 26, 2012.
- Revision received May 2, 2013.
- Accepted May 20, 2013.