Dissociation of Regional Adaptations to Ischemia and Global Myolysis in an Accelerated Swine Model of Chronic Hibernating Myocardium

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Abstract
We tested the hypothesis that an acute critical limitation in coronary flow reserve could rapidly recapitulate the physiological, molecular, and morphological phenotype of hibernating myocardium. Chronically instrumented swine were subjected to a partial occlusion to produce acute stunning, followed by reperfusion through a critical stenosis. Stenosis severity was adjusted serially so that hyperemic flow was severely reduced yet always higher than the preocclusion resting level. After 24 hours, resting left anterior descending coronary artery (LAD) wall thickening had decreased from 36.3±4.0% to 25.5±3.7% (P10%) and increased glycogen typical of hibernating myocardium in the LAD region (33±3% of myocytes from animals with hibernating myocardium versus 15±4% of myocytes from sham-instrumented animals, P<0.05). Surprisingly, the frequency of myolysis was similar in normally perfused remote regions from animals with hibernating myocardium (32±7%). We conclude that the regional physiological and molecular characteristics of hibernating myocardium develop rapidly after a critical limitation in flow reserve. In contrast, the global nature of myolysis and increased glycogen content dissociate them from the intrinsic adaptations to ischemia. These may be related to chronic elevations in preload but appear unlikely to contribute to chronic contractile dysfunction.