Early changes in collateral blood flow during myocardial infarction in conscious dogs

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Abstract
Early changes in colateral blood flow (CBF) after acute coronary artery occlusion and the relation of these changes to subsequent necrosis were studied. CBF was measured with 7-9 .mu.m radioactive microspheres before and at various times after circumflex artery occlusion in 42 conscious dogs killed 48 h later. CBF increased from 20 s postocclusion to later measurements (5 min, 15 min, 1 h or 6 h) and did so in both necrotic and nonnecrotic areas of the occluded bed. The increase in CBF over time was not gradual, but occurred between 20 s and 5 min, with no further changes for up to 6 h. There was a gradation of CBF in the occluded bed, from periphery to center and subepicardium to subendocardium. Central and subendocardial regions with CBF < 0.40 ml/min per g at 5-15 min postocclusion subsequently showed necrosis; epicardial and lateral regions with CBF > 0.50 ml/min did not. CBF increases very early throughout the occluded coronary bed and the level of CBF by 5 min determines whether necrosis ultimately occurs.