Pathophysiology of Irreversible Ischemic Injury
At the present time our experimental findings plus the weight of other experimental evidence suggest that there is unlikely to be a quantitatively significant border zone in the lateral plane. The transition from normal to ischemic tissue is likely to be accomplished over a distance of 1.0 mm or less and possibly in as little as the dimensions of one cell. The situation in the transmural plane is less well established, but if the same situation occurs, then the absence of a spatially indentifiable border zone of intermediate injury will require a major reappraisal, although not an abandonment, of concepts for the therapeutic limitation of infarct size. Any extrapolation of the observations, comments, and conclusions made in this paper to the human heart should be made with extreme caution. Major species differences exist, particularly in relation to the characteristics of collateral flow. Most experimental studies have involved single or multiple coronary artery ligation, a situation that generates large areas of sharply demarcated ischemia. These areas are very severely ischemic and short of reperfusion, which is hardly a practical consideration in the early phases of evolving myocardial infarction; the affected tissue is inevitably condemned to cell death and necrosis. The situation prevailing in man with partial coronary artery occlusion or diffuse ischemic heart disease may well be be very different and is clearly in urgent need of investigation.
KeywordsInfarct Size Ischemic Tissue Border Zone Sharp Interface Ischemic Area
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