The development of ischemia in the perfused rat heart was investigated using NADH fluorescence photography to demonstrate that ischemia is not a homogeneous process. Ischemia was induced by placing a 1-way check valve in the aortic outflow tract to decrease coronary perfusion pressure while initially maintaining cardiac work. Zones of high NADH content, denoting anaerobic metabolism, appear early during the development of ischemia, while the effluent oxygen tension is still well above zero. This is in contrast to high-flow hypoxia where the effluent oxygen tension falls to nearly zero before anoxic zones become prominent. Deterioration of myocardial function during ischemia parallels the increase in the number and size of the anoxic zones. The data indicate that the distribution of coronary flow is determined by factors other than the tissue oxygen tension. Acidosis may mediate the development of the anoxic zones since anoxic areas also occur during respiratory acidosis below pH 6.8 even though oxygen delivery is nearly double oxygen consumption. In addition to suggesting a mechanism for the development of ischemia, the data demonstrate that, tissue oxygen gradients are very steep and that the tissue adjacent to the anoxic zones appears to be relatively unaffected by the ischemic process during its early stages.
|Original language||English (US)|
|Pages (from-to)||No. 1215|
|State||Published - Jan 1 1977|
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