Regional myocardial ischemia: characterization of temporal, transmural and lateral flow interfaces in the porcine heart.

The three-dimensional distribution of coronary flow and tissue adenosine triphosphate was characterized in the anaesthetized open pig chest after 10, 15, 30, 45, 60 and 120 min of coronary artery ligation. Radioactive microspheres were given at the onset (153-gadolinium) and end (113-tin) of ischemia. A simultaneous multiple biopsy device was used to obtain 50 contiguous transmural biopsies from each heart over an area (40 mm X 28 mm) of tissue which incorporated the centre of the ischemic zone, a lateral interface of injury and normally perfused tissue. Frozen biopsies were lyophilized, subfractionated into 2 mm transmural sections, and taken for radioactive counting. There was little or no detectable collateral flow in the ischemic zone. There was a sharp lateral flow interface which fell from 2.2 +/- 0.04 mL/min/g in normally perfused tissue to less than 2% of this value over a transition zone of less than 2 mm width. Myocardial adenosine triphosphate content showed a similar sharp interface and was severely depressed throughout the ischemic zone at all the ischemic times studied. During the 2 h ischemic period there was no increase in flow to any part of the ischemic zone and there was no change in the position, or sharpness, of the lateral interface. The absence of either lateral or transmural borderzones of intermediate injury in the pig makes pharmacological infarct size limitation highly improbable in this species.