Myocardial blood flow conditions at re-perfusion following acute ischaemia

The purpose of this study was to investigate the effect of re-perfusion upon distribution of radioactive microspheres in ischaemic myocardium. Ten anaesthetized cats were given 15-micron microspheres prior to left anterior coronary artery occlusion, at 1 h of occlusion, and after 1 h of subsequent re-perfusion. Pre-occlusion blood flow estimates were lower in tissue which had been ischaemic compared with nonischaemic regions in the same heart (1.44 versus 1.87 ml X min-1 X g-1, p less than 0.001), corresponding to 23% apparent loss. Loss also occurred in ischaemic right ventricular tissue (32%). In left ventricular ischaemic endocardium, apparent loss was due to development of oedema. Oedema was also significant in epicardial ischaemic tissue. Correction for oedema eliminated two-fifths of the loss, while three-fifths was due to physical loss. Oedema increased linearly with the level of re-perfusion. During re-perfusion, myocardial blood flow in previously ischaemic tissue was inhomogeneously distributed and, on average, 28% lower than in non-ischaemic myocardium. The 15-micron spheres appeared to pass through capillaries in the ischaemic subepicardium, but this process was not enhanced by reperfusion.