Reactive hyperemia following total and subtotal coronary occlusion in the awake dog

This study examined the reactive hyperemia following total and subtotal coronary artery occlusions. Studies were carried out in awake dogs with electromagnetic flowmeters and hydraulic occluders on the left circumflex coronary artery; the regional distribution of perfusion was examined with radionuclide-labeled microspheres. Reactive hyperemia following total and subtotal occlusions resulted in similar mean blood flow debt repayments of 451±34% and 492±51%, respectively. However, the distribution of perfusion was markedly different, with the ratio of subendocardial to subepicardial blood flow being 1.77±0.22 after total occlusion and 4.14±0.73 after subtotal occlusion (p<0.01). Further examination of the pattern of perfusion during reactive hyperemia demonstrated a direct relationship between the local blood flow debt and blood flow during the subsequent reactive hyperemia. These data demonstrate that coronary reactive hyperemia does not occur uniformly throughout the distribution of the vascular bed served by the previously occluded artery, but rather is coupled to the degree of hypoperfusion during the preceding occlusion.