Functional and morphological changes in the microcirculation of the dog following acute coronary artery ligation

Acute ligation of the anterior descending coronary artery in the dog had little immediate effect on heat clearance but immediately lowered heat production, which fell to its minimum level in 1/2 hr, after which it began to recover; recovery was complete in 6 hr. After 1/2 hr heat clearance also began to fall and reached a minimum level in 1 1/2 hr. Ligation increased oxygen extraction but reduced oxygen consumption markedly though temporarily. Complete recovery followed. After 3 months, there was full recovery in flow, oxygen extraction ratio, and oxygen consumption mVO2. In morphological studies using Microfil injections soon after ligation, capillaries failed to fill retrogradely, though network vessels were perfused. After 1 hr of acute artery ligation, capillaries still did not perfuse but by 3 hr there was some reperfusion. After 6 hr there was marked capillary reperfusion. In dogs kept for 3 months after ligation the microcirculation was normal. These studies confirm that immediate circulatory failure occurred in capillaries (probably critical closure) which accounts for the immediate fall in venous outflow, heat production, and mVO2. Flow continued in network vessels which traversed the ischemic zone without perfusing capillaries. These results are contrasted with the findings of some other workers who found a continued functional decline leading to infarction. The present results were accounted for by closure and reopening to capillaries.