Coronary blood flow in acute experimental pulmonary embolization

Abstract

Summary Coronary blood flow was measured in five groups (total 60) of open-chest dogs subjected to sublethal pulmonary embolization. The coronary blood flow increased following acute pulmonary embolization in all groups. The increases in coronary flow could not be related to the systemic arterial pressure, cardiac output, or heart rate and is probably related to a decrease in coronary vascular resistance. The coronary vascular response was not significantly affected by a pharmacologic blockade of both the sympathetic nervous system and circulating catecholamines. This response was not affected by atropine-induced cholinergic blockade which would effectively inhibit responses mediated by the vagus, sympathetic-cholinergic fibers or circulating acetylcholine. Finally, the response, although to a lesser degree, was also present in dogs on cardiopulmonary bypass even though we would assume that with empty ventricles, a controlled systemic arterial PO 2 and PCO 2 , aortic pressure, cardiac output, and coronary perfusing pressure, there would be no appreciable change in the physical, myogenic, or metabolic factors affecting the coronary vascular resistance. These findings suggest that the observed increases in coronary blood flow following acute nonlethal pulmonary embolization are mediated by multiple mechanisms. Among the most important of these are (1) local myocardial factors resulting from an increased oxygen requirement and (2) concomitant arterial oxygen desaturation. A currently unidentified coronary vasodilator reflex is suggested.