Effects of Selective Coronary Embolization on Coronary Blood Flow and Coronary Sinus Venous Blood Oxygen Saturation in Dogs

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Abstract
The cardiovascular effects of selective coronary embolization were studied with improved techniques in an attempt to obtain evidence for the existence of intercoronary reflexes and their role in potentiating myocardial ischemia. These studies demonstrated that embolization of the coronary arterial bed by lycopodium spores produced an initial marked decrease in coronary blood flow followed by a maintained (approximately 10 minutes) increase which was accompanied by an increase in coronary sinus venous oxygen saturation. Supporting evidence was obtained from selective coronary angiograms and from changes in coronary vascular resistance. Attempts at eliminating these responses by certain autonomic blocking agents (atropine, hydralazine, tetraethylammonium chloride, hexamethonium, and dibozane), surgical denervation of the heart, and adrenalectomy were all ineffective. Experimental evidence obtained by comparing the initial effect of embolization with pitressin vasoconstriction and coronary occlusion all led to the conclusion that reflex coronary spasm does not occur during coronary occlusion. The cause of the initial decrease in coronary blood flow during embolization (lycopodium spores) is, therefore, mechanical block within the distribution of the vessel by the emboli.