Studies on the Coronary Circulation during Rejection of the Heterotopically Transplanted Dog Heart

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Abstract
Coronary blood flow and vascular reactivity were studied at intervals after donor dog hearts were transplanted into the necks of recipient dogs. Coronary blood flow was measured with an electromagnetic flow transducer on the carotid artery of the recipient dog, and coronary vascular reactivity was assessed from the response of the coronary vessels to the vasodilator drugs, dipyridamole and adenosine. During the first 4 days after the transplant, resting coronary blood flow and vascular resistance did not change. Responses to dipyridamole and adenosine were unchanged during the first 2 days but were reduced on the third and fourth days. Increased vascular permeability to circulating Evans blue dye and deposition of colloidal carbon in venules occurred in association with small increases in left ventricular myocardial water content 3 and 4 days after the transplant. These changes indicate that an inflammatory response accompanies the onset of histological evidence of rejection at 3 and 4 days. The reduced vascular reactivity of the transplanted heart at 3 and 4 days may be related to morphological changes in arterioles rather than to gross edema formation during rejection.