Participation of coronary perfusion pressure in transmural energy metabolism in the hypoperfused canine heart.

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Abstract
The participation of coronary perfusion pressure in hemodynamic and transmural metabolic changes was examined in the open chest canine heart. At a pressure lower than 50% of the control, reactive hyperemia disappeared and the coronary arterial inflow precipitously decreased. In 8 dogs, when the coronary arterial inflow was decreased to 47-49% of the control by coronary constriction for 15 min, the coronary perfusion pressure fell in various degrees ranging from 39 to 73% of the control. At a pressure lower than 60% of the control, creatine phosphate (CP) content and its ratio of subendocardium (ENDO) to subepicardium (EPI) decreased, while lactate (LA) content and its ratio of ENDO to EPI increased depending on the degree of the fall in coronary perfusion pressure. A little decrease in ATP content was produced only in the ENDO under the pressure lower than 50% of the control. When the CP content decreased to below 1/3 of the control, the significant accumulation of lactate and the precipitous decrease in ATP occurred. Apparently the coronary perfusion pressure has an important role for a severity of the transmural energy metabolism in the hypoperfused ventricle.