Adenosine on myocardial oxygen consumption.

1 A 3 min intracoronary infusion of adenosine (50 mug/min) produced a significant decrease in coronary artery perfusion pressure, left ventricular systolic pressure and myocardial O2 consumption in the isolated supported heart preparation of the dog perfused at a constant coronary blood flow. Heart rate was controlled at 150, 190 or 230 beats/minute. 2 Myocardial contractile force and maximal left ventricular dp/dt were not changed by adenosine infusion. 3 The absolute decrease in myocardial O2 consumption was greater at increasing heart rates whereas the decrease in coronary artery perfusion pressure and peak left ventricular systolic pressure were similar. 4 The results suggest that the reduction in myocardial O2 consumption produced by adenosine is not related to coronary vasodilatation or to a negative chronotropic or inotropic action, but may be due to a functional shunting of blood flow from high O2 extracting regions of the myocardium to low O2 extracting ones and/or important effects on myocardial substrate utilization.