The mechanism of coronary hyperemia induced by increased cardiac work.

The interrelation between coronary flow, heart work, coronary venous pO2, and tissue contents of energy-rich phosphates were studied in isolated guinea pig hearts performing external work. Within the range studied, energy-rich phosphates were dependent on left ventricular output, but not on arterial pO2. At constant arterial pO2, changes in coronary flow were associated with changes in energy-rich phosphates, but not systematically with changes in coronary venous pO2. Simultaneous increases in ventricular output and arterial pO2 resulted in increased coronary flow even though coronary venous pO2 rose. It is concluded that work-induced coronary dilation may occur independently on a decrease in coronary venous pO2. The possibility that energy-rich phosphates might be linked with a non-hypoxic dilation mechanism is discussed.