Distribution of myocardial blood flow measured by hydrogen polarography.

Distribution of myocardial blood flow was studied by polarographic recording of hydrogen desaturation in open chest dogs. Flow was measured during normal cardiac activity, reactive hyperemia following 60 seconds of coronary artery occlusion, and left ventricular hypertension produced by either partial supravalvular aortic occlusion or subvalvular outflow constriction. During normal cardiac function, blood flows in the subepicardium and subendocardium were approximately equal. Reactive hyperemia increased flow to both the subepicardium and subendocardium. Left ventricular hypertension decreased subendocardial flow relative to subepicardial flow in proportion to the degree of hypertension. Marked supravalvular obstruction with ventricular hypertension reduced subendocardial flow to two-thirds that of subepicardial flow. This decrease was further accentuated when the left ventricular end diastolic pressure was elevated.