Phasic coronary blood flow patterns as related to the balance between oxygen demand and supply in the myocardium

To explore possible relationship between changing coronary arterial flow patterns and states of coronary circulation, the left circumflex arterial flow (mean and phasic) was measured simultaneously with the oxygen saturation of the great cardiac vein blood (SGCVO2) in anesthetized open-chest dogs. Coronary vasomotion was altered either with administration of drugs or with mechanical interventions. The "intermittent" flow pattern observed in the resting state persisted as far as SGCVO2 remained unchanged or lowered regardless of changes in coronary flow, aortic pressure or heart rate. On the other hand, when increase in circumflex flow occurred simultaneously with elevation of SGCVO2, a "continuous" flow pattern of the circumflwx flow was noticed. We suggest that (1) the "intermittent" flow pattern would indicate that efficient O2 uptake from the supplied arterial blood is taking place in the myocardium and (2) the "continuous" flow pattern would indicate presence of arterial flow excess to the myocardial requirement, rendering the increased coronary blood flow less effective for its amount in terms of O2 supply to the myocardium.