Coronary venous outflow persists after cessation of coronary arterial inflow

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Abstract
During single long diasoples coronary arterial blood flow and coronary venous outflow were simultaneously measured in dogs. When vasomotor tone was intact, .apprx. 20% of the total volume of diastolic coronary venous outflow appeared after cessation of inflow. During maximal coronary dilation, .apprx. 40% of the total volume of diastolic coronary venous outflow appeared after cessation of inflow. Theoretically, coronary capacitance could enable persistence of diastolic coronary venous outflow during zero coronary artery inflow. Intramyocardial coronary capacitance calculated from these data was 0.10 ml .cntdot. mmHg-1 per 100 g with vasomotor tone intact and 0.21 during maximal coronary dilation. The diastolic coronary arterial stop-flow pressure cannot be equated with cessation of flow throughout the coronary vasculatur due to the significant contribution of intramyocardial capacitance. The arterial pressure at which coronary outflow stopped (10-14 mmHg) was found to be substantially less than that at which coronary artery inflow ceased (19-31 mm Hg), yet slightly above right atrial pressure (5-9 mmHg). Coronary venous outflow stops at a lower pressure than arterial inflow. The cessation of venous blood flow in the coronary system during long diastoles occurs at pressures only a few mmHg above right atrial pressure.

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