Venous flow in the great cardiac vein of the dog.

The venous blood flow in the great cardiac vein (GCV) was measured with an ultrasonic transit-time flowmeter during brief occlusion of major branches of the coronary arteries in open-chest dogs. Occlusion of the right coronary artery did not affect GCV outflow. GCV outflow vanished when the left anterior descending artery (LAD) was occluded proximal to the bifurcation of the septal artery. When the LAD was occluded distal to the septal artery, the GCV flow reduction averaged 70%. Occlusion of the left circumflex artery resulted in a slight but significant decrease, followed by an increase in GCV outflow. Partial occlusion of the coronary sinus or GCV by a catheter resulted in a decrease in outflow. This suggests that the absolute value of coronary venous flow obtained by the thermodilution technique should be evaluated carefully.