The reversal of flow in the cardiac veins

Abstract

The myocardial capillary bed has three sets of connecting vessels. Named in the order of their embryological appearance and function these are: the sinusoidal vessels (in which are included the Thebesian Veins), the cardiac veins, and the coronary arteries. With the elimination of the arteries as in double coronary occlusion, the mode of irrigation of the capillaries has not been understood. The direction of flow in the cardiac vessels joining the right heart was investigated under conditions simulating double coronary artery occlusion. Particles too large to pass through the lungs were injected into the veins, toward the heart, in anesthetized, heparinized dogs. These particles were uniformly found in the coronary sinus and the coronary veins. Their size was too great, and the arborizing and anastomosing veins were too small, to allow for any course of flow other than from right atrium to veins. The sinusoidal vessels (Thebesian veins) were excluded as a possible source of these particles in the veins, although irrigation of the capillaries in part, by them, was not excluded. With a low pressure in the capillary bed (as in cases of double coronary occlusion or as in our experiments), flow in the veins during atrial systole is probably toward the capillary bed, the capillary bed being emptied during the ensuing ventricular systole. In arterial occlusion this would give a flow and ebb circulation for the myocardial capillaries by way of the veins. This irrigation by venous channels may explain the disappearance of pain in angina pectoris, with the inception of those complications accompanied by a fall in the coronary artery pressure.