Venous Pressure as a Factor in Determining Collateral Circulation in the Heart

In tying off the left descending coronary artery of the dog, it was noted by LaBree that the apex was rarely infarcted if the veins were tied at the same time as the artery. Gross showed that there was a markedly increased opening up of collateral circulation if the coronary artery of a dog was ligated after first ligating the coronary sinus. Many clinicians have noted that angina pectoris symptoms and the symptoms of coronary thrombosis are apt to be less severe in cases with severe right heart failure, i. e., with a high venous pressure. With these observations in mind, we decided to ligate the left circumflex artery both with and without previous ligation of the accompanying veins and also after the production of a high pressure in the coronary sinus, one approximating the venous pressure in the coronary sinus during severe heart failure. We made use of the heart-lung preparation of Starling except that the heart and the lungs were removed from the thorax of the dog and placed on a tray for greater ease of experimental approach to the coronary vessels. In 3 hearts the circumflex veins were tied first. The veins appeared to be distended and after a few moments arterial blood could be seen coming into the smaller veins. A few minutes later the circumflex artery was ligated but no infarction occurred. In one heart the main branch of the circumflex artery was tied at the same time that the veins were tied, leaving only a small branch of the artery free. Under these circumstances there was a small amount of infarction of the posterior surface of the heart. When the small free branch of the circumflex artery was tied, this infarction became complete. In 3 hearts the circumflex artery was tied without previous or concomitant ligation of the accompanying veins and in all 3 cases there was infarction of the posterior wall of the heart.