Arterial and Venous Circulation in Ischaemic Foci in the Myocardium

Abstract

Blood flow through the anterior interventricular vein was measured in 17 dogs under normal conditions and after ligating the descending artery. In 10 of these dogs retrograde blood flow was measured in the peripheral stump of the descending ramus and in the anterior interventricular vein 10 and 11 min later. After ligating the descending ramus 16.6–70.5% blood flowed through the ischaemic area into the anterior interventricular vein. The origin of the blood is two-fold: (a) arterial – blood reaching the ischaemic area via arterio-arterial anastomoses and the capillary bed into the vein; (b) venous – from veins of the nonischaemic area via venous anastomoses into veins of the ischaemic area. This flow was explained on a morphological basis by veno-venous anastomoses and by finding a venous pressure gradient between the ischaemic and nonischaemic area. In most cases (in 8 dogs), venous flow from the infarcted area was 14–91 % greater (average 47%) than retrograde flow in the peripheral stump of the artery. In two dogs only was venous blood flow the same or less than arterial. In casts of these two hearts, unlike the previous cases, the supply area of the descending artery and the drainage area of the anterior interventricular vein did not coincide and blood was partly drained into veins of the nonischaemic part. The results show that some of the blood flowing through the ischaemic focus is inadequate for the myocardium on account of its place of origin and consequent lack of oxygen. The possibility of influencing the retrograde arterial blood flow by ligating the septal artery or not is dealt with in the discussion.