AbstractAngiographically “terminal” coronary arterial branches were counted in 100 normal coronary cineangiograms to investigate the possibility that three left ventricular wall regions might be defined by identifying patterns of arterial inflow. An average of 45% of the terminal branches were counted in the anterior region supplied by the anterior descending coronary artery; 25% were counted in the lateral region supplied by diagonal and obtuse marginal arteries, and 30% were counted in the inferior region supplied by the distal circumflex and distal right arteries. Based upon the hypothesis that blood flow through an artery is directly proportional to the number of small branches into which it ramifies, this approach affords an estimate of the relative contribution by individual coronary arteries to total left ventricular perfusion. This concept could prove useful in defining a quantitative grading system of coronary arterial Inflow obstruct