Regional Blood Flow in the Left Ventricular Wall of Dogs with a Graded Coronary Artery Stenosis

Abstract Blood flow in the circumflex branch of the left coronary artery was recorded by electromagnetic flowmeter. In the area supplied by this branch vasodilatation was produced by progressive constriction until the diastolic reactive hyperemic response to 10 s occlusion disappeared (“optimum” stenosis). This degree of stenosis was accompanied by a 20% decrease in diastolic circumflex flow, while systolic flow remained unchanged. The distribution of blood flow in the left ventricular free wall was evaluated at “optimum” stenosis by counting activity in tissue blocks following bolus injection of Xe‐133 into the aortic root. When Xe‐133 was injected immediately after occlusion of the left anterior descending branch the Xe‐133 concentration of the endocardial part of the area supplied by the circumflex branch was about half the concentration in the epicardial part. The concentrations in the two parts did not, however, differ significantly when occlusion of the left anterior descending branch was omitted. This indicates that the endocardial blood flow reserve is lower than the epicardial, and that, yet, a preferential fall in blood flow in the endocardial part of a post‐stenotic area can be rapidly eliminated when blood supply from a neighbouring artery is available.