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

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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; systolic flow remained unchanged. The distribution of blood flow in the left ventricular free wall evaluated at optimum stenosis by counting activity in tissue blocks following bolus injection of 133Xe into the aortic root. When 133Xe was injected immediately after occlusion of the left anterior descending branch, the 133Xe 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 2 parts did not differ significantly when occlusion of the left anterior descending branch was omitted. The endocardial blood flow reserve is apparently lower than the epicardial, 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 neighboring artery is available.