Regional myocardial volume perfused by the coronary artery branch: Estimation in vivo

Seven closed-chest dogs were anesthetized with intramuscular Innovar and a N₂O/O₂ gas mixture. Maximal coronary vasodilatation was induced by intra-aortic injection of nitroglycerin (200 μg/kg) and continuous infusion of adenosine (1 mg/kg/min) into the main pulmonary artery. Superselective coronary arteriograms were obtained at varying distances along the left circumflex and left anterior descending coronary arteries during scans using the dynamic spatial reconstructor rapid tomographic x-ray scanner. At end-diastole the images of the coronary arteries and opacified myocardium were analyzed for cross-sectional area (CSA) of the coronary artery lumen and regional myocardial volume (Vdsr) perfused by that coronary artery. Postmortem regional myocardial volume (Vpath) was related to the volume perfused by the same artery measured in vivo by the dynamic spatial reconstructor as follows: Vdsr = 4.56 + 0.93 Vpath (r = .98, p < .001). In addition, the cross-sectional area of the coronary artery supplying a volume of myocardium was related to that volume as follows: Vdsr = -1.95 + 6.34 CSAmax (r = .88, p < .001). This suggests that a maximally dilated coronary artery luminal cross-sectional area is linearly related to the volume of muscle it perfuses. We speculate that this relationship may be useful in expressing the physiologic significance of coronary arterial narrowing.