MICROVASCULAR BLOOD VOLUME-TO-FLOW RELATIONSHIPS IN PORCINE HEART WALL - WHOLE-BODY CT EVALUATION IN-VIVO

The goal of this study was to evaluate the functional behavior of recruitable (mostly capillary) and nonrecruitable (mostly arte; rioles and venules) components of the intramyocardial microvasculature in the in situ heart of intact experimental animals. For this purpose fast X-ray computerized tomography (CT) scans were performed in a group of anesthetized pigs. Each scan was performed during an aortic root angiogram and was repeated after sequential injections of a suspension of nonradioactive microspheres into a selected coronary artery. Regional myocardial perfusion (F, ml . g(-1). min(-1)) and intramyocardial blood volume (rho, ml/g) were estimated from the dynamic CT image sequences. For the intramyocardial microcirculation, rho = AF + B root F [where A = 0.016 min and B = 0.076 (ml . min/g)(1/2)] was shown to describe the rho-to-F relationship over the entire range of flows observed. With increasing embolization with 15-mu m diameter microspheres, the coefficients A and B changed in a way consistent with A describing the transit time through the functionally recruitable component and B/root F describing the transit time through the functionally nonrecruitable component of the microcirculation.