DIFFERENTIAL CHARACTERIZATION OF BLOOD-FLOW, VELOCITY, AND VASCULAR-RESISTANCE BETWEEN PROXIMAL AND DISTAL NORMAL EPICARDIAL HUMAN CORONARY-ARTERIES - ANALYSIS BY INTRACORONARY DOPPLER SPECTRAL FLOW VELOCITY

To characterize coronary blood flow velocity parameters and to determi ne the relation among velocity, volumetric flow, and vascular resistan ce in awake human beings, we performed paired proximal and distal velo city measurements in 28 angiographically normal coronary arteries. Mea n velocity, peak velocity, diastolic-to-systolic velocity ratio, and d iameter and cross-sectional area of proximal and distal arteries were determined and coronary flow and vascular resistance computed. Mean ve locity and coronary vasodilator reserve were similar for all three nat ive arteries and were preserved from proximal to distal segments. Volu metric flow decreased from proximal to distal segments. The demonstrat ed inverse and curvilinear (polynomial) relation between volumetric fl ow and vascular resistance agrees with theoretical and animal models o f coronary physiologic characteristics and suggests a nadir of coronar y vascular resistance below which coronary flow no longer increases.