Normal and Stenotic Blood Flow Velocities in Human Left Coronary Artery Measured by an 80 Channel 20 MHz Pulsed Doppler Velocimeter

Abstract

The purpose of our studies was two-fold: [1] to investigate the phasic characteristics of normal coronary artery flow as well as velocity profiles across the vessel, and [2] to analyze the characteristics of the post-stenotic coronary artery flow in man. We measured blood velocities in the left anterior descending coronary artery (LAD) by an 80 channel 20 MHz pulsed Doppler velocimeter. To investigate the characteristics of normal coronary artery flow, blood flow velocity measurements were performed in segments 7 or 8 of LAD in ten patients with an atrial septal defect (ASD) after the defect closure. None of these patients had any detectable coronary artery stenosis or left ventricular hypertrophy. The velocity waveform displayed diastolic predominant pattern, which is a characteristic of left coronary artery flow. The diastolic-to-total velocity area ratio of normal coronary velocity waveforms was about 80%. During systole, two different types of reverse flow were observed time sequentially, i.e., an early-systolic reverse flow and a mid- (and late-) systolic one. During diastole, the blood velocity profiles were classified into three types: a parabolic pattern, a skewed pattern (toward the near wall or far wall) and an M-shaped pattern. The direction of skewing was not consistent among patients, but the number of parabolic profiles increased in late diastole. Post-stenotic blood flow velocities were measured in nine patients with 75% to 99% stenosis of the LAD during coronary artery bypass graft surgery in the nine patients. The coronary artery velocity waveform through a severe stenosis was characterized by augmentation of the systolic velocity component and a relatively small diastolic velocity component. The diastolic-to-total velocity area ratio was about 50%. The velocity spectrum of post-stenotic coronary artery was wider in the distant distal portion than the immediately distal portion. The velocity profile in the vicinity of the vessel wall was irregular in the immediately distal portion, indicating the presence of flow separation.