Blood Velocity Patterns in Coronary Arteries

A pulsed ultrasound Doppler velocity meter has been used to map the time varying velocity waveforms in the exposed left coronary arteries of anesthetized ponies. Velocity measurements were made without invading the vessels or disturbing the hemodynamic patterns. Typical recordings of velocity waveforms and calculated velocity profiles in the main, descending and circumflex branches are presented. Marked velocity fluctuations in the frequency range of 5 to 10 Hz were measured in the major coronary branches and may influence the stability of the flow and the development of separated flows. Peak Reynolds numbers normally ranged from 300 to 600 and the Womersley unsteadiness parameter based on the heart frequency was usually less than 4.0. Maximum shear rates at the wall were estimated from the calculated velocity profiles and ranged from 400 to 600 sec⁻¹.