Augmentation of Coronary Blood Flow in Systole by Reflected Waves in the Proximal Aorta

Abstract

It has been proposed that blood flow in coronary arteries is augmented by backward travelling (reflected) waves in the proximal aorta that arise from distal reflection sites and propagate as forward travelling waves in the coronary arteries. However, these waves have never been identified and measured. We used wave intensity analysis to quantify forward and backward travelling waves in the proximal aorta and coronary arteries at various times in the cardiac cycle, and assess their relationship to changes in coronary blood flow. In 19 subjects (age 35-73 years), sensor-tipped intra-arterial wires were used to measure pressure and flow velocity in the coronary arteries and in the proximal aorta. A backward travelling (reflected) wave was seen in the proximal aorta in systole in all subjects (159±12ms after the ECGR-wave). A forward travelling wave that corresponded to this reflected wave could be seen in the coronary arteries approximately 30ms later: left main stem (187±11 ms), left anterior descending (194 ±7 ms) and circumflex (189 ±7 ms) . In the coronary arteries the wave that corresponded to the reflected wave in the aorta represented 20.3±2.1% of the peak intensity of the wave generated by ventricular systole (incident wave), and was associated with a 38.9±8.4% instantaneous increase in systolic coronary blood flow velocity (0.2 to 0.28m/s, p<0.002). In conclusion, reflected waves in the proximal aorta appear to propagate into the coronary arteries and augment coronary systolic blood flow.