Turbulent blood flow in the ascending aorta of humans with normal and diseased aortic valves

Abstract

Turbulent blood flow may contribute to a variety of pathophysiological effects. Because of its postulated importance, this study was undertaken to determine whether turbulent flow does in fact occur in the human body. In 15 persons (seven normal, seven aortic valvular disease, one prosthetic aortic valve), point velocity was measured in the ascending aorta with a hot-film anemometer probe. In one normal individual with a high cardiac output, turbulent flow occurred above the aortic valve during peak flow which corresponded to a peak Reynolds number of 10,000. In the other six normal subjects (peak Reynolds numbers of 5,700-8,900), flow was highly disturbed during peak ejection. Each of the subjects with aortic valvular disease and the subject with a prosthetic aortic valve showed turbulent flow during nearly the entire period of ejection, with Fourier components of velocity of significant magnitude up to 320 Hz (the maximum frequency we could evaluate with the equipment available). The turbulence energy density was higher in subjects with abnormal valves (3.2-14.6 ergs/cm3), than in normal subjects (0.6-2.9 ergs/cm3). In subjects with aortic stenosis, turbulence was observed throughout the ascending aorta and in the innominate artery. In others, the turbulence dissipated more proximally. The results of this study indicate that turbulent flow can occur in the ascending aorta of subjects with normal cardiac function; and it occurs consistently in the ascending aorta of individuals with abnormal aortic valves.