Variations in flow-velocity waveforms obtained by pulsed Doppler echocardiography in the normal human aorta

Abstract

To characterize the contour and duration of aortic flow-velocity waveforms in the normal human, the ascending aorta of 23 persons without evidence of cardiovascular disease was examined systematically with pulsed Doppler echocardiography. In 16 of the 23 subjects, measurements throughout the ascending aorta showed flow-velocity waveforms of similar contour and duration, characterized by flow-velocity peaking in early to midsystole, with most flow velocity (60 ± 4%) occurring in the first half of the available systolic ejection period, and then gradually decreasing to 0 baseline coincident with aortic valve closure. In the other 7 subjects, aortic flow-velocity waveforms recorded at most of the sampling sites also revealed a normal flow-velocity pattern; however, in each of these subjects, 1 to 3 sites that displayed a distinct alteration from the normal pattern were also identified. The waveforms recorded from these latter sites were characterized by flow-velocity peaking earlier in systole and decelerating to 0 baseline approximately 100 ms before aortic valve closure; consequently, a particularly large fraction of flow velocity (88 ± 9%) occurred in the first half of the systolic ejection period. These apparently shortened waveforms were always detected at sites near the medial aortic wall and often at or near the junction of the ascending and transverse aorta. Hence, aortic flow-velocity waveforms with altered contour and duration (resembling those recorded in patients with obstructive hypertrophic cardiomyopathy) were infrequently identified by pulsed Doppler echocardiography in subjects with normal hearts and were not characteristic of the overall aortic flow-velocity pattern in any of these subjects. The origin of these waveforms is uncertain, although it is likely that they reflect local aberrations in aortic flow velocity. Occasional detection of such isolated shortened waveforms by Doppler in a minority of normal subjects serves to emphasize the necessity for thorough investigation of the ascending aorta when characterizing aortic flow-velocity patterns.