Wave-velocity in the proximal aorta.

Abstract

The wave velocity in the ascending aorta has been measured by 2 methods; (1) from the transit-time of the wave front between 2 points (the wave-front velocity) and (2) from the mean value of the phase shift of the harmonic components of both pressure waves (mean phase velocity). Close agreement was found between values obtained by both methods. With mean arterial pressure (M.A.P.) in the range 90–120 mm Hg the velocities recorded were (1) wave-front velocity, 4·04±(S.E.M.)0·14 m/s; (2) mean phase velocity, 3·98±0·12 m/s. With an electromagnetic flow probe on the ascending aorta the velocity was 3·98±0·09 m/s. Mean phase velocities were based on the values at frequencies above 2 Hz as wave reflection causes a large increase in measured phase-velocity below this frequency. Decrease in M.A.P. below 100 mm Hg produced no significant change in wave-velocity; above 100 mm Hg there was an increase in velocity to 5·6 m/s with a M.A.P. of 160 mm Hg. The wave-velocity in the ascending aorta is somewhat lower than that in the thoracic aorta.