Noninvasive determination of pulse-wave velocity in mice

Some transgenic mice have abnormal vascular function, but arterial geometry and dynamics are difficult to evaluate. To examine whether ultrasonic velocimetry could be used to determine arterial pulse-wave velocity (PWV) in mice, a custom-made 20-MHz pulsed Doppler instrument was used to obtain blood flow velocity signals from the aortic arch and the abdominal aorta 4 cm downstream. The upstroke (foot) of the velocity wave was timed at each site with respect to the R wave of the electrocardiogram, and PWV was calculated by dividing the separation distance by the difference in R-foot times. Doppler determinations were compared with invasive tonometry, and PWV was altered pharmacologically. It was found that the upstrokes of pressure (by tonometry) and velocity were coincident (+/-1 ms) and that PWV could be calculated by either method on exposed vessels. With the use of Doppler methods, pulse transit time was determined noninvasively with +/-1-ms resolution in 140 of 142 attempts in 82 mice. The calculated PWV in mice ranged from 220 to 850 cm/s with vasodilating anesthetics producing the low values and vasoconstricting agents producing the higher values. Thus PWV can be determined noninvasively in mice, is similar to that in other mammals, and responds as expected to vasoactive agents.