Kc. White et al., HEMODYNAMICS AND WALL SHEAR RATE IN THE ABDOMINAL-AORTA OF DOGS - EFFECTS OF VASOACTIVE AGENTS, Circulation research, 75(4), 1994, pp. 637-649
Vasoactive drugs are known to affect impedance (pressure/flow) and ves
sel wall motion in arteries. The nonlinear theory of oscillatory flow
in straight elastic vessels indicates that wall shear rate is affected
by changes in impedance phase angle and wall motion. To test whether
wall shear rate depends on impedance phase angle and wall motion in vi
vo, wall shear rate was measured in the abdominal aorta of anesthetize
d dogs by using a flush-mounted hot-film anemometer, and the hemodynam
ic state was characterized by pressure, flow, and vessel dimension mea
surements. Vasodilators (nitroprusside and isoproterenol) and vasocons
trictors (angiotensin II and norepinephrine) were administered acutely
, and the responses of wall shear rate and hemodynamics were determine
d. In the control state (no drugs), peak wall shear rate was 1835+/-15
3 s(-1) (mean+/-SEM). The vasodilators induced large increases in impe
dance phase angle and wall motion concomitant with large increases in
peak wall shear rate (62.4+/-20.4% for nitroprusside and 68.9+/-28.3%
for isoproterenol), which were not predicted accurately by Womersley's
theory of oscillatory flow in a rigid vessel or the nonlinear theory
of oscillatory flow in an elastic vessel, with measured flow and vesse
l dimension used as inputs. The vasoconstrictors induced small decreas
es in impedance phase angle and wall motion and small changes in peak
wall shear rate (increase, 30.5+/-8.0% for norepinephrine; decrease, 1
8.2+/-7.1% for angiotensin II), which were predicted accurately by Wom
ersley's theory. The present study shows that vasoactive drugs, partic
ularly vasodilators, can have significant effects on wall shear rate (
stress) in the abdominal aorta that appear to be related to changes in
impedance phase angle and vessel wall motion. However, the effects on
wall shear rate are not predicted accurately by straight-tube theory.