Background Wall shear stress (WSS) is closely associated with arteriosclero
sis. WSS values for various vessels and species are available, but fully in
-vivo measurements in human coronary arteries have not yet been reported.
Objective To measure WSS in undiseased coronary arteries of adult patients
at rest.
Methods We recorded the temporal average value (APV) of the instantaneous m
aximal blood velocity in the three vessel segments of angiographically norm
al coronary artery bifurcations in 21 patients undergoing cardiac catheteri
zation to treat various diseases by means of a 0.036 cm Doppler wire (FloWi
re), In total, 36 bifurcations were examined. The 36 X 3 cross-sectional ar
eas (CSA) were determined by means of a three-dimensional angiographic tech
nique. The three flows, Q(1) (inflow), Q(2), and Q(3) of each bifurcation w
ere calculated according to Q = 0.5 X APV X CSA. For each segment, WSS was
calculated as WSS = 32 eta Q/(pi D-3) (where blood viscosity eta = 3.5 mPa
s and D is vessel diameter). Only the 54 WSS values obtained from the 18 fl
ow triplets which satisfied the equation Q(1)/(Q(2) + Q(3)) = 1 better than
did the 18 other ones were retained. Results The 54 WSS values ranged from
0.33 to 1.24 Pa (mean 0.68 Pa, SEM, 0.027 Pa). They did not depend signifi
cantly on Q (r = 0.07; P = 0.60) and the CSA (r = 0.24, P = 0.08) but the s
econd relationship approached significance.
Conclusion The obtained mean WSS value (0.68 Pa) is half the value predicte
d for coronary arteries from optimality principles. It is also smaller than
many values reported for human carotid, renal, and femoral arteries. Coron
Artery Dis 11:495-502 (C) 2000 Lippincott Williams & Wilkins.