In-vivo measurements of wall shear stress in human coronary arteries

Background Wall shear stress (WSS) is closely associated with arteriosclerosis. 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 maximal blood velocity in the three vessel segments of angiographically normal coronary artery bifurcations in 21 patients undergoing cardiac catheterization to treat various diseases by means of a 0.036 cm Doppler wire (FloWire), In total, 36 bifurcations were examined. The 36 X 3 cross-sectional areas (CSA) were determined by means of a three-dimensional angiographic technique. The three flows, Q(1) (inflow), Q(2), and Q(3) of each bifurcation were 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 flow 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 significantly on Q (r = 0.07; P = 0.60) and the CSA (r = 0.24, P = 0.08) but the second relationship approached significance. Conclusion The obtained mean WSS value (0.68 Pa) is half the value predicted 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.