Adjusting flow-mediated dilation for shear stress stimulus allows demonstration of endothelial dysfunction in a population with moderate cardiovascular risk.
OBJECTIVE
Although normalization of brachial artery flow-mediated dilation (FMD) to individual shear stress (FMD:shear stress ratio) has been proposed to improve this measure of endothelial function, the clinical utility of FMD normalization has not yet been demonstrated. We tested (1) whether following conventional 5-min forearm occlusion, the FMD:shear stress ratio would discriminate a population with moderate cardiovascular risk (MR) from a low-risk (LR) population, and (2) whether the dose-response profile relating shear stress to FMD would be different between the 2 populations.


METHODS
Five different magnitudes of reactive hyperemia-induced shear stress were applied to 20 MR and 20 LR subjects by manipulating forearm cuff occlusion duration. Brachial artery diameters and velocities were measured via high-resolution ultrasound. To quantify the hyperemic stimulus, shear stress area under the curve was individually calculated for the duration of time-to-peak dilation.


RESULTS
Following 5-min of forearm occlusion, FMD:shear stress ratio (p = 0.041), but not FMD (p = 0.286), discriminated MR from LR. The slope of the shear stress-FMD regression line was lower in MR compared to the LR (p < 0.001).


CONCLUSIONS
The FMD:shear stress ratio distinguished reduced endothelial function in a population with MR. The dose-response profile of the shear stress-FMD relationship appears to differ between populations of distinct cardiovascular risk.
Padilla
Jaume
J
Kinesiology, Indiana University, Bloomington, Ind., USA. padillaja@missouri.edu
Johnson
Blair D
BD
Newcomer
Sean C
SC
Wilhite
Daniel P
DP
Mickleborough
Timothy D
TD
Fly
Alyce D
AD
Mather
Kieren J
KJ
Wallace
Janet P
JP
D000328:Adult; D001783:Blood Flow Velocity; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D006940:Hyperemia; D017078:Laser-Doppler Flowmetry; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow; D018570:Risk Assessment; D012307:Risk Factors; D013314:Stress, Mechanical; D013997:Time Factors; D014463:Ultrasonography; D014664:Vasodilation