Wall shear stress in the superficial femoral artery of healthy adults and its response to postural changes and exercise.

OBJECTIVES

Alterations of wall shear stress (WSS) are considered to precede atherosclerosis. Local variations of WSS might contribute to the typical distribution of atherosclerotic lesions along the superficial femoral artery (SFA). We investigated the course of WSS and its response to postural changes and exercise along the SFA of healthy adults.

METHODS

In forty-six healthy subjects, we determined flow velocities and internal vessel diameters in five predefined segments of the SFA using duplex ultrasound; measurements were done at rest, following exercise (30 toe raises) and after postural changes (supine and sitting). Peak and mean WSS were calculated from peak systolic and mean velocities, vessel diameter and whole blood viscosity.

RESULTS

At rest, peak and mean WSS did not vary along the femoro-popliteal axis (p > 0.05); peak and mean WSS were lower in the sitting than in the supine position (p < 0.0001). After exercise, peak and mean WSS increased in all segments (p < 0.0001), showing the lowest increase in the distal Hunter's canal.

CONCLUSION

Healthy adults do not exhibit local variations of WSS in the SFA at rest, but segmental differences in WSS occur after exercise. Whether these findings are related to the typical distribution of atherosclerotic lesions later in life requires further investigation.