Helical Blood Flow in Hemodynamically Significant Carotid Stenosis

To define helical blood flow (HBF) characteristics in hemodynamically significant atherosclerotic stenosis of the internal carotid artery (ICA) by means of duplex scanning.

Twenty-five hemodynamically significant (65.0% [range, 63.0%-69.0%]) carotid stenoses were examined in 23 patients. The severity of the stenosis was calculated by the European Carotid Surgery Trial grading method by transverse section scanning in the B-mode. Rotational components were estimated in color flow mapping by transverse-section scanning of a vessel at the most narrowed site, as well as in the prestenotic and poststenotic segments. A quantitative evaluation of HBF was performed on the basis of pulsed wave Doppler imaging of longitudinal and transverse sections of the arterial lumen.

Helical blood flow was most often (68%) registered in the poststenotic segment of the ICA as a single vortex (52%) or double vortices (16%). At the most narrowed site, HBF was registered in 48% of the cases (44% single vortex and 4% double vortices), whereas in the prestenotic segment of the blood vessel, it was registered in only 16% of the cases (8% single vortex and 8% double vortices). The time-averaged maximum blood flow velocities at the most narrowed site were 88.5 cm/s (25th-75th percentiles, 73.8-127.8 cm/s) for the axial component and 33.1 cm/s (22.7-40.9 cm/s) for the rotational component. The calculated summary velocity of motion of the blood particles in helical paths was 92.2 cm/s (75.7-144.2 cm/s).

It has been shown that HBF can be registered by Doppler ultrasound in atherosclerotic stenosis, and its registration rate increases while passing through the narrowed segment of the ICA.