Quantification of Blood Flow in the Carotid Bifurcation of Healthy Subjects

Locally disturbed blood flow patterns are known to create an atherogenic environment, particularly in the presence of other cardiovascular risk factors. Given the geometry of a healthy carotid artery, complex flow patterns are expected to be present. This study aims to characterize (complex) blood flow patterns and estimate flow-derived parameters in the carotid bifurcation of healthy subjects. Ultrasound-based velocity vector imaging (US-VVI) was acquired in the carotid bifurcation of 20 healthy subjects. Hemodynamic parameters, including temporal velocity profile, vector complexity (VC), vortex presence, and wall shear stress (WSS), were derived and compared between two age groups (20-30 and 65-75 years). Lower velocities and higher VC values were observed in the older age group for all timepoints. The highest presence of vortices was observed during the systolic deceleration, which was more exposed in younger subjects (5 out of 10) compared to older subjects (3 out of 9). A quick build-up and consequent resolving of the vortices was reflected by the relatively short vortex duration, with a vortex presence of 11.4% (7.9-15.6) and 13.1% (5.9-18.6) as a percentage of the cardiac cycle in younger and older subjects, respectively. Larger WSS estimates, represented as median along the complete vessel wall, were found in the younger subjects at all timestamps, except at systolic deceleration. In conclusion, the presence of complex flow patterns was confirmed in healthy subjects and multiple flow-derived hemodynamic parameters were evaluated in two age groups, providing an insight into age-related differences in hemodynamics. Aging seemed to result in higher vector complexities, whereas the presence of recirculating flow is less in older subjects.