Blood flow characteristics in the femoral bifurcation of healthy subjects

Background: Blood flow disturbances are local risk factors for atherosclerosis. This study aims to quantify time-resolved two-dimensional blood flow velocity patterns in the femoral bifurcation of healthy subjects. Based on the known association between complex vessel geometry and local flow disturbances, we hypothesize that complex flow features are likewise present in healthy subjects. Methods: Twenty healthy subjects underwent high-frame-rate ultrasound vector flow imaging (VFI) examinations of the common femoral artery, femoral bifurcation, and superficial femoral artery. Measurements were performed with and without the addition of ultrasound contrast agents. Velocity vector fields were obtained through speckle-based particle image velocimetry analysis. Hemodynamic parameters, including vector complexity and vorticity, were quantified, and recirculation zones were identified for the entire lumen. These flow features were compared between subgroups based on age and sex. Results: VFI recordings revealed laminar flow patterns during peak forward and backward flow. Multiple instances with multidirectional flow patterns were captured through the cardiac cycle in all subjects. Various recirculation zones were sufficiently resolved and identified mainly during flow reversal. The hemodynamic parameters confirmed these observations with low vector complexity and no identified vortices during systole and distinct peaks in vector complexity and vortex identification during flow reversal. In contrast, increased vorticity was found during systole. Significantly lower diastolic forward flow velocities and higher vector complexity were observed in the older subjects. No differences were found between sexes. Conclusions: Blood flow quantification through ultrasound VFI revealed multiphasic flow dynamics with complex recirculating flow phenomena in the femoral bifurcation of healthy subjects. Age differences appeared to be largest in diastolic flow features, where older subjects are exposed to a prolonged period of blood stasis. Clinicaltrials.gov, Number: NTC05451485.