The multigate Doppler approach for assessing hemodynamics in a forearm vascular access for hemodialysis purposes

We compared the multigate and single gate pulsed wave Doppler (PWD) approach to assess the hemodynamics in an arteriovenous fistula for hemodialysis purposes. In particular, we evaluated volume flow and wall shear rate measurements based on PWD because: (i) volume flow measurements are typically performed to assess the maturation of the arteriovenous fistula (AVF), with low postoperative fistula flow a prognostic marker for failure of the AVF; (ii) wall shear stress may play an important role in vascular remodeling processes of the fistula. As in-vivo validation of fistula flow measurements is cumbersome, we performed simulations integrating computational fluid dynamics with an ultrasound (US) simulator. Flow in the arm was calculated, based on a patient-specific model of the arm vasculature pre and post AVF creation. Next, raw ultrasound signals were simulated and processed using a multigate and single gate Doppler approach in the radial artery, both for the preop and postop setting. Results showed that the extreme postop flow conditions (high velocity magnitudes and complex flow profiles) hampered accurate assessment of both wall shear rate and volume flow, while reasonable estimates were obtained preop (lower velocity magnitudes and laminar flow).