PARTICLE VELOCITY AND SHEAR STRESS ARE INCREASED IN ADJUSTABLE SYSTEMIC-PULMONARY ARTERY SHUNTS

Objective: Adjustable systemic-pulmonary artery (ASPA) shunts may provide improved hemodynamic control but increased flow disturbances versus unadjustable shunts. The objective of the study was to measure maximum particle velocity (Vmax) and shear stress (SSmax) in an in vitro model of an ASPA shunt using particle image velocimetry (PIV). Methods: 4 mm and 5 mm polytetrafluoroethylene shunts were constricted to match the flow rate of an unconstricted 3.5 mm shunt. Each lumen shape was converted into an optically clear tube for PIV analysis. Reynolds and Womersley numbers simulated in viva, pulsatile conditions. N = 128 image pairs per position. Results: Vmax and Ssmax were 21.80 ± 1.77 cm/s and 4.03 ± 0.33 dynes/cm² for the 3.5 mm shunt. For the 4 mm shunt, Vmax was 29.03 ±3.02^* and 26.07 ± 2.48^* cm/s, and SSmax was 6.32 ±.66^* and 5.94 ±.61^* dynes/cm² at 0–2 and 2–4 diameters downstream from the constriction. For the 5 mm shunt, Vmax was 35.04 ± 3.95^* and 25.24 ± 3.04^* cm/s, and SSmax was 9.25 ± 1.16^* and 5.57 ±.88^* dynes/cm² at 0–2 and 2–4 diameters downstream. (*p<.01 vs unconstricted shunt) Conclusions: Particle velocity and shear stress are higher in constricted shunts. PIV is useful for quantifying flow fields through an ASPA shunt.

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