Abstract

Tetralogy of Fallot (TOF), which causes 8-10% of all congenital defects, is a concern for 1 in 2518 parents. Although the effects of this disease can be remedied by a surgery at birth, regurgitation from the pulmonary valve seems to occur two to three decades after this repair in 50% of the operated cases. Since little is known regarding the cause of this regurgitation or simply the natural flows in the right ventricle (RV), this research, which is the first of its kind, aims to shed light on fluid flow in the right ventricle during normal function as well as the effects on the fluid flow due to the introduction of regurgitation from the pulmonary valve. An in-house cardiovascular simulator was used to simulate the pumping action of the right ventricle through the use of a linear motor, which gave rise to the E-wave, while a servo motor gave rise to the A-wave. Various severities of regurgitation, defined by ratio of the effective regurgitant orifice area over the total valve orifice area (ROA/A), (0 ROA/A, 0.012 ROA/A, 0.063 ROA/A and 0.174 ROA/A) were simulated through the restriction of the valve closure while the fluid used was a 60%-40% water-glycerol mixture in order to mimic human blood viscosity. Planar time-resolved particle image velocimetry measurements have been performed on a custom-made double activation simulator reproducing flow conditions in a model of a right ventricle. Changes in flow characteristics in the right ventricle have been evaluated in terms of velocity fields and profiles, tricuspid inflow jet orientation and viscous energy dissipation. Our results show that pulmonary valve regurgitation significantly alters the flow in the right ventricle mostly by impairing the diastolic inflow through the tricuspid valve and by increasing viscous energy loss. This fundamental work should allow for a better understanding of such changes in the RV flow dynamics. It may also help in developing new strategies allowing for a better follow-up of patients with repaired TOF and for decision-making in terms of pulmonary valve replacement.