Haemodynamic Efficacy of Tissue-Engineered Pulmonary Monocusp Valves

Purpose: A stenotic right ventricular outflow tract is often reconstructed with a transannular patch and a monocusp valve. However, because there are no set standards for the monocusp valve design, these designs vary from clinic to clinic. The aim of this investigation is to propose an optimal tissue-engineered monocusp valve design with favourable hemodynamic characteristics such as minimal flow regurgitation and low risk of thrombosis.

Methods: Dynamic valve behaviour and blood flow in an idealized pulmonary artery was simulated using fluid-structure interaction (FSI) simulations. Blood flow was simulated by numerically solving the conservation equations while the opening and closing behaviour of the valve was resolved naturally by the resulting haemodynamic forces.

Results: For the first instance, FSI simulations were performed for a hypothetical tissue-engineered monocusp valve design which is meant to be implanted in the open position with a convex transannular patch. Numerical results elucidated that this design opens and closes in a physiological manner without folding of the free-edge. Coaptation length for this design, when the valve was fully closed, was approximately 2.1 mm. In terms of haemodynamics, during early outflow, when the valve was opening, a flow recirculation zone was present between the valve and the transannular patch. However, soon after peak outflow, no recirculation zone was found behind the valve as the convex shape of the transannular patch and the closing valve movement smoothly channelled the flow back into the main pulmonary artery. This channelling of flow back into the main pulmonary artery decreased the blood residence time around the transannular patch, thus potentially reducing the thrombogenicity of the valve. There was minimal flow regurgitation due to good coaptation between the valve and the pulmonary wall.

Conclusion and future work: FSI results from this investigation suggest that this hypothetical valve opens and closes in a physiologic manner, offers good coaptation with minimal regurgitation and because of low blood residence time, might also be non-thrombogenic. This is an ongoing research project and further FSI simulations are currently being performed for other valve designs including a pulmonary monocusp valve which is currently under pre-clinical evaluation within the 1Valve program.