In Vitro Hydrodynamic Evaluation of Pulmonary Expanded Polytetrafluoroethylene Valved Conduits

Various designs are proposed for pulmonary expanded polytetrafluoroethylene (ePTFE) conduits and have been applied in clinical practice. However, experimental data to support them are limited. We conducted an in vitro experiment using a circulatory simulator to evaluate their haemodynamic performance and hydrodynamic characteristics.

Three root models with a 24-mm basal ring (A, straight; B, with small sinuses; C, with large sinuses) were 3D-printed. Cusps were uniformly cut out from a 0.1-mm-thick ePTFE membrane and sewn to the inter wall of the models. Model A had a single suture on the free margins near the commissures. Each model was tested with a pump size of 70 mL, 70 beats/min, and arterial pressure of 30/10 mmHg. The valve behaviour was recorded by a high-speed camera, and particle image velocimetry (PIV) was performed in the region behind the model housing section.

Peak transvalvular pressure gradients were 4.0, 4.8, and 4.3 mmHg (P = .95), and geometric orifice areas were 2.34, 2.38, and 2.46 cm2 (P = .96) in models A, B, and C, respectively. Particle image velocimetry revealed peak instantaneous velocity was 1.69, 1.69, and 1.65 m/s (P = .74) and peak Reynolds shear stress in the midsystolic phase was 56.8, 49.5, and 25.5 Pa (P = .05) in models A, B, and C, respectively. Model C tended to have a lower distribution of turbulent flow than the other models.

All models exhibited sufficient opening and acceptable Reynolds shear stress values. The sinus contributed to the suppression of turbulent flow, which may lead to an improvement of conduit durability, but its effect was dependent on the sinus size.