In Vitro Comparison of a Closed and Semi-closed Leaflet Design for Adult and Pediatric Transcatheter Heart Valves

Transcatheter heart valve replacements (TVR) are mostly designed in a closed position (c) with leaflets coaptating. However, recent literature suggests fabricating valves in semi-closed (sc) position to minimize pinwheeling. With about 100,000 children in need of a new pulmonary valve each year worldwide, this study evaluates both geometrical approaches in adult as well as pediatric size and condition. Three valves of each geometry were fabricated in adult (30 mm) and pediatric (15 mm) size, using porcine pericardium. To evaluate performance, the mean transvalvular pressure gradient (TPG), effective orifice area (EOA), and regurgitation fraction (RF) were determined in three different annulus geometries (circular, elliptic, and tilted). For both adult-sized valve geometries, the TPG (TPG_C = 2.326 ± 0.115 mmHg; TPG_SC = 1.848 ± 0.175 mmHg)* and EOA (EOA_C = 3.69 ± 0.255 cm²; EOA_SC = 3.565 ± 0.025 cm²)* showed no significant difference. Yet the RF as well as its fluctuation was significantly higher for valves with the closed geometry (RF_C = 12.657 ± 7.669 %; RF_SC = 8.72 ± 0.977 %)*. Recordings showed that the increased backflow was caused by pinwheeling due to a surplus of tissue material. Hydrodynamic testing of pediatric TVRs verified the semi-closed geometry being favourable. Despite the RF (RF_C = 7.721 ± 0.348 cm²; RF_SC = 5.172 ± 0.679 cm²), these valves also showed an improved opening behaviour ((TPG_C = 20.929 ± 0.497 cm²; TPG_SC = 15.972 ± 1.158 cm²); (EOA_C = 0.629 ± 0.017 cm²; EOA_SC = 0.731 ± 0.026 cm²)). Both adult and pediatric TVR with semi-closed geometry show better fluiddynamic functionality compared to valves with a closed design due to less pinwheeling. Besides improved short-term functionality, less pinwheeling potentially prevents early valve degeneration and improves durability. *Results are representatively shown for a circular annulus geometry.