Effects of under- and overexpansion on performance of Edwards SAPIEN 3 and MyVal OCTACOR transcatheter heart valves

Balloon-expandable Edwards SAPIEN 3 (23 mm) and MyVal OCTACOR (21.5 mm) valves were tested in 3D-printed silicone tubes using a low-pressure, water-perfused simulator with ultrasound and video monitoring. Balloons were inflated in 2 mm increments from 18 to 30 mm. Both valves were easily inflated from 18 to 24 mm with 2-3 atm inflation pressures and required 5.5 atm and 7 atm, respectively, to reach an inner diameter of 26 mm at the outflow level for the SAPIEN 3 and OCTACOR valves. Further expansion was not achievable. At 18 mm, leaflet opening was mildly asymmetric, but laminar flow was preserved. Circular geometry improved at 20 mm and normalised at 22 mm for both valves. At 24 mm, SAPIEN 3 showed trivial regurgitation, while OCTACOR exhibited a central coaptation defect with mild-to-moderate regurgitation. At 26 mm, SAPIEN 3 leaflets were maximally stretched yet functional with central regurgitation, whereas OCTACOR failed with leaflet tears at the frame attachment. These results indicate both valves can be implanted at small diameters and stepwise dilated to nominal size, tolerating overexpansion up to 3 mm for SAPIEN 3 (+13% overexpansion) and 4.5 mm for OCTACOR (+20.9% overexpansion) at outflow level, with SAPIEN 3 remaining functional and OCTACOR requiring valve-in-valve replacement. Pending clinical validation, this versatility could support their use for infant mitral and pulmonary replacements as alternatives to the Melody valve; though, under- or overexpansion should be reserved for clinically essential situations.