Impact of Over-Expansion on SAPIEN 3 Transcatheter Heart Valve Pericardial Leaflets

<b>Background</b>: This study sought to investigate the impact of extensive over-expansion of transcatheter heart valves (THVs) on leaflet structure. THVs may be over-expanded beyond recommended labeling in certain clinical scenarios. However, it is unknown whether over-expansion damages pericardial leaflets. Therefore, we assessed the effect of over-expansion on THV leaflets. <b>Methods</b>: SAPIEN 3 THVs (one of each a 23mm, 26mm, and 29mm valve) were expanded to nominal dimensions and then over-expanded to larger than the recommended diameters. Leaflets from a nominally expanded THV were used as control. Structural changes to the leaflets were assessed by histology, scanning electron microscopy (SEM), and second-harmonic generation (SHG) microscopy. <b>Results</b>: Analysis of leaflets by SHG microscopyusing texture analysis demonstrated that over-expansion of 23mm, 26mm, and 29mm THVs resulted in significant disorganization of the fibrilar collagen on both aortic and ventricular surfaces (p&lt;0.05 for all). Histological analysis demonstrated significant thinning of leaflets in over-expanded THVs compared to control (p&lt;0.05 for over-expanded THVs) as well as a significant increase in pericardial tissue density within the leaflet (p&lt;0.05 for all over-expanded THVs) compared to control conditions. SEM analysis demonstrated breaks, stretching, and disorganization of collagen fibers within over-expanded THVs. <b>Conclusions</b>: Sequential over-expansion by 1mm increments up to 3mm, which is not typically used in clinical practice, of SAPIEN 3 valves on the bench results in damage to the aortic and ventricular surfaces of pericardial leaflets. Whether a lesser degree of over-expansion or degree of over-expansion used clinically will cause similar leaflet injury will require further investigation.