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

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.
SAPIEN 3 THVs (one of each a 23 mm, 26 mm, and 29 mm 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.
Analysis of leaflets by SHG microscopy using texture analysis demonstrated that over-expansion of 23 mm, 26 mm, and 29 mm THVs resulted in significant disorganization of the fibrilar collagen on both aortic and ventricular surfaces (p < 0.05 for all). Histological analysis demonstrated significant thinning of leaflets in over-expanded THVs compared to control (p < 0.05 for over-expanded THVs) as well as a significant increase in pericardial tissue density within the leaflet (p < 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.
Sequential over-expansion by 1 mm increments up to 3 mm, 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.
AS: Aortic stenosis; A.U.: Arbitrary units; CT: Computed tomography; ECM: Extracellular matrix; GLCM: Gray level co-occurrence matrix (GLCM); H&E: Hematoxylin and eosin; ROI: Region of interest; S3: SAPIEN 3 transcatheter valve; SEM: Scanning electron microscopy; SHG: Second-harmonic generation; TAVR: Transcatheter aortic valve replacement; THV: Transcatheter heart valve