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Aims: Bioprosthetic valve fracture (BVF) may improve transvalvular gradients and transcatheter heart valve (THV) expansion during VIV interventions. However, the optimal timing of BVF is unknown. We assessed the impact of timing of BVF (before versus after) for valve-in-valve (VIV) intervention, on hydrodynamic function and THV expansion., Methods and Results: Three THV designs were assessed, a 23 mm SAPIEN 3 (S3), small ACURATE neo (ACn) and 23 mm Evolut R, deployed into 21 mm Mitroflow bioprosthetic surgical valves. We evaluated each THV in three groups: 1) no BVF, 2) BVF before VIV, and 3) BVF after VIV. Hydrodynamic testing was performed using a pulse duplicator to ISO 5840:2013 standard. Transvalvular gradients were lower when BVF was performed after VIV for the S3 (no BVF 15.5 mmHg, BVF before VIV 8.0 mmHg, BVF after VIV 5.6 mmHg), and the ACn (no BVF 9.8 mmHg, BVF before VIV 8.4 mmHg, BVF after VIV 5.1 mmHg). Transvalvular gradients were similar for the Evolut R, irrespective of performance of BVF or timing of BVF. BVF performed after VIV resulted in better expansion in all three THV designs. The ACn and Evolut R samples all had a mild degree of pinwheeling, and BVF timing did not impact on pinwheeling severity. The S3 samples had severe pinwheeling with no BVF, and significant improvement in pinwheeling when BVF was performed after VIV., Conclusions: BVF performed after VIV was associated with superior THV expansion in all three THV designs tested, with lower residual transvalvular gradients in the S3 and ACn THVs. The Evolut R had similar hydrodynamic performance irrespective of BVF timing. Timing of BVF has potential implications on THV function.

An original in vitro/in silico method was developed to estimate the local and global mechanical stress applied on the bioprosthetic valve leaflet, which can be important for better understanding of the valve durability. A non-contact system based on stereophotogammetry and digital image correlation enabled filming and studying the valve leaflet movement frame by frame and performing three-dimensional analysis. The deformation was applied in a finite element model in order to calculate the local mechanical stress applied. High stress regions were primarily observed in the upper leaflet edge and belly and to a lesser extent at the free leaflet edge.

Calcified aortic stenoses are among the most prevalent form of cardiovascular diseases in the industrialized countries. This progressive disease, with no effective medical therapy, ultimately requires aortic valve replacement – either a surgical or very recently transcatheter aortic valve implantation. Increase leaflet mechanical stress is one of the main determinants of the structural deterioration of bioprosthetic aortic valves. We applied a coupled in vitro/in silico method to compare the timing, magnitude, and regional distribution of leaflet mechanical stress in porcine versus pericardial bioprostheses (Mosaic and Trifecta). A double activation simulator was used for in vitro testing of a bioprosthesis with externally mounted pericardium (Abbott, Trifecta) and a bioprosthesis with internally mounted porcine valve (Medtronic, Mosaic). A non-contact system based on stereophotogammetry and digital image correlation (DIC) with high spatial and temporal resolution (2000 img/s) was used to visualize the valve leaflet motion and perform the three-dimensional analysis. A finite element model of the valve was developed, and the leaflet deformation obtained from the DIC analysis was applied to the finite element model calculate local leaflet mechanical stress throughout the cardiac cycle. The maximum leaflet stress was higher with the pericardial versus the porcine bioprosthesis (2.03 vs. 1.30 MPa) For both bioprostheses the highest values of leaflet stress occurred during diastole and were primarily observed in the upper leaflet edge near the commissures and to a lesser extent in the mid-portion of the leaflet body. In conclusion, the coupled in vitro/in silico method described in this study shows that the highest levels of leaflet stress occur in the regions of the commissures and mid-portion of the leaflet body. This method may have important insight with regard to bioprosthetic valve durability. Our results suggest that, compared to porcine bioprostheses, those with externally mounted pericardium have higher leaflet mechanical stress, which may translate into shorter durability. [ABSTRACT FROM AUTHOR]

Transcatheter aortic valve (TAV) replacement has become a viable alternative to surgery for high and intermediate risk patients with severe aortic stenosis. This technology may extend to the younger and lower risk patients. In this population, long‐term durability of the TAV is key. Increased leaflet mechanical stress is one of the main determinants of valve structural deterioration. This in vitro study aims at evaluating leaflet bending stress (LBS) in the self‐expanding TAV for different valve sizes, stroke volumes (SV), and degrees of valve oversizing (OS). Three different sizes (23, 26, and 29 mm) of CoreValve (CV) were tested on a pulse duplicator in annulus size ranging from 17 to 26 mm. Leaflet bending stress and bending of the leaflet coaptation line in diastole pinwheeling index (PI) were measured using high‐speed camera imaging (1000 images/s). For each given CV and annulus size, geometric orifice area (GOA) increased significantly with OS (P <.001) and SV (P =.001). LBS decreased with increasing prosthesis size and aortic annulus (AA) size while increasing with SV (P <.03). The largest value of peak LBS (3.79 MPa) was obtained with the CV 23 mm in AA of 17 mm (%OS = 35%), SV 90 mL and the smallest value (0.99 MPa) for the CV 29 mm in AA of 26 mm (%OS = 12%), SV 30 mL. On multivariable analysis, LBS increased independently with larger OS, smaller AA size and higher SV. The PI increased with decreasing AA size and increasing OS. Moderate valve OS, such as generally used for transcatheter aortic valve implantation, is associated with increased LBS during valve opening and closing, especially in small annuli. Hence, TAV OS may negatively impact long‐term valve durability. [ABSTRACT FROM AUTHOR]