Assessment of Paravalvular Leak Severity and Thrombogenic Potential in Transcatheter Bicuspid Aortic Valve Replacements Using Patient-Specific Computational Modeling

Abstract

Bicuspid aortic valve (BAV), the most common congenital valvular abnormality, generates asymmetric flow patterns and increased stresses on the leaflets that expedite valvular calcification and structural degeneration. Recently adapted for use in BAV patients, TAVR demonstrates promising performance, but post-TAVR complications tend to get exacerbated due to BAV anatomical complexities. Utilizing patient-specific computational modeling, we address some of these complications. The degree and location of post-TAVR PVL was assessed, and the risk of flow-induced thrombogenicity was analyzed in 3 BAV patients - using older generation TAVR devices that were implanted in these patients, and compared them to the performance of the newest generation TAVR devices using in silico patient models. Significant decrease in PVL and thrombogenic potential was observed after implantation of the newest generation device. The current work demonstrates the potential of using simulations in pre-procedural planning to assess post-TAVR complications, and compare the performance of different devices to achieve better clinical outcomes. Patient-specific computational framework to assess post-transcatheter bicuspid aortic valve replacement paravalvular leakage and flow-induced thrombogenic complications and compare device performances.

Keywords: Bicuspid aortic valve (BAV); Computational fluid dynamics (CFD); Paravalvular leakage (PVL); Patient-specific computational modeling; Thrombogenicity; Transcatheter aortic valve implantation (TAVI); Transcatheter aortic valve replacement (TAVR).

Fig. 1

(Top row, a - c) Patient-specific finite element BAV models, with leaflet calcium distribution; (Middle row, d - f, and bottom row, g - i) Post deployment configuration of the self-expandable stents (originally implanted) in each patient model. The annular calcification in patient-2 is circled in red. (BAV – Bicuspid aortic valve)

Fig. 2

A freeze frame of injection of platelets (particles in blue) flowing through the PVL channels in the aortic root of one patient case. The injection plane, which was placed ~20 mm above the annulus plane, is highlighted in the zoomed in section. (PVL – Paravalvular leak)

Fig. 3

(Top row, a - c) Lateral view of the velocity streamlines illustrating the flow paths of the PVL jets during peak diastole. (2nd row, d - e) Polar projection of the velocity streamlines illustrating the entire circumferential image of aortic root and all the PVL that were detected in each patient case. The dashed line highlights the attachment region. First two rows represent the CFD data obtained from the original patient cases. (3rd row, g - i) Freeze frame from Echo Doppler color flow, demonstrating the PVL jets in the patients and the location of the native leaflets. (Bottom row, j - l) Polar projection of the velocity streamlines through the aortic root in the newest generation device (Evolut Pro+) cases. PVL locations in each case are circled in red in the streamline images. (RCL – Right coronary leaflet, LCL – Left coronary leaflet, NCL – Non-coronary leaflet, PVL – Paravalvular leak)

Fig. 4

Transient volumetric flowrate through the PVL channels during one cardiac cycle in each case. No PVL flow was present in patient-3 Evolut Pro+ case. (PVL – Paravalvular leak)

Fig. 5

PDFs of the accumulated stress values in all cases (a – c). This function is independent of the number of platelets seeded. (PDF – Probability density function; SA – Stress accumulation)