Despite the increased global experience with transcatheter aortic valve replacement (TAVR), there remain 3 major adverse events. Aortic rupture, coronary artery obstruction, and paravalvular leakage (PVL) may occur with valve implantation. Oversizing or excessive radial expansion force with the TAVR stent may cause aortic rupture, while insufficient dilatation may lead to PVL and device migration. During TAVR implantation, native leaflet material may produce occlusion of the coronary ostia. A reliable prediction of the biomechanical interaction between native tissue and device in TAVR is critical for the success of this procedure.
In this study, an imaged-based engineering analysis and prediction of TAV deployment was performed using computational models reconstructed from multi-slice computed tomography images obtained from patients undergoing pre TAVR evaluation. Four patients with tricuspid aortic valve stenosis patients subsequently received 23 mm Edwards Sapien TAV valves (Table 1). Finite element models of the patients included aortic root, aortic leaflets, calcification, mitral-aortic intervalvular fibrosa, anterior mitral leaflet, fibrous trigones, and left ventricle. Simulations of the balloon deployment of the Sapien valve were utilized to evaluate the potential for the aforementioned complications. The models presented in this paper assumed an optimal height and angulation of the stent, which is not necessarily true in all cases and it is dependent, among others, on the angle between the ventricle and the aorta.
Table 1.
A summary of the 4 TAV implantation cases examined in the current study
| Age | Gender | Annulus size from perimeter measurement |
Results | |
|---|---|---|---|---|
| Case 1 | 94 | Female | 19.6 | Aortic root rupture |
| Case 2 | 72 | Female | 22.9 | Normal Implant |
| Case 3 | 89 | Female | 23.9 | Paravalvular Leak |
| Case 4 | 65 | Female | 23.7 | Coronary Occlusion |
The method presented herein could be utilized as a pre-procedural planning tool to virtually predict device performance for TAVR and improve clinical outcomes.
Figure 1. Aortic Annulus Rupture.
During the TAVR procedure of Case 1, tearing and rupture occurred below the left main coronary artery. Simulation: (a) local and (b) full views of the deformed the aortic root and (c) balloon deployment show annulus tearing under the left coronary ostium due to dislodgement of calcification into the vulnerable part of the aortic sinus. (For illustration purposes, the yellow geometry in our finite element models represented the aortic root, the green geometry represented native aortic leaflets, the red geometry represented calcification, and the grey geometry represented the TAV stent.)
Figure 2. Coronary Occlusion.
Side views of the deformed aortic root after the maximum stent deployment were used to evaluate the potential coronary artery occlusion. Case 2 shows successful TAVR in the aortic valve position. Case 4 demonstrates coronary occlusion with TAVR.
Figure 3. Paravalvular Leak.
Short axis views of the TAV stent inside deformed native leaflets were utilized to assess the possible paravalvular leak. Case 3 demonstrates PVL following TAVR. The implant site of the first TAV was suboptimal, as the native leaflet insertion point was adjacent to the lower edge of the stent. A large PVL was present after the deployment of the first TAV. Subsequently, a second TAV was deployed inside the first one, to correct the defect due to suboptimal valve positioning. The valve positioning of the first TAV was replicated in the FE model simulation, demonstrating a large PVL which was noted clinically.
Figure 4. Sequences in the development of the aortic root model of Case 4.
(a) initial image segmentation, (b) reconstructed models of aortic leaflets and calcification, (c) top view of the whole aortic root model, and (d) side view showing left main ostial occlusion (without showing the calcification). Pre procedure simulation analysis suggested the possibility of left main ostial occlusion and the potential for aortic annulus rupture. Repeat echocardiographic and angiographic evaluation was performed, also suggesting the potential risk for coronary artery occlusion and annulus rupture. The TAVR procedure was cancelled for this patient.
Acknowledgements
This work was supported in part by NIH 1R01HL104080, 1R21HL108239 grants, and AHA predoctoral fellowship 13PRE14830002. We would also like to thank Caitlin Martin, Thuy Pham, and Kewei Li for providing experimental data of the heart tissues, Rebecca Newman for FE model reconstruction and technical support provided by Dura Biotech.
Footnotes
Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Conflict of Interest
All authors disclose any financial and personal relationships with other people or organizations that could inappropriately influence (bias) their work.
Video 1. Simulation of TAVR deployment into a patient stenotic aortic root. Left: Balloon TAVR expansion simulation. Center: Side view of TAVR stent deployment simulation Right: Top view of TAVR stent deployment simulation.