Total ellipse of the heart valve: the impact of eccentric stent distortion on the regional dynamic deformation of pericardial tissue leaflets of a transcatheter aortic valve replacement

Abstract

Transcatheter aortic valve replacements (TAVRs) are a percutaneous alternative to surgical aortic valve replacements and are used to treat patients with aortic valve stenosis. This minimally invasive procedure relies on expansion of the TAVR stent to radially displace calcified aortic valve leaflets against the aortic root wall. However, these calcium deposits can impede the expansion of the device causing distortion of the valve stent and pericardial tissue leaflets. The objective of this study was to elucidate the impact of eccentric TAVR stent distortion on the dynamic deformation of the tissue leaflets of the prosthesis in vitro . Dual-camera stereophotogrammetry was used to measure the regional variation in strain in a leaflet of a TAVR deployed in nominal circular and eccentric (eccentricity index = 28%) orifices, representative of deployed TAVRs in vivo . It was observed that (i) eccentric stent distortion caused incorrect coaptation of the leaflets at peak diastole resulting in a ‘peel-back’ leaflet geometry that was not present in the circular valve and (ii) adverse bending of the leaflet, arising in the eccentric valve at peak diastole, caused significantly higher commissure strains compared with the circular valve in both normotensive and hypertensive pressure conditions (normotension: eccentric = 13.76 ± 2.04% versus circular = 11.77 ± 1.61%, p = 0.0014, hypertension: eccentric = 15.07 ± 1.13% versus circular = 13.56 ± 0.87%, p = 0.0042). This study reveals that eccentric distortion of a TAVR stent can have a considerable impact on dynamic leaflet deformation, inducing deleterious bending of the leaflet and increasing commissures strains, which might expedite leaflet structural failure compared to leaflets in a circular deployed valve.

Transcatheter Valve Underexpansion Limits Leaflet Durability: Implications for Valve-in-Valve Procedures

“…Sun et al 42 used FE analysis to investigate the effect of elliptical stent deployment on TAV leaflet stresses and strains, which they found to be significantly increased compared to those in the nominal cylindrical stent. These simulation results were later confirmed by in vitro results reported by Gunning et al 14 , in which elliptically deployed TAVs were shown to have increased leaflet strains compared to nominally deployed valves particularly in the commissural regions. Abbasi and Azadani 1 have shown that TAV leaflet stresses and strains increase at the commissures in the underexpanded configuration as well due to sharp bending through FE analysis.…”

“…TAV structural failures as early as 3 years after implantation have been cited 3, 17, 20 . Furthermore, it has been shown that poor leaflet coaptation 27, 45 will reduce the durability of bioprosthetic SAVs; thus, it follows that the durability of TAVs that exhibit poor leaflet coaptation as seen under non-optimal deployment conditions (elliptical, underexpanded, non-uniformly expanded) 14, 15, 43 , would be further reduced. Therefore, there is a critical need for more comprehensive studies on the long-term durability of TAV devices in various configurations to assess deployment strategies and provide insight for improved design.…”

Leaflet Kinematics of Mechanical and Bioprosthetic Aortic Valve Prostheses

“…Resolving the 3D leaflet motion would require 3D imaging and subsequent surface reconstruction. 32,33 This was beyond the scope of this work and may be topic of future investigations.…”

Bioprosthetic aortic valve durability in the era of transcatheter aortic valve implantation

“…However, this strategy may result in incomplete expansion of the transcatheter valves and thus some degree of valve leaflet—stent orifice mismatch 51. This may, in turn, cause pin-wheeling motion of leaflets during closure with ensuing increased mechanical stress 54.…”