Self-Expandable Prosthesis Valve Adaptation: Non-Uniform Expansion and Stent Frame Decoupling

The incidence of non-uniform expansion in the context of the self-expandable transcatheter heart valve (THV) is little investigated, along with stent-frame decoupling, which is a form of stent adaptation, in which the lower part of the THV stent conforms to both the ellipticity of the left ventricle outflow tract and the native annulus while maintaining the higher part of the valve more circular. We analyzed post-implant multi-detector computed tomography scans in 50 patients. Prosthesis non-uniform expansion was assessed by computing the prosthesis eccentricity on 6 prespecified levels: (1) frame inflow, (2) native annulus, (3) leaflet inflow, (4) prosthesis waist, (5) leaflet outflow, and (6) frame outflow. Stent-frame decoupling was assessed by comparing the mean eccentricity on 6 different prosthesis levels. Implantation depth, leaflet expansion and alignment, and residual anatomic sinus area ratios were also calculated. Subclinical leaflet thrombosis was defined as hypoattenuated lesion of a meniscal shape. At a 12-month follow-up, non-uniform expansion was consistently detected at each valvular level. Highest eccentricity was measured at the native annulus level (eccentricity: 0.54 ±  0.12), while the lowest index at the frame outflow level (0.23 ± 0.11). Similar results were observed in the subgroup analyses of sizes 23, 26, 29, and 34. Eccentricity significantly decreased from the annulus level to the prosthesis frame outflow (p <0.001). Notably, the incidence of mild-to-severe subclinical leaflet thrombosis was relevant (16%). In conclusion, prosthesis non-uniform expansion and stent frame decoupling frequently occur after self-expandable THV replacement. The clinical and hemodynamic implications remain uncertain.