Acute expansion of nitinol-based self-expandable device in patients undergoing transfemoral aortic valve implantation

Background The acute adaptation of the nitinol-based stent frame self expandable valve to the aortic root after deployment is poorly understood. Accordingly, this study aimed to assess the occurrence, degree and determinants of acute adaptation of the nitinol-based stent frame self-expandable valves after implantation. Methods This is a single-site prospective registry including patients undergoing transcatheter aortic valve replacement (TAVR) with a widely used second-generation nitinol-based self-expandable device (Evolut R, Medtronic, Minneapolis, Minnesota, USA). We measured valve diameters at three different sections: distal (aortic) level, central (annulus) level and proximal (ventricular) level. Valve expansion was estimated by the difference between the diameters calculated immediately after valve deployment (A) and at the end of the procedure (B). The absolute and relative stent changes were defined as B-A and (B-A)/B∗100, respectively. A linear regression model was performed to test the association between the degree of valve extension at each segment with baseline and procedural characteristics. Results A total of 58 consecutive TAVR patients were included in this analysis, with a mean age of 82.12 ± 5.28 years. Out of the total, 46% of the patients had chronic kidney disease, 32% had diabetes and 76% had dyslipidaemia. The mean procedural time was 28.11 ± 11.6 min, with 53.45% of predilation. Postdilation was performed only in 3.5% of patients. Final stent diameters were significantly higher than those achieved immediately after valve implantation – an observation that was consistent for all the segments: 0.50 ± 0.51 mm and 2.48 ± 2.57% (P < 0.01) in the proximal, 0.46 ± 0.57 mm and 2.39 ± 2.96% (P < 0.01) in the central, as well as 0.58 ± 0.59 mm and 2.14 ± 2.14% (P < 0.01) at the distal segments. Postdilation significantly affected the expansion of the central segment, and, albeit not significantly, the proximal one, while no changes were observed for the distal portion of the platform. Conclusion This is the first study to have documented a significant degree of the Evolut R self-expandable valve expansion after deployment. However, further studies are required to assess the short- and long-term time course of self-expandable valve enlargement and the clinical relevance of this finding.