690 Acute post-implantation enlargement of transcatheter self-expandable valve: insights from a single-centre prospective registry

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Abstract Aims Transcatheter implantation of a balloon-expandable aortic valve is associated with an acute stent recoil . Conversely, the acute effects of nitinol-based stent frame- self expandable valve on post-deployment dimensions have not been reported. Accordingly, the aim of this study was to assess the occurrence and degree of acute prosthetic dimension changes after Evolute R valve implantation. Methods A total of 58 consecutive patients undergoing transcatheter aortic valve intervention (TAVI) with a widely used nitinol based self-expandable device (Evolute R, Medtronic, Minneapolis, USA) were included in this study. We measured valve diameters at three different sections: a) distal (aortic) level, b) central (annulus) level, and c) proximal (ventricular) level. Valve expansion was calculated as the difference between the diameters calculated immediately after valve deployment (A) and at the end of the procedure (B). The absolute and relative acute stent recoil 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, with baseline, as well as procedural characteristics. Results Final stent diameters were significantly higher compared to those achieved immediately after valve implantation in proximal (20.87±3.20 mm versus 20.37±3.27 mm, P <0.001), central (19.58±1.63 mm versus 19.12±1.75 mm, P <0.001) as well as distal (26.99±1.53 mm versus 26.41±1.57 mm, P <0.001) segments. The mean absolute and relative enlargement of the valve was respectively 0.50±0.51 mm and 2.48±2.57% in the proximal, 0.46±0.57 mm and 2.39±2.96% in the central and 0.58±0.59 mm and 2.14±2.14% in the distal segment. Among baseline and procedural characteristics assessed in the logistic regression model no association was observed between pre-dilation and valve expansion across all the segments (proximal: r2=0.004, P=0.885, central: r2=0.004, P=0.637, and distal r2=0.05, P=0.10). Of interest, post dilation affected only the expansion of the central segment (r2=0.241, P<0.001), while no association was observed for the proximal (r2=0.059, P=0.065) and distal (r2=0.0002, P=0.916) parts. The expansion of the proximal segment was associated with higher maximum/minimum diameter ratio measured by CT (r2=0.08, P=0.045), while no association was observed for the central (r2= 0.020; P=0.992) and distal (r2=1.111, P=0.683) segments. Conclusions This is the first study that documented a significant degree of post-deployment recoil of the Evolute R self-expandable valve, that was consistent across all the segments. The stent-valve expansion of the proximal segment was associated with a greater annulus dissymmetry reported by the maximum and minimum diameter ratio assessed by CT scan. 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.

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