Impact of implant depth on hydrodynamic function with the ACURATE neo transcatheter heart valve following valve-in-valve transcatheter aortic valve replacement in Mitroflow bioprosthetic valves: an ex vivo bench study

Aims: We aimed to assess the impact of implant depth on hydrodynamic function following valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) using the ACURATE neo transcatheter heart valve (THV) through an ex vivo bench study.Methods and results: Multiple implantation depths were tested at incremental depths of 2 mm using a small size ACURATE neo valve for VIV TAVR in 19 mm, 21 mm, 23 mm, and 25 mm Mitroflow bioprosthetic valves. Multimodality imaging and hydrodynamic evaluation was performed at each implantation depth. A low implantation was associated with higher transvalvular gradients. The highest transvalvular gradient was observed at -10 mm depth for 19 mm (40.00 +/- 0.5 mmHg), -8 mm for 21 mm (15.31 +/- 0.2 mmHg), -6 mm for 23 mm (14.7 +/- 02.3 mmHg) and -8 mm for 25 mm (8.41 +/- 0.2 mmHg) surgical valves. The lowest transvalvular gradient was observed at 0 mm depth for the 19 mm (14.91 +/- 0.2 mmHg)/21 mm (7.2 +/- 0.1 mmHg), and +2 mm depth for the 23 mm (5.7 +/- 0.1 mmHg)/25 mm (5.81-0.1 mmHg) surgical valves. At low implantation depth, there was worse leaflet pin-wheeling and also evidence of interaction of THV leaflets with those of the surgical valve that impaired leaflet coaptation, resulting in a high regurgitant fraction (42.5% in the 21 mm and 83.3% in the 23 mm surgical valve at -10 mm depths).Conclusions: A high implant is desirable to facilitate favourable hydrodynamic function when performing VIV TAVR using the ACURATE neo THV for Mitroflow aortic bioprostheses sized +/- 25 mm. In a 19 mm Mitroflow valve, positioning the upper crown of the ACURATE neo THV above the posts of the surgical valve is desirable to facilitate favourable transvalvular gradients. Low implantation results in higher transvalvular gradients and worse pin-wheeling, and THV leaflet dysfunction can be severe due to interaction with the surgical valve