Navitor valve implantation for double-track LVOT calcification: mechanistic insight into paravalvular leak suppression

An 87-year-old man with symptomatic severe aortic stenosis was planned for transcatheter aortic valve replacement. Computed tomography (CT) revealed an annulus area of 364 mm2, double-track left ventricular outflow tract (LVOT) calcification, circumferential calcification of the sinotubular junction, and a membranous septum measuring 5.0 mm (Panels A–D and Supplementary material online, Video S1). Both external iliac arteries were narrowed (4.1 mm) with soft plaques, and the cervical and subclavian arteries also showed stenoses. Considering the risks of annulus rupture and paravalvular leakage (PVL) through the gap between the calcific nodules,1 Navitor Vision (Abbott Vascular, Santa Clara, CA, USA) was selected. After aortic valvuloplasty with an 18-mm Inoue balloon (Toray Industries, Tokyo), a 25-mm Navitor valve was deployed with a planned depth of 5 mm below the annulus, aligning the upper portion of the Naviseal cuff (6–9 mm above the inflow edge) with the anticipated sealing zone 2–3 mm above the annulus. Aortography and echocardiography revealed trivial PVL (Panels E and F, Supplementary material online, Videos S2 and S3). Post-procedural CT showed elliptical and mildly non-uniform expansion of the Navitor frame, with relatively wider strut spacing on the left atrial side. Calcified masses became partially embedded within the stent cells, effectively smoothing the irregular sealing surface and contributing to improved mechanical apposition (Panels G–J and Supplementary material online, Videos S4 and S5). In a 25-mm Navitor valve, the frame circumference corresponds to ∼25 × π mm and is divided into nine stent cells; therefore, the inter-strut spacing in the unconstrained state is ∼8.7 mm. The Naviseal, located between the lowest stent cells in an inverted-triangular configuration, expands by only about 1.5 mm when pulled ex vivo with forceps (Panel K). Inter-strut spacing typically decreases after deployment as the valve frame conforms to the annulus, allowing outward Naviseal expansion to contribute to sealing (Panel L and Supplementary material online, Video S6). However, in the present case, maximal inter-strut spacing of 8.7 mm persisted on the left atrial side, suggesting that Naviseal expansion alone was unlikely to account for PVL reduction. Taken together, these findings suggest that PVL reduction was achieved predominantly through frame conformability and mechanical interlocking of calcifications within the stent cells rather than through active gap filling by Naviseal expansion between LVOT calcifications. Double-track LVOT calcification often leads to PVL due to gaps between calcified nodules.1 However, the Navitor Vision valve, with relatively wide cell architecture and favourable frame conformability, may accommodate protruding calcifications while the Naviseal provides additional supra-annular sealing, thereby reducing PVL even in challenging anatomies. These findings suggest that careful depth control and frame conformability of the Navitor valve may offer a practical strategy to mitigate PVL in anatomies with complex LVOT calcification. Supplementary material is available at European Heart Journal – Case Reports online. Aoi Omori (Writing—review & editing [supporting]), Tomohiko Taniguchi (Writing—review & editing [supporting]), and Yutaka Furukawa (Writing—review & editing [supporting]) Consent: The authors confirm that written consent for submission and publication of this case report has been obtained from the patient in line with COPE guidance. None declared. The data underlying this article are available in the article and its online Supplementary material. Further inquiries can be shared on reasonable request to the corresponding author.