(CCSP033) HYDRODYNAMIC ASSESSMENT OF EXPLANTED DEGENERATED TRANSCATHETER HEART VALVES: NOVEL INSIGHTS INTO NON-CALCIFIC VALVE DEGENERATION

Background: The aetiology of transcatheter heart valve (THV) degeneration is poorly understood. In this study, we sought to better understand calcific and non-calcific mechanisms of THV degeneration and their impact on leaflet kinematics and function by evaluating the in vitro hydrodynamic performance of explanted degenerated THVs. This work will be initially presented at EuroPCR (16-19 May 2023) as an E-poster.

METHODS AND RESULTS: Explanted THVs were obtained from the Explant THV registry (Vancouver, Canada) and Medtronic (Minneapolis, USA). The Explant THV registry is a multicentre, international registry of patients who underwent surgical device explantation for THV failure. In vitro hydrodynamic testing of explanted THVs was performed using a heart valve pulse duplicator system (HDTi-6000, BDC Laboratories, Wheat Ridge, USA) in accordance with ISO 5840-3:2021. Mean pressure gradient (mmHg) and effective orifice area (EOA) (cm2) were assessed. Hydrodynamic performance data of explanted THVs were compared to pre-explant echocardiographic data, if available. Additionally, THVs underwent multimodality imaging with high resolution photography, high speed video, and micro-computed tomography (CT).

A total of 14 explanted THVs were included in this study: 10 supra-annular, self-expanding CoreValve/Evolut (Medtronic, Minneapolis, USA), 3 intra-annular, balloon-expandable Sapien-3 (Edwards Life Sciences, Irvine, USA), and 1 intra-annular, mechanically expandable Lotus (Boston Scientific, Natick, USA) (Figure). Median time from initial TAVI to explant was 4 years and 2 months. In vitro gradients (mean ± SD) were 32.5 ± 19.9, 44.5 ± 28.8, and 75.6 mmHg for the CoreValve/Evolut, Sapien-3 and Lotus THVs, respectively. EOAs were 1.37 ± 0.55, 1.12 ± 0.40, and 0.73 cm2, respectively. There was no significant difference between in-vitro gradients and echo measurements (42.3 ± 24.5 vs 33.2 ± 21.7 mmHg, p=0.21), demonstrating good correlation of hydrodynamic testing with clinical echocardiograms. Six explanted THVs were found to have leaflet calcification (219.3 ± 220.7 mm3) and 8 THVs had no calcium burden by micro-CT quantification. There was no significant difference in mean gradient between calcified and non-calcified THVs (47.5 vs 31.2 mmHg, p=0.23). Observed burden of leaflet calcification correlated poorly with an increased hydrodynamic mean gradient, (r=0.47, p=0.09).

Conclusion: Leaflet function and performance can be severely impacted by both calcific and non-calcific mechanisms of THV degeneration. Importantly, functional stenosis can occur in THVs in the absence of obvious and significant leaflet calcification. As TAVI shifts into lower-risk patients, identification and management of causes of THV failure will be crucial, particularly in patients who will require repeat THV procedures.