Hydrodynamic Assessment of Explanted Degenerated Transcatheter Aortic Valves: Novel Insights Into Noncalcific and Calcific Mechanisms.

BACKGROUND: The etiology of transcatheter aortic valve (TAV) degeneration is poorly understood, particularly noncalcific mechanisms. OBJECTIVES: The authors sought to investigate noncalcific and calcific mechanisms of TAV degeneration and evaluate their impact on leaflet function by bench testing, imaging, and histology. METHODS: TAV explants were obtained from the EXPLANT THV registry and clinical institutions. Hydrodynamic assessment was performed using a heart valve pulse duplicator system under physiological conditions. Micro-computed tomography, high-resolution photography, high speed video, and hematoxylin and eosin staining were used to evaluate the morphological appearance, leaflet kinematics, and calcium burden of TAVs. RESULTS: A total of 14 explants were evaluated: 10 self-expanding CoreValve/Evolut TAVs (Medtronic), 3 balloon-expandable SAPIEN 3 TAVs (Edwards Lifesciences), and 1 mechanically expandable Lotus TAV (Boston Scientific). The median patient age at explantation was 73.0 years (Q1-Q3: 64.5-80.0 years), with a time to explantation of 4 years 1 month (1 year 5 months to 4 years 11 months). Six TAV explants were found to have leaflet calcification (162.4 mm3; 58.8-603.0 mm3), and 8 had no calcification detectable by micro-computed tomography and histology. All samples had impaired leaflet kinematics. There was no significant difference in the hydrodynamic mean gradient between calcified (47.2 mm Hg; 26.6-74.1 mm Hg) and noncalcified (27.6 mm Hg; 15.2-36.7 mm Hg; P = 0.28) TAVs. Leaflet calcification had a weak but nonsignificant association with the hydrodynamic mean gradient (r = 0.42; P = 0.14). CONCLUSIONS: TAV function can be severely impacted by noncalcific and calcific mechanisms of tissue degeneration. Importantly, functional stenosis can occur in TAVs in the absence of obvious and significant calcification.

Redo-TAVI with SAPIEN 3 in SAPIEN XT or SAPIEN 3 - impact of pre- and post-dilatation on final THV expansion.

BACKGROUND: When a balloon-expandable transcatheter heart valve (THV) is chosen to treat a failed balloon-expandable THV, there is a risk of underexpansion with a potential impact on performance. AIMS: We aimed to assess the impact of pre- and post-dilatation on the expansion of balloon-expandable THVs after redo-transcatheter aortic valve implantation (TAVI). METHODS: Redo-TAVI was performed on the bench with a 23 mm SAPIEN 3 (S3) implanted within a 23 mm SAPIEN XT (SXT) or a 23 mm S3, both of which served as the "failed" THVs. Pre- and/or post-dilatation was performed using a 23 mm non-compliant TRUE balloon. Expansion of the index and redo-THVs were assessed before and after pre-/post-dilatation using microcomputed tomography (micro-CT), and THV hydrodynamic testing was conducted. RESULTS: Without pre- or post-dilatation, the S3 was underexpanded, for all combinations, particularly in the mid-portion of the THV (18.6 mm and 19.7 mm representing 81% and 86% of the nominal diameter inside the SXT and S3, respectively). Pre- and post-dilatation had an additive effect on diameter expansion of the redo-THV, which remained constrained in most combinations. The only combination to achieve nominal expansion was the S3 in S3 when both pre- and post-dilatation were performed. The S3 remained underexpanded inside the SXT despite pre- and post-dilatation (93% in the mid-portion). Improved redo-THV expansion was accompanied by 2.7 mm (12%) overexpansion of the index THV. While all samples had acceptable hydrodynamic performance, the underexpanded samples had worse leaflet pinwheeling. CONCLUSIONS: When performing redo-TAVI with a 23 mm S3 inside a 23 mm SXT or S3, only the S3 in S3 with the use of pre- and post-dilatation reached full expansion. This underlines the importance of CT assessment of THV expansion and the role of pre-/post-dilatation.

Bioprosthetic Valve Remodeling in Nonfracturable Surgical Valves: Impact on THV Expansion and Hydrodynamic Performance.

BACKGROUND: There are limited data on the effect of bioprosthetic valve remodeling (BVR) on transcatheter heart valve (THV) expansion and function following valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) in a nonfracturable surgical heart valve (SHV). OBJECTIVES: This study sought to assess the impact of BVR of nonfracturable SHVs on THVs after VIV implantation. METHODS: VIV TAVR was performed using 23-mm SAPIEN3 (S3, Edwards Lifesciences) or 23/26-mm Evolut Pro (Medtronic) THVs implanted in 21/23-mm Trifecta (Abbott Structural Heart) and 21/23-mm Hancock (Medtronic) SHVs with BVR performed with a noncompliant TRUE balloon (Bard Peripheral Vascular Inc). Hydrodynamic assessment was performed, and multimodality imaging including micro-computed tomography was performed before and after BVR to assess THV and SHV expansion. RESULTS: BVR resulted in limited improvement of THV expansion. The largest gain in expansion was observed for the S3 in the 21-mm Trifecta with up to a 12.7% increase in expansion at the outflow of the valve. Minimal change was observed at the level of the sewing ring. The Hancock was less amenable to BVR with lower final expansion dimensions than the Trifecta. BVR also resulted in notable surgical post flaring of up to 17.6°, which was generally more marked with the S3 than with the Evolut Pro. Finally, BVR resulted in very limited improvement in hydrodynamic function. Severe pinwheeling was observed with the S3, which improved slightly but persisted despite BVR. CONCLUSIONS: When performing VIV TAVR inside a Trifecta and Hancock SHV, BVR had a limited impact on THV expansion and resulted in SHV post flaring with unknown consequences on coronary obstruction risk and long-term THV function.