A low implant depth for balloon-expandable Sapien 3 valves in failed self-expanding Evolut valves could help facilitate future coronary access, new in vitro results suggest. The study – funded by Evolut manufacturer Medtronic – was published Monday online ahead of the Feb. 28 issue of JACC: Cardiovascular Interventions, led by Mariama Akodad, MD, from the University of British Columbia and Cardiovascular Translational Laboratory, Vancouver. Transcatheter heart valves (THVs) like Evolut have the potential to fail due to structural valve deterioration, requiring repeat intervention through surgical aortic valve replacement (SAVR) or redo transcatheter aortic valve replacement (TAVR). Although redo TAVR has emerged as a safe option, the optimal THV design and implantation technique have remained poorly understood, the researchers said. What is known is that the leaflets of the failed THV could create a “tube graft,” jailing the index THV leaflets between the two THV frames and creating a neoskirt of tissue from the failed device’s inflow to the top of the jailed leaflet, “which may limit subsequent coronary access and flow,” the authors wrote. Yet the entire leaflet of the index THV may not be fully entrapped between the two THVs “depending on the frame height and position of the second THV,” the researchers said. This could have important technical implications on neoskirt height and leaflet overhang of the Evolut THV with redo TAVR using a shorter valve frame, the researchers noted. “With a shorter neoskirt height and a greater degree of leaflet overhang, there may be a higher success rates of coronary access though the Evolut THV frame,” they hypothesized. The researchers, therefore, set out to run “bench testing” – in vitro studies performed under physiological test conditions with no human or animal participants – using the self-expanding Evolut R THV as the index valve and a Sapien 3 (Edwards Lifesciences) balloon-expandable valve placed at various positions in the original valve to determine the effect on THV expansion, neoskirt height changes, leaflet overhang and hydrodynamic performance. Sapien 3 THVs of 20-mm, 23-mm, 26-mm and 29-mm sizes were deployed within 23-mm, 26-mm 29-mm and 34-mm Evolut R devices, respectively. The Sapien 3 outflow was positioned at various depths to align at node 4, 5 and 6 of the Evolut R. Multimodality imaging was performed, including fluoroscopy and high-resolution photography using a digital microscope for each THV and each implantation configuration. The neoskirt height was defined as the distance between the Evolut R inflow and the pinned leaflet free edge height of the index THC at the Sapien 3’s outflow. The HDT-500 heart valve pulse duplicator test system (BDC Laboratories) was used to assess hydrodynamic performance for all redo TAVR configurations, with the index Evolut R placed in a silicone holder. Sapien 3 devices implanted within the Evolut R resulted in neoskirt heights between 16.3 mm and 27 mm. The researchers found that the neoskirt height for the Evolut R was shorter when the Sapien 3 outflow was positioned at node 4 versus node 6, while higher neoskirt heights were seen in node 6 implantation positions (node 4 height for 23 mm = 16.3 mm, 26 mm = 17.1 mm, 29 mm = 18.3 mm, and 34 mm = 19.9 mm versus node 6 height for 23 mm = 23.9 mm, 26 mm = 23.4 mm, 29 mm = 24.7 mm, and 34 mm = 27 mm Evolut R). “A lower implant position with the [Sapien 3] outflow at node 4 can reduce the neoskirt height by as much as 7.6 mm compared with node 6 position,” said the researchers. Bar one, all configurations still exhibited acceptable hydrodynamic performance irrespective of the degree of leaflet overhang. Only the 29-mm Sapien 3 implanted in 34-mm Evolut R at node 4 led to a regurgitant fraction over 20% (26.4% ± 1.2%), the researchers said. For this configuration, there was minimal overlap of the paravalvular leak skirt feature of the Sapien 3 and the Evolut THV inflow resulted in higher inter-THV leakage. The risk of Sapien 3 migration was also low at all implantation depths and test configurations, with no significant movement seen after cycling each test configuration assembly at a 155-mmHg hypertensive back pressure condition for 15 minutes. “Although the original index THV implant depth has to be considered, we found that lower implantation of a short frame THV within an Evolut resulted in a reduction in the neoskirt height, which mitigates the risk of coronary obstruction and facilitates future coronary access,” said the researchers. And despite lower Sapien 3 implant positions being associated with a higher degree of leaflet overhang of the index THV, “the lower position did not impact [Sapien 3] valve function for all but 1 tested valve configuration ([Sapien 3 29mm outflow aligned to node 4 of the Evolut 34 mm).” A low Sapien 3 implant depth may, therefore, help facilitate future coronary access after redo TAVR, the researchers concluded. The long-term implications of redo TAVR on THV performance and durability, plus the feasibility of coronary access after redo TAVR, will be assessed in clinical studies, they added. In an accompanying editorial, University Hospital of Geneva’s Sarah Mauler-Wittwer, MD, and Stephane Noble, MD, stressed the importance of studies into studies into TAV-in-TAV studies given the anticipated rise of degenerated THVs as younger and lower risk patients are increasingly treated, “who may well outlive their valves.” “THV surgical explantation will remain the preferred treatment option in patients with endocarditis and in those with unfavorable anatomy for TAV-in-TAV,” said the editorialists. “Ultimately, research and development teams should design dedicated devices for TAV-in-TAV in order to secure access to the coronary arteries.” Sources: Akodad M, Sellers S, Landes U, et al. Balloon-Expandable Valve for Treatment of Evolut Valve Failure: Implications on Neoskirt Height and Leaflet Overhang. JACC Cardiovasc Interv 2022;15:368-377. Mauler-Wittwer S, Noble S. Where Are We Now With TAV-in-TAV? JACC Cardiovasc Interv 2022;15:378-380. 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