Background: Transseptal access for large sheaths may be encumbered by tissue resistance against the sheath–dilator stepped interface. The ExpanSure Large Access Transseptal Dilator (Baylis Medical) is designed as a single introducer and dilation device with a smooth sheath–dilator transition to support transseptal puncture. It may facilitate ease and efficiency of interatrial crossing. Methods: This study experimentally evaluated the crossing force of ExpanSure relative to a conventional 8.5 F Swartz SL1 transseptal sheath and dilator in a benchtop septum model. Its ability to reduce the subsequent crossing force of a 14 F WATCHMAN delivery sheath was also tested. The clinical use of ExpanSure, including procedure time, was then validated in a series of left atrial appendage closure (LAAC) procedures. Results: In a benchtop septum model (N = 12), less peak force (1.90 ± 0.08 N vs. 2.36 ± 0.09 N; p <.001) and overall work (17.3 ± 1.2 mJ vs. 28.0 ± 1.9 mJ; p <.001) were required to advance ExpanSure relative to a conventional SL1 transseptal sheath and dilator system. Peak force (2.34 ± 0.24 N vs. 2.65 ± 0.21 N; p <.003) and overall work (28.5 ± 3.9 mJ vs. 35.4 ± 2.1 mJ; p <.001) to advance a WATCHMAN sheath were also significantly lower after using ExpanSure than after using a conventional transseptal system. In 19 LAAC procedures, ExpanSure crossed the septum smoothly and integrated readily, which enabled efficient procedure completion (mean total procedure time 37.6 ± 13.5 min), with 100% success and no procedure-related complications. Conclusion: Experimental force measurements, combined with early clinical experience using ExpanSure, suggest that the tapered design with smooth transition without dilator–sheath step-up and the larger diameter, both facilitated ease and efficiency of interatrial crossing.
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