Background: The REDUCE LAP-HF II (Reduce Elevated Left Atrial Pressure in Patients With Heart Failure II) trial found that, compared with a sham procedure, the Corvia Atrial Shunt did not improve outcomes in heart failure with preserved or mildly reduced ejection fraction. However, after 12-month follow-up, "responders" (peak-exercise pulmonary vascular resistance <1.74 WU and absence of a cardiac rhythm management device) were identified., Objectives: This study sought to determine: 1) the overall efficacy and safety of the atrial shunt vs sham control after 2 years of follow-up; and 2) whether the benefits of atrial shunting are sustained in responders during longer-term follow-up or are offset by adverse effects of the shunt., Methods: The study analyzed 2-year outcomes in the overall REDUCE LAP-HF II trial, as well as in responder and nonresponder subgroups. The primary endpoint was a hierarchical composite of cardiovascular death or nonfatal ischemic/embolic stroke, total heart failure events, and change in health status., Results: In 621 randomized patients, there was no difference between the shunt (n = 309) and sham (n = 312) groups in the primary endpoint (win ratio: 1.01 [95% CI: 0.82-1.24]) or its individual components at 2 years. Shunt patency at 24 months was 98% in shunt-treated patients. Cardiovascular mortality and nonfatal ischemic stroke were not different between the groups; however, major adverse cardiac events were more common in those patients assigned to the shunt compared with sham (6.9% vs 2.7%; P = 0.018). More patients randomized to the shunt had an increase in right ventricular volume of ≥30% compared with the sham control (39% vs 28%, respectively; P < 0.001), but right ventricular dysfunction was uncommon and not different between the treatment groups. In responders (n = 313), the shunt was superior to sham (win ratio: 1.36 [95% CI: 1.02-1.83]; P = 0.037, with 51% fewer HF events [incidence rate ratio: 0.49 [95% CI: 0.25-0.95]; P = 0.034]). In nonresponders (n = 265), atrial shunting was inferior to sham (win ratio: 0.73 [95% CI: 0.54-0.98])., Conclusions: At 2 years of follow-up in REDUCE LAP-HF II, there was no difference in efficacy between the atrial shunt and sham groups in the overall trial group. The potential clinical benefit identified in the responder group after 1 and 2 years of follow-up is currently being evaluated in the RESPONDER-HF (Re-Evaluation of the Corvia Atrial Shunt Device in a Precision Medicine Trial to Determine Efficacy in Mildly Reduced or Preserved Ejection Fraction Heart Failure) trial. (Reduce Elevated Left Atrial Pressure in Patients With Heart Failure II [REDUCE LAP-HF II]; NCT03088033)., Competing Interests: Funding Support and Author Disclosures The REDUCE LAP-HF II trial was funded by Corvia Medical, Inc. Dr Gustafsson has served as an unpaid advisor to Corvia; has received consulting fees from Bayer, AstraZeneca, Abbott, Ionis, Alnylam, Pfizer, FineHeart, CorWave, and AdjuCor; and has received speaker fees from Novartis. Dr Petrie has received research funding from Boehringer Ingelheim, Roche, SQ Innovations, AstraZeneca, Novartis, Novo Nordisk, Medtronic, Boston Scientific, and Pharmacosmos; and has served as a consultant and on trial committees for Akero, Applied Therapeutics, AnaCardio, Biosensors, Boehringer Ingelheim, Novartis, AstraZeneca, Novo Nordisk, Abbvie, Bayer, Horizon Therapeutics, Takeda, Cardiorentis, Pharmacosmos, Siemens, Lilly, Vifor, New Amsterdam, Moderna, and Teikoku. Dr Komtebedde is an employee of Corvia Medical, Inc. Dr Borlaug has received research support from the National Institutes of Health, and the U.S. Department of Defense; has received research grants from AstraZeneca, Axon, GlaxoSmithKline, Medtronic, Mesoblast, Novo Nordisk, Rivus, and Tenax Therapeutics; has served as a consultant for Actelion, Amgen, Aria, Axon Therapies, BD, Boehringer Ingelheim, Cytokinetics, Edwards Lifesciences, Eli Lilly, Imbria, Janssen, Merck, Novo Nordisk, NGM, NXT, and VADovations; and is a named inventor (US Patent number 10,307,179) for the tools and approach for a minimally invasive pericardial modification procedure to treat heart failure. Dr Mohan has received research funds paid to his institution from Corvia, Alleviant Medical, and V-Wave; has received consulting fees from Corvia, Alleviant Medical, AstraZeneca, Pfizer, and Boston Scientific, and has received speaker honoraria from Bristol-Myers Squibb, Pfizer, and AstraZeneca. Dr Sverdlov has received support from the National Heart Foundation of Australia Future Leader Fellowship (Award ID 106025); has received research grants from the Department of Health and Aged Care (Australia) Medical Research Future Fund (MRF2017053), New South Wales (NSW) Health (Australia), AstraZeneca, Novartis, Biotronik, RACE Oncology, Bristol-Myers Squibb, Roche Diagnostics, and Vifor; and has received personal fees from Novartis, Bayer, Bristol-Myers Squibb, AstraZeneca, Janssen, and Boehringer Ingelheim. Dr Chung has received consulting fees from Abbott, Medtronic, InterShunt, Cardionomic, EBR, CVRx, LivaNova; and has served on the Speakers Bureau for Boehringer Ingelheim. Dr Lurz has received institutional fees and research grants from Abbott Vascular, Edwards Lifesciences, and ReCor; has received honoraria from Edwards Lifesciences, Abbott Medical, Innoventric, ReCor; and Boehringer Ingelheim; and has held stock options with Innoventric. Dr Cikes has received investigator-initiated research grants to her institution from Novartis, Abbott, and Pfizer; has received clinical study contracts for her institution from Novo Nordisk and Corvia; and has served in an advisory role and received speaker honoraria and/or travel grants from Abbott, Abiomed, Amgen, Amicus Therapeutics, AstraZeneca, Bayer, Boehringer Ingelheim, GE Healthcare, Livanova, Krka Pharma, Novartis, Novo Nordisk, Pfizer, Pulsify Medical, Roche, Swixx, Takeda, Teva Pharmaceutical Industries, and Viatris. Dr Shah has received grant support from the National Heart, Lung and Blood Institute (grants U54 HL160273, R01 HL107577, R01 HL127028, R01 HL140731, and R01 HL149423), AstraZeneca, Corvia, and Pfizer; and has received consulting fees from Abbott, Alleviant, AstraZeneca, Amgen, Aria CV, Axon Therapies, Bayer, Boehringer Ingelheim, Boston Scientific, Bristol-Myers Squibb, Cyclerion, Cytokinetics, Edwards Lifesciences, Eidos, Imara, Impulse Dynamics, Intellia, Ionis, Lilly, Merck, MyoKardia, Novartis, Novo Nordisk, Pfizer, Prothena, ReCor, Regeneron, Rivus, Sardocor, Shifamed, Tenax, Tenaya, and Ultromics. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)