Background: Although some patients with heart failure (HF) with mildly reduced/preserved ejection fraction have low natriuretic peptide levels, there are no large-scale systematic studies of how common these individuals are or what happens to them., Objectives: The purpose of this study was to examine the proportion of patients in the I-PRESERVE (Irbesartan in Heart Failure with Preserved Ejection Fraction) trial with an N-terminal pro-B-type natriuretic peptide (NT-proBNP) level <125 pg/mL, their clinical characteristics, and outcomes., Methods: I- PRESERVE enrolled patients with symptomatic HF and a LVEF ≥45% but who did not have NT-proBNP or body mass index inclusion/exclusion criteria. Baseline NT-proBNP was measured after enrollment but not reported to investigators. The primary outcome in this analysis was the composite of cardiovascular death or HF hospitalization., Results: Overall, 808 of 3,480 patients (23.2%) had NT-proBNP <125 pg/mL. Patients with a low NT-proBNP were younger (68.6 years vs 72.6 years; P < 0.001), were less often men (36.1% vs 40.9%; P = 0.015), and had a higher body mass index (48.4% vs 38.7% obese; P < 0.001) than those with a higher NT-proBNP level. Patients with a low NT-proBNP had less atrial fibrillation (8.5% vs 35.1%; P < 0.001), myocardial infarction, diabetes, chronic obstructive pulmonary disease, and anemia but better kidney function. Patients with a lower NT-proBNP level had less marked echocardiographic abnormalities and were less likely to experience cardiovascular death or HF hospitalization; adjusted HR: 0.35 (95% CI: 0.27-0.46; P < 0.001). However, health status was similarly impaired in patients with lower and higher NT-proBNP levels (median Minnesota Living with Heart Failure Questionnaire 43 vs 43; P = 0.95)., Conclusions: Almost one-quarter of patients with HF with mildly reduced/preserved ejection fraction had a low NT-proBNP level. Although these patients have a favorable prognosis, compared to those with a high NT-proBNP level, they have similarly impaired health status which should be a target for treatment. (Irbesartan in Heart Failure With Preserved Systolic Function [I- PRESERVE]; NCT00095238)., Competing Interests: Funding Support and Author Disclosures Dr Kondo has received speaker fees from Abbott, Ono Pharma, Otsuka Pharma, Novartis, AstraZeneca, Bristol Myers Squibb, Boehringer Ingelheim, and Abiomed. Dr Jhund has received speaker fees from AstraZeneca, Novartis, Alkem Metabolics, ProAdWise Communications, Sun Pharmaceuticals, and Intas Pharmaceuticals; has received advisory board fees from AstraZeneca, Boehringer Ingelheim, and Novartis; has received research funding from AstraZeneca, Boehringer Ingelheim, and Analog Devices Inc; his employer, the University of Glasgow, has been remunerated for clinical trial work from AstraZeneca, Bayer AG, Novartis, and Novo Nordisk; and he is a Director of Global Clinical Trial Partners. Drs Jhund and McMurray are supported by a British Heart Foundation Centre of Research Excellence Grant RE/18/6/34217 and the Vera Melrose Heart Failure Research Fund. Dr Anand has received consulting fees from Amgen, ARCA Pharma, AstraZeneca, Boehringer Ingelheim, Boston Scientific, LivaNova, and Novartis. Dr Carson has received honoraria as a CEC member from Novartis. Dr Lam is supported by a Clinician Scientist Award from the National Medical Research Council of Singapore; has received research support from Novo Nordisk and Roche Diagnostics; has served as consultant or on the Advisory Board/Steering Committee/Executive Committee for Alleviant Medical, Allysta Pharma, Amgen, AnaCardio AB, Applied Therapeutics, AstraZeneca, Bayer, Boehringer Ingelheim, Boston Scientific, CardioRenal, Cytokinetics, Darma Inc, EchoNous Inc, Eli Lilly, Impulse Dynamics, Intellia Therapeutics, Ionis Pharmaceutical, Janssen Research and Development LLC, Medscape/WebMD Global LLC, Merck, Novartis, Novo Nordisk, Prosciento Inc, Quidel Corporation, Radcliffe Group Ltd, Recardio Inc, ReCor Medical, Roche Diagnostics, Sanofi, Siemens Healthcare Diagnostics, and Us2.ai; and serves as cofounder and non-executive director of Us2.ai. Dr Shah has received either personal or institutional research support from AstraZeneca. Dr Vadagunathan has received research grant support, served on advisory boards, or had speaker engagements with American Regent, Amgen, AstraZeneca, Bayer AG, Baxter Healthcare, Boehringer Ingelheim, Chiesi, Cytokinetics, Lexicon Pharmaceuticals, Merck, Novartis, Novo Nordisk, Pharmacosmos, Relypsa, Roche Diagnostics, Sanofi, and Tricog Health; and participates on clinical trial committees for studies sponsored by AstraZeneca, Galmed, Novartis, Bayer AG, Occlutech, and Impulse Dynamics. Dr Zannad has received consulting fees from Amgen, Applied Therapeutics, AstraZeneca, Bayer, Boehringer Ingelheim, Cardior, Cereno Scientific, Cellprothera, CEVA, CVRx, Merck, Novartis, Servier, and Vifor-Pharma; and has been a founder of CardioRenal and CVCT. Dr Zile reports research funding from Novartis; and has been a consultant for Novartis, Abbott, Boston Scientific, CVRx, EBR, Endotronics, Ironwood, Merck, Medtronic, and Myokardia V Wave. Dr Solomon has received research grants from Actelion, Alnylam, Amgen, AstraZeneca, Bellerophon, Bayer, Bristol Myers Squibb, Celladon, Cytokinetics, Eidos, Gilead, GlaxoSmithKline, Ionis, Lilly, Mesoblast, MyoKardia, National Institutes of Health/National Heart, Lung, and Blood Institute, Neurotronik, Novartis, Novo Nordisk, Respicardia, Sanofi Pasteur, Theracos, and US2.AI; and has consulted for Abbott, Action, Akros, Alnylam, Amgen, Arena, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Cardior, Cardurion, Corvia, Cytokinetics, Daiichi Sankyo, GlaxoSmithKline, Lilly, Merck, Myokardia, Novartis, Roche, Theracos, Quantum Genomics, Cardurion, Janssen, Cardiac Dimensions, Tenaya, Sanofi-Pasteur, Dinaqor, Tremeau, CellPro-Thera, Moderna, American Regent, and Sarepta. Dr McMurray has received payments through Glasgow University for work on clinical trials, consulting, and other activities from Amgen, AstraZeneca, Bayer, Cardurion, Cytokinetics, GlaxoSmithKline, KBP Biosciences, and Novartis; has received personal consultancy fees from: Alnylam Pharma, Bayer, Bristol Myers Squibb, George Clinical PTY Ltd, Ionis Pharma, Novartis, Regeneron Pharma, and River 2 Renal Corporation; has received personal lecture fees from Abbott, Alkem Metabolics, AstraZeneca, Blue Ocean Scientific Solutions Ltd, Boehringer Ingelheim, Canadian Medical and Surgical Knowledge, Emcure Pharma. Ltd, Eris Lifesciences, European Academy of CME, Hikma Pharmaceuticals, Imagica health, Intas Pharma, J.B. Chemicals and Pharma. Ltd, Lupin Pharma, Medscape/Heart.Org, ProAdWise Communications, Radcliffe Cardiology, Sun Pharma., The Corpus, Translation Research Group, and Translational Medicine Academy; and is a Director of Global Clinical Trial Partners., (Copyright © 2024 The Authors. 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