Abstract Body (Do not enter title and authors here): BACKGROUND: The impact of hospital admission timing on outcomes in acute heart failure (AHF) remain unclear. Prior studies suggest that timing of hospital presentation may affect early management. This study aimed to determine whether admission timing was associated with differences in patient characteristics, acute management, and in-hospital outcomes for AHF.

METHODS: We conducted a retrospective analysis of the Canadian Heart Failure (CAN-HF) registry of hospitalized patients with AHF across multiple Canadian centers. We categorized patient presentation by admission timing: weekday vs weekend, and daytime (8am to 8pm) vs nighttime (8pm to 8am). Baseline patient characteristics and clinical presentation details were compared between timing groups. Emergency department (ED) treatment patterns and key in-hospital outcomes were assessed for differences based on admission timing.

RESULTS: Of 943 patients hospitalized with AHF, 21.6% were admitted on weekends and 28.6% during nighttime hours. Patients with weekend admissions were older (77.8 vs. 75.5 years, p = 0.03), had more chronic kidney disease (12.7% vs. 6.9%, p = 0.01), and presented more frequently with pulmonary congestion on imaging (72.1% vs. 64.8%, p = 0.05). ED treatment was more intensive during off-hours: weekend admissions received more IV diuretics (71.6% vs. 61.7%, p = 0.01) and non-invasive ventilation (9.3% vs. 4.6%, p = 0.01); nighttime admissions had higher use of IV nitrates (5.6% vs. 1.5%, p < 0.01) and non-invasive ventilation (9.3% vs. 4.2%, p < 0.01). There were no delays (> 6 hours) in cardiology consultation based on timing of presentation (p = 0.50 weekday vs weekend, p = 0.56 daytime vs nighttime). Median time to diuretics was shorter at night (185 vs. 224.5 minutes, p = 0.02), and trended towards significance after adjustment (Table 1); ED length of stay (LOS) was modestly shorter at night (10.5 vs. 11.0 hours, p = 0.04). Nighttime admission remained independently associated with shorter hospital stay while weekend admission did not impact LOS. Admission timing did not affect adjusted in-hospital mortality (Table 1).

CONCLUSION: Patients presenting during off-hours were more acute and required more intensive, expeditious therapies in the ED. However, key in-hospital outcomes did not differ by admission timing. These findings suggest that prompt delivery of HF therapy rather than timing of presentation may drive outcomes.