Background/Objectives: The “weekend effect,” characterized by increased mortality and complication rates for weekend hospital admissions, is well documented in myocardial infarction and stroke but has been less thoroughly investigated in acute decompensated heart failure (ADHF). This study evaluates the weekend effect in ADHF using a national cohort. Methods: A retrospective cohort study was conducted using the 2016–2020 Nationwide Inpatient Sample (NIS). Adult ADHF admissions were identified by ICD-10 codes and classified as weekend or weekday admissions. Over 30 variables, including age, sex, and comorbidities, were analyzed. Propensity score matching (1:1) yielded 489,204 patients per group. Univariate and multivariate logistic regression models were used to assess outcomes, adjusting for key covariates. Results: Of 2,131,915 ADHF hospitalizations, 501,076 (23.5%) occurred on weekends. The cohort was 48% female, with a mean age of 72 years (SD ± 12.3). After 1:1 matching, weekend admissions had higher odds of cardiac arrest (aOR: 1.10; 95% CI: 1.06–1.13, p < 0.001), inpatient mortality (aOR: 1.07; 95% CI: 1.05–1.09, p < 0.001), acute kidney injury (AKI; aOR: 1.07; 95% CI: 1.06–1.08, p < 0.001), and acute respiratory failure (ARF; aOR: 1.28; 95% CI: 1.27–1.30, p < 0.001). No significant differences were observed in mechanical circulatory support (MCS) use or length of stay. Conclusions: Weekend ADHF admissions were associated with a higher risk of mortality and complications, which may be attributable to reduced specialist availability or delayed diagnostics. These findings underscore the need for standardized ADHF protocols to ensure equitable care throughout the week.

Background: Sepsis-associated cardiac dysfunction has historically been characterized as predominantly systolic, yet the burden of heart failure with the preserved ejection fraction (HFpEF) phenotype among patients with heart failure (HF) first documented during sepsis remains poorly defined. Methods: In a single-center retrospective cohort of adults (≥18 years) admitted to a tertiary-care hospital between 1 January 2022 and 31 December 2024, we identified patients whose first sepsis diagnosis (ICD-10) coincided with their first HF diagnosis (ICD-10 I50.x) during the same encounter, with no prior HF in the EHR. Patients were classified by ICD-10 subtype as HFpEF, HFrEF, combined, or unspecified; the unspecified group underwent echocardiographic reclassification when LVEF was documented. Demographics, selected comorbidities, peak inflammatory markers, and unadjusted in-hospital and subsequent-encounter outcomes were compared between HFpEF and HFrEF. Results: Of 924 patients with HF first documented during sepsis, 438 (47.4%) were ICD-10–coded HFpEF and 405 (43.8%) HFrEF. HFpEF patients were older (74.0 vs. 69.2 years; p < 0.001) and more often female (53.0% vs. 37.0%; p < 0.001), with higher prevalence of COPD exacerbation (21.5% vs. 13.1%; p = 0.004) and hypothyroidism (26.3% vs. 17.5%; p = 0.034). HFrEF patients exhibited higher peak lactate (2.88 vs. 2.48 mmol/L; p = 0.009) and procalcitonin (8.52 vs. 7.24 ng/mL; p = 0.011). Unadjusted in-hospital mortality (28.1% vs. 27.7%; p = 0.95), ICU admission (75.8% vs. 74.8%; p = 0.80), and length of stay did not differ. Subsequent encounters were descriptively more frequent after HFpEF (11.0% vs. 6.2%). Conclusions: ICD-10–coded HFpEF and HFrEF occurred at nearly equal frequency among adults with HF first documented during sepsis, challenging the systolic-centric paradigm. Despite distinct demographic and biochemical profiles, unadjusted in-hospital outcomes did not differ. These descriptive findings, limited by administrative-coding-based phenotype classification, the absence of multivariable adjustment, and unmeasured sepsis-severity and comorbidity variables, are hypothesis-generating and support phenotype-aware prospective study of HF arising during sepsis.