A single-center cohort study was conducted using a retrospective analysis of prospectively collected data. Adult patients consecutively admitted to a cardiovascular specialty hospital with a primary diagnosis of AHF (acute or acute-on-chronic) between January 2015 and January 2020 were included. The diagnosis was independently confirmed by 2 HF specialist cardiologists based on clinical history, physical examination, and complementary studies. Patients with AHF secondary to acute myocardial infarction, severe sepsis, or pulmonary thromboembolism, as well as those in LCOS or CS at the time of hospital admission, were excluded.

The primary endpoint of the study was the occurrence of LCOS or CS, defined as stages C to E of the SCAI classification.

The secondary endpoint was all-cause in-hospital mortality.

Data were prospectively collected from the hospital’s electronic health records and manually reviewed in the clinical histories. Initial demographic data, comorbidities, physical examination findings at admission, clinical presentation type, previous medical treatment, implemented therapy, and clinical outcomes were recorded in a dedicated institutional database. Laboratory values were assessed at admission. Echocardiographic data were evaluated from echocardiograms performed within 3 months before hospitalization. Functional class before admission was assessed as part of the patient history in those with HF.

Patients were categorized using the SCAI classification for CS based on the consensus statement at the time of admission and subsequently during hospitalization, with the most advanced stage during their clinical course recorded in the database:

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  Stage A (“At risk”) : Patients without current signs or symptoms of CS but at risk of developing it. This includes patients with large acute myocardial infarctions or previous myocardial infarctions and/or HF symptoms.

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  Stage B (“Beginning”) : Patients with clinical evidence of relative hypotension or tachycardia without hypoperfusion.

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  Stage C (“Classic”) : Patients with hypoperfusion requiring initial interventions (inotropes, vasopressors, mechanical support, or extracorporeal membrane oxygenation [ECMO]) beyond volume resuscitation to restore perfusion.

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  Stage D (“Deteriorating”) : Patients who fail to stabilize despite initial intensive efforts, requiring further escalation. Classification in this stage requires adequate previous medical treatment/stabilization. At least one hour must have elapsed without resolution of hypotension or target organ hypoperfusion.

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  Stage E (“Extremis”) : Patients in circulatory collapse, often with refractory cardiac arrest requiring ongoing cardiopulmonary resuscitation (CPR) or supported by multiple acute simultaneous interventions, including ECMO-facilitated CPR (eCPR).

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  Age and sex: Patient age at the time of admission was recorded in years, and sex was classified as male or female.

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  Cardiovascular risk factors: Included hypertension (HTN), diabetes mellitus, dyslipidemia, and body mass index (BMI).

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  Cardiovascular history: Documented the presence of coronary artery disease (history of coronary angioplasty or coronary artery bypass surgery), cerebrovascular accident (CVA) or transient ischemic attack, and peripheral vascular disease (e.g., peripheral angioplasty or surgeries).

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  Systolic and diastolic blood pressure at admission: Continuous variables, expressed in mmHg.

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  Creatinine clearance (CrCl): Calculated using the Cockcroft-Gault formula, categorized as ≥60 ml/min/m² or <60 ml/min/m².

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  Left ventricular ejection fraction (LVEF): Assessed via echocardiography, categorized as ≥40% or <40%.

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  Tricuspid annular plane systolic excursion (TAPSE): An echocardiographic measure of right ventricular systolic function, categorized as ≥18 mm or <18 mm.

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  Previous hospitalizations for HF: Categorical (yes/no).

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  HF etiology: Classified as coronary artery disease, hypertension, valvular disease, idiopathic, infiltrative, or other.

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  Cardiogenic shock (CS): Defined according to the SCAI criteria as CS stages C to E.

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  LCOS or CS: Identified as the need for vasoactive drugs during hospitalization, including dobutamine, dopamine, norepinephrine, epinephrine, milrinone, isoproterenol, levosimendan, vasopressin, and/or phenylephrine, or the use of mechanical circulatory support such as an intra-aortic balloon pump or ECMO.

Continuous variables were expressed as mean and standard deviation or median and interquartile range (IQR), depending on their distribution. Categorical variables were reported as numbers and percentages. Comparisons of continuous variables were performed using the Student’s t -test or Wilcoxon rank-sum test, based on their distribution. Comparisons of proportions were conducted using the chi-squared test or Fisher’s exact test, depending on the expected frequency of values. A two-tailed alpha error of less than 5% was assumed to determine statistical significance.

A two-step analysis was used to evaluate factors associated with the primary endpoint. First, a univariate logistic regression analysis was performed. Clinically relevant variables, determined a priori, along with those with a p-value <0.10, were included in a multivariable logistic regression analysis. Results are reported as odds ratios (OR) with 95% confidence intervals (CI). Two-tailed p-values <0.05 were considered statistically significant.

All statistical analyses were performed using STATA software, version 14.1 (StataCorp, College Station, Texas).

The study was approved by the institutional ethics and research committee and registered on the PRIISA.BA platform of the Ministry of Health of Buenos Aires City. At the time of hospitalization, patients signed consent forms for the use of personal data for scientific purposes. The study adhered to national and international standards for the protection of research subjects, including the Declaration of Helsinki, Resolution 1480/2011 of the National Ministry of Health, Buenos Aires City Law 3301, and ANMAT Resolutions 6677/10 and amendments 4008 and 4009.