BREATHE III is a prospective, multicenter, observational registry designed to provide contemporary insights into the epidemiological, clinical, and prognostic characteristics of patients hospitalized with acute heart failure (AHF) in Brazil, including those with decompensated heart failure or new-onset ventricular dysfunction during acute myocardial infarction.

Recent evidence, such as the STRONG-HF trial, has demonstrated the prognostic benefit of rapid initiation and up-titration of guideline-directed medical therapy (GDMT) in patients with heart failure with reduced ejection fraction (HFrEF). However, prior phases of the BREATHE registry did not evaluate the timing of therapeutic optimization or barriers to implementing these strategies. Additionally, the therapeutic landscape of heart failure has evolved substantially in recent years, with the introduction of novel pharmacological agents, expanded indications for existing therapies, and new treatment options for heart failure with preserved ejection fraction (HFpEF).

BREATHE III aims to address these knowledge gaps by systematically assessing, over a 12-month follow-up, patient characteristics, treatment patterns, adherence to guideline-recommended therapies, time to treatment optimization, and clinical outcomes. The study will also identify barriers to the implementation and titration of evidence-based therapies, evaluate regional variations in care, and describe contemporary management practices across public and private healthcare settings in Brazil.

The results of this registry are expected to inform strategies to improve quality of care, optimize resource allocation, and guide future interventions aimed at reducing morbidity and mortality associated with heart failure in Brazil.

Inclusion Criteria

Adult patients (≥ 18 years) admitted to public and private hospitals with one of the two clinical conditions below:

• Admission for AMI (Acute Myocardial Infarction) presenting with reduced ejection fraction during hospitalization (LVEF ≤ 40%) and which had not been previously identified (limit of 25% of the study sample included by this criterion)
• Primary diagnosis of decompensated HF (regardless of ejection fraction), with the HF diagnosis established according to the universal definition of heart failure. In cases of HF with HFpEF, in addition to the data from the universal heart failure criteria, H2FPEF and HFA PEFF data will be collected.

Exclusion Criteria

• Refusal to participate in the study during the informed consent process;
• Surgical myocardial revascularization in the last month;
• Heart failure secondary to sepsis (sepsis as the origin of heart failure);
• Cardiogenic shock.

This study will include adult patients (≥18 years) admitted to public and private hospitals in Brazil with acute heart failure-related presentations. Eligible participants comprise two main groups: (1) patients hospitalized for acute myocardial infarction (AMI) who develop newly identified left ventricular systolic dysfunction during hospitalization (LVEF ≤40), limited to up to 25% of the total study population; and (2) patients admitted with a primary diagnosis of decompensated heart failure, regardless of ejection fraction, defined according to the universal criteria for heart failure. In patients with heart failure with preserved ejection fraction (HFpEF), additional characterization will include H2FPEF and HFA-PEFF scores.

Patients will be excluded if they decline participation during the informed consent process, have undergone surgical myocardial revascularization within the previous month, present with heart failure secondary to sepsis, or are admitted with cardiogenic shock.