The SURE-HF trial is a pragmatic, multicentre, randomized controlled study evaluating natriuresis-guided optimization of intravenous loop diuretic therapy in patients hospitalized with worsening heart failure (WHF). The study aims to determine whether serial urinary sodium assessment combined with a structured decongestive treatment algorithm improves decongestion, reduces the need for therapy escalation, and enhances discharge readiness compared with standard care.

Participants will be randomized to standard urine output-guided therapy or natriuresis-guided decongestive strategies using different intravenous loop diuretic administration regimens. The study integrates bedside diagnostic tools including lung ultrasound, inferior vena cava assessment, focused echocardiography, and serial clinical congestion monitoring.

The primary endpoint is a hierarchical composite outcome including escalation of heart failure therapy, persistent congestion at discharge, inability to transition to oral loop diuretics by Day 5, and residual ultrasound congestion. The findings of the SURE-HF trial may support implementation of urinary sodium-guided and ultrasound-assisted decongestive therapy in routine heart failure management.

Inclusion Criteria:

• Age ≥18 years.
• Confirmed diagnosis of worsening heart failure (WHF), characterized by symptoms and signs of acute decompensation requiring hospitalization for intensification of intravenous diuretic therapy.
• Previous intake of a loop diuretic (torasemide or furosemide) in any dose for at least 2 days before hospitalization.
• Presence of clinical signs and symptoms of congestion (e.g., dyspnea, orthopnea, peripheral edema, pulmonary congestion).
• Provision of written informed consent.

Exclusion Criteria:

• Acute coronary syndrome within the previous 30 days.
• Acute heart failure requiring urgent invasive intervention, including cardiogenic shock or mechanical circulatory support.
• Current admission to an intensive care unit.
• Systolic blood pressure ≤90 mmHg or requirement for inotropic/vasopressor support.
• Recent use (≤48 hours) of inotropic agents affecting fluid and electrolyte balance.
• Estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m² or requirement for renal replacement therapy.
• Hypokalemia (<3.5 mmol/L) or hyperkalemia (≥5.5 mmol/L).
• Clinically significant hyponatremia (<130 mmol/L) or hypernatremia (>150 mmol/L).
• Significant comorbidities affecting sodium-water balance (e.g., liver cirrhosis with ascites, nephrotic syndrome, severe infection or sepsis).
• Pregnancy or breastfeeding.
• Active malignancy.
• Inability to comply with the study protocol or participation in another interventional clinical trial.

De-identified individual participant data underlying the reported results may be shared upon reasonable request to the corresponding author following publication of the primary study results, subject to institutional approval and applicable data protection regulations.

De-identified individual participant data and supporting documents will become available beginning 6 months after publication of the primary study results and will remain available for 5 years.

Access to de-identified individual participant data and supporting documents will be provided to qualified researchers upon reasonable request to the corresponding author and after approval by the study investigators and participating institution. Data sharing will be limited to non-commercial scientific research purposes and subject to applicable ethical and data protection requirements.

Due to the nature of the intervention, the study is conducted in an open-label design. Urinary sodium measurements in the standard-of-care group will remain concealed from treating physicians and will not be used for protocol-driven treatment adjustment. Whenever feasible, investigators responsible for outcome assessment and statistical analysis will remain blinded to treatment allocation.