Effects of Repletion of Sodium Chloride on Natriuresis, Blood Pressure, and Neurohormonal Activity in Patients With Chronic Heart Failure With Reduced Ejection Fraction

The study is a single-center, prospective, randomized, placebo-controlled, double-blind trial conducted at the Institute of Heart Diseases and the Department of Cardiology of Wroclaw Medical University Hospital. It aims to evaluate the effects of three-month oral sodium chloride supplementation (3 g/day, equivalent to 1.2 g of sodium) versus placebo (lactose) in patients with chronic heart failure with reduced ejection fraction (HFrEF) and low serum sodium, who have not reached the maximum recommended doses of guideline-directed medical therapy (GDMT). A total of 30 patients will be enrolled, with 15 randomized to the experimental group receiving sodium chloride and 15 to the control group receiving placebo. Patient selection will involve careful screening, including recent serum sodium measurements, to ensure all inclusion and exclusion criteria are met. Participants will attend bi-weekly visits to assess clinical parameters (medical history, EVEREST heart failure symptoms score, blood pressure, body weight), biochemical markers (serum: morphology, urea, creatinine, sodium, chloride, potassium, NT-proBNP, aldosterone, renin; urine: urea, creatinine, sodium, chloride, potassium), and the safety of supplementation (body weight, serum sodium and chloride, exercise tolerance). Visits will also allow attempts to optimize GDMT doses where clinically feasible, based on objective criteria (e.g., systolic blood pressure \>110 mmHg and/or diastolic blood pressure \>60 mmHg). Capsules containing sodium chloride or placebo will be prepared according to pharmacy standards to ensure intestinal release and maintain blinding. The Primary Investigator will remain blinded to treatment allocation. Follow-up will include both in-person and telephone visits, monitoring clinical status and safety parameters throughout the study period. Sample size was calculated based on previous studies in this field, to achieve a type I error probability of 0.05 and a power of 0.80. At the end of