Prognostic association of circulating relaxin-2 in acute heart failure.

Background: Despite the increasing interest in the study of the endogenous relaxin system in heart failure (HF), its role as a prognostic marker in acute HF remains unclear. We aimed to evaluate the association of relaxin-2 circulating levels with 6 months' mortality in acute HF.

Methods: We evaluated relaxin-2 serum levels at admission in a cohort of patients with acute HF (n = 202) using an enzyme immunoassay. The ability of relaxin-2 to predict all-cause death (primary outcome) and HF-specific death (secondary outcome) at 6 months was assessed using Cox-regression analysis.

Results: The median age was 79 (70-85) years old, 44% of the patients were male, and 43% had preserved ejection fraction (≥50%). Median serum relaxin-2 level was 25 pg/mL. Patients with higher relaxin-2 levels had more peripheral oedemas, higher sodium retention score, higher pulmonary artery pressures, higher prevalence of right ventricle dysfunction and lower inferior vena cava collapse at inspiration. Conversely, there was no association with left chambers parameters or with B-type natriuretic peptide (BNP). Higher relaxin-2 concentrations were associated with a higher risk of all-cause death [HR 1.15; 95%CI 1.01,1.30; P = 0.030] and HF-specific death [HR 1.21; 95% CI 1.03-1.42; P = 0.018], after adjustment for classical prognostic factors such as age, sex and BNP.

Conclusions: In our acute HF population, relaxin-2 circulating levels were associated with clinical and echocardiographic markers of systemic congestion and with 6-months' mortality, independently of BNP. These results lay the groundwork for future investigations on the potential of relaxin-2 as an auxiliary biomarker in HF.