Relaxin serum levels in acute heart failure are associated with pulmonary hypertension and right heart overload

Aims Despite the promising results of serelaxin as a new potential acute heart failure (HF) therapy, its clinical use preceded the understanding of the endogenous relaxin system in HF. We aimed to evaluate relaxin circulating levels in a population of acute HF and their association with clinical and echocardiographic parameters. Methods and results We included 117 patients from a registry of acute HF. Admission serum relaxin was measured using an enzyme-linked immunosorbent assay (ELISA) kit. Clinical, analytical, and echocardiographic parameters were compared between patients with relaxin levels above and below the median. Median age was 82 years [interquartile range (IQR) 72-87], 41% of the patients were male, and 63% had systolic dysfunction. Median serum relaxin was 31.4 pg/mL (IQR 0.6-89.8). Patients with relaxin levels above the median had more peripheral oedema (89.8% vs. 68.4%, P = 0.004) and a significantly higher sodium retention score (mean 4.8 +/- 1.5 vs. 3.6 +/- 2.0, P < 0.001). These patients also had significantly higher systolic pulmonary arterial pressure [median 47.0 (IQR 36.0-61.0) vs. 34.5 (IQR 25.0-51.0) mmHg, P = 0.002], higher prevalence of right ventricular (RV) systolic dysfunction (28.1% vs. 10.3%, P = 0.02), RV dilation (31.0% vs. 5.3%, P < 0.001), and right atrial dilation (66.1% vs. 36.5%, P = 0.002), and less inferior vena cava diameter variability (40% vs. 60%, P = 0.009). No differences were noted regarding admission blood pressure, left chamber dimensions, or LV function. Conclusion In our population of acute HF patients, admission relaxin serum levels were associated with clinical and echocardiographic markers of pulmonary hypertension, RV dysfunction, and overload, suggesting a role for circulating relaxin as a biomarker in this setting.