Study of the Effect of Serelaxin on High-sensitivity Cardiac Troponin I (Hs-cTnI) Release in Patients With Chronic Heart Failure

Key Inclusion Criteria: * Male or female ≥ 18 years of age, with body weight ≤ 160 Kg * Diagnosis of stable CHF: * New York Heart Association (NYHA) functional Class II/III. * Receiving guideline-recommended treatment for CHF. * Left ventricular ejection fraction \< 45%, obtained within the last 3 months prior to screening. * NT-proBNP \> 300 ng/L in sinus rhythm or \> 900 ng/L if not in sinus rhythm (determined locally). * Ability to exercise for at least 10 to 12 minutes based on investigator's judgment. * Systolic BP ≥ 125 mmHg at randomization * Renal function defined as an eGFR of ≥ 25 mL/min/1.73 m\^2 at screening (sMDRD formula). Key Exclusion Criteria: * Dyspnea primarily due to non-cardiac causes. * Increased risk of developing hypotension during vasodilator therapy according to investigators judgement. * Any contraindication for exercise testing and spirometry. * Stopping of the spiroergometry at screening according to the stopping rules, unless the patient has reached maximum exercise capacity defined as carbon dioxide production/oxygen consumption (VCO2/VO2) \> 1.05. * Change in guideline-recommended CHF treatment within 1 month prior to screening.