Hemodynamic Evaluation of Levosimendan in Patients With PH-HFpEF

Inclusion Criteria: Criteria to enter Open-label, Lead-in Dose Phase: * Diagnosis of World Health Organization (WHO) Group 2 Pulmonary Hypertension (PH) with Heart Failure with Preserved Ejection Fraction (HFpEF) confirmed at the time of the diagnosis of pulmonary hypertension. * Baseline Pulmonary Arterial Pressure (PAP) ≥35, Pulmonary Capillary Wedge Pressure (PCWP) ≥20, New York Heart Association (NYHA) Class IIb/III, Left Ventricular Ejection Fraction (LVEF) ≥40% * Ability to walk at least 50 meters, but not more than 550 meters in a six-minute walk test. * Stable oxygen treatment (if applicable), and medications for heart failure, hypertension, and respiratory condition Criterion for Randomization to Double-blind Phase: * Response to Open-label, Lead-in Levosimendan: Patients who demonstrate a ≥4mmHg reduction in PCWP from baseline measured at bicycle exercise (25 watts) with no more than a 10% decrease from baseline in cardiac index Exclusion Criteria: * Subject has a primary diagnosis of PH other than Group 2 PH-HFpEF * Previous Percutaneous Coronary Intervention (PCI) or cardiac surgery (CABG), unless they have a negative stress test in the last 12 months) * Congenital heart disease * Clinically significant lung disease * Planned heart or lung surgery * Cardiac Index \>4.0 L/min/m2 * Concomitant administration of pulmonary vasodilator therapy or taken within 14 days * Dialysis or Glomerular Filtration Rate (GFR) \<30 mL/min/1.73 m2 * Liver dysfunction with Child-Pugh Class B or C * Evidence of systemic infection * Weight \> 150kg * Symptomatic systolic blood pressure (SBP) cannot be managed to ensure SBP \>100 mmHg * Heart rate \>= 100 bpm with the study drug, symptomatic and persistent for at least 10 minutes * Hemoglobin \< 80 g/L * Serum potassium \< 3.0 mmol/L or \> 5.5 mmol/L at baseline * Patients having severely compromised immune function * Pregnant, suspected to be pregnant, or breast-feeding