in this prospective, randomized, controlled double blinded study conducted at Helwan University Hospitals include 52 patients with rheumatic mitral and/or aortic valve disease and pulmonary arterial hypertension at the start of rewarming, patients will be randomly assigned into either group 1 (levosimendan) or group 2 (dobutamine ) Group 1 patients will receive dobutamine, 3-5 microgram/kg group 2 patients will receive levosimendan 6 ug/kg bolus over 10 minutes, followed by infusion at a rate of 0.1 mg/kg/min Transthoracic echocardiography performed before induction of anaesthesia (baseline), 6 and 12 hours post surgery . In addition, transthoracic echocardiography also performed 24 hours post extubating. Transoesophageal echocardiography (TEE) examination performed during the intraoperative period before the initiation of CPB (pre CPB) and 30 minutes after separation from CPB (post-CPB) Echocardiographic parameters measured will include tricuspid annular plane systolic excursion (TAPSE), Tei index and myocardial systolic velocities at the tricuspid annulus (S/) for the assessment of right ventricular systolic function, and ratio of tricuspid inflow to tricuspid annular diastolic velocity (E/E/) for the assessment of right ventricular diastolic function.

Pulmonary artery pressure will be assessed frequently by transthoracic echo during every assessment.

Inclusion Criteria:

• Age ≥18 years
• Undergoing mitral and/or aortic valve replacement
• PAH (an estimated right ventricular systolic pressure more than 50 mmHg, or mean PAP more than 40 mmHg, or systolic PAP exceeding 50% of systemic systolic pressure).

Exclusion Criteria:

• Potential pregnancy.
• Refusal to participate.
• Patients with severe renal dysfunction (GFR 15 to 29 ml/min per 1.73 m2 )
• Severe hepatic dysfunction.( Grade 4: AST/ALT >20.0 x(upper limit normal )
• Prolonged QT interval.
• Emergency surgery,
• Requiring preoperative inotropes.
• Uncontrolled diabetes mellitus (HBA1C more than 8 )

Adult patients scheduled for valve replacement surgery with PAH (an estimated right ventricular systolic pressure more than 50 mmHg, or mean PAP more than 40 mmHg, or systolic PAP exceeding 50% of systemic systolic pressure). Pregnant Patients or .

Patients with severe renal dysfunction (GFR 15 to 29 ml/min per 1.73 m2 )or Severe hepatic or patients with Uncontrolled diabetes mellitus (HBA1C more than 8 )or patients needed inotropic support before surgery were excluded from the study.