In patients undergoing cardiac surgery, perioperative anemia is an important factor in surgical recovery. In addition to the low preoperative hemoglobin level, the delayed recovery of the postoperative hemoglobin level is an important problem affecting the incidence of postoperative anemia. Erythroferron is the early response to of the red blood cell production in stressful situations such as anemia, bleeding, and hypoxia. Therefore, it is thought that acute blood loss and systemic inflammatory reaction that inevitably occurs after cardiac surgery will synthesize erythroferron, which helps to restore hemoglobin level at postoperative period by promoting hematopoiesis by simultaneously inhibiting hepcidin and activating hematopoiesis.

In this study, the investigators will investigate the association between Erythroferron and perioperative hemoglobin levels in patient undergoing heart valve surgery.

Inclusion Criteria:

• Patients older than 20 years
• undergoing elective valvular heart surgery

Exclusion Criteria:

• Emergency operation
• Co-operation with other surgeries
• Patients with cardiogenic shock or ventricular-assist device (eg. ECMO, IABP)
• Patients requiring mechanical ventilator care in preoperative period
• Patient with severe chronic kidney disease (GFR(CKD-EPI) <30ml/min/1.73m2)
• Patients with preoperative infection status (Eg. Sepsis)
• Patients with acute bleeding status
• Hemoglobin concentration below 10g/dL
• Disease directly affecting hematopoiesis (eg. Leukemia, myeloma, aplastic anemia)
• Uncompensated liver cirrhosis, acute hepatitis, alcoholics
• Patients who participated in other clinical studies that could affect prognosis
• Patients who cannot understand the informed consent (eg. Foreigner)

Patient older than 20 years and undergong elective valvular heart surgery.