Since the pulmonary artery hypertension is defined based on MPAP and the two previous formulae relating MPAP and PAT were derived in western population, the investigator planned to conduct a prospective study to derive a new formula for measuring MPAP from PAT in Indian population and compare the accuracy of all the three formulae

After obtaining ethics committee approval and informed patient consent, minimum 25 patients > 18 years of age who are undergoing cardiac surgery with the invasive monitoring of pulmonary artery pressure will be enrolled in this study.The demographics and the preoperative echocardiographic measurement will be noted. In the operating room, once the intravenous access is obtained, central venous catheterisation and pulmonary artery catheterisation will be done as per the institutional protocol. Once the Transthoracic echocardiogram (TTE) is performed patient will be induced with opioids, intravenous or inhalational agents, and muscle relaxant according to the patient clinical and hemodynamic condition. Once the patient airway is secured with tracheal tube, transesophageal echocardiogram (TEE) will be performed before and after bypass, which is routine in all patients undergoing cardiac surgery in the institution. Echocardiographic images will be analysed by two separate echocardiographers to detect inter-individual variability. Patient blood pressure and heart rate will be maintained within 20% of their baseline value throughout surgery. Based on the patient condition at the end of surgery, extubation will be done in the operating room or in intensive care unit (ICU) after a period of elective ventilation.

Inclusion Criteria:

• 18 years of age who are undergoing cardiac surgery with the invasive monitoring of pulmonary artery pressure

Exclusion Criteria:

• Patients with known right ventricular outflow tract obstruction, intra-cardiac shunt lesions will be excluded

> 18 years of age who are undergoing cardiac surgery with the invasive monitoring of pulmonary artery pressure