The objective of this observational study is to compare cardiac output evaluation by the Direct Fick method, Indirect Fick method and Thermodiluition in pulmonary hypertension (PH) patients undergoing right heart catheterization (RHC).

The main questions it aims to answer are:

• Are these methods interchangeable?
• Can possible discrepancies influence risk stratification and therapeutic management of PH patients? All consecutive patients aged ≥18 years, referred for RHC for suspected PH, will be included. Exclusion criteria will be contraindications to RHC, cardiac shunts and failure to obtain informed consent. Patients will undergo RHC by a Swan-Ganz catheter through the right internal jugular vein ultrasound-guided cannulation and cardiac output will be calculated using the three above-mentioned methods.

Inclusion Criteria:

• Age ≥18 years
• Suspected pulmonary hypertension at clinical and echocardiographic evaluation

Exclusion Criteria:

• contraindication to Right Heart Catheterization (RHC)
• cardiac shunt
• inability to provide informed consent

All consecutive patients aged ≥18 years, referred for RHC for suspected PH, were included.