Abstract: A system and method sense a pressure signal in a pulmonary artery and compute a stroke volume and cardiac output. A pressure signal is received from an implantable pressure sensor disposed in a pulmonary artery. The pressure signal includes a systolic period and a diastolic period for determining a heart rate (HR) and a heart cycle. An iteratively-updating model can relate pressure signal and HR to a stroke volume (SV) and a cardiac output (CO). The model extracts a mean pulse pressure (MPP) from the PAP signal and receives a patient-specific vascular resistance model parameter and a patient-specific arterial compliance model parameter. CO can be calculated using the HR, the PAP signal, and the model. The vascular resistance model parameter and the arterial compliance model parameter are iteratively updated using the output of the model.