In general, PPH is diagnosed 4-7 years after the patient is diagnosed with portal hypertension^[1] and in roughly 65% of cases, the diagnosis is actually made at the time of invasive hemodynamic monitoring following anesthesia induction prior to liver transplantation.^[2]

After the initial echocardiography, patients are referred for pulmonary artery catheterization.

The limitations of echocardiography are related to the derivative nature of non-invasive PAP estimation. The measurement of PAP by echocardiogram is made using a simplified Bernoulli equation. The speed of a fluid through a narrow orifice is proportional to the difference of the pressures on either side – in this case, the right atrium and ventricle. Therefore the velocity of tricuspid regurgitation (which occurs at a measurable but normal level in the vast majority of humans) is squared, multiplied by four and added to the estimated right atrial pressure. Right atrial pressure is a derivative value, found by examining the inferior vena cava in the following sense: If, on inspiration, it should collapse roughly 50%, then the right atrial pressure is roughly 5mm_Hg; some collapse gives a right atrial pressure of 10 mm_Hg and no collapse, pressure of 15 mm_Hg. High cardiac index and pulmonary capillary wedge pressures, however, may lead to false positives by this standard. By one institution’s evaluation, the correlation (simple linear regression) between estimated systolic PAP and directly measured PAP was poor, 0.49.^[3] For these reasons, right heart catheterization is needed to confirm the diagnosis.