Portopulmonary Hypertension - Diagnosis

Diagnosis

The diagnosis of portopulmonary hypertension is based on hemodynamic criteria:

1. . Portal hypertension and/or liver disease (clinical diagnosis—ascites/varices/splenomegaly)
2. . Mean pulmonary artery pressure—MPAP > 25 mmHg at rest
3. . Pulmonary vascular resistance—PVR > 240 dynes s cm−5
4. . Pulmonary artery occlusion pressure— PAOP < 15mmHg or transpulmonary gradient—TPG > 12 mmHg where TPG = MPAP − PAOP.

The diagnosis is usually first suggested by a transthoracic echocardiogram, part of the standard pre-transplantation work-up. Echocardiogram estimated pulmonary artery systolic pressures of 40 to 50 mm Hg are used as a screening cutoff for PPH diagnosis, with a sensitivity of 100% and a specificity as high as 96%. The negative predictive value of this method is 100% but the positive predictive value is 60%. Thereafter, these 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. High cardiac index and pulmonary capillary wedge pressures, however, may lead to false positives by this standard. By one institution’s evaluation, the correlation between estimated systolic PAP and directly measured PAP was poor, 0.49. For these reasons, right heart catheterization is needed to confirm the diagnosis.