Pulmonary hypertension is defined as pulmonary arterial pressures > 25mm Hg at rest or > 30mm Hg with exercise, with mean pulmonary artery occlusion pressure < 15 mm Hg.

Portopulmonary hypertension occurs in approximately 3-5% of patients with advanced liver disease. There are three basic mechanisms associated with the development of POPH:

1. Hyperkinetic Circulation. Increased cardiac output in the setting of decreased vascular resistance, leading to the distension of arterial vessels and the recruitment of upper lung blood vessels, which worsens V/Q mismatch. This is similar to the mechanism of hepatopulmonary syndrome (the clinical triad of chronic liver disease, arterial oxygenation defect and intrapulmonary vascular dilitation; see my other article).
2.  LV Dysfunction, leading to increased pulmonary venous volume and thereby increased pulmonary arterial pressures, commonly seen in alcoholic cirrhotics.
3. Vascular obstruction, or true POPH, secdonary to intimal fibrosis, medial hypertrophy, and plexiform lesions of small arteries (thickening of the arteries along with their reduplication), leading to increased pulmonary vascular resistance. This may also be associated with thrombosis, which is thought to be secondary to portosystemic shunting of vasoactive substances with or without pulmonary endothelial dysfunction.

Symptoms include:

• Dyspnea on exertion
• Chest pain
• Syncope
• Hemoptysis

Radiographically, POPH is manifest as:

• Enlarged cardiac silhouette
• Pulmonary arterial prominence

PFTs demonstrate:

• Normal lung volvumes
• Normal air flow rates
• decreased DLCO (not as low as HPS)
• decreased PaO2 (not as low as HPS)
• decreased A-a PO2 (not as low as HPS)

Diagnosis is based on right heart catherization after screening with doppler echocardiography that demonstrates RV systolic pressures > 50 mm Hg. Bubble studies are typically negative.

Treatment rests first on the assessment of the reversibility of the pulmonary vascular constriction with vasodilators, such as nifedipine, NO, and prostacyclin, with a 20% reduction in PA pressures and PVR considered to vascular responsiveness. Unlike HPS, liver transplantation does not improve the condition.