Pulmonary Arterial Hypertension in Patients with Portal Hypertension

A rare exception to the usual systemic, splanchnic, and pulmonary vasodilation in patients with portal hypertension is the occurrence of pulmonary hypertension. In the lung, the most frequent change associated with portal hypertension is functional vasodilation with low pulmonary vascular resistance, resulting in a relative ventilation/perfusion mismatch and hypoxia. In contrast, pulmonary hypertension is characterized by an elevated pulmonary vascular resistance. Although this is an uncommon complication in patients with portal hypertension, pulmonary hypertension seems to appear too frequently to be a mere association. In these patients, pulmonary hypertension is characteristic of primary plexogenic pulmonary hypertension, defined by the presence of plexogenic lesions of the pulmonary arteries. The increase in pulmonary vascular resistance is of the pre-capillary type and no cardiac or lung disease is detectable. Pulmonary hypertension can be a complication in all types of portal hypertension and is thought to be more frequent in patients with surgical portal-systemic shunts. Thus, although the mechanism for this uncommon complication is unknown, it would seem directly related to portal-systemic shunting.