(so-called primary pulmonary hypertension) or secondary to conditions, such as connective tissue disease, sarcoidosis, and certain inherited conditions. Pulmonary hypertension may develop as the result of chronic pulmonary thromboembolism. The condition may also develop secondary to lung disease or hypoxemia, such as chronic obstructive pulmonary disease, interstitial lung disease, and obstructive sleep apnea. Pulmonary hypertension secondary to lung disease is termed cor pulmonale (cor pulmonale is not discussed further because disability criteria are established in the pulmonary disease listings). Pulmonary hypertension is a relatively common complication of left-sided heart disease, such as mitral valvular disease or cardiomyopathy, or due to congenital heart disease. Pulmonary hypertension that develops as a secondary manifestation of another primary form of heart disease should be evaluated using the disability criteria established for the primary disease, and so is not discussed further in this chapter.

Pulmonary hypertension is associated with high mortality and with marked functional limitations. The condition is often quite advanced at the time of diagnosis, largely because its symptoms are nonspecific and the diagnosis is difficult to make.

EPIDEMIOLOGY

Pulmonary hypertension is an uncommon disease with an estimated prevalence of 2 per million in the United States. Women are affected much more often than men, and the typical age at the time of diagnosis is between 30 and 50. The disease is associated with genetic markers (mutations and polymorphisms in the Type II bone morphogenic protein receptor), and with the use of appetite suppressants.

DIAGNOSTIC CRITERIA AND METHODS

The definitive method for the diagnosis of pulmonary hypertension is a right heart catheterization with hemodynamic measurements.

Right Heart Catheterization

Pressures in the pulmonary artery, right ventricle, and right atrium can be measured directly during a right heart catheterization. Cardiac output and pulmonary capillary wedge pressure should also be measured to characterize fully the state of the pulmonary vessels.

Pulmonary hypertension is considered present when the mean pulmonary artery pressure is greater than 25 mm Hg at rest. Pulmonary arterial hypertension is a more specific diagnostic term that requires a pulmonary capillary wedge pressure of 15 mm Hg or less with a pulmonary vascular



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