Primary pulmonary hypertension is defined as pulmonary hypertension and elevated pulmonary vascular resistance in the absence of other disease of the lungs or heart. Pathologically, it is characterized by diffuse narrowing of the pulmonary arterioles. Circumstantial evidence suggests that unrecognized recurrent pulmonary emboli or in situ thrombosis may play a role in some cases. However, the latter may well be an exacerbating factor (precipitated by local endothelial injury) rather than a cause of the syndrome. Primary pulmonary hypertension must be distinguished from chronic pulmonary heart disease (cor pulmonale), recurrent pulmonary emboli, mitral stenosis, and congenital heart disease; cirrhosis of the liver is another cause. The diet pills fenfluramine, dexfenfluramine, and phentermine may cause a picture indistinguishable from that of Primary pulmonary hypertension, which is frequently irreversible. Exclusion of secondary causes by echocardiography and lung scanning - and, if necessary, pulmonary angiography - is essential.

The clinical picture is similar to that of pulmonary hypertension from other causes. Patients - characteristically young women - present with evidence of right heart failure that is usually progressive, leading to death in 2-8 years.

Patients have manifestations of low cardiac output, with weakness and fatigue, as well as edema and ascites as right heart failure advances. Peripheral cyanosis is present, and syncope on effort may occur.

The chest x-ray shows enlarged main pulmonary arteries with reduced peripheral branches. The right ventricle is enlarged. The ECG shows right ventricular and atrial hypertrophy.

Some authorities advocate chronic oral anticoagulation. The efficacy of vasodilator drugs is controversial. They may lower systemic arterial pressure more than pulmonary arterial pressure, resulting in hypotension that may be life-threatening. The calcium channel blockers nifedipine and diltiazem may be effective early in the course of the disease but offer little in advanced stages. More advanced disease has been managed successfully with chronic infusions of prostacyclin, a potent pulmonary vasodilator. This agent often improves symptoms, sometimes dramatically, in patients who have not responded to other vasodilators. An oral endothelin antagonist, bosentan, has proved very effective in treating moderate to severe Primary pulmonary hypertension and may become the treatment of choice for all stages of the disease. Inhaled nitric oxide has been used in patients who do not respond to prostacyclin.

Even with prostacyclin therapy, the symptoms usually progress, and most patients will ultimately require heart-lung transplantation.

Chatterjee K et al: Pulmonary hypertension: hemodynamic diagnosis and management. Arch Intern Med 2002;162:1925.

Lehrman S et al : Primary pulmonary hypertension and cor pulmonale. Cardiol Rev 2002;10:265.

McLauglin VV: Survival in Primary pulmonary hypertension: the impact of epoprostenol therapy. Circulation 2002;15:1477.

Olschewski H et al: Inhaled iloprost for severe pulmonary hypertension. N Engl J Med 2002;347:322.

Paramothayan NS et al: Prostacyclin for pulmonary hypertension. Cochrane Database Syst Rev 2002;(3):CD002994.

Rubin LJ et al: Bosentan therapy for pulmonary arterial hypertension. N Engl J Med 2002;346:806.

Sitbon O et al: Primary pulmonary hypertension: current therapy. Prog Cardiovasc Dis 2002;45:115.