Chronic thromboembolic pulmonary hypertension.

Copyright © 2011 Massachusetts Medical Society. Chronic thromboembolic pulmonary hypertension is defined as mean pulmonary-artery pressure greater than 25 mm Hg that persists 6 months after pulmonary embolism is diagnosed. The 2008 World Symposium on Pulmonary Hypertension1 emphasized the importance of chronic thromboembolic pulmonary hypertension, which occurs in 2 to 4% of patients after acute pulmonary embolism.2,3 The frequency of this condition among patients with pulmonary hypertension is unknown. Patients with chronic thromboembolic pulmonary hypertension generally present in their 40s, although this condition has been reported in patients in other age groups.2 The diagnosis is often overlooked because many patients do not have a history of clinically overt pulmonary embolism.4 The natural history of chronic thromboembolic pulmonary hypertension has been difficult to determine because a subgroup of patients have had occult pulmonary embolism, with subtle clues to the diagnosis that became apparent only in retrospect. Patients with chronic thromboembolic pulmonary hypertension typically have a honeymoon period after acute pulmonary embolism, during which symptoms are absent despite the onset of pulmonary hypertension. Long-term follow-up of patients with chronic thromboembolic pulmonary hypertension, including those with mild symptoms and those who are asymptomatic, is needed to elucidate the natural history of this disease. Although symptomatic disease develops in a substantial proportion of patients, the clinical importance of asymptomatic chronic thromboembolic pulmonary hypertension remains controversial. This condition is usually detected when pulmonary hypertension worsens and causes dyspnea, hypoxemia, and right ventricular dysfunction. Death is usually due to progressive pulmonary hypertension culminating in right ventricular failure. The risk of the development of chronic thromboembolic pulmonary hypertension is increased by factors associated with pulmonary embolism, certain chronic medical conditions, thrombophilia, and a genetic predisposition (Table 1).2,3,5-9 Thyroid disease is a risk factor for both chronic thromboembolic pulmonary hypertension and idiopathic pulmonary arterial hypertension.8,10 Currently, no pharmacologic regimen helps prevent chronic thromboembolic pulmonary hypertension, except anticoagulation with or without fibrinolysis. When administered in hemodynamically stable patients with right ventricular dysfunction due to acute pulmonary embolism (submassive pulmonary embolism), fibrinolytic therapy has been shown to reduce the frequency of chronic thromboembolic pulmonary hypertension.11 Such therapy, which is most effective if administered within 2 weeks after acute pulmonary embolism is detected, is considered a lifesaving intervention in patients with massive pulmonary embolism but remains