ABSTRACT
Idiopathic pulmonary arterial hypertension (IPAH) is a disease of unclear etiology that is characterized by a mean pulmonary arterial pressure ≥25 mm Hg and a pulmonary artery wedge pressure of ≤15 mm Hg in the absence of other demonstrable causes. IPAH can be diagnosed only when pulmonary arterial hypertension is present in patients without other defined risk factors. These include congenital heart disease, connective tissue disease, significant parenchymal lung disease, chronic thromboembolic disease, or left-sided valvular or myocardial disease, among others (1). Pulmonary hypertension may be suspected when echocardiographic estimates of systolic pulmonary artery pressure exceed 40 mm Hg, corresponding to a tricuspid regurgitant velocity on Doppler echocardiography of 3 to 3.5 m/sec (see Chapter 10). However, these estimates of pulmonary artery systolic pressure are not reliable enough to make a definitive diagnosis. IPAH is rare, with a prevalence estimated at between 5 and 25 cases per million population. Because other forms of pulmonary hypertension are more common, they should be considered even in the absence of overt signs and symptoms. The pathophysiology, clinical characteristics, and prognosis of idiopathic pulmonary arterial hypertension will be briefly reviewed here. The treatment of this disorder, along with other forms of PAH, is discussed separately.
