Discussion of Pulmonary hypertension
- Pulmonary hypertension is defined as a mean pulmonary artery pressure greater than 25 mm Hg during rest (normal level, 10 mm Hg) or greater than 30 mm Hg during exercise (normal level, 15 mm Hg), as determined with right heart catheterization.
- Pulmonary hypertension secondary to known cardiac, pulmonary, or hepatic disease is far more common than is primary pulmonary hypertension, which has no identifiable cause.
- Pulmonary hypertension may be categorized as either precapillary (with changes limited to the pulmonary arterial circulation, mainly at the level of the muscular arteries) or postcapillary (with findings located within the pulmonary venous circulation, between the capillary bed and the left atrium).
- Primary pulmonary hypertension is an idiopathic condition at the precapillary level, and its postcapillary counterpart is pulmonary veno-occlusive disease, a rare idiopathic condition.
- Hypoxic lung disease is the most common cause of pulmonary hypertension in clinical practice, and it is precapillary in origin.
- Precapillary pulmonary hypertension also may be associated with connective tissue disorders, particularly in patients with scleroderma and the so-called CREST (calcinosis, Raynaud phenomenon, esophageal motility disorders, sclerodactyly, and telangiectasia) syndrome.
- An increased incidence of pulmonary hypertension, six to 12 times the frequency in the general population, has been observed in patients with human immunodeficiency virus infection.
- Other causes of precapillary pulmonary hypertension include long-standing left-to-right shunt, chronic thromboembolic disease, in situ pulmonary arterial thrombotic disease (eg, polycythemia vera, sickle cell disease), and widespread pulmonary embolism.
- Causes of postcapillary pulmonary hypertension include diseases that increase pulmonary venous pressure, such as left heart failure, mitral valve disease, left atrial tumor, pulmonary veno-occlusive disease, and mediastinal fibrosis.
 Imaging Findings for Pulmonary hypertension
- The presence of pulmonary hypertension should be suspected when the diameter of the main pulmonary artery on CT scans is greater than 29 mm (sensitivity of 87% and specificity of 89% for a diagnosis of pulmonary hypertension).
- When the ratio of the diameter of the main pulmonary artery to the diameter of the aorta is greater than 1:1, as determined on the basis of CT scans, a strong correlation with elevated pulmonary artery pressure also has been shown.
- The diameters of the left and right pulmonary arteries (normal upper limit, 16 mm) appear to be poorer indicators of the presence of pulmonary hypertension.
Patient #1: Pulmonary artery hypertension
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 References for Pulmonary hypertension
- Eva Castañer, Xavier Gallardo, Jordi Rimola, Yolanda Pallardó, Josep M. Mata, Joan Perendreu, Cesar Martin, and Damian Gil. Congenital and Acquired Pulmonary Artery Anomalies in the Adult: Radiologic Overview. RadioGraphics 2006 26: 349-371.