Idiopathic dilatation of the pulmonary artery.

Idiopathic dilatation of the pulmonary artery is an uncommon cause of a large main pulmonary artery whose diagnosis is dependent on the exclusion of other causes of central pulmonary artery dilatation. We present four new cases who have been known to have large central pulmonary arteries for many years, and suggest that a long period of observation should be considered to be a further criterion for diagnosis as, in some patients who appear to have this condition, an underlying pathology will become apparent.