Primary Pulmonary Hypertension

Morphologic and morphometric studies were carried out on pulmonary vessels in lung tissue from 156 patients, for whom a diagnosis of primary pulmonary hypertension had been made. This material was collected from 51 medical centers. Chronic pulmonary thromboembolism can be recognized by organizing thrombi, patchy intimal fibrosis, and intra-arterial septa. The media is only slightly thicker than normal; in 31 of the 156 cases the vascular lesions corresponded to this pattern. Other conditions such as chronic pulmonary venous hypertension, pulmonary veno-occlusive disease, sarcoidosis, chronic bronchitis, and pulmonary schistosomiasis could also be classified from the morphologic criteria. The largest group comprised 110 cases showing medial hypertrophy, laminar intimal fibrosis, and often fibrinoid necrosis, arteritis, and plexiform lesions. These alterations suggest that they were initiated by vasoconstriction. In children the sex ratio is equal; in adults there are almost four females to one male. In these patients with vasoconstrictive primary pulmonary hypertension, various stimuli are likely to bring about vasoconstriction in the presence of a pronounced pulmonary vascular hyperreactivity. A review of 602 cases from the literature is given.