Primary Pulmonary Hypertension: A Histopathologic Study of 80 Cases

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Among 80 cases with a clinical diagnosis of primary (unexplained) pulmonary hypertension, 45 (56%) had thromboembolic disease and 22 (28%) had plexogenic arteriopathy; the remaining 13 (16%) had pulmonary veno-occlusive disease, primary medial hypertrophy, primary pulmonary arteritis, or changes consistent with pulmonary venous hypertension. The mean age was 16 years for primary pulmonary arteritis, 21 to 34 years for plexogenic pulmonary arteriopathy, primary medial hypertrophy, and pulmonary veno-occlusive disease, and 41 and 45 years for thromboembolic disease and pulmonary venous hypertension, respectively. In all forms except pulmonary veno-occlusive disease and apparent pulmonary venous hypertension, female patients were involved twice as often as male patients. With the exception of apparent pulmonary venous hypertension, patients with plexogenic pulmonary arteriopathy had the longest survival (63 months). Sudden death, however, occurred most frequently in patients with plexogenic disease (45%) and occurred 2.5 times as often in this group as in patients with thromboembolic disease. Among our 80 cases, the most frequent histopathologic lesions were medial hypertrophy, intimal proliferation and fibrosis, fibrinoid degeneration and necrosis, and thrombosis. Thrombi were commonly observed and may have developed in situ or by embolization; they were often rich in platelets when they occurred in small pulmonary vessels. These histologic features may form the morphologic substrate for elevated pulmonary vascular resistance, and their recognition may provide the rationale for possible intervention with pulmonary vasodilators, anticoagulants, or platelet inhibitors.

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METHODS

From the tissue registry at our institution, we identified 80 cases of primary pulmonary hypertension that had been diagnosed between 1930 and 1983. These 80 cases form the basis of our report and include 73 autopsies, 6 open-lung biopsy specimens, and 1 case with both biopsy and autopsy tissue; the clinical features of 53 of these cases are being reported in a separate communication.6 Excluded from our study were cases with congenital cardiac shunts, obstructive lesions of the left side of the

Histopathologic Classification.

The cases were grouped on the basis of the dominant structural abnormalities present. Thromboembolic pulmonary hypertension was characterized by thrombi of various ages and by eccentric intimal proliferation and fibrosis.2, 3, 4 Plexiform lesions were the histopathologic hallmark of primary plexogenic pulmonary arteriopathy, but concentric intimal proliferation and fibroelastosis were also highly suggestive of this disorder.2, 3, 4 When a case had both plexiform and thrombotic lesions, it was

DISCUSSION

The histopathologic types of clinical primary pulmonary hypertension were described in detail by the Wagenvoorts in 1970 in a classic study of 156 autopsy cases2 and in 1980 in an appraisal of 40 open-lung biopsy specimens.5 To these two elegant studies, we add our own observations based on a semiquantitative histopathologic study of 80 cases (Table 2).

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*

Mayo Graduate School of Medicine, Rochester, Minnesota. Present address: University of Iceland, Reykjavik, Iceland.

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