Longitudinal smooth muscle in pulmonary arteries. Occurrence in congenital heart disease.

In lung biopsy specimens of 19 patients with congenital heart disease and pulmonary hypertension, in addition to the common features of plexogenic arteriopathy, longitudinal smooth muscle cells were found in small pulmonary arteries. These cells were arranged in bundles or layers, particularly in the intima but sometimes within the media or adventitia of the arteries. They often caused severe narrowing of the lumen. Corrective surgery of the cardiac defect was performed in 14 patients. The results suggested that even when these changes are wide-spread and severe, they do not stand in the way of a favourable post-operative course. In one patient who underwent a banding procedure of the pulmonary artery, virtually complete regression of the smooth muscle layers could be demonstrated in a second biopsy, taken 5 years later during a corrective operation.