Short-term survivors of pediatric heart transplantation: an autopsy study of their pulmonary vascular disease.

BACKGROUND

The most common indications for heart transplantation in children are congenital heart disease and cardiomyopathy. Intracardiac lesions that vary widely in morphology may have a similar impact on pulmonary vascular morphology; for example, any lesion that increases left-sided intracardiac pressure will affect pulmonary venous pressure and morphology and, if long-standing, may affect pulmonary arteries also.

METHODS

The lungs of eight children who died 2 days to 7 months after receiving a heart transplant at ages 8 days to 4 years were examined at autopsy with particular regard to the pulmonary arteries and veins. Arteries were evaluated for medial thickness, intimal proliferation, and peripheral extension of muscle; veins for medial thickness and mural elastic tissue configuration; and lymphatics for degree of dilation.

RESULTS

The main pulmonary arteries of the children with congenital heart disease showed an abnormal elastic tissue pattern, similar to the pattern of the aorta, indicating that pulmonary arterial hypertension was present in these children at birth. In contrast, the pulmonary trunk of a child who had myocarditis beginning at age 2 years had a normal pulmonary elastic tissue pattern, consistent with normal neonatal pulmonary pressure. Five children with morphologic evidence of early pulmonary arterial hypertension had a left-to-right atrial shunt before the operation and elevated pulmonary artery pressure immediately after transplantation. The pulmonary arteries of all five patients had medial hypertrophy or peripheral extension of muscle; the most advanced pathologic condition occurred in the arteries of the oldest child, who was 5 months of age, at the time of transplantation who died 2 days after the operation with pulmonary arterial hypertension. In the lungs of all eight patients, pulmonary veins showed medial hypertrophy and excess elastic tissue fibers (arterialization), consistent with venous hypertension. The most impressive venous changes in the lungs of the children with hypoplastic left heart syndrome occurred in the two children who had the smallest left ventricles (4 x 6 mm and 8 x 8 mm), and in another child with hypoplastic and anomalous extrapulmonary pulmonary veins. The most impressive lymphangiectasis occurred in the lungs of the child with hypoplastic left heart syndrome who was oldest at the time of transplantation and in the lungs of a child with obstructed venous drainage.

CONCLUSIONS

Pulmonary vasculopathy in children who require heart transplantation because of congenital heart disease or long-standing congestive heart failure may involve arteries, veins, and lymphatics. Among the eight patients in this autopsy study of children who died less than a year after heart transplantation, arterial vasculopathy associated with congenital heart disease appeared more pronounced in the five who survived less than 30 days compared with the two longer survivors. The lack of morphologic progression in short-term survivors of pulmonary arterial vasculopathy after heart transplantation correlates with clinical follow-up of long-term survivors who do not have problematic pulmonary arterial hypertension. Pulmonary venous vasculopathy is determined by the degree of pretransplantation left-sided obstruction caused by congenital or acquired disease and may be more persistent morphologically than arterial vasculopathy. This morphologic study of the pulmonary vasculature of short-term survivors of heart transplantation supports the concept that palliative surgical procedures may benefit children awaiting heart transplantation, especially infants with hypoplastic left heart syndrome for whom suitable donors are scarce.