The pathology of balloon pulmonary valvoplasty.

The pulmonary valve was examined following balloon dilation of pulmonary valve stenosis in six children. Stenosis was due to commissural fusion in two. In these patients, cineangiography showed that the valve was slightly thickened and "domed" during systole. Balloon valvoplasty produced complete separation of fused commissures in one and partial separation in the other. Commissural splitting is likely to be the most common mechanism of relief of pulmonary stenosis by balloon dilation. Incomplete separation could account for the partial reduction of the gradient in most children treated with this technique. Four children had pulmonary valve dysplasia. Balloon valvoplasty did not produce haemodynamic improvement or morphological changes that were identifiable at the time of surgical correction. Tearing of pulmonary valve tissue and avulsion of pulmonary cusps were not seen in this series.