Background—Experience of balloon dilation of peripheral pulmonary stenosis (PPS) in Williams syndrome (WS) is limited.

Methods and Results—Catheterizations in all patients with WS undergoing therapy for PPS from 1984 to 1999 were reviewed. Criteria for successful dilation included an increase >50% in predilation diameter and a decrease >20% in ratio of right ventricular (RV) to aortic (Ao) systolic pressure. Median age and weight were 1.5 years and 9.5 kg. There were 134 dilations during 39 procedures in 25 patients. The success rate for initial dilations was 51%. In multivariate analysis, successful dilation was more likely (1) in distal than in central pulmonary arteries (P=0.02), (2) if the balloon waist resolved with inflation (P=0.001), and (3) with larger balloon/stenosis ratio (P<0.001). RV pressure was unchanged after dilation (96±30 versus 97±31 mm Hg), primarily because of failure to enlarge central pulmonary arteries. The Ao pressure increased (102±14 versus 109±19 mm Hg, P=0.03), and the RV/Ao pressure ratio decreased (0.97±0.34 versus 0.91±0.30, P=0.05). Aneurysms developed after 24 dilations (18%) and were not related to balloon/stenosis ratio. Balloon rupture in 12 dilations produced an aneurysm in all 7 cases when rupture was in a hypoplastic segment. Three patients died, none from pulmonary artery trauma, and all before 1994.

Conclusions—Mortality occurred early in our experience. Despite successful dilation of distal pulmonary arteries, there was modest initial hemodynamic improvement, mainly because of persistent central pulmonary artery obstruction. A serial approach of distal dilations followed by surgical repair of proximal obstruction may be a rational and successful therapy.