AbstractObstruction of the reconstructed aortic arch, or the neoaortic arch, is now known to be an important factor increasing mortality after the Norwood operation for hypoplastic left heart syndrome. Transcatheter balloon angioplasty has been shown to provide effective relief of both native aortic coarctation and obstructions of the aortic arch occurring subsequent to therapeutic intervention. We sought to determine the outcomes of balloon angioplasty used as an initial treatment for obstruction of the neoaortic arch occurring after the Norwood operation. We gathered the characteristics of 58 patients with such obstruction from 8 institutions, noting procedural factors and outcomes of initial balloon dilation. Obstruction occurred at a median interval of 4 months, with a range from 1.5 months to 6.3 years, after a Norwood operation. Ventricular dysfunction was present before dilation in 13 patients. Mean peak to peak systolic pressure gradients were acutely reduced from 31±20 mm Hg to 6±9 mmHg (p<0.001), with outcome subjectively judged to be successful in 89%- Three patients with pre-existing ventricular dysfunction died within 48 hours of dilation. There were 10 additional deaths during the period of followup, with Kaplan Meier estimates of survival after intervention of 87% at 1 month, 77% at 12 months, and 72% after 15 months. In addition, 9 patients required re-intervention during the period of follow-up, with Kaplan Meier estimates of freedom from re-intervention after dilation of 87% at 6 months, 78% at 12 months and 74% after 18 months. Although transcatheter dilation of neoaortic arch obstructions after Norwood operation is successful, there is a high risk of re-intervention and ongoing mortality in this subgroup of patients. Close follow-up is recommended.