A 26-year-old woman with a history of cardiac surgeries (unknown details) presents with syncope and palpitations. Records obtained from outside institutions show that she has history of dextrocardia with situs solitus, atrioventricular and ventricular arterial discordance with pulmonary atresia, and right ventricular hypoplasia with a large ventricular septal defect. In childhood, she underwent fenestrated lateral tunnel Fontan repair. Later, at 4 years of age, she underwent transcatheter closure of baffle leak with Fontan fenestration and no residual shunt.

She is referred for diagnostic workup (Figure 1). Cardiac computed tomography findings include significant stenosis with thrombosis of the lateral tunnel Fontan with evidence of venous-venous collaterals of deoxygenated blood from the pulmonary artery circulation connecting to the pulmonary venous circulation (Figure 1, panels 1a, 1b). On the basis of these findings, she is started on anticoagulation and scheduled for cardiac catheterization for possible percutaneous intervention of the stenosed Fontan conduit. Cardiac catheterization findings include a significant gradient (4-6 mm Hg) in the lateral tunnel (Figure 1, panel 1c). She undergoes successful percutaneous transluminal angioplasty with a 4.5 cm covered stent (Figure 1, panels 1d, 1e). Post intervention, there is no gradient observed from pullback from high to low along the Fontan conduit.

Figure 1: Cardiac CTA and ICA Findings