Junctional Rhythm as Reversible Driver of Fontan Failure

BACKGROUND: In Fontan circulation, pulmonary blood flow depends on low atrial pressure and preserved atrioventricular (AV) synchrony. AV dyssynchrony as a driver of Fontan failure and Fontan-associated liver disease remains under-recognized. CASE SUMMARY: A 17-year-old boy with Fontan failure, Fontan-associated liver disease, portal hypertension, and effusions had elevated Fontan pressures despite subaortic obstruction relief and Fontan tunnel stenting. Invasive pressure tracings identified junctional rhythm with AV dyssynchrony. Epicardial atrial pacing, preserving AV conduction and avoiding ventricular pacing, normalized Fontan pressures with clinical improvement and a reduction in liver stiffness. DISCUSSION: In patients with failing Fontan circulation and junctional rhythm, restoring AV synchrony by atrial pacing may reverse Fontan hypertension and improve end-organ congestion. TAKE-HOME MESSAGES: Junctional rhythm should be considered a reversible contributor to elevated Fontan pressures before attributing failure to anatomy. Atrial pacing, when AV conduction is intact, can improve Fontan hemodynamics and hepatic congestion while avoiding ventricular pacing.