Catheter ablation achieved a 73.5% acute success rate in treating supraventricular tachyarrhythmias among 49 Fontan circulation patients, with only 4.1% experiencing complications. The multicenter study found intra-atrial reentrant tachycardia was the most common arrhythmia (39%), typically originating from the right atrial lateral wall. Patients with newer Fontan procedures—lateral tunnel and extracardiac conduit—had significantly lower recurrence rates compared to older atriopulmonary connections over 78 months follow-up. This represents meaningful progress for a vulnerable population where cardiac arrhythmias pose substantial health risks. Fontan circulation, created surgically for patients born with single-ventricle heart defects, fundamentally alters cardiac anatomy and blood flow, making arrhythmia treatment exceptionally challenging. The relatively high success rate suggests catheter ablation could become standard care for these patients, potentially improving quality of life and reducing hospitalizations. However, the 34.7% recurrence rate indicates ongoing monitoring remains essential. As this is a preprint study awaiting peer review, these promising results require validation through the formal review process before clinical practice changes.