Refractory Atrial Tachyarrhythmias Management in Severely Dilated Right Atrium Due to Complex Congenital Heart Disease: Clinical Perspectives Beyond Catheter Ablation.

Refractory atrial tachyarrhythmias frequently occur in patients with congenital heart disease (CHD) who have a markedly enlarged right atrium (RA). The obfective of this study was to elucidate arrhythmogenic substrates and evaluate the comprehensive treatment outcomes in patients with complex CHD and a giant RA (≥190 mL). Ten patients with complex CHD and a giant RA who underwent catheter ablation (CA) were evaluated (median age, 40 [interquartile range (IQR), 33 to 52] years). A total of 23 tachyarrhythmias were identified during CA. Three distinct electrophysiological mechanisms were observed: atrial fibrillation with coexisting reentrant atrial tachycardia in 3 patients, reentrant atrial tachycardia localized to low-voltage scar areas (<0.03 mV) in 2 patients, and atrial tachycardia likely involving epicardial pathways in 3 patients. CA alone achieved an overall success rate of 70%, with partial success in 50% of cases. Post-CA, 6 patients underwent surgical intervention, including RA volume reduction (RAVR) and RA/coronary sinus cryoablation, while 8 patients received pacemaker-based rhythm management. Among the 9 patients treated with either surgical or device-based therapy, the clinical arrhythmia severity score showed significant improvement (median Δ, -3 [IQR, -4.5 to -2], p = 0.004), accompanied by reductions in brain natriuretic peptide levels (median Δ = -39.5 [IQR, -114.7 to -26.0] pg/mL, p = 0.004) and cardiothoracic ratio (Δ = -6.8 [IQR, -11.9 to 0.1]%, p = 0.039). In conlusion, in CHD patients with markedly enlarged RA, CA alone is often insufficient. A combined strategy involving surgical intervention and pacemaker-based rhythm control appears to offer superior outcomes for both arrhythmia management and hemodynamic status.