Beta blockers may decrease catecholamine-related triggers and provide AV nodal blockade during recurrent atrial arrhythmias. One study of adults with transposition of the great arteries and prior atrial switch repairs with implanted defibrillators demonstrated SVT preceding VT in 50% of patients; use of beta-blocker medications in this population was associated with decreased incidence of appropriate defibrillator shocks.486 Observational studies on the use of sotalol in ACHD patients report freedom from recurrent AT in 41% to 46% of patients during short-term follow-up.218,487,488 Use of either medication in the setting of significant sinus node dysfunction may exacerbate bradycardia and requires careful monitoring. Initiation of sotalol in this population is recommended during inpatient monitoring for proarrhythmia for 48 to 72 hours. IIa B-NR 3. Catheter ablation is reasonable for treatment of recurrent symptomatic SVT in ACHD patients.330,449,452,454,457,458,489 492 See Online Data Supplement 20. Multiple observational and multicenter studies have demon strated acute success rates between 65% and 100% for treatment of SVT associated with ACHD.452,454,455,457,489,493,494 Acute success rates vary by tachycardia mechanism and type of congenital heart disease and repair. 