These drugs are effective in approximately 85% to 90% of patients, with 30% reporting an absence of tachycardia.45,108,109,112,288 Both drugs have a risk of proarrhythmia resulting in VT that is increased in patients with structural heart disease or ischemic heart disease; in such patients, these drugs are generally avoided. Side effects occur in up to 60% of patients, and approximately 20% discontinue the medications because of adverse effects.45,108,109,112,288 IIb B-R Oral dofetilide or sotalol may be reasonable for ongoing management in patients with AVRT and/or pre-excited AF who are not candidates for, or prefer not to undergo, catheter ablation.99,106 See Online Data Supplement 9. Unlike flecainide and propafenone, sotalol and dofetilide can be used in patients with structural heart disease or coronary artery disease.105 Given the potential for significant QT prolongation and torsades de pointes, inpatient monitoring with serial ECGs is generally performed when these agents are initiated. IIb C-LD Oral amiodarone may be considered for ongoing management in patients with AVRT and/or pre-excited AF who are not candidates for, or prefer not to undergo, catheter ablation and in whom beta blockers, diltiazem, flecainide, propafenone, and verapamil are ineffective or contraindicated.289,290 See Online Data and 12. Small observational studies support the use of amiodarone for preventing recurrent AVRT, but long-term efficacy has not been reported.289,290 Because of the important toxicity associated with long-term use of amiodarone, the drug is usually reserved for patients who are not candidates for catheter ablation and who have failed to respond to or have contraindications to other antiarrhythmic drugs. Page et al 2015 ACC/AHA/HRS SVT Guideline e537 6.2. Management of Asymptomatic Pre-Excitation 6.2.1. 