The lowest recommended dose should be used initially, accompanied by regular monitoring of clinical response. 9.3.1. Acute Treatment: Recommendations IIb B-NR 2. Oral dofetilide may be reasonable for prevention of recurrent AT or atrial flutter in ACHD patients.447,474,487,488 See Online Data Supplement 20. Two small observational studies on the use of oral dofetilide for ACHD patients report a high rate of acute conversion of AT or atrial flutter, with longer-term efficacy of the drug (defined by either complete suppression or partial improvement of symptoms) ranging from 70% to 85%. The benefit was tempered by an association with torsades de pointes in 10%.471,484 Although many patients continued to experience recurrence, these episodes were better tolerated and were of limited duration.471,484 Because of the potential risk of proarrhythmia, dofetilide is usually a second-line medication after failure of beta blockers and sotalol. Initiation of oral dofetilide is recommended during 72-hour inpatient monitoring. IIb B-NR Amiodarone may be reasonable for prevention of recurrent AT or atrial flutter in ACHD patients for whom other medications and catheter ablation are ineffective or contraindicated.447 See Online Data Supplement 20. An observational study reported efficacy of amiodarone in maintaining sinus rhythm, although side effects were noted frequently, including thyroid disorders or AV block.447 The risk of significant side effects increases with chronic use and with higher dosages; using the minimal effective chronic dosage is recommended. Observational studies reported thyroid disorders in 13% to 36% of ACHD patients receiving amiodarone; risk factors for thyrotoxicosis include female sex, cyanotic heart disease, low body mass index, prior Fontan procedure, or dosages >200 mg daily.511,512 Amiodarone is recommended for short-term use or for patients for whom alternative therapy is not an option for prevention of recurrent AT. III: Harm B-NR 1. 