title: Catheter ablation of paroxysmal atrial fibrillation in patients with previous amiodarone-induced hyperthyroidism: a case-control study.
abstract: BACKGROUND
  Many patients with atrial fibrillation (AF) receive amiodarone. Amiodarone-induced hyperthyroidism (AIH) may develop as a complication. We hypothesized that pulmonary vein (PV) isolation in patients with paroxysmal AF and history of AIH may yield a lower success rate.
  
  
  RESULTS
  Among 704 patients who underwent AF ablation in our center between 2007 and 2010, we identified 20 patients (mean age 58.3 ± 5.0 years; 11 males) with paroxysmal AF and overt AIH in the past. The control group consisted of 40 patients with amiodarone-refractory AF and no thyroid dysfunction. All patients underwent circumferential PV isolation. During redo procedures all tachycardias were targeted for ablation. During a 12-month follow-up, in the AIH group 6 (30%) patients were arrhythmia free after a single procedure, in comparison to 25 (62.5%) controls (P = 0.01). Atrial tachycardia (AT) was registered in 7 (35%) AIH patients and in 1 (2.5%) control patient (P = 0.001). AF recurred in 10 (50%) AIH versus 15 (37.5%) control patients (P = 0.2). Redo ablation was performed in 7 (35%) AIH patients and in 3 (7.5%) non-AIH patients (P = 0.01). During a redo procedure a PV-unrelated tachycardia was diagnosed in 5 (25%) AIH patients (vs 0 in the controls, P = 0.003). After the last performed ablation, 12 (60%) AIH patients and 28 (70%) controls had no recurrence, P = 0.56. AIH was an independent predictor of ATs.
  
  
  CONCLUSIONS
  PV isolation alone has a lower efficacy for preventing recurrence in paroxysmal AF in AIH patients. After repeat ablations, overall freedom from tachyarrhythmias is similar to patients with no history of thyroid dysfunction.
authors.affiliation: Department of Electrophysiology, Almazov Federal Heart, Blood and Endocrinology Centre, Saint-Petersburg, Russian Federation. evgenymikhaylov@gmail.com
authors.forename: Evgeny N
authors.initials: EN
authors.lastname: Mikhaylov
authors.forename: Viktorya S
authors.initials: VS
authors.lastname: Orshanskaya
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Lebedev
authors.forename: Tamas
authors.initials: T
authors.lastname: Szili-Torok
authors.forename: Dmitry S
authors.initials: DS
authors.lastname: Lebedev
mesh_terms: D000638:Amiodarone / Q000009:adverse effects*; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D000925:Anticoagulants / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000601:surgery*; D016022:Case-Control Studies; D017115:Catheter Ablation / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000139:chemically induced*; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011667:Pulmonary Veins / Q000601:surgery; D012008:Recurrence; D012086:Reoperation; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D000889:Anti-Arrhythmia Agents; D000925:Anticoagulants; D000638:Amiodarone
keywords: ablation; amiodarone; atrial fibrillation; hyperthyroidism; pulmonary vein isolation