title: Asymptomatic or "silent" atrial fibrillation: frequency in untreated patients and patients receiving azimilide.
abstract: BACKGROUND
  Asymptomatic, or "silent" atrial fibrillation could increase the risk of stroke. Little is known about the frequency of asymptomatic atrial fibrillation in patients who also have symptomatic atrial fibrillation; similarly, little is known about the effect of antiarrhythmic drug therapy on asymptomatic atrial fibrillation.
  
  
  RESULTS
  Patients in sinus rhythm with a history of symptomatic atrial fibrillation or atrial flutter received placebo or azimilide (35 to 125 mg) once daily for 6 or 9 months in 4 similar double-blind trials. The end point was the first recurrence of a symptomatic ECG-documented supraventricular arrhythmia. Routine transtelephonic electrocardiograms, in the absence of symptoms, were recorded for 30 seconds every 2 weeks until patients completed follow-up or documented a symptomatic supraventricular arrhythmia. Of the 1380 patients, 489 received placebo. Among these patients receiving placebo, 303 transmitted at least one routine ECG while asymptomatic. Asymptomatic atrial fibrillation was recorded in 50 (17%) within 6 months and before recurrence of symptomatic supraventricular arrhythmia. In the 3 trials evaluating azimilide in therapeutic doses (100 and 125 mg), asymptomatic atrial fibrillation occurred in 49 of 382 (13%) receiving azimilide and 43 of 233 (18%) receiving placebo. Although drug effect on time to first asymptomatic event was not statistically significant (hazard ratio, 0.70; P=0.09), there was a 40% reduction in asymptomatic atrial fibrillation on azimilide compared with placebo (P=0.03) when repeated observations were considered.
  
  
  CONCLUSIONS
  Asymptomatic atrial fibrillation is common in untreated patients with a history of symptomatic atrial fibrillation (and is likely underestimated by this analysis). Azimilide may reduce the occurrence of this silent arrhythmia.
authors.affiliation: Cardiovascular Division, Clinical Cardiac Electrophysiology, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, USA. rpage@u.washington.edu
authors.forename: Richard L
authors.initials: RL
authors.lastname: Page
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Tilsch
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Connolly
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Schnell
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Marcello
authors.forename: William E
authors.initials: WE
authors.lastname: Wilkinson
authors.forename: Edward L C
authors.initials: EL
authors.lastname: Pritchett
mesh_terms: D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004562:Electrocardiography; D023381:Endpoint Determination; D005260:Female; D006801:Humans; D006827:Hydantoins; D007093:Imidazoles / Q000627:therapeutic use*; D048289:Imidazolidines; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000627:therapeutic use*; D055502:Secondary Prevention
chemical_list: D000889:Anti-Arrhythmia Agents; D006827:Hydantoins; D007093:Imidazoles; D048289:Imidazolidines; D010879:Piperazines; C086123:azimilide