title: Increase in QT/QTc dispersion after low energy cardioversion of chronic persistent atrial fibrillation.
abstract: BACKGROUND
  The effects of atrial internal cardioversion on QT interval and QT dispersion (parameters associated with increased risk of ventricular tachyarrhythmias) are unknown. We investigated changes in QT interval, QTc and QT dispersion immediately after shock delivery for internal cardioversion in patients with chronic persistent atrial fibrillation.
  
  
  METHODS
  Twenty-two patients with chronic persistent atrial fibrillation (mean duration, 17+/-23 months) underwent transvenous low-energy internal atrial cardioversion with a step-up protocol of shocks delivered between catheters in the right atrium and coronary sinus. (successful shock, 7.2+/-4.2 J). RR interval, QT interval, QTc interval, QT dispersion, and QTc dispersion were all measured on three consecutive beats (at 75 mm/s on at least 9 of 12 leads) and then averaged both before and after (1) the last unsuccessful shock, and (2) sinus rhythm restoration.
  
  
  RESULTS
  All parameters remained similar in the minute before and after the last unsuccessful shock. At 1 min after the successful shock, abrupt increases in QT dispersion (+43.8% vs. pre-shock; P<0.001 at least significant difference analysis) and QTc dispersion (+30.0%; P<0.05) were observed, followed by a gradual return to pre-shock values at 15 min.
  
  
  CONCLUSIONS
  These findings strongly suggest the likely existence of a brief period of increased electrical vulnerability immediately after restoration of sinus rhythm by internal cardioversion. Particular caution should therefore be applied whenever class III antiarrhythmic drugs are administered immediately after successful internal atrial cardioversion.
authors.affiliation: Institute of Cardiology, University of Bologna, Policlinico S. Orsola via Massarenti n 9, 40138, Bologna, Italy. cardio1@almadns.unibo.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
authors.forename: Cinzia
authors.initials: C
authors.lastname: Valzania
authors.forename: Mauro
authors.initials: M
authors.lastname: Biffi
authors.forename: Ivan
authors.initials: I
authors.lastname: Corazza
authors.forename: Claudia
authors.initials: C
authors.lastname: Camanini
authors.forename: Cristian
authors.initials: C
authors.lastname: Martignani
authors.forename: Letizia
authors.initials: L
authors.lastname: Bacchi
authors.forename: Romano
authors.initials: R
authors.lastname: Zannoli
authors.forename: Angelo
authors.initials: A
authors.lastname: Branzi
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000628:therapy*; D002908:Chronic Disease; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D000889:Anti-Arrhythmia Agents