Increase in QT/QTc dispersion after low energy cardioversion of chronic persistent atrial fibrillation.
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.
Boriani
Giuseppe
G
Institute of Cardiology, University of Bologna, Policlinico S. Orsola via Massarenti n 9, 40138, Bologna, Italy. cardio1@almadns.unibo.it
Valzania
Cinzia
C
Biffi
Mauro
M
Corazza
Ivan
I
Camanini
Claudia
C
Martignani
Cristian
C
Bacchi
Letizia
L
Zannoli
Romano
R
Branzi
Angelo
A
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
D000889:Anti-Arrhythmia Agents