title: Atrial activation occurring immediately after successful cardioversion of atrial fibrillation.
abstract: OBJECTIVE
  Electrical defibrillation is very effective in interrupting atrial fibrillation (AF). However, its mechanism is not completely understood. We report our observations in patients subjected to external electriocardioversion (ECV) of atrial fibrillation and contrast them with recent theories about defibrillation mechanism.
  
  
  METHODS
  In 13 consecutive patients transthoracic electrical cardioversion for AF was performed during an electrophysiological study (11 monophasic -200-360 J- and 9 biphasic shocks -50-150 J-). About 10-16 electrograms were obtained with multipolar catheters recording right atrium, coronary sinus, and right pulmonary artery. AF was defined by interelectrogram intervals and changing sequences among recordings, indicating complete lack of organization. We evaluated the presence of propagated activations immediately (<300 ms) after successful shocks (>or=1 discrete electrogram in all recordings). In unsuccessful shocks we evaluated changes in electrogram morphology (discrete/fragmented) and interelectrogram intervals before and after defibrillation.
  
  
  RESULTS
  About 16/20 shocks terminated AF. In 6/16 one or two cycles of atrial activation were recorded just after the shock and before AF ended. In 10/16 AF was interrupted immediately after the shock. 4/20 shocks did not interrupt the arrhythmia. After these shocks, transient organization of recorded activity with longer interelectrogram cycle length and disappearance of fragmented activity were transiently observed.
  
  
  CONCLUSIONS
  Our clinical findings in atrial defibrillation in vivo reproduce experimental data that show myocardial activations early after successful direct current shocks. These observations suggest that successful defibrillation depends not only on the immediate effects of the shock, but also on transient effects on electrophysiological properties of the myocardium, capable of interrupting persistent or reinitiated activations.
authors.affiliation: Servicio de Cardiología, Complejo Hospitalario Torrecardenas, Almería, Spain. amartinp@secardiologia.es
authors.forename: Arturo Martín Peñato
authors.initials: AM
authors.lastname: Molina
authors.forename: Francisco G
authors.initials: FG
authors.lastname: Cosío
authors.forename: Agustín
authors.initials: A
authors.lastname: Pastor
authors.forename: Ambrosio
authors.initials: A
authors.lastname: Núñez
authors.forename: Paula
authors.initials: P
authors.lastname: Awamleh
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D016009:Chi-Square Distribution; D004554:Electric Countershock; D005260:Female; D006325:Heart Atria / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome