Atrial defibrillation. New frontiers.
External electrical atrial defibrillation was developed in the early 1960s. Direct current electrical external shocks convert atrial fibrillation to sinus rhythm in the majority of patients. Although much has been learned about the mechanisms of the arrhythmia and those responsible for successful external direct current atrial defibrillation, the technique has remained essentially unchanged since it was first described by Lown and colleagues. Animal and human studies have shown that atrial defibrillation can be terminated by shocks delivered by way of internal electrode catheters. The technique is most effective when biphasic waveform shocks are delivered by way of large surface area electrodes in the right atrium and the coronary sinus. Synchronization of shocks to R waves greater than 500 msec after the previous beat prevents induction of ventricular tachyarrhythmias. Therefore, internal atrial defibrillation provides an effective and safe method for restoring sinus rhythm in patients who fail external direct current cardioversion. The success of the implantable cardioverter-defibrillator and the encouraging safety and efficacy data from studies of internal atrial defibrillation have generated considerable interest in developing an implantable atrial defibrillator. The efficacy of low-energy shocks to terminate the arrhythmia suggests that such a device might be tolerated by patients. Data about the pathogenesis of atrial fibrillation suggest that rapid detection and immediate termination of atrial fibrillation theoretically might prevent recurrence of the arrhythmia. These data support the development of an implantable atrial defibrillator and the initiation of clinical trials to determine its utility.
Carlson
M D
MD
Division of Cardiology, Case Western Reserve University, Cleveland, Ohio, USA.
Biblo
L A
LA
D000818:Animals; D001281:Atrial Fibrillation / Q000628:therapy*; D001919:Bradycardia / Q000209:etiology; D002986:Clinical Trials as Topic; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000379:methods; D004567:Electrodes, Implanted; D006801:Humans; D010146:Pain / Q000209:etiology; D017180:Tachycardia, Ventricular / Q000209:etiology