Intra-atrial defibrillation of human atrial fibrillation.

Low-energy intra-atrial defibrillation is a new therapeutic option for restoring sinus rhythm in patients with atrial fibrillation (AF). The success rate is quite high when right atrium-coronary sinus or right atrium-pulmonary artery electrode configurations are used, although the former is associated with a slightly lower defibrillation threshold. Several issues regarding the safety and tolerability of the procedure remain unresolved. Our experience and that of others indicate that low-energy intra-atrial cardioversion is safe even during exercise, provided the shock is well synchronized with the QRS and the preshock RR interval is > 500 msec. Reported defibrillation thresholds in patients with persistent AF range from 4 to 8 J, and shocks of this type inevitably are associated with some degree of discomfort. Measures aimed at lowering the defibrillation threshold (e.g., use of biphasic waveforms, antiarrhythmic pretreatment, and use of a single effective shock, as opposed to the multiple shocks delivered in research settings) can be expected to increase patient tolerance and extend the indications for low-energy intra-atrial cardioversion. The procedure currently is indicated for patients with persistent AF who are resistant to external defibrillation unable or unwilling to undergo general anesthesia. The procedure could be expanded to patients affected by obesity in whom the efficacy of external cardioversion is lower.