Internal cardioversion with low energy shocks of atrial fibrillation resistant to external cardioversion

Background and objective. Although external electrical cardioversion is eff ective in most patients with atrial fibrillation, there are cases refractor y to external cardioversion. This study is aimed at showing our initial exp erience with an internal cardioversion system in patients with previous uns uccessful external cardioversion. Patients and methods. Between February, 1997 and September, 1998 nine conse cutive patients with spontaneous chronic or persistent atrial fibrillation that failed external cardioversion, were included. Internal cardioversion w as performed under sedation with two electrodes that had a 5.5 cm coil plac ed in the lateral right atrium and coronary sinus. Both electrodes were con nected to an external defibrillator capable of delivering R-wave synchroniz ed low-energy biphasic shocks following a minimum RR interval of 500 ms. En ergy between 2 J and 10 J was applied until the restoration of sinus rhythm or a maximum of 2 shocks of 10 J. Results. Sinus rhythm was achieved in the nine patients, but in two of them atrial fibrillation recurred after a few beats. Both had underlying struct ural heart disease. The other 7 patients, 5 of them without structural hear t disease, were in sinus rhythm at discharge. No mechanic complications or ventricular arrhythmias were observed. Six patients are in sinus rhythm aft er 4 +/- 3 months of follow-up. Conclusions. Low-energy intracardiac cardioversion is useful in some patien ts with atrial fibrillation that had failed external cardioversion and can be performed without general anesthesia.