LOW-ENERGY INTERNAL CARDIOVERSION OF ATRIAL-FIBRILLATION RESISTANT TOTRANSTHORACIC SHOCKS

Objective-To investigate the efficacy of internal cardioversion using low energy shocks delivered with a biatrial electrode configuration in chronic atrial fibrillation resistant to transthoracic shocks. Method s-Low energy internal cardioversion was attempted in 11 patients who h ad been in atrial fibrillation for 233 (SD 193) days and had failed to cardiovert with transthoracic shocks of 360 J in both apex-base and a nterior-posterior positions. Synchronised biphasic shocks of up to 400 V (approximate to 6 J) were delivered, usually with intravenous sedat ion only, between high area electrodes in the right and the left atriu m (coronary sinus in nine, left pulmonary artery in one, left atrium v ia patent foramen ovale in one). Results-Sinus rhythm was restored in 8/11 patients. The mean leading edge voltage of successful shocks was 363 (46) V [4.9 (1.2) J]. Higher energy shocks induced transient brady cardia [time to first R wave 1955 (218) ms]. No proarrhythmia or other acute complications were observed. Conclusions-Low energy internal ca rdioversion of atrial fibrillation can restore sinus rhythm in patient s in whom conventional transthoracic shocks have failed.