INTERNAL CARDIOVERSION IN 2 PATIENTS WITH ATRIAL-FIBRILLATION REFRACTORY TO EXTERNAL CARDIOVERSION

A 26-year-old man underwent an electrophysiological study evaluation o f a history of congenital heart disease, presyncope, and wide complex tachycardia. During the study the patient developed sustained atrial f ibrillation with a rapid ventricular response. A 17-year-old man with a history of sick sinus syndrome developed sustained atrial fibrillati on. Both patients failed four attempts at external cardioversion with a. maximum delivered energy of 360 J. Low energy cardioversion was suc cessful in both patients using biphasic waveforms and internal transve nous defibrillation electrodes. Internal cardioversion using a transve nous electrode system can be successful in patients with atrial fibril lation refractory to external cardioversion.