Initial energy setting, outcome and efficiency in direct current cardioversion of atrial fibrillation and flutter

OBJECTIVES The purpose of this study was to design a more efficient protoco l for the electrical cardioversion of atrial arrhythmias. BACKGROUND Guidelines for electrical cardioversion of atrial arrhythmias re commend starting with low energy shocks, which are often ineffective. METHODS We recorded the sequence of shocks in 1,838 attempts at cardioversi on for atrial fibrillation (AF) and 678 attempts at cardioversion for atria l flutter. These data were used to calculate the probability of success for each shock of a standard series and the probability of success with a sing le shock at each intensity. In 150 cases, a rhythm strip with the time of e ach shock allowed us to calculate the time expended on unsuccessful shocks. RESULTS We analyzed the effects of 5,152 shocks delivered to patients for A F and 1,238 shocks delivered to patients for atrial flutter. The probabilit y of success on the first shock in AF of >30 days duration was 5.5% at <200 J, 35% at 200 J and 56% at 360 J. In atrial flutter, an initial 100 J shoc k worked in 68%. In AF of >30 days duration, shocks of <200 J had a 6.1% pr obability of success; this fell to 2.2% with a duration > 180 days. In thos e with AF for >190 days, the initial use of a 360 J shock was associated wi th the eventual use of less electrical energy than with an initial shock of :less than or equal to 100 J (581 +/- 316 J vs. 758 +/- 433 J, p < 0.01, M ann-Whitney U test). CONCLUSIONS An initial energy setting of : 360 J can achieve cardioversion of AF more efficiently in patients than traditional protocols, particularly with AF of longer duration. (J Am Coll Cardiol 2001;38:1498-504) (C) 2001 by the American College of Cardiology.