Reduced cardioversion thresholds for atrial fibrillation and flutter using the rectilinear biphasic waveform. 
The RLB waveform has been shown to be superior in overall efficacy to the MDS waveform for cardioversion of AF in one prospective study and one large retrospective analysis.  However, little is known about the efficacy of the RLB waveform at lower energies.  This study was undertaken to define the cardioversion thresholds for atrial fibrillation (AF) and flutter (FL) using the rectilinear biphasic (RLB) waveform and compare these to the cardioversion threshold using the conventional monophasic damped sine (MDS) waveform.  All patients underwent transthoracic cardioversion of persistent AF and FL.  We performed step-up cardioversion thresholds for AF in 180 RLB patients and 38 MDS patients and compared those results.  We also performed cardioversion threshold determinations in 39 RLB patients with typical right atrial FL.  For the RLB patients, an initial energy setting of 5 Joules (J) was selected, with increasing energy steps until success, up to 200 J. The MDS energy sequence was 50 up to 360 J. The average selected energy threshold for AF using the RLB waveform was 70.6 J (median=50 J) versus 193.4 J (median=150 J) for the MDS waveform (p<0.001).  For FL, the average cardioversion threshold using the RLB waveform was 33.2 J (median=20 J; p<0.001 vs. AF with the RLB waveform).  Our results show that the transthoracic AF cardioversion threshold using the RLB waveform is significantly lower than the MDS waveform.  As expected, the cardioversion threshold for FL was significantly lower than that of AF using the RLB waveform.