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Comparison of the Rectilinear BiphasicWaveform With the Monophasic Damped

Sine Waveform for ExternalCardioversion of Atrial Fibrillation

and FlutterMark J. Niebauer, PhD, MD, James E. Brewer, MS, Mina K. Chung, MD, and

Patrick J. Tchou, MD

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xternal cardioversion using the monophasic dampedine (MDS) waveform is successful 70% to 94% of theime when using up to 360 J. The rectilinear biphasicRLB) defibrillator has been shown to be superior infficacy to the MDS waveform in atrial cardioversion in

small randomized study. This larger, retrospectivetudy compares the results of the RLB waveform withhose of the MDS waveform for cardioversion of atrialbrillation (AF) and atrial flutter in a large cohort ofatients. We performed 1,877 external cardioversionrocedures in 1,361 patients for AF and atrial flutter bysing the RLB defibrillator. We compared these resultsith those of the MDS defibrillator in 2,025 patients whonderwent 2,818 cardioversion procedures. The overalluccess rates for the RLB defibrillator were 99.1% for AFnd 99.2% for atrial flutter, and the corresponding suc-

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2004 by Excerpta Medica, Inc. All rights reserved.he American Journal of Cardiology Vol. 93 June 15, 2004

ess rates for the MDS defibrillator were 92.4% and9.8% (p <0.001; RLB superior for AF). The medianverall successful energy level for the MDS waveformas 200 J, whereas the corresponding RLB energy levelas 100 J. Multivariate analyses demonstrated thatnderlying clinical conditions or use of antiarrhythmicrugs does not significantly affect overall success rates.ur results from >4,000 procedures confirmed and ex-

ended those of the previous report by showing a veryigh success rate for cardioversion of AF and atrialutter using the RLB waveform. The MDS waveform wasqually effective for atrial flutter but significantly lessffective in terminating AF. �2004 by Excerpta Med-ca, Inc.

(Am J Cardiol 2004;93:1495–1499)

ince its introduction in 1962 by Lown et al,1external direct-current cardioversion has been the

ethod of choice2 for terminating atrial fibrillationAF) and atrial flutter. This method is safe and 70% to4% effective3–8 when the conventional monophasicamped sine (MDS) shock waveform is used (Figure). An external defibrillator has been developed thatelivers a rectilinear biphasic (RLB) waveform (Fig-re 1). This defibrillator, manufactured by Zoll Corp.Burlington, Massachusetts), was approved based on aandomized comparison with the MDS waveform in amall prospective, multicenter trial.1 The trial demon-trated that RLB shocks, using a set energy up to 170, are significantly more effective than MDS wave-orm shocks of up to 360 J for the external cardiover-ion of AF. Since acquiring the RLB defibrillator earlyfter its release in 1999, we have used it for cardio-ersion of AF in a larger sample of patients with AFnd atrial flutter. Patients with AF and atrial flutter hadot been evaluated in the previous study.7 We then

rom the Department of Cardiovascular Medicine, Cleveland Clinicoundation, Cleveland, Ohio; the Section of Cardiology, University ofebraska Medical Center, Omaha, Nebraska; and Zoll Medical,urlington, Massachusetts. Manuscript received November 19,003; revised manuscript received and accepted March 2, 2004.

Address for reprints: Mark J. Niebauer, PhD, MD, Department ofnternal Medicine, Section of Cardiology, 982265 Nebraska Medi-al Center, Omaha, Nebraska 68198-2265. E-mail: mniebaue@

etrospectively compared the RLB results with ourrevious MDS waveform cardioversion results to as-ess differences in effectiveness in achieving tran-ient, persistent, and overall successful cardioversiono sinus rhythm.

ETHODSThis study was a retrospective trial that evaluated

he results of external transthoracic electrical cardio-ersion using the RLB waveform in a general clinicaletting. The study was reviewed and approved by thenstitutional review board of the Cleveland ClinicCleveland, Ohio).

From October 1999 to September 2001, there were,056 patients (outpatients and inpatients) who under-ent 1,503 external cardioversion procedures for AFith a RLB defibrillator in our electrophysiologic

aboratory. During this same period, we performed37 cardioversion procedures in 305 patients for atrialutter using the RLB waveform. Hence, 1,361 pa-

ients underwent 1,877 cardioversion procedures withhe RLB defibrillator. The results of all RLB cardio-ersion procedures were reviewed to determine theverall efficacy of this waveform in our large clinicalopulation. We compared the overall success rate ofLB shocks with that of our previous cardioversion

tudy in 2,025 patients (1,490 for AF and 535 for atrial

utter) who underwent 2,848 external cardioversions

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2,200 for AF and 648 for atrial flutter) using an MDSaveform defibrillator from August 1996 to Septem-er 1999. The MDS defibrillator delivered up to 360 J,nd the RLB defibrillator delivered up to 200 J (inontrast to the device used in the seminal clinicaltudy by Mittal et al7 in which a maximum of 170 Jas available).

Definitions: Overall shock success was defined asonversion to a sinus atrioventricular junctionalhythm with retrograde P waves or as paced atrialhythm immediately after the shock with �1 identifi-ble atrial depolarization. This confirmed the termina-ion of ongoing atrial reentry. If AF was not presenthen the patient left the laboratory (usually 15 to 30inutes after the shock), we termed the procedure a

persistent success.” However, AF or atrial flutter didecur in �10% of patients before leaving the labora-ory despite additional shocks with transient conver-ion from the presenting dysrhythmia in some cases.n those cases in which the patient left the laboratoryn AF or atrial flutter after an initially successfulhock, we termed the procedure a “transient success.”ecent publications have addressed the phenomenonf AF recurrence after cardioversion. The term “im-ediate recurrence” of AF is now used generally to

escribe a recurrence that occurs within 1 to 2 minutesfter cardioversion, and “subacute recurrence” de-cribes a recurrence 2 minutes to 2 weeks after suc-essful cardioversion. Unfortunately, much of our datareceded these definitions, and review of the patientrocedure records was unclear, in most cases, as torecisely when AF recurred before patient dismissalrom our electrophysiologic laboratory. Hence, ourransient success procedures include all immediateecurrence and early subacute recurrence procedures.Overall success” was defined as the sum of the tran-ient and persistent success rates for a given arrhyth-ia and waveform, signifying shock effectiveness. Ife were unable to terminate the arrhythmia to even a

ingle organized atrial beat, the procedure was termed“failure.” To confirm whether a procedural result is

ccurately reported, our database records this result in

IGURE 1. The current profile of the first phase of the RLB wave-orm is relatively flat compared with the higher current peakalue seen with the MSD waveform.

different fields: the final procedural result field, a p

496 THE AMERICAN JOURNAL OF CARDIOLOGY� VOL. 93

econd field reporting the final heart rhythm, and ahird field reporting the result after each shock to theatient. Any conflicts were resolved by review of theatient’s chart, where initial and final rhythm stripsre saved, and the written summary of the procedure.n the very rare cases in which failure and transientuccess could not be resolved by review of the data-ase or the chart, a failure was reported.

Shock waveforms: The RLB waveform was gener-ted with an external RLB defibrillator (Zoll Seriesiphasic Defibrillator, Zoll Corp.). The waveform wasenerated by a 115-�F capacitive discharge, compris-ng an essentially constant-current 6-ms first phasend a truncated, exponential 4-ms second phase (Fig-re 1). The amplitude of the phases changed with theelected energy, up to a maximum of 200 J. The MDSaveform shocks were delivered from a Zoll PD-1200efibrillator, which delivers up to 360 J of energy.

Shock electrodes: Adhesive pads for external car-ioversion (Zoll Cardiology Specialty Pad) were usedo deliver the RLB and MDS shocks delivered fromhe corresponding Zoll defibrillators. These electrodeatches were positioned in a left or right anteriorrientation (depending on the physician’s preference)nd left posterior chest wall orientation (in all cases).he anterior electrode was circular and had an activeurface area of 78 cm2. The posterior electrode wasectangular and had an active surface area of 113 cm2.

Cardioversion procedure: The standard guidelinesor anticoagulation of patients recommended by themerican College of Physicians were adhered to inur laboratory.8 Specifically, patients with AF �48ours’ duration were anticoagulated for �3 weeksefore the cardioversion procedure or underwentransesophageal echocardiography, where no lefttrial thrombus was visualized in the presence ofherapeutic anticoagulation with warfarin or intrave-ous heparin. Patients were sedated with intravenousodium methohexital or etomidate, with constantonitoring of respiration, blood pressure, and trans-

ermal partial pressure of oxygen. Ventilatory supportas provided, if needed, to maintain an adequateartial pressure of oxygen. In all cases, the procedureas directed by electrophysiologists at the Clevelandlinic, and the initial shock energy, anterior patchositions, and magnitude of any subsequent shocksaried according to the preferences of the staff cardi-logist. There was no specific protocol for selection ofhe initial energy setting or for any subsequent energyteps or number of shocks before termination of therocedure. At least 1 surface electrocardiographic leadas monitored throughout the cardioversion proce-ure to determine rhythm before and after shock.hen failure (no discernible P wave) occurred at theaximum set energy (200 J for RLB or 360 J forDS), then pressure over the anterior patch during

hock delivery and/or repositioning of that patch waserformed before another attempt. Any concomitantse of antiarrhythmic drugs was noted. In rare in-tances, intravenous antiarrhythmic drugs were givenfter initial failure or transient success to produce a

ersistent success.

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Statistical analysis: All continuous variables are ex-ressed as mean � SD. Univariate efficacy compari-ons across waveforms, arrhythmias, and other non-uantitative data were performed with the chi-squareest. Unpaired t test was used to compare quantitativeesults. Multivariate analysis of clinical characteristicsas performed with multivariate linear regression. For

ll comparisons, p �0.05 was considered statisticallyignificant.

ESULTSClinical characteristics: The clinical characteristics

f all patients with AF and atrial flutter are listed in

able 1. Mean ejection fraction, left atrial diameter, s

ARRHYTHMIA AND CONDUCTION DISTURBAN

age, and proportions of men andwomen were not significantly differ-ent between the corresponding AFand atrial flutter groups. However,there was a significant difference inage between men and women withAF (women were �3 years older),but this difference was the same forRLB and MDS groups. This differ-ence was not seen in the atrial fluttergroup.

We recorded clinical disease infor-mation in 969 patients who underwentcardioversion for AF using the RLBwaveform and 1,359 patients in whomthe MDS waveform was used for thatarrhythmia. We also recorded thesedata in 275 patients with atrial flutterwho were cardioverted with the RLBwaveform and 470 corresponding pa-tients in whom the MDS waveformwas used. Many patients had a combi-nation of �2 cardiac diseases. Univar-iate analysis of these data showed thatpatients with AF in the RLB group hadmore structural heart disease (19.5%)than did those in the MDS group byunivariate analysis (15.9%; p �0.05).However, the effect of structural dis-ease on cardioversion outcome wasnot confirmed by multivariate analysisof (p � 0.22).

Arrhythmia duration: The arrhyth-mia duration data are presented inTable 2. Our database recorded ar-rhythmic duration as 3 categories, ifknown: �2 days, 2 to 7 days, and �7days. We had complete data concern-ing AF duration in 1,441 RLB pro-cedures and 2,014 MDS procedures.Corresponding data were availablefor 308 patients in the RLB groupand 590 patients in the MDS groupwho underwent cardioversion foratrial flutter. Using univariate analy-sis, significantly more MDS cardio-versions were performed for epi-sodes of AF �2 days in duration

18.0%) compared with the RLB group (13.5%; p0.05). However, multivariate analysis failed to con-

rm arrhythmia duration as a significant factor inverall cardioversion success (p � 0.08) when cor-ected for other variables. When the arrhythmia dura-ion data for atrial flutter were analyzed, the MDSroup had significantly more patients with atrial flutterhat was �2 days in duration and significantly feweratients with atrial flutter �7 days in duration. Pa-ients with atrial flutter demonstrated the arrhythmiaor a longer period before cardioversion than did thoseith AF.

Procedural outcome: A persistently successful re-

ll Four

AF

MDS

1,490

67.4 � 11.666.1 � 11.870.1 � 10.6*

1,027 (68.9%)463 (31.1%)0.44 � 0.1548.5 � 9.0

1,359216 (15.9%)547 (40.2%)487 (38.4%)252 (18.5%)112 (8.2%)33 (2.4%)

for Patients

roup

MDS

2,1701,890 (87.1%)*

116 (5.3%)*164 (7.6%)*267 � 82

200

2,014363 (18.0%)*287 (14.2%)

1,364 (67.8%)

nalysis details and

TABLE 1 Demographics and Clinical Characteristics of Patients in AArrhythmia and Waveform Groups

Atrial Flutter

RLB MDS RLB

Patients (n) 305 535 1,056Age (yrs)

All patients 64.5 � 12.4 65.5 � 12.3 67.0 � 12.3Men 64.3 � 12.0 65.4 � 12.1 65.5 � 12.5Women 64.9 � 13.4 65.9 � 12.8 70.5 � 11.0*

Men 229 (75.1%) 412 (77.0%) 742 (69.8%)Women 76 (24.9%) 123 (23.0%) 321 (30.2%)Ejection fraction 0.44 � 0.15 0.42 � 0.15 0.45 � 0.14Left atrial diameter (mm) 50.4 � 8.6 47.8 � 7.9 48.6 � 9.4Heart diseasePatients (n) 275 470 969No structural disease‡ 44 (16.0%) 75 (16.0%) 189 (19.5%)†Coronary artery disease 114 (41.5%) 346 (46.6%) 349 (36.0%)Valvular heart disease 100 (36.4%) 283 (36.8%) 321 (33.1%)Hypertensive heart disease 31 (11.3%) 60 (12.8%) 174 (18.0%)Dilated cardiomyopathy 18 (6.5%) 28 (6.0%) 90 (9.3%)Hypertrophic cardiomyopathy 7 (2.5%) 8 (1.7%) 28 (2.9%)

Univariate results for structural disease data are shown.*p �0.05, age for men versus age for women.†p �0.05 versus MDS waveform group.‡Multivariate analysis showed no differences for structural heart disease.

TABLE 2 Cardioversion Procedure Results and Arrhythmia DurationWith Atrial Fibrillation and Atrial Flutter

Atrial Flutter Group AF G

RLB MDS RLB

Cardioversion outcomeProcedures (n) 337 648 1,540

Persistently successful 324 (96.1%) 637 (98.3%)† 1,416 (91.9%)Transiently successful 11 (3.1%)† 10 (1.5%)† 111 (7.2%)Failure 2 (0.8%) 1 (0.2%)† 13 (0.9%)Mean overall successful

energy level (J)61 � 46 231 � 108 96 � 50

Median overall successfulenergy level (J)

50 200 100

Arrhythmic duration (total) 308 590 1,441�48 h 54 (17.5%) 156 (26.4%)† 195 (13.5%)2–7 days 67 (21.7%)† 137 (23.3%)† 189 (13.1%)�7 days 183 (59.4%)† 297 (50.3%)*† 1,057 (73.4%)

Univariate analysis results are shown for the arrhythmic duration data. See text for adiscussion.

*p �0.05, MDS versus RLB (same arrhythmic).†p �0.01, atrial flutter versus AF (same waveform).

ult occurred in 91.9% of RLB cardioversions for AF,

CES/AF CARDIOVERSION USING THE RLB WAVEFORM 1497

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nd an additional 7.2% of the procedures producedransiently successful cardioversion. Hence, the over-ll success rate for the RLB waveform was 99.1%1,527 of 1,540). In comparison, MDS waveformhocks resulted in persistent success in 87.1% of cor-esponding procedures, and an additional 5.3% wereonverted only transiently, resulting in an overall suc-ess rate of 92.4% (2,006 of 2,170). The differenceetween waveform groups was highly significant in allesult subgroup comparisons, with fewer failures andore persistently and transiently successful cardiover-

ions in the RLB group. This difference was con-rmed in the univariate (p �0.001) and multivariatep �0.0001) analyses.

The average persistently successful energy selectedor cardioversion of AF using the RLB waveform was3 � 49 J (median 100), and the corresponding valueor the MDS waveform was 264 � 82 J (median 200).or transiently successful cardioversions of AF, theverage energy selected was 127 � 59 J (median 100)or the RLB waveform and the corresponding MDSalue was 319 � 68 J (median 360). We did not

TABLE 3 Antiarrhythmic Drug Use in the Atrial Fibrillation Group

Persistent Success Trans

MDS RLB MDS

Amiodarone 626 (92.3%) 373 (93.5%) 24 (3.5%)*� Blocker 493 (90.1%) 538 (93.6%) 24 (4.4%)Sotalol 272 (87.2%) 163 (87.2%) 26 (8.3%)Flecainide 189 (88.3%) 147 (92.5%) 12 (5.6%)Propafenone 37 (94.9%) 50 (96.2%) 0 (0%)*Procainamide 104 (88.9%) 34 (89.5%) 10 (8.5%)Quinidine 8 (72.7%) 25 (89.3%) 3 (27.3%Moricizine 4 (100%) 11 (73.3%) 0 (0%)Disopyramide 10 (90.9%) 26 (78.8%) 1 (9.1%)Dofetilide 0 (0%) 75 (83.3%) 0 (0%)*Any AAD 1,541 (86.5%) 1,173 (92%) 92 (5.1%)None 386 (89.4%) 243 (90%) 24 (5.6%)All patients 1,927 (87.2%) 1,416 (91.7%) 116 (5.2%)

Combinations of drugs were used in some patients.*p �0.05 versus no-drug group.AAD � antiarrhythmic drug.

TABLE 4 Antiarrhythmic Drug Use in the Atrial Flutter Groups

MSD

Persistent Success Transient Success Failure

Amiodarone 189 (97.4%) 5 (2.6%) 0 (0%)� Blocker 151 (99.3%) 1 (0.7%) 0Sotalol 48 (98%) 0 1 (2%)Flecainide 65 (98.5%) 1 (1.5%) 0Propafenone 21 (100%) 0 0Procainamide 64 (100%) 0 0Quinidine 7 (100%) 0 0Moricizine 2 (100%) 0 0Disopyramide 9 (100%) 0 0Dofetilide 0 0 0No AAD 167 (97.7%) 3 (1.8%) 1 (0.6%)All patients 637 (98.3%) 10 (1.5%) 1 (0.2%)

There were no significant effects of AADs use in patients of either waveform gropatients. See Table 3 for abbreviation.

erform a statistical analysis to compare the average �

498 THE AMERICAN JOURNAL OF CARDIOLOGY� VOL. 93

nergy values between the 2 waveforms because thenergies were selected in a nonsystematic manner.

We previously reported the superior efficacy ofual simultaneous external shocks using maximumutput of 2 MDS waveform defibrillators in patients inhom the maximum 360-J output of a single devicead failed.9 Because of the unusually high energies ofhose cardioversion procedures, those data were notncluded in the overall analysis in our MDS group.owever, we performed external cardioversions using

he RLB waveform in 14 of those same patients whoad developed recurrent AF some months after therevious 720-J cardioversions with the MDS wave-orm. In all 14 patients, we succeeded in convertingF to sinus rhythm using 50- to 200-J RLB shocks.

The RLB and MDS waveforms were highly suc-essful in cardioversion of atrial flutter, with no sig-ificant difference between groups (Table 2). Specif-cally, the persistent success rates for the RLB and

DS waveforms were 96.1% and 98.3%, respec-ively. As expected, the persistent success rate of atrialutter cardioversion was significantly greater (p

success Failure Total

RLB MDS RLB MDS RLB

21 (5.3%)* 28 (4.1%) 5 (1.2%) 678 39930 (5.2%) 30 (5.5%) 7 (1.2%) 547 57523 (12.3%) 14 (4.5%) 1 (0.5%) 312 18711 (6.9%) 13 (6.1%) 1 (0.6%) 214 1592 (3.8%)* 2 (5.1%) 0 (0%) 39 523 (7.9%) 3 (2.6%) 1 (2.6%) 117 383 (10.7%) 0 (0%) 0 (0%) 11 281 (6.7%) 0 (0%) 3 (20%) 4 153 (9.1%) 0 (0%) 4 (12.1%) 11 33

13 (14.4%)* 0 (0%) 2 (2.2%) 0 9091 (7.1%) 145 (8.1%) 11 (0.9%) 1,782 1,27526 (9.6%) 22 (5.1%) 1 (0.4%) 432 270

117 (7.6%) 167 (7.6%) 12 (0.8%) 2,210 1,545

RLB Waveform

Total Persistent Success Transient Success Failure Total

194 103 (98.1%) 2 (1.9%) 0 (0%) 105152 135 (95.7%) 5 (3.5%) 1 (0.7%) 14149 24 (92.3%) 2 (7.7%) 0 2666 23 (92%) 2 (8%) 0 2521 18 (90%) 2 (10%) 0 2064 12 (85.7%) 2 (14.3%) 0 147 1 (100%) 0 0 12 0 0 0 09 3 (100%) 0 0 30 8 (72.7%) 2 (18.2%) 1 (9.1%) 11

171 58 (98.3%) 1 (1.7%) 0 59648 324 (96.1%) 11 (3.3%) 2 (0.6%) 337

ompared with patients without AADs. Combinations of drugs were used in some

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aveform. However, a significantly smaller percent-ge of atrial flutter cardioversion procedures (1.5% to.1%) resulted in transient success, compared with theF patients (5.3% to 7.6%; p �0.001). The percent-

ge of cardioversion procedural failures was signifi-antly greater in patients with AF in the MDS grouphan in patients in all other arrhythmic subgroups (p

0.001). The use of antiarrhythmic drugs on the over-ll cardioversion success rate was not significant byultivariate analysis (p � 0.06) (Tables 3 and 4).Adverse events: There were 15 adverse events re-

orded during all cardioversion procedures. Thereere no deaths, but 6 patients (5 in the MDS group

nd 1 in the RLB group) required hemodynamic sup-ort and/or pressors after successful cardioversion dueo bradycardia and hypotension. Six patients (2 in the

DS group, 2 in the RLB group, and 2 in whom nohocks were delivered) required aggressive ventilatoryupport (endotracheal intubation or bag mask) due toespiratory insufficiency after receiving intravenousedation. All 12 of these patients recovered com-letely with supportive treatment. Two patients (in theLB group) developed ventricular fibrillation afterirect-current shock due to poor synchronization ofhe shock. These patients were promptly defibrillatedithout sequelae. One patient reported a rotator cuff

njury after successful MDS cardioversion. Thereere no strokes or transient ischemic cerebral events

eported within 30 days after cardioversion. However,hese data may be incomplete because long-term re-ults are not routinely followed in our electrophysi-logic laboratory database.

ISCUSSIONOur results confirmed and extended our previous

esults in the smaller, prospective, randomized study,hich demonstrated the superiority of the RLB wave-

orm over the MDS waveform. Most striking was theignificant decrease in overt failures for cardioversionf AF observed with the RLB waveform. The resultsf our cardioversion procedures for atrial flutterhowed that external electrical cardioversion is highlyuccessful in this type of arrhythmia, regardless of theaveform used.

Another, recently approved biphasic waveform de-brillator uses a truncated exponential biphasic wave-orm and has also been shown to be superior to the

DS waveform in conversion from AF for �30 sec- c

ARRHYTHMIA AND CONDUCTION DISTURBAN

nds after the shock.10 These 2 waveforms are dis-inct, however, and only the RLB waveform defibril-ator was used in this study. In this study, we reportedhe transient success rates for AF cardioversion withhe 2 waveforms and for atrial flutter, which have noteen previously reported. We saw no significant de-rease in the proportion of patients with AF who hadransient success after RLB shocks compared withhose receiving MDS shocks, but we found a signifi-antly smaller percentage of overt failures with theLB waveform. Our results showed a significantly

arger proportion of patients with transient successesn addition to persistent successes with the RLB wave-orm. However, the relative increase in transientlyuccessful cardioversions in the RLB group can bexplained by the overall reduction in cardioversionailures because the percentage of persistently suc-essful cardioversions also increased in the RLBroup.

Acknowledgment: We thank Dianna Bash, RN, forital assistance in patient data management and Sawnarion-Phillips for expert secretarial assistance in

reparing this report.

. Lown B, Amarasingham R, Newman J. New method for terminating cardiacrrhythmias: use of synchronized capacitor discharge. JAMA 1962;182:548–555.. Lown B, Perloth MG, Kaidbey S, Abe T, Harken DW. “Cardioversion” oftrial fibrillation: a report on the treatment of 65 episodes in 50 patients. N EnglMed 1963;269:325–331.. Hagemeijer F, Van Houwe E. Titrated energy cardioversion of patients onigitalis. Br Heart J 1975;37:1303–1307.. Lundstrom T, Ryden L. Chronic atrial fibrillation. Acta Med Scand 1988;223:3–59.. Van Gelder IC, Crijns HJ, Van Gilst WH, Verwer R, Lie KI. Prediction ofneventful cardioversion and maintenance of sinus rhythm from direct currentlectrical cardioversion of chronic atrial fibrillation and flutter. Am J Cardiol991;68:41–46.. Van Gelder IC, Crijns HJ, Tielman RG, Brugeman J, de Kam PJ, GosselinkTM, Verheught FWA, Lie KI. Chronic atrial fibrillation: success of serial

ardioversion therapy and safety of oral anticoagulation. Arch Intern Med 1996;56:2585–2592.. Mittal S, Ayati S, Stein KM, Schwartzmann D, Cavlovich D, Tchou PJ,arkowitz SM, Slotwiner DJ, Scheiner MA, Lerman BB. Transthoracic cardio-

ersion of atrial fibrillation: comparison of rectilinear biphasic versus dampedine wave monophasic shocks. Circulation 2000;101:1282–1287.. Albers GW, Dalen JE, Laupacis A, Manning W, Petersen P, Singer D.ntithrombotic therapy in atrial fibrillation. Chest 2001;119:194S–206S.. Saliba W, Juratli N, Chung MK, Niebauer MJ, Erdogan O, Trohman R,ilkoff BL, Augostini R, Mowrey KA, Nadzam GR, Tchou PJ. Higher energy

ynchronized external direct current cardioversion for refractory atrial fibrillation.Am Coll Cardiol 1999;34:2031–2034.0. Page RL, Kerber RE, Russell JK, Trouton T, Wakare J, Gallik D, Olgin JE,icard P, Dalzell GW, Reddy R, et al. Biphasic versus monophasic waveform for

ardioversion of atrial fibrillation. J Am Coll Cardiol 2002;39:1956–1963.

CES/AF CARDIOVERSION USING THE RLB WAVEFORM 1499