Efficacy of Biphasic Waveform Cardioversion for AtrialFibrillation and Atrial Flutter Compared With
Conventional Monophasic Waveforms
Cengiz Ermis, MD, Alan X. Zhu, MD, Sunil Sinha, MD, Demosthenes Iskos, MD,Scott Sakaguchi, MD, Keith G. Lurie, MD, and David G. Benditt, MD
Based on extensive experience with implantablecardioverter-defibrillators and automatic externaldefibrillators, the utility of biphasic transthoracicshock has been demonstrated in the setting of life-threatening ventricular tachyarrhythmias.13 Theseobservations have led to the application of biphasicwaveforms during elective transthoracic cardioversionfor atrial fibrillation (AF).4 The present report com-pares cardioversion outcomes in 2 sequential groupsof patients with AF undergoing transthoracic cardio-version. It was undertaken in an attempt to ascertainthe extent to which biphasic waveform technique en-hances transthoracic AF cardioversion success rates.
Records of 145 patients were reviewed. The pa-tients were referred to our center for elective transtho-racic cardioversion between January 1999 and Sep-tember 2001, and had undergone this procedure in theelectrophysiologic laboratory. Patients with atrial flut-ter (20 patients, 14%) were also included because ofthe similarity of the arrhythmia and the treatmentrequired.
Demographic and clinical dataincluding arrhyth-mia type and duration, underlying disease, and con-comitant medicationswere documented, along withechocardiographic data including left atrial diameterand left ventricular ejection fraction. Procedural da-taincluding the number of cardioversion attemptsmade, energy levels used, and anesthetic employedwere documented. Similarly, complications were re-corded, particularly skin irritation.
A successful cardioversion procedure was definedas restoration of sinus rhythm for 1 cycle afterenergy application. Recurrence of the arrhythmia 2hours after a successful cardioversion (i.e., before thepatient left the observation unit) was deemed an earlyrecurrence.
The statistical significance of the efficacy of bipha-sic waveform cardioversion compared with monopha-sic waveform shock cardioversion was evaluated us-ing chi-square and Fishers exact tests. A p value of0.05 was considered statistically significant.
Data were obtained in 145 sequential patients whounderwent elective electrical cardioversion for AF or
atrial flutter. Eighty-two patients (mean age 67 15years) received biphasic waveform cardioversion, andthe remaining 63 patients (mean age 66 14 years)underwent cardioversion with a monophasic wave-form device. The ratio of men to women was 1.8:1 and2:1 for the biphasic and monophasic waveform car-dioversion study groups, respectively.
The presenting arrhythmia was AF in 70 patients(85%) in the biphasic group and in 55 patients (87%)in the monophasic group. Atrial flutter was present in12 patients (15%) in the biphasic group and in 8patients (13%) in the monophasic group. The meanduration of patients treatment for the arrhythmiaevent was 36 56 and 60 106 days (p NS) forthe biphasic and monophasic groups, respectively.
Baseline clinical characteristics for patients in eachtreatment group are listed in Table 1. Underlyingdisease processes (i.e., cardiomyopathy, coronary ar-tery disease, valvular heart disease, lung disease, andother structural heart disease) were found to be simi-larly prevalent in both treatment groups. Patients inthe monophasic waveform group tended to use moredigoxin, amiodarone, and other antiarrhythmic medi-cations compared with biphasic group patients. Thefrequencies of usage of blockers, calcium channelblockers, and angiotensin-converting enzyme inhibi-tors were similar in both groups.
The mean left atrial diameter was 46 10 mm inthe biphasic group and 45 12 mm in the monopha-sic waveform group. Mean left ventricular ejectionfraction was similar for the biphasic and monophasicgroups (49 13% and 49 15%, respectively).
Procedure success rate was 99% (81 patients) inthe biphasic waveform cardioversion group comparedwith 81% (51 patients) in the group treated withmonophasic waveform (p 0.001). The mean energyrequired for procedural success was 126 46 J and228 83 J for the biphasic and monophasic wave-form groups, respectively (p 0.001). The meannumber of attempts before achieving procedural suc-cess was 1.3 0.8 for the biphasic cardioversiongroup and 1.2 0.4 for the monophasic cardioversiongroup.
The treated arrhythmia recurred in 10 biphasicgroup patients (12%) and in 6 monophasic grouppatients (12%). All recurrences were in patients withAF. Skin irritation was not observed in any of thepatients who received biphasic waveform shock,whereas 2 patients (3%) who received monophasicwaveform shock required topical treatment for irrita-tion at patch sites.
From the Cardiac Arrhythmia Center, Cardiovascular Division, Depart-ment of Medicine, Minneapolis, Minnesota. Dr. Ermis is supported inpart by a grant from the Midwest Arrhythmia Research Foundation,Minneapolis, Minnesota. Dr. Benditts address is: Cardiac ArrhythmiaCenter, MMC 508, 420 Delaware Street, Minneapolis, Minnesota55455. Manuscript received April 9, 2002; revised manuscript re-ceived and accepted June 7, 2002.
8912002 by Excerpta Medica, Inc. All rights reserved. 0002-9149/02/$see front matterThe American Journal of Cardiology Vol. 90 October 15, 2002 PII S0002-9149(02)02717-0
In this report, biphasic waveform cardioversionappeared to enhance the overall effectiveness of trans-thoracic cardioversion, while at the same time requir-ing less energy delivery. Despite a higher success ratewith transthoracic cardioversion, biphasic waveformshock was not accompanied by less risk of eitherarrhythmia recurrence or skin irritation compared withmonophasic waveform shock. This finding may berelated to the very low complication rates for bothgroups. Skin irritation was observed in only 2 of 145patients.
Multiple factors have been associated with the suc-cess or failure of atrial cardioversion using conventionalmonophasic transthoracic shock. Some of these factorsare: duration of the AF event, left atrial diameter, bodymass, local inflammation process (e.g. pleuro-pericardi-tis, pericardial effusions), the technique used during car-dioversion (e.g., inadequate electrode-skin contact, un-desirable electrical vector), and other technical issuesincluding energy levels employed and the transthoracicimpedance. In this report the only statistically significantdifference between the 2 groups was the usage ofdigoxin, amiodarone, and other antiarrhythmic medica-tions (i.e., sotalol, propafenone, flecainide). Patients inthe monophasic waveform cardioversion group tended totake these medications more frequently than patients inthe biphasic waveform group. Sotalol is known to de-crease and flecainide is known to increase defibrillationthresholds, whereas the previously mentioned medica-tions either have no effect or may have variable effects.Thus, it is unlikely that the higher usage rates of thesemedications contributed to the lower success rates in themonophasic waveform cardioversion group.
In terms of transthoracic defibrillation, biphasicwaveforms became important because reduced sizerequirements for portable automatic external defibril-lators demanded the development of more efficientsystems. In this regard, Schneider et al5 demonstratedthat biphasic defibrillator shocks of 150 J were moreeffective than 200- to 360-J monophasic shocks inresuscitating out-of-hospital cardiac arrest fatalities.In that study of cardiac arrest, defibrillation was ac-
complished using 3 biphasic waveforms in 98% ofpatients, compared with 67% when using 3 conven-tional shocks. With respect to AF, biphasic shockshave been evaluated as a means of facilitating low-energy cardioversion by implantable devices,612 andit appears that this approach offers important advan-tages over monophasic waveforms. However, less isknown regarding the merits of biphasic transthoracicshock for atrial cardioversion. Mittal et al12 reportedfindings of a randomized study comparing the efficacyof rectilinear biphasic to conventional damped sinewave monophasic cardioversion in patients who un-derwent elective cardioversion of AF. First shock ef-ficacy with 70-J biphasic (68%) was significantlygreater than with 100-J monophasic (21%), as was thecumulative efficacy after completion of the protocol(94% vs 79%, p 0.005). Thus, although experienceis limited, biphasic transthoracic cardioversion ap-pears to be more effective than monophasic shocks ina broad population of patients with AF.
The findings in our report reveal that biphasicwaveform shock transthoracic cardioversion forAF and flutter is associated with both a highercardioversion success rate and lower energy re-quirements compared with conventional monopha-sic waveform shocks. These findings may result inmore widespread use of devices utilizing biphasicwaveforms.
1. Bardy GH, Ivey TD, Allen MD, Johnson G, Mehra R, Greene HL. Aprospective randomized evaluation of biphasic versus monophasic waveformpulses on defibrillation efficacy in humans. J Am Coll Cardiol 1989;14:728733.2. Saksena S, An H, Mehra R, DeGroot P, Krol RB, Burkhardt E, Mehta D, John T.Prospective comparison of biphasic and monophasic shocks for implantable cardio-verter-defibrillators using endocardial leads. Am J Cardiol 1992;70:304310.3. Wyse DG, Kavanaugh KM, Gillis AM, Mitchell LB, Duff HJ, Sheldon RS,Kieser TM, Maitland A, Flanagan P, Rothschild J, Mehra R. Comparison ofbiphasic and monophasic shocks for defibrillation using a nonthoracotomy sys-tem. Am J Cardiol 1993;71:197202.4. Benditt DG, Samniah N, Iskos D, Lurie KG, Padanilam BJ, Sakaguchi S.Biphasic waveform cardioversion as an alternative to internal cardioversion foratrial fibrillation refractory to conventional monophasic waveform transthoracicshock. Am J Cardiol 2001;88:14261428.5. Schneider T, Martens PR, Paschen H, Kuisma M, Wolcke B, Gliner BE,Russell JK, Weaver WD, Bossaert L, Chamberlain D, for the Optimized Re-sponse to Cardiac Arrest (ORCA) Investigators. Multicenter randomized con-trolled trial of 150-J biphasic compared with 200- to 360-J monophasic shocks inthe resuscitation of out-of-hospital cardiac arrest victims. Circulation 2000;102:17801787.6. Cooper RAS, Alferness CA, Smith WM, Ideker RE. Internal cardioversion ofatrial fibrillation in sheep. Circulation 1993;87:16731686.7. Keane D, Boyd E, Anderson D, Robles A, Deverall P, Morris R, Jackson G,Sowton E. Comparison of biphasic and monophasic waveforms in epicardialatrial defibrillation. J Am Coll Cardiol 1994;24:171176.8. Tomassoni G, Newby KH, Kearney MM, Brandon MJ, Barold H, Natale A.Testing different biphasic waveforms and capacitances: effect on atrial defibril-lation threshold and pain perception. J Am Coll Cardiol 1996;28:695699.9. Harbinson MT, Allen JD, Imam Z, Dempsey G, Anderson JM, Ayers GM,Adgey AA. Rounded biphasic waveform reduces energy requirements for trans-venous catheter cardioversion of atrial fibrillation and flutter. PACE 1997;20:226229.10. Sra J, Bremner S, Krum D, Dhala A, Blanck Z, Deshpande S, Biehl M, Li H,Jazayeri MR, Akhtar M. The effect of biphasic waveform tilt in transvenous atrialdefibrillation. PACE 1997;20:16131618.11. Tse HF, Lau CP, Camm AJ. Transvenous atrial defibrillationtechniquesand clinical applications. Clin Cardiol 1999;22:614622.12. Mittal S, Ayati S, Stein KM, Schwartzmann D, Cavlovich D, Tchou PJ,Markowitz SM, Slotweiner D, Scheiner MA, Lerman BB. Transthoracic cardio-version of atrial fibrillation: comparison of rectilinear biphasic versus dampedsine wave monophasic shocks. Circulation 2000;101:12821287.
TABLE 1 Baseline Characteristics of Patients
(n 63) p Value
Underlying diseaseCoronary artery disease 19 (23%) 7 (11%)Cardiomyopathy 29 (36%) 25 (39%)Valvular heart disease 9 (11%) 11 (17%) 0.10Lung disease 6 (7%) 1 (2%)Other 4 (5%) 1 (2%)None 15 (18%) 18 (29%)
MedicationsDigoxin 17 (21%) 28 (44%) 0.002ACE inhibitor 21 (26%) 24 (38%) 0.11Calcium antagonists 12 (15%) 14 (22%) 0.24 blockers 38 (46%) 21 (33%) 0.11Amiodarone 13 (16%) 22 (35%) 0.001Other antiarrhythmics 21 (26%) 23 (37%) 0.001
ACE angiotensin-converting enzyme.
892 THE AMERICAN JOURNAL OF CARDIOLOGY VOL. 90 OCTOBER 15, 2002
Efficacy of Biphasic Waveform Cardioversion for Atrial Fibrillation and Atrial Flutter Compared With Conventional Monophasic