OBJECTIVE: To compare the efficacy of cardioversion in patients with
      atrial fibrillation between monophasic damped sine waveform and
      rectilinear biphasic waveform shocks at a high initial energy level and
      with a conventional paddle position. DESIGN: Prospective randomised study.
      PATIENTS AND SETTING: 227 patients admitted for cardioversion of atrial
      fibrillation to a tertiary referral centre. RESULTS: 70

Jordaens, L.J.L.M. (Luc)

Klootwijk, A.P.J. (Peter)

Scholten, M.F. (Marcoen)

Szili-Török, T. (Tamás)

OBJECTIVE: To compare the efficacy of cardioversion in patients with
      atrial fibrillation between monophasic damped sine waveform and
      rectilinear biphasic waveform shocks at a high initial energy level and
      with a conventional paddle position. DESIGN: Prospective randomised study.
      PATIENTS AND SETTING: 227 patients admitted for cardioversion of atrial
      fibrillation to a tertiary referral centre. RESULTS: 70% of 109 patients
      treated with an initial 200 J monophasic shock were cardioverted to sinus
      rhythm, compared with 80% of 118 patients treated with an initial 120 J
      biphasic shock (NS). After the second shock (360 J monophasic or 200 J
      biphasic), 90% of the patients were in sinus rhythm in both groups. The
      mean cumulative energy used for successful cardioversion was 306 J for
      monophasic shocks and 159 J for biphasic shocks (p < 0.001). CONCLUSIONS:
      A protocol using monophasic waveform shocks in a 200-360 J sequence has
      the same efficacy (90%) as a protocol using rectilinear biphasic waveform
      shocks in a 120-200 J sequence. This equal efficacy is achieved with a
      significantly lower mean delivered energy level using the rectilinear
      biphasic shock waveform. The potential advantage of lower energy delivery
      for cardioversion of atrial fibrillation needs further study

Erasmus University Digital Repository

doi:10.1136/heart.89.9.1032  2003;89;1032-1034 Heart  M Scholten, T Szili-Torok, P Klootwijk and L Jordaens    transthoracic cardioversion of atrial fibrillationComparison of monophasic and biphasic shocks for http://heart.bmj.com/cgi/content/full/89/9/1032Updated information and services can be found at:  These include: References http://heart.bmj.com/cgi/content/full/89/9/1032#otherarticles6 online articles that cite this article can be accessed at:    http://heart.bmj.com/cgi/content/full/89/9/1032#BIBLThis article cites 14 articles, 9 of which can be accessed free at: Rapid responses http://heart.bmj.com/cgi/eletter-submit/89/9/1032You can respond to this article at:  serviceEmail alertingtop right corner of the article Receive free email alerts when new articles cite this article - sign up in the box at theTopic collections (700 articles) Arrhythmias   Articles on similar topics can be found in the following collections  Notes    http://www.bmjjournals.com/cgi/reprintformTo order reprints of this article go to:  http://www.bmjjournals.com/subscriptions/ go to: HeartTo subscribe to  on 8 November 2006 heart.bmj.comDownloaded from CARDIOVASCULAR MEDICINEComparison of monophasic and biphasic shocks fortransthoracic cardioversion of atrial fibrillationM Scholten, T Szili-Torok, P Klootwijk, L Jordaens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Heart 2003;89:1032–1034Objective: To compare the efficacy of cardioversion in patients with atrial fibrillation betweenmonophasic damped sine waveform and rectilinear biphasic waveform shocks at a high initial energylevel and with a conventional paddle position.Design: Prospective randomised study.Patients and setting: 227 patients admitted for cardioversion of atrial fibrillation to a tertiary referralcentre.Results: 70% of 109 patients treated with an initial 200 J monophasic shock were cardioverted tosinus rhythm, compared with 80% of 118 patients treated with an initial 120 J biphasic shock (NS).After the second shock (360 J monophasic or 200 J biphasic), 90% of the patients were in sinus rhythmin both groups. The mean cumulative energy used for successful cardioversion was 306 J for monopha-sic shocks and 159 J for biphasic shocks (p < 0.001).Conclusions: A protocol using monophasic waveform shocks in a 200–360 J sequence has the sameefficacy (90%) as a protocol using rectilinear biphasic waveform shocks in a 120–200 J sequence. Thisequal efficacy is achieved with a significantly lower mean delivered energy level using the rectilinearbiphasic shock waveform. The potential advantage of lower energy delivery for cardioversion of atrialfibrillation needs further study.External electrical cardioversion remains the technique ofchoice for restoring sinus rhythm in patients withpersistent atrial fibrillation.1 Most currently used exter-nal defibrillators deliver monophasic damped sine waveformshocks. However, it has been shown that a comparable or evenhigher rate of transthoracic cardioversion can be achievedwith biphasic shocks.2 3 These studies assessed efficacy usingstep up protocols starting at low energy levels. However, 75%of the patients can be cardioverted successfully by thecurrently recommended 200 J initial energy level4 usingmonophasic shock waveforms. Our aim in this prospectiverandomised study was thus to compare the efficacy ofmonophasic and biphasic waveform shocks for cardioversionof patients with atrial fibrillation at this initial energy level,using a conventional paddle position.METHODSPatient populationTwo hundred and twenty seven consecutive patients wereenrolled in this prospective randomised single centre studybetween August 2000 and January 2002. Criteria for inclusionwere as follows: atrial fibrillation lasting more than 24 hours;a minimum period of medical treatment of three weeks withacenocoumarol or fenprocoumon, with an internationalnormalised ratio (INR) of > 2.5; and absence of anintracardiac thrombus on a transoesophageal echocardiogramdone within 24 hours of the cardioversion. Transthoracicechocardiograms were done in all patients within 30 days ofthe cardioversion in order to measure left atrial dimensions.Patients with untreated hyperthyroidism and pregnantwomen were excluded from the study. Patients who were car-dioverted for arrhythmias other than atrial fibrillation(including atrial flutter) were not included in the analysis.Sixteen patients undergoing cardioversion for atrial fibrilla-tion in the study period were excluded because of violation ofthe study protocol by the treating physician.Protocol for cardioversionCardioversions were done under deep sedation using weightadjusted intravenous diazepam and ethomidate in the postab-sorptive state. Randomisation was achieved on the basis of theTable 1 Clinical characteristics of the patientsMonophasic Biphasic p ValueNumber 109 118Female (%) 24.8 25.4 NSAge (years) 59.9 (14.0) 59.6(12.4) NSHeight (cm) 176.4 (10.0) 177.9 (10.7) NSWeight (kg) 82.5 (19.8) 81.9 (20.8) NSBody mass index (kg/m2) 26.5 (5.2) 26.5 (5.7) NSLA diameter (mm) 46.3 (8.4) 44.4 (8.9) NSMean impedance (ohm) 68.5 (18.5) 80.1 (19.7) NSImpedance measured (n (%)) 45 (41) 70 (59) NSDuration AF (days) (median (range)) 41.0 (1–450) 20.5 (1–390) NSDuration AF unknown (n) 70 72 NSValues are mean (SD) unless stated.AF, atrial fibrillation; LA, left atrial.See end of article forauthors’ affiliations. . . . . . . . . . . . . . . . . . . . . . .Correspondence to:Dr Marcoen Scholten,Department of ClinicalElectrophysiology,Thoraxcentre, ErasmusUniversity Medical Centre,Dr Molewaterplein 40,3015 GM, Rotterdam,Netherlands;m.f.scholten@erasmusmc.nlAccepted 25 March 2002. . . . . . . . . . . . . . . . . . . . . . .1032www.heartjnl.com on 8 November 2006 heart.bmj.comDownloaded from patient’s birthday. Patients born on an uneven day received a200–360 J monophasic shock sequence; patients born on aneven day received a 120–200 J biphasic shock sequence.Shocks were delivered by commercially available defibrillators.The monophasic damped sine wave shock was delivered by aHewlett Packard M1722B defibrillator (Hewlett Packard Co,Andover, Massachusetts, USA) and the rectilinear biphasicwaveform by a Zoll M series biphasic defibrillator (Zoll Medi-cal Corporation, Burlington, Massachusetts, USA). Cardiover-sions were undertaken using an anterolateral paddle position,and were considered successful if sinus rhythm was restoredfor more than five seconds. Measurement of the shock imped-ance was given by the defibrillator.Statistical analysisVariables were expressed as mean (SD) or median (range) asrequired. Student’s t test was used to compare continuousvariables. A χ2 test was done for comparison of non-dichotomous variables. A probability value of p < 0.05 wasconsidered significant.RESULTSIn the study period, 359 patients were cardioverted in ourdepartment. One hundred and thirty two were excluded fromthe analysis either because the cardioversion was done foratrial flutter or atrial tachycardia (n = 116), or because of vio-lation of the protocol (n = 16). Using the above mentionedselection criteria, 227 patients were enrolled into the finalanalysis.The clinical characteristics of the 227 patients who fulfilledthe criteria for inclusion are listed in tables 1 and 2. Themonophasic and biphasic groups were similar in age, sex dis-tribution, body weight, height, body mass index, left atrialdiameter, and antiarrhythmic drug treatment. The measuredshock impedance showed no difference between the twogroups. Shock impedance values were not available in allpatients. Information about the duration of the atrial fibrilla-tion was also not always available. In about half the patientswhere data were available, there was no significant differencein shock impedance and atrial fibrillation duration betweenthe two groups.Monophasic and biphasic shock efficacyThe comparisons of monophasic and biphasic shock efficacyare shown in fig 1. The first shock (200 J) was successful in 77of 109 patients (71%) in the monophasic waveform group, andin 95 of 118 patients (81%) in the biphasic waveform group.This difference was not significant (p = 0.08). The cumulativesuccess of two shocks was 106 of 118 patients (91%) for thebiphasic waveform group (120 J and 200 J) and 98 of 109patients (90%) for the monophasic waveform group (200 Jand 360 J). Similar efficacy was achieved with a significantlylower mean delivered energy level (p < 0.001) using thebiphasic shock waveform (159 J) compared with themonophasic shock waveform (306 J). There were no compli-cations related to the method of anaesthesia used. In sevenpatients treated with the biphasic protocol there was earlyrecurrence of atrial fibrillation within five seconds after thefirst (120 J) or second (200 J) shock. In the monophasic groupearly recurrence of atrial fibrillation occurred in three patients.These were all considered unsuccessful results. In one patientsuccessfully treated with the biphasic protocol, recurrence ofTable 2 Drug treatment and underlying diseases inthe patientsMonophasic BiphasicDrug treatmentDigoxin 29 (27%) 13 (11%) NSClass Ic AAD 8 (7%) 13 (11%) NSβ Blocker 18 (16%) 14 (12%) NSClass III AAD* 56 (51%) 75 (63%) NSUnderlying diseasesValvar disease 19 (17%) 15 (13%) NSLone AF 15 (14%) 25 (21%) NSCongestive HF 12 (11%) 11 (9%) NSHypertension 12 (11%) 9 (7%) NSCAD 6 (6%) 5 (4%) NS*Sotalol or amiodarone.AAD, antiarrhythmic drug; AF, atrial fibrillation; CAD, coronaryartery disease; HF, heart failure.Figure 1 Study protocol and dataon shock efficacy (%).Transthoracic cardioversion of atrial fibrillation 1033www.heartjnl.com on 8 November 2006 heart.bmj.comDownloaded from atrial fibrillation was noted after five seconds but within fiveminutes. This was considered as successful treatment.DISCUSSIONIn this study we could not confirm that cardioversion efficacyimproves when biphasic shocks are used. The major finding ofthe study was that identical success rates can be achieved withmonophasic and biphasic shock waveforms, selecting aninitial energy level of 200 J and 120 J, respectively. As efficacywas similar with a lower delivered energy using biphasic shockwaveforms, it seems necessary to investigate the potentialclinical value of low energy cardioversion for patients withpersistent atrial fibrillation.Clinical value of the shock waveformBiphasic shocks are more effective for endocardial defibrilla-tion than monophasic shocks.5 6 For transthoracic ventriculardefibrillation, biphasic and monophasic shocks are equallyeffective, but biphasic shocks require less energy for the sameefficacy.7 A similar superiority for external cardioversion ofatrial fibrillation has been reported recently by Mittal and col-leagues using rectilinear biphasic waveform shocks.2 Ricardand colleagues showed that for the same energy levelstruncated exponential biphasic waveform shocks are superiorin efficacy to monophasic waveform shocks.3 For defibrillationof ventricular fibrillation it was found that the ST segment 10seconds after the shock was less impaired by biphasicwaveform shocks than by monophasic waveform shocks in astudy that included 297 patients.7Biphasic waveform defibrillation produced less impairmentof cardiac function as measured by echocardiography, arterialpressure, and recurrence of heart rate in a study usingmechanically ventilated pigs.8 However, biochemical studiesdid not suggest any myocardial damage after cardioversion foratrial fibrillation.3 9 10Selection of the initial energy levelBased on a study by Joglar and colleagues,11 it has beenrecommended12 that a 100 J monophasic shock should not beused as the initial energy level for cardioversion of atrial fibril-lation because of the relatively low success rate. Currentrecommendations13 14 suggest using higher initial energy levelsbecause the success rate only becomes satisfactory at anenergy level of 200 J or more (for monophasic waveforms),with a consequent decrease in cumulative delivered energy.According to the results of former studies with biphasiccardioversions, we hypothesised that a biphasic shock of 120 Jmay be as effective as a monophasic shock of 200 J.3 4 Indeedthis study did not show any difference in first shock efficacyand cumulative efficacy between two step protocols usingmonophasic (200 J and 360 J) and biphasic (120 J and 200 J)shock waveform sequences for cardioversion. The advantagesof low energy cardioversion are not yet proven, but it couldhave an important clinical impact. Furthermore we achieved aremarkable 90% overall success rate using biphasic low energycardioversion. This may influence further strategic planningas it could reduce the need for internal cardioversion, aneffective but invasive form of treatment.Limitations of the studyBecause different defibrillators were used, the study was notdouble blind. The number of patients was limited butrelatively large compared with previous reports. Data were notcomplete regarding the duration of the current atrial fibrilla-tion episode, a known predictor of successful cardioversion.Although we clearly demonstrated that equal efficacy could beachieved with less delivered energy using biphasic shockwaves, we did not attempt to assess its effect on atrialfunction, including differences in the development of atrialstunning.ConclusionsFor electrical cardioversion of atrial fibrillation, a protocolusing biphasic waveform shocks in a 120–200 J sequence hasthe same efficacy as a protocol using monophasic waveformshocks in a 200–360 J sequence. This equal efficacy is achievedwith a significantly lower mean delivered energy level in therectilinear biphasic shock waveform. The potential advantagesof a lower energy requirement for cardioversion of atrial fibril-lation require further study in patients with persistent atrialfibrillation. However, as myocardial damage after cardiover-sion for atrial fibrillation has not so far been reported, there isno need for the immediate replacement of all defibrillatorsdelivering monophasic waveform shocks.ACKNOWLEDGEMENTSWe thank Andrew Thornton MD for reading of the manuscript and forhis valuable suggestions.. . . . . . . . . . . . . . . . . . . . .Authors’ affiliationsM Scholten, T Szili-Torok, P Klootwijk, L Jordaens, Erasmus UniversityMedical Centre, Thoraxcentre, Department of Clinical Electrophysiology,Rotterdam, NetherlandsREFERENCES1 Levy S, Breithardt G, Campbell RW, et al. Atrial fibrillation: currentknowledge and recommendations for management. Working group onarrhythmias of the European Society of Cardiology. Eur Heart J1998;19:1294–320.2 Mittal S, Ayati S, Stein KM, et al. Transthoracic cardioversion of atrialfibrillation: comparison of rectilinear biphasic versus damped sine wavemonophasic shocks. Circulation 2000;101:1282–7.3 Ricard P, Levy S, Boccara G, et al. External cardioversion of atrialfibrillation: comparison of biphasic vs monophasic waveform shocks.Europace 2001;3:96–9.4 Ricard P, Levy S, Trigano J, et al. Prospective assessment of the minimumenergy needed for external electrical cardioversion of atrial fibrillation.Am J Cardiol 1997;79:815–16.5 Fain ES, Sweeney MB, Franz MR. Improved internal defibrillationefficacy with a biphasic waveform. Am Heart J 1989;117:358–64.6 Bardy GH, Ivey TD, Allen MD, et al. A prospective randomizedevaluation of biphasic versus monophasic waveform pulses ondefibrillation efficacy in humans. J Am Coll Cardiol 1989;14:728–33.7 Bardy GH, Marchlinski FE, Sharma AD, et al. Multicenter comparison oftruncated biphasic shocks and standard damped sine wave monophasicshocks for transthoracic ventricular defibrillation. TransthoracicInvestigators. Circulation 1996;94:2507–14.8 Tang W, Weil MH, Sun S, et al. The effects of biphasic and conventionalmonophasic defibrillation on postresuscitation myocardial function. J AmColl Cardiol 1999;34:815–22.9 Neumayr G, Hagn C, Ganzer H, et al. Plasma levels of troponin T afterelectrical cardioversion of atrial fibrillation and flutter. Am J Cardiol1997;80:1367–9.10 Rao AC, Naeem N, John C, et al. Direct current cardioversion does notcause cardiac damage: evidence from cardiac troponin T estimation.Heart 1998;80:229–30.11 Joglar JA, Hamdan MH, Ramaswamy K, et al. Initial energy for electiveexternal cardioversion of persistent atrial fibrillation. Am J Cardiol2000;86:348–50.12 Prystowsky EN. Cardioversion of atrial fibrillation to sinus rhythm: who,when, how, and why? Am J Cardiol 2000;86:326–7.13 Fuster V, Ryden LE, Asinger RW, et al. ACC/AHA/ESC guidelines forthe management of patients with atrial fibrillation: executive summary.A report of the American College of Cardiology/American HeartAssociation task force on practice guidelines and the European Society ofCardiology committee for practice guidelines and policy conferences(committee to develop guidelines for the management of patients withatrial fibrillation): developed in collaboration with the North AmericanSociety of Pacing and Electrophysiology. J Am Coll Cardiol2001;38:1231–66.14 Gallagher MM, Guo XH, Poloniecki JD, et al. Initial energy setting,outcome and efficiency in direct current cardioversion of atrial fibrillationand flutter. J Am Coll Cardiol 2001;38:1498–504.1034 Scholten, Szili-Torok, Klootwijk, et alwww.heartjnl.com on 8 November 2006 heart.bmj.comDownloaded from 

Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation

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Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation

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