Comparison of the rectilinear biphasic waveform with the monophasic damped sine waveform for external cardioversion of atrial fibrillation and flutter

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  • Comparison of the Rectilinear BiphasicW

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    Exsintim(RLeffiastuthofibpaprousiwiunsuccess rates for the RLB defibrillator were 99.1% for AFand 99.2% for atrial flutter, and the corresponding suc-

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    (Am J Cardiol 2004;93:14951499)

    Sme(A94da1).deure(BransmstrJ,forsion of AF. Since acquiring the RLB defibrillator earlyafter its release in 1999, we have used it for cardio-veanno

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    thevesetins(C1,056 patients (outpatients and inpatients) who under-went 1,503 external cardioversion procedures for AF

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    2Thersion of AF in a larger sample of patients with AFd atrial flutter. Patients with AF and atrial flutter hadt been evaluated in the previous study.7 We then

    with a RLB defibrillator in our electrophysiologiclaboratory. During this same period, we performed337 cardioversion procedures in 305 patients for atrialflutter using the RLB waveform. Hence, 1,361 pa-tients underwent 1,877 cardioversion procedures withthe RLB defibrillator. The results of all RLB cardio-version procedures were reviewed to determine theoverall efficacy of this waveform in our large clinicalpopulation. We compared the overall success rate ofRLB shocks with that of our previous cardioversionstudy in 2,025 patients (1,490 for AF and 535 for atrialflutter) who underwent 2,848 external cardioversions

    m the Department of Cardiovascular Medicine, Cleveland Clinicndation, Cleveland, Ohio; the Section of Cardiology, University ofbraska Medical Center, Omaha, Nebraska; and Zoll Medical,lington, Massachusetts. Manuscript received November 19,03; revised manuscript received and accepted March 2, 2004.Address for reprints: Mark J. Niebauer, PhD, MD, Department ofrnal Medicine, Section of Cardiology, 982265 Nebraska Medi-Center, Omaha, Nebraska 68198-2265. E-mail: mniebaue@c.edu.ince its introduction in 1962 by Lown et al,1external direct-current cardioversion has been the

    thod of choice2 for terminating atrial fibrillationF) and atrial flutter. This method is safe and 70% to% effective38 when the conventional monophasicmped sine (MDS) shock waveform is used (Figure

    An external defibrillator has been developed thatlivers a rectilinear biphasic (RLB) waveform (Fig-

    1). This defibrillator, manufactured by Zoll Corp.urlington, Massachusetts), was approved based on adomized comparison with the MDS waveform in aall prospective, multicenter trial.1 The trial demon-ated that RLB shocks, using a set energy up to 170are significantly more effective than MDS wave-m shocks of up to 360 J for the external cardiover-004 by Excerpta Medica, Inc. All rights reserved.American Journal of Cardiology Vol. 93 June 15, 2004rospectively compared the RLB results with ourvious MDS waveform cardioversion results to as-s differences in effectiveness in achieving tran-nt, persistent, and overall successful cardioversionsinus rhythm.

    ETHODSThis study was a retrospective trial that evaluatedresults of external transthoracic electrical cardio-

    rsion using the RLB waveform in a general clinicalting. The study was reviewed and approved by thetitutional review board of the Cleveland Clinicleveland, Ohio).From October 1999 to September 2001, there wereaveform With the MSine Waveform

    Cardioversion of Aand Fl

    Mark J. Niebauer, PhD, MD, James E. BPatrick J. T

    ternal cardioversion using the monophasic dampede (MDS) waveform is successful 70% to 94% of thee when using up to 360 J. The rectilinear biphasicB) defibrillator has been shown to be superior incacy to the MDS waveform in atrial cardioversion insmall randomized study. This larger, retrospectivedy compares the results of the RLB waveform withse of the MDS waveform for cardioversion of atrialrillation (AF) and atrial flutter in a large cohort oftients. We performed 1,877 external cardioversioncedures in 1,361 patients for AF and atrial flutter byng the RLB defibrillator. We compared these resultsth those of the MDS defibrillator in 2,025 patients whoderwent 2,818 cardioversion procedures. The overallonophasic Dampedfor Externalrial Fibrillationtterwer, MS, Mina K. Chung, MD, andou, MD

    s rates for the MDS defibrillator were 92.4% and.8% (p 4,000 procedures confirmed and ex-ded those of the previous report by showing a veryh success rate for cardioversion of AF and atrialtter using the RLB waveform. The MDS waveform wasually effective for atrial flutter but significantly lessective in terminating AF. 2004 by Excerpta Med-, Inc.14950002-9149/04/$see front matterdoi:10.1016/j.amjcard.2004.03.006

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    second field reporting the final heart rhythm, and athird field reporting the result after each shock to thepapaareInsucba

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    14200 for AF and 648 for atrial flutter) using an MDSveform defibrillator from August 1996 to Septem-r 1999. The MDS defibrillator delivered up to 360 J,d the RLB defibrillator delivered up to 200 J (inntrast to the device used in the seminal clinicaldy by Mittal et al7 in which a maximum of 170 Js available).Definitions: Overall shock success was defined as

    nversion to a sinus atrioventricular junctionalthm with retrograde P waves or as paced atrialthm immediately after the shock with 1 identifi-

    le atrial depolarization. This confirmed the termina-n of ongoing atrial reentry. If AF was not presenten the patient left the laboratory (usually 15 to 30nutes after the shock), we termed the procedure aersistent success. However, AF or atrial flutter didur in 10% of patients before leaving the labora-y despite additional shocks with transient conver-n from the presenting dysrhythmia in some cases.those cases in which the patient left the laboratoryAF or atrial flutter after an initially successfulck, we termed the procedure a transient success.

    cent publications have addressed the phenomenonAF recurrence after cardioversion. The term im-diate recurrence of AF is now used generally to

    scribe a recurrence that occurs within 1 to 2 minuteser cardioversion, and subacute recurrence de-ibes a recurrence 2 minutes to 2 weeks after suc-sful cardioversion. Unfortunately, much of our dataceded these definitions, and review of the patientcedure records was unclear, in most cases, as tocisely when AF recurred before patient dismissalm our electrophysiologic laboratory. Hence, ournsient success procedures include all immediateurrence and early subacute recurrence procedures.verall success was defined as the sum of the tran-nt and persistent success rates for a given arrhyth-a and waveform, signifying shock effectiveness. Ifwere unable to terminate the arrhythmia to even a

    gle organized atrial beat, the procedure was termedfailure. To confirm whether a procedural result isurately reported, our database records this result in

    different fields: the final procedural result field, a

    URE 1. The current profile of the first phase of the RLB wave-m is relatively flat compared with the higher current peakue seen with the MSD waveform.96 THE AMERICAN JOURNAL OF CARDIOLOGY VOL. 93tient. Any conflicts were resolved by review of thetients chart, where initial and final rhythm strips

    saved, and the written summary of the procedure.the very rare cases in which failure and transientcess could not be resolved by review of the data-

    se or the chart, a failure was reported.Shock waveforms: The RLB waveform was gener-d with an external RLB defibrillator (Zoll Seriesphasic Defibrillator, Zoll Corp.). The waveform wasnerated by a 115-F capacitive discharge, compris-

    an essentially constant-current 6-ms first phased a truncated, exponential 4-ms second phase (Fig-

    1). The amplitude of the phases changed with theected energy, up to a maximum of 200 J. The MDSveform shocks were delivered from a Zoll PD-1200fibrillator, which delivers up to 360 J of energy.Shock electrodes: Adhesive pads for external car-version (Zoll Cardiology Specialty Pad) were useddeliver the RLB and MDS shocks delivered fromcorresponding Zoll defibrillators. These electrode

    tches were positioned in a left or right anteriorentation (depending on the physicians preference)d left posterior chest wall orientation (in all cases).e anterior electrode was circular and had an activeface area of 78 cm2. The posterior electrode wastangular and had an active surface area of 113 cm2.Cardioversion procedure: The standard guidelinesanticoagulation of patients recommended by theerican College of Physicians were adhered to in

    r laboratory.8 Specifically, patients with AF 48urs duration were anticoagulated for 3 weeksfore the cardioversion procedure or underwentnsesophageal echocardiography, where no leftial thrombus was visualized in the presence ofrapeutic anticoagulation with warfarin or intrave-us heparin. Patients were sedated with intravenousium methohexital or etomidate, with constantnitoring of respiration, blood pressure, and trans-

    rmal partial pressure of oxygen. Ventilatory supports provided, if needed, to maintain an adequatertial pressure of oxygen. In all cases, the procedures directed by electrophysiologists at the Clevelandinic, and the initial shock energy, anterior patchsitions, and magnitude of any subsequent shocksried according to the preferences of the staff cardi-gist. There was no specific protocol for selection ofinitial energy setting or for any subsequent energy

    ps or number of shocks before termination of thecedure. At least 1 surface electrocardiographic leads monitored throughout the cardioversion proce-re to determine rhythm before and after shock.hen failure (no discernible P wave) occurred at