The catheter was safely sent through the left pulmo-nary artery in all our patients. Second, touching thecatheter against the right atrial wall diminishes thedefibrillation threshold. This contact can be clearlyobserved by TEE.

1. Alt E, Schmitt C, Ammer R, Coenen M, Fotuhi P, Karch M, Blasini R. Initialexperience with intracardiac atrial defibrillation in patients with chronic atrialfibrillation. PACE 1994;17:1067–1078.2. Levy S, Ricard P, Gueunoun M, Yapo F, Trigano J, Mansouri C, Paganelli F.

Low energy cardioversion of spontaneous atrial fibrillation. Immediate and long-term results. Circulation 1997;96:253–259.3. Santini M, Pandozi C, Toscano S, Castro A, Altamura G, Jesi AP, GentilucciG, Villani M, Scianaro MC. Low energy intracardiac cardioversion of persistentatrial fibrillation. PACE 1998;21:2641–2650.4. Alt E, Ammer R, Lehman G, Schmitt C, Pasquantonio J, Schomig A. Efficacyof new balloon catheter for internal cardioversion for chronic atrial fibrillationwithout anaesthesia. Heart 1998;79:119–127.5. Schmeider S, Schneider MAE, Karch MR, Schmitt C. Internal low en-ergy cardioversion of atrial fibrillation using a single lead system: comparisonof a left and right pulmonary artery catheter approach. PACE 2001;24:1108–1112.

Successful Cardioversion of Atrial Fibrillation Using360-Joules Biphasic Shock

Vikas C. Jain, MD, and Kevin Wheelan, MD

Conversion of atrial fibrillation (AF) to sinusrhythm (SR) is a continuing challenge for physi-

cians, hospitals, and industry. New external defibril-lators with the capacity of delivering energies with abiphasic waveform have recently become available.These biphasic defibrillators require less energy tocardiovert AF to SR than do monophasic defibrilla-tors. No experience with biphasic shocks �200 J havebeen reported. We describe 3 patients who had suc-cessful conversion from AF to SR using 360-J bipha-sic shock.

• • •Pertinent findings in each of the 3 patients are

listed in Table 1. Each patient underwent externalcardioversion using methohexital anesthesia withstandard (right sternal to left lateral) paddle positionusing synchronized biphasic shocks on MedtronicPhysio-Control Lifepak-12 (Minneapolis, Minnesota).All 3 patients were obese and on daily amiodarone andwarfarin before cardioversion. All patients experi-enced dyspnea or decreased exercise capacity when inAF. Patient 3 had had a coronary bypass operation 8years earlier.

The above cases illustrate that biphasic 360-Jshock may be successful in converting AF to SRwithout adverse effects. The timing of cardioversion,the use of paddles versus adhesive pads, the leadposition, the concurrent use of antiarrhythmics, thenumber of attempts, and amount of energy result invariable outcomes. In general, the lowest energy levellikely to cardiovert a patient from AF to SR is utilized.Traditionally, an initial 100-J monophasic shock wasrecommended. Recently, the American College ofCardiology and the American Heart Association rec-ommended using an initial 200-J monophasic externalshock.1 Gallagher et al2 reported that an initial energy

setting of 360-J monophasic could achieve successfulcardioversion more efficiently.

• • •The experience with internal cardioversion for

atrial and ventricular arrhythmias via implanted de-vices has shown that biphasic waveform shocks re-quire less energy than do monophasic waveforms.3

These findings have been extended to external cardio-version attempts. As a result, external defibrillatorscapable of producing biphasic waveform shocks havebecome available. Most devices can deliver a maxi-mum biphasic shock of 150 to 200 J. Recent studiescomparing monophasic versus biphasic waveformssuggest that these biphasic energy levels are sufficientto cardiovert about 90% of patients with AF to SR.Mittal et al4 compared a rectilinear biphasic versusdamped sine wave monophasic shock in patients withAF. The results showed a cumulative efficacy with thebiphasic waveform of 94% compared with 79% with amonophasic waveform in 200 patients. The maximumbiphasic shock was 170 J. This study confirms thattransthoracic external defibrillation for AF can beperformed more effectively at lower energy levelsusing a biphasic waveform.

Furthermore, the body habitus of patients requiringcardioversion may influence success of attempts.More obese patients may require more energy giventhe increased distance between the lead position andthe heart. Patients with a barrel-shaped chest or withchronic obstructive lung disease may be more difficultto cardiovert. Our patients were obese or morbidlyobese. At follow-up all patients were asymptomaticwith no recurrence of AF. The use of 360-J biphasicshocks in the obese patient may be helpful in convert-ing these patients from AF to SR.

Three patients with recurrent AF were success-fully cardioverted with an external defibrillatorusing a synchronized, biphasic 360-J shock withoutadverse effects. A biphasic 360-J shock should beattempted before labeling an obese patient as hav-ing refractory AF.

From the Section of Cardiology, Department of Internal Medicine,Baylor Heart & Vascular Hospital, Dallas, Texas. Dr. Wheelan’s ad-dress is: Director, Pacing and Electrophysiology, Baylor UniversityMedical Center, 3600 Gaston Avenue, Dallas, Texas 75246. E-mail:vikasjain@pol.net. Manuscript received March 19, 2002; revisedmanuscript received and accepted April 5, 2002.

331©2002 by Excerpta Medica, Inc. All rights reserved. 0002-9149/02/$–see front matterThe American Journal of Cardiology Vol. 90 August 1, 2002 PII S0002-9149(02)02477-3

1. Fuster V, Ryden LE, Asinger RW, Cannom DS, Crijns HJ, Frye RL,Halperin JL, Kay GN, Klein WW, Levy S, et al, American College ofCardiology/American Heart Association/ European Society of CardiologyBoard. ACC/AHA/ESC guidelines for the management of patients with atrialfibrillation: executive summary. A Report of the American College of Car-diology/American Heart Association Task Force on Practice Guidelines andthe European Society of Cardiology Committee for Practice Guidelines andPolicy Conferences (Committee to Develop Guidelines for the Managementof Patients With Atrial Fibrillation): developed in Collaboration With theNorth American Society of Pacing and Electrophysiology. J Am Coll Cardiol2001;38:1231–1266.

2. Gallagher M, Guo X, Poloniecki J, Yap Y, Ward D, Camm J. Initial energysetting, outcome and efficiency in direct current cardioversion of atrial fibrillationand flutter. J Am Coll Cardiol 2001;38:1498–1504.3. 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;20:226–229.4. Mittal S, Ayati S, Stein KM, Schwartzman D, Cavlovich D, Tchou PJ,Markowitz SM, Slotwiner DJ, Scheiner MA, Lerman BB. Transthoracic cardio-version of atrial fibrillation: comparison of rectilinear biphasic versus dampedsine wave monophasic shocks. Circulation 2000;101:1282–1287.

Relation Between Sinus Rates Preceding and FollowingEctopic Beats Occurring in Isolation and as Episodes of

Bigeminy in Young Healthy Subjects

Jorge O. Diaz, MD, Agustin Castellanos, MD, Federico Moleiro, MD,Alberto Interian, Jr., MD, and Robert J. Myerburg, MD

The first studies evaluating sinus rate behavior aftersingle ventricular premature complex (VPC) con-

sidered that 2 numerical parameters, namely, heartrate turbulence slope and heart rate turbulence onset(HRTO), could be used for risk stratification in pa-tients with previous myocardial infarction and conges-tive heart failure.1–4 However, there are few publishedreports dealing with HRTO in young persons who donot have structural heart disease and with the possibledifferences between the characteristics of HRTO ofisolated VPCs and the relation between sinus ratechanges occurring before and after episodes of inter-mittent ventricular bigeminy (VB).5,6

• • •For this study, we selected 24-hour ambulatory

Holter recordings from 18 young nonmedicated sub-jects without structural heart disease but with unifocalVPC. All had normal physical examinations, labora-tory findings, 12-lead electrocardiograms, 2-dimen-sional echocardiograms; 6 of the subjects had normal

(group 2, to be described in the following) exercisetests (Bruce protocol). They were divided into 2groups: group 1 consisted of 12 subjects who only hadsingle unifocal VPCs (Table 1). Group 2 consisted of6 subjects of similar ages (mean 31.2 years, range 18to 38) who had unifocal VPCs appearing as singles aswell as in the form of intermittent VB. In addition, thetotal number of VPCs was greater in group 2 than ingroup 1 because they ranged from 156 to 1,038 (mean488) (compare with Table 1). The tapes were initially

From the Division of Cardiology of the University of Miami School ofMedicine, Miami, Florida; and Universidad Central de Venezuela,Caracas, Venezuela. Dr. Castellanos’ address is: Division of Cardiol-ogy (D-39), University of Miami School of Medicine, P.O. Box016960, Miami, Florida 33101. E-mail: acastell@med.miami.edu.Manuscript received February 12, 2002; revised manuscript receivedand accepted April 10, 2002.

TABLE 1 Pertinent Clinical Data in the Three Patients

CaseAge (yrs)/

sexBMI

(kg/m2) CA CADDilatedLA/LV

EF(%) DM SH

Age of1st

Episodeof AF

Cardioversions Attempted (successful)

Follow-up(mos)

200 J(M)

300 J(M)

360 J(M)

200 J(B)

300 J(B)

360 J(B)

1 49 F 49 � 0 0/0 60 � 0 46 �(0) �(0) �(0) �(0) � �(�) 3.02 61 M 43 � � �/� � � � 60 � � � �(0) � �(�) 1.03 75 M 34 � � �/� 25 � � 75 � � � �(0) � �(�) 1.5

B � biphasic; BMI � body mass index; CA � coronary angiography; CAD � coronary artery disease; DM � diabetes mellitus; EF � ejection fraction; LA � leftatrium; LV � left ventricle; M � monophasic; SH � systemic hypertension.

TABLE 1 Clinical and Electrocardiographic Information inSubjects With Isolated Unifocal Ventricular PrematureComplexes (group 1)

CaseAge

(yrs)/SexTotal No.

VPCsNo. of

VPCs Analyzed HRTO

1 23 M 235 77 �1.12 27 M 33 21 �1.23 34 F 76 48 �1.74 24 F 155 45 �2.75 21 F 88 22 �2.86 31 M 66 37 �3.57 37 M 94 38 �4.38 28 F 20 16 �59 18 M 101 46 �5.5

10 29 F 88 42 �9.311 33 F 150 45 �11.112 23 F 79 40 �11.2

Mean � SD 27 � 6 99 � 58 40 � 16 �4.9 � �3.6

332 ©2002 by Excerpta Medica, Inc. All rights reserved. 0002-9149/02/$–see front matterThe American Journal of Cardiology Vol. 90 August 1, 2002 PII S0002-9149(02)02478-5