CARDIOVERSION EN FA

1. Transthoracic Cardioversion of Atrial Fibrillation
Comparison of Rectilinear Biphasic Versus Damped Sine Wave
Monophasic Shocks
Suneet Mittal, MD; Shervin Ayati, MSEE; Kenneth M. Stein, MD; David Schwartzman, MD;
Doris Cavlovich, RN, BSN; Patrick J. Tchou, MD; Steven M. Markowitz, MD;
David J. Slotwiner, MD; Marc A. Scheiner, MD; Bruce B. Lerman, MD
Background—Clinical studies have shown that biphasic shocks are more effective than monophasic shocks for ventricular
defibrillation. The purpose of this study was to compare the efficacy of a rectilinear biphasic waveform with a standard
damped sine wave monophasic waveform for the transthoracic cardioversion of atrial fibrillation.
Methods and Results—In this prospective, randomized, multicenter trial, patients undergoing transthoracic cardioversion
of atrial fibrillation were randomized to receive either damped sine wave monophasic or rectilinear biphasic shocks.
Patients randomized to the monophasic protocol (nϭ77) received sequential shocks of 100, 200, 300, and 360 J. Patients
randomized to the biphasic protocol (nϭ88) received sequential shocks of 70, 120, 150, and 170 J. First-shock efficacy
with the 70-J biphasic waveform (60 of 88 patients, 68%) was significantly greater than that with the 100-J monophasic
waveform (16 of 77 patients, 21%, PϽ0.0001), and it was achieved with 50% less delivered current (11Ϯ1 versus 22Ϯ4
A, PϽ0.0001). Similarly, the cumulative efficacy with the biphasic waveform (83 of 88 patients, 94%) was significantly
greater than that with the monophasic waveform (61 of 77 patients, 79%; Pϭ0.005). The following 3 variables were
independently associated with successful cardioversion: use of a biphasic waveform (relative risk, 4.2; 95% confidence
intervals, 1.3 to 13.9; Pϭ0.02), transthoracic impedance (relative risk, 0.64 per 10-⍀ increase in impedance; 95%
confidence intervals, 0.46 to 0.90; Pϭ0.005), and duration of atrial fibrillation (relative risk, 0.97 per 30 days of atrial
fibrillation; 95% confidence intervals, 0.96 to 0.99; Pϭ0.02).
Conclusions—For transthoracic cardioversion of atrial fibrillation, rectilinear biphasic shocks have greater efficacy (and
require less energy) than damped sine wave monophasic shocks. (Circulation. 2000;101:1282-1287.)
Key Words: cardioversion Ⅲ atrial fibrillation Ⅲ shock
Atrial fibrillation is the most commonly encountered
sustained clinical arrhythmia.1 Since its introduction 3
decades ago, transthoracic electrical cardioversion has re-
mained the most effective method for terminating atrial
fibrillation.2 However, currently available defibrillators use a
damped sine wave monophasic waveform, which may be
effective in Ͻ80% of patients.3–6
Multiple studies have shown that biphasic waveforms have
greater efficacy than monophasic waveforms for endocardial
defibrillation.7–12 More recent studies of transthoracic ven-
tricular defibrillation have also shown that, compared with
monophasic shocks, biphasic shocks are equally effective and
use less delivered energy,13,14 which may result in less
post-shock myocardial dysfunction.13,15–17 To determine
whether a biphasic waveform provides increased efficacy
with less energy during the transthoracic cardioversion of
atrial fibrillation, we prospectively compared the efficacy of
a standard damped sine wave monophasic waveform with a
rectilinear biphasic waveform in patients undergoing trans-
thoracic cardioversion of atrial fibrillation.
Methods
Study Population
This study was a prospective, randomized, multicenter trial that
compared the efficacy of a rectilinear biphasic waveform with a
damped sine wave monophasic waveform for the transthoracic
cardioversion of atrial fibrillation. During the study period (between
August 1998 and February 1999), 174 patients were enrolled from 7
centers. Patients were eligible for the study if they were undergoing
electrical cardioversion of atrial fibrillation. Patients with atrial
fibrillation for Ն48 hours were anticoagulated with warfarin for Ն3
weeks and achieved an international normalized ratio Ն2.0. Patients
who had not been anticoagulated for Ն3 weeks underwent a
Received July 21, 1999; revision received September 29, 1999; accepted October 12, 1999.
From The New York Hospital-Cornell Medical Center, New York, NY (S.M., K.M.S., S.M.M., D.J.S., M.A.S., B.B.L.); Zoll Medical Corporation,
Burlington, Mass (S.A.); University of Pittsburgh Medical Center, Pittsburgh, Pa (D.S., D.C.); and Cleveland Clinic Foundation, Cleveland, Ohio (P.J.T.).
Mr Ayati is an employee of Zoll Medical Corporation, which makes the defibrillators and gel pads used in this study. The remaining authors, including
Dr Lerman who is a consultant to the Zoll Medical Corporation, do not have a financial interest in these devices.
Correspondence to Bruce B. Lerman, MD, Division of Cardiology, The New York Hospital-Cornell Medical Center, 525 East 68th Street, Starr 4, New
York, NY 10021. E-mail blerman@mail.med.cornell.edu
© 2000 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
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2. transesophageal echocardiogram while receiving therapeutic heparin
(or warfarin) immediately before the cardioversion that documented
the absence of a left atrial thrombus.18 All patients were then
required to be anticoagulated for 3 to 4 weeks after cardioversion. In
addition, all patients were required to have had an echocardiogram
within 3 months of the cardioversion for assessment of the left atrial
size and left ventricular (LV) ejection fraction. Patients were
ineligible if they were Ͻ18 years of age, were pregnant, or were
undergoing cardioversion of an atrial arrhythmia other than atrial
fibrillation. The Institutional Review Board at each participating
institution approved the investigational protocol, and informed
written consent was obtained from all patients.
Study Design
The primary hypothesis of the study was that rectilinear biphasic
shocks would have a greater cardioversion efficacy than monophasic
shocks. Assuming an 80% cumulative efficacy with the damped sine
wave monophasic waveform, 154 patients were required to detect a
Ͼ15% difference in efficacy between the monophasic and biphasic
waveforms and to have a power of 80% and a significance level of
0.05.
Shock Waveforms
Figure 1 depicts a representative 100-J damped sine wave monopha-
sic waveform and a 70-J rectilinear (constant-current first phase)
biphasic waveform delivered across a 50-⍀ load. The monophasic
waveforms were generated by a Zoll PD-2000 defibrillator, which
delivered the stored charge on a 45-␮F capacitor through a 20-MHz
inductor and an internal resistance of 14 ⍀. Biphasic waveforms
were generated from a 100-␮F capacitor using the Zoll PD-2100
defibrillator. The rectilinear biphasic waveform consisted of a
constant-current 6-ms first phase, followed by a truncated, exponen-
tial 4-ms second phase. The time between the trailing edge of the
first phase and the leading edge of the second phase was 100 ␮s. For
a selected energy, a constant-current first phase was produced by
automatically adjusting the internal resistance of the defibrillator
circuit on the basis of the patient’s transthoracic impedance, which
was automatically determined at the onset of shock delivery.
The defibrillator’s internal switching resistors, along with imped-
ance compensation, provided a constant first-phase current as well as
the step ripple. The amplitude of the first and second phases varied
with the selected energy. The initial amplitude of the second phase
was approximately equal to the final amplitude of the first phase.
When 170 J was selected for the biphasic waveform and the
measured patient impedance was Ն85 ⍀, the first phase of the
biphasic waveform tilted. However, all other waveform parameters,
including phase duration, interphase delay, and integrated impedance
measurement-sensing pulse, were unchanged. The effect of transtho-
racic impedance on delivered current for the monophasic and
biphasic waveforms is outlined in Table 1.
Shock Electrodes
Wet polymer gel pads19 (Zoll Cardiology Specialty Pad) for trans-
thoracic cardioversion were applied to the right parasternal area and
to the left scapula posteriorly.20 The anterior electrode was circular
and had a diameter of 10 cm, which corresponded to an active
surface area of 78 cm2
. The posterior electrode was rectangular and
had a diagonal length of 14.5 cm, which corresponded to an active
surface area of 113 cm2
. The pads were connected to a multiple-
defibrillation interface unit, which in turn was connected to the
monophasic and biphasic defibrillators. This setup was used to
ensure that both defibrillators delivered a shock into the same pad
and same location. Furthermore, the interface unit transferred the
voltage and current delivered to the patient to a laptop personal
computer for data collection purposes.
Protocol for Cardioversion
Patients were randomized at each center, using a simple block-
randomization scheme, to either the monophasic or biphasic wave-
form protocol. Patients randomized to the monophasic protocol
received sequential shocks of 100, 200, 300, and 360 J, if necessary.
If the 360-J shock failed to cardiovert the patient, a final 170-J
biphasic shock was delivered. Patients randomized to the biphasic
protocol received sequential shocks of 70, 120, 150, and 170 J, if
necessary. If the 170-J shock failed to cardiovert the patient, a final
360-J monophasic shock was delivered. Successful cardioversion
was defined as the conversion of atrial fibrillation to sinus rhythm for
Ն30 s after the shock.
Statistical Analysis
All continuous variables are expressed as meanϮSD. Comparisons
of dichotomous and continuous variables between the monophasic
and biphasic waveform groups were calculated using the ␹2
and
Student’s t tests, respectively. The first-shock efficacy of the 70-J
biphasic and 100-J monophasic shocks and the cumulative efficacy
of biphasic and monophasic shocks were compared using Fisher’s
Figure 1. Defibrillation waveforms. Top, Representative 100-J
damped sine wave shock delivered across 50-⍀ load. Bottom,
Representative 70-J rectilinear biphasic waveform delivered
across 50-⍀ load.
TABLE 1. Peak Current (A) Delivered by the 2 Waveforms at
an Impedance of 50 to 125 ⍀.
50 ⍀ 75 ⍀ 100 ⍀ 125 ⍀ Study Population*
Biphasic shocks
70 J 12 11 10 8 11Ϯ1
120 J 16 15 13 11 14Ϯ1
150 J 18 17 15 13 15Ϯ2
170 J 24 23 19 15 21Ϯ2
Monophasic shocks
100 J 29 22 18 15 22Ϯ4
200 J 43 34 27 24 31Ϯ5
300 J 53 42 33 29 38Ϯ6
360 J 58 46 36 32 41Ϯ4
*This column reflects the delivered current as a function of delivered energy
(J). Impedance was 78Ϯ16 ⍀ in patients who received monophasic shocks
and 76Ϯ17 ⍀ in patients who received biphasic shocks.
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3. exact test. To determine the variables independently associated with
successful cardioversion, multivariate forward stepwise logistic re-
gression was performed using the following clinical variables:
patient weight, duration of atrial fibrillation, left atrial size, LV
ejection fraction, transthoracic impedance, and shock waveform
used. We calculated 95% confidence intervals for each relative risk.
For all comparisons, PϽ0.05 was considered statistically significant.
Results
Patient Characteristics
Cardioversion was performed in 174 patients. Nine patients
were excluded from analysis. Reasons for exclusion included
(1) failure of the investigator to follow the prespecified
step-up shock protocol (nϭ7), (2) pretreatment with ibutilide
(nϭ1), and (3) inability to access cardioversion shock data
due to a computer malfunction (nϭ1). The remaining 165
patients constituted the study population.
The population was 66Ϯ12 years of age (range, 30 to 92
years), had a mean weight of 91Ϯ23 kg (range, 46 to 168 kg),
and was predominantly male (70%). The size of the left
atrium was 4.7Ϯ0.9 cm (range, 2.7 to 9.7 cm), and the LV
ejection fraction was 50Ϯ14% (range, 15% to 75%). Struc-
tural heart disease (including hypertension) was present in
69% of patients. Of the 165 patients who underwent cardio-
version, 88 (53%) were randomized to the biphasic group and
77 (47%) to the monophasic group. The 2 groups were similar
with respect to age, sex, weight, left atrial size, LV ejection
fraction, underlying cardiac disease, New York Heart Asso-
ciation class, duration of atrial fibrillation, and use of cardio-
active drugs, including antiarrhythmic medications (Table 2).
Cardioversion Data
The first-shock cardioversion data for the 2 groups are
summarized in Table 3. First-shock efficacy with the 70-J
rectilinear biphasic waveform (60 of 88 patients, 68%) was
significantly greater than that with the 100-J damped sine
wave monophasic waveform (16 of 77 patients, 21%;
PϽ0.0001) (Figure 2). In addition, increased efficacy with
the 70-J biphasic shocks was achieved with 50% less deliv-
ered current (11Ϯ1 versus 22Ϯ4 A, PϽ0.0001). No signifi-
cant difference existed in the transthoracic impedance be-
tween the biphasic (76Ϯ17 ⍀) and monophasic (78Ϯ16 ⍀,
PϭNS) waveform groups.
The cumulative cardioversion efficacy of the 100, 200,
300, and 360 J monophasic shocks was 21%, 44%, 68%, and
79%, respectively. In contrast, the cumulative cardioversion
efficacy of the 70, 120, 150, and 170 J biphasic shocks was
68%, 85%, 91%, and 94%, respectively. The cumulative
efficacy with the rectilinear biphasic waveform (83 of 88
patients, 94%) was significantly greater than that with the
damped sine wave monophasic waveform (61 of 77 patients,
79%; Pϭ0.005) (Figure 2). Of note, the mean peak current
delivered to patients with the 100-J monophasic shocks was
equal to that delivered with 170-J rectilinear biphasic shocks
(Table 1). Furthermore, 170-J biphasic shocks delivered
Ϸ50% less current than 360-J monophasic shocks.
Sixteen patients in the monophasic group could not be
cardioverted with a maximal monophasic shock of 360 J.
Eight of these patients (50%) were successfully cardioverted
with a 170-J biphasic shock. Five patients in the biphasic
group could not be cardioverted with a maximal biphasic
shock of 170 J. These patients received a 360-J monophasic
shock, which was also unsuccessful in each patient. There
were no complications associated with either the monophasic
or biphasic shocks.
The cumulative cardioversion efficacy was significantly
affected by the patient’s baseline transthoracic impedance
(Figure 3). For patients with an impedance Յ70 ⍀, the
TABLE 2. Patient Characteristics and Clinical Demographics
Shocks
Biphasic Monophasic
No. of patients 88 (53) 77 (47)
Age, y 65Ϯ12 66Ϯ12
Sex
Male 59 (67) 56 (73)
Female 29 (33) 21 (27)
Weight, kg 89Ϯ21 93Ϯ24
Left atrial size, cm 4.7Ϯ1.0 4.6Ϯ0.8
LV ejection fraction, % 50Ϯ14 48Ϯ14
Transthoracic impedance, ⍀ 78Ϯ16 76Ϯ17
Heart disease
Coronary artery disease 22 (25) 24 (31)
Coronary artery and valvular disease 7 (8) 7 (9)
Valvular disease 18 (21) 13 (18)
Idiopathic cardiomyopathy 3 (3) 8 (18)
Hypertension 7 (8) 3 (4)
Other 0 (0) 1 (1)
None 31 (35) 21 (27)
NYHA class
I 59 (67) 47 (61)
II 23 (26) 27 (35)
III 4 (5) 3 (4)
IV 2 (2) 0 (0)
Atrial fibrillation duration
Յ48 hours 15 (17) 15 (19)
Ͼ48 hours–Յ6 months 64 (73) 47 (61)
Ͼ6 months 9 (10) 12 (16)
Unknown 0 (0) 3 (4)
Previous electrical cardioversion 37 (42) 28 (36)
Medications
ACE inhibitor 23 (26) 23 (30)
Amiodarone 24 (27) 18 (23)
␤-Blocker 41 (47) 35 (45)
Calcium-channel blocker 27 (31) 26 (33)
Digoxin 38 (43) 35 (45)
Diuretic 19 (22) 21 (27)
Nitrate 5 (6) 6 (8)
Type IA antiarrhythmic 6 (7) 7 (9)
Type IC antiarrhythmic 4 (5) 1 (1)
Sotalol 8 (9) 6 (8)
Values are meanϮSD or n (%). NYHA indicates New York Heart Association.
PϭNS for all comparisons between monophasic and biphasic groups.
1284 Circulation March 21, 2000
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4. cumulative efficacy of the biphasic waveform (29 of 29
patients, 100%) was equivalent to that of the monophasic
waveform (27 of 28 patients, 96%; PϭNS). In contrast, in
patients with an impedance Ͼ70 ⍀, the cumulative efficacy
of the biphasic waveform (53 of 58 patients, 91%) was
significantly greater than that of the monophasic waveform
(30 of 44 patients, 68%; Pϭ0.004). Compared with patients
with an impedance Յ70 ⍀ (60Ϯ8 ⍀), patients with an
impedance Ͼ70 ⍀ (86Ϯ12 ⍀) were heavier (98Ϯ24 versus
78Ϯ12 kg, PϽ0.0001) and had a larger left atrium (4.8Ϯ1.0
versus 4.5Ϯ0.8 cm, Pϭ0.04). However, no significant differ-
ences existed in weight, duration of atrial fibrillation, left
atrial size, LV ejection fraction, and transthoracic impedance
between patients treated with the monophasic and biphasic
waveforms in either the Յ70 or Ͼ70 ⍀ groups.
Use of a biphasic waveform (Pϭ0.005), patient weight
(Pϭ0.002), and baseline transthoracic impedance (Pϭ0.005)
were univariate predictors of successful cardioversion (Table
4). In addition, a trend toward a lower success rate was
observed in patients with a longer duration of atrial fibrilla-
tion (Pϭ0.08). Multivariate logistic regression identified 3
variables independently associated with cardioversion suc-
cess; they were shock waveform used for cardioversion
(Pϭ0.02), baseline transthoracic impedance (Pϭ0.01), and
duration of atrial fibrillation (Pϭ0.02). The adjusted relative
risks (95% confidence intervals) for cumulative efficacy were
4.2 (1.3, 13.9) for use of a biphasic shock waveform, 0.64
(0.46, 0.90) for each 10-⍀ increase in transthoracic imped-
ance, and 0.98 (0.97, 0.99) for each additional 30-day period
of atrial fibrillation (Table 5).
Discussion
The principal finding of this study is that rectilinear
biphasic shocks are significantly more effective than
damped sine wave monophasic shocks for the transthoracic
cardioversion of atrial fibrillation. Use of a rectilinear
biphasic waveform was the most significant independent
predictor of successful cardioversion. In addition to in-
creased efficacy, rectilinear biphasic shocks could cardio-
vert with markedly less delivered current. The advantage
of biphasic shocks was most pronounced in patients with a
transthoracic impedance Ͼ70 ⍀.
In the 3 decades since the introduction of transthoracic
electrical cardioversion, 2 alternative nonpharmacological
approaches have been introduced for patients who fail the
conventional cardioversion of atrial fibrillation: dual external
defibrillators using an orthogonal electrode array, resulting in
a 720-J defibrillator discharge,3 and internal catheter-based
cardioversion.4 The limitations of these alternatives include
potential muscular damage from high-energy shocks3 and the
attendant inconvenience and risks of the invasive internal
approach. More recently, it has been suggested that the
cardioversion efficacy of damped sine wave monophasic
shocks can be improved with ibutilide pretreatment.21 How-
ever, this approach is limited by the increased cost associated
with the use of ibutilide and the cost and inconvenience of 3
to 4 hours of continuous electrocardiographic monitoring
Figure 2. Cumulative cardioversion efficacy of monophasic and
biphasic shocks.
Figure 3. Effect of transthoracic impedance on cardioversion
efficacy. Left, In patients with impedance Յ70 ⍀, biphasic and
monophasic shocks had equivalent cumulative efficacy. Right, In
patients with an impedance Ͼ70 ⍀, biphasic shocks had signifi-
cantly greater cumulative efficacy than monophasic shocks.
TABLE 3. First-Shock Cardioversion Data for Monophasic and Biphasic Waveform Groups
Patients
Delivered
Energy, J Voltage Current, A† Impedance, ⍀
Cardioversion
Efficacy,
n (%)
100-J Monophasic shock* 77 105Ϯ4 1592Ϯ139 22Ϯ4 76Ϯ17 16/22 (21%)
(94–112) (1074–1802) (16–32) (40–112)
70-J Biphasic shock* 88 77Ϯ7 733Ϯ85 11Ϯ1 78Ϯ16 60/88 (68%)
(54–86) (493–892) (8–14) (41–124)
P Ͻ0.0001 Ͻ0.0001 Ͻ0.0001 NS Ͻ0.0001
Values are meanϮSD (range), unless otherwise indicated.
*Energy delivered into a 50-⍀ load.
†Peak current (for biphasic group, the average current was Ϸ1 A less than the peak current).
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5. after cardioversion to exclude ibutilide-induced torsade de
pointes. In addition, the approach may not be applicable to
patients with severely depressed LV systolic function because
of an increased risk of torsade de pointes in these patients.
Rectilinear biphasic cardioversion has no such limitation. Our
study suggests that the routine use of rectilinear biphasic
shocks for the transthoracic electrical cardioversion of atrial
fibrillation should significantly reduce the need to resort to
these less desirable alternatives.
Most currently available defibrillators use a damped sine
wave monophasic waveform, which is not impedance-
compensated. Although the operator is required to select a
particular energy setting, it is known that transthoracic
current is a more precise descriptor of defibrillation thresh-
old.22,23 Because at a given energy setting the current deliv-
ered is dependent on transthoracic impedance, excessive
current may be delivered to patients with low transthoracic
impedance (increased toxicity), and insufficient current may
be delivered to patients with high impedance (decreased
efficacy).24 In fact, in this study, higher baseline transthoracic
impedance was an independent predictor of shock failure.
In contrast to the damped sine wave monophasic wave-
form, the rectilinear biphasic waveform is advantageous in
high-impedance patients because it is relatively insensitive to
changes in transthoracic impedance. This is because of
impedance compensation, which ensures a constant current in
the first phase. For example, the peak current delivered to a
patient with a 125-⍀ impedance from a monophasic shock is,
on average, only 55% of that delivered to a patient with a
50-⍀ impedance. In contrast, the peak current delivered by a
biphasic shock to a patient with a 125-⍀ impedance is, on
average, 68% of that delivered to a patient with a 50-⍀
impedance, thereby reducing the adverse effect of increased
transthoracic impedance on delivered current.24,25 Consistent
with this relationship was the increased efficacy of the
rectilinear biphasic shocks observed in patients with an
impedance Ͼ70 ⍀. On the basis of the mean human trans-
thoracic impedance of Ϸ70 ⍀,24,25 the increased efficacy of
rectilinear biphasic shocks is pertinent to Ϸ50% of patients
undergoing cardioversion.
It is important to note that increased efficacy with rectilin-
ear biphasic shocks was achieved with significantly lower
delivered current than with monophasic shocks. Previous
studies during ventricular defibrillation have demonstrated
that biphasic shocks, which defibrillate with less delivered
current, result in less post-shock myocardial dysfunction than
monophasic shocks.13,15–17
Prior Studies
Lown et al2 initially reported a cardioversion efficacy of
Ϸ90%; however, their patients differed significantly from the
patients who undergo electrical cardioversion in the current
era in that their patients were younger, most had rheumatic
mitral valve disease, and many were receiving treatment with
quinidine. In contrast, our patients were older, had a mixed
cardiac origin of atrial fibrillation, and were receiving a
variety of antiarrhythmic drugs, including amiodarone.
More recently, the reported efficacy of monophasic shocks
for the cardioversion of atrial fibrillation has varied widely,
ranging from 38% to 96%.2–6,26,27 This variation largely
reflects differences in the baseline characteristics of patients
selected for cardioversion. As in our study, prior studies have
demonstrated that a longer duration of atrial fibrillation and
an increased transthoracic impedance predict unsuccessful
cardioversion.5,6,24,25 In this study, the superiority of the
rectilinear biphasic waveform over the damped sine wave
monophasic waveform was demonstrated in 2 groups who
were similar at baseline with respect to variables reported to
affect shock success, including weight, transthoracic imped-
ance, and duration of atrial fibrillation.
Limitations
A potential limitation of this study is that it is not possible to
extrapolate the benefit observed with the rectilinear biphasic
waveform to other types of biphasic waveforms. In addition,
it is unknown whether other types of monophasic waveforms,
unrelated to a damped sine wave, would be associated with a
higher success rate.
Conclusions
Rectilinear biphasic shocks have a significantly greater effi-
cacy than damped sine wave monophasic shocks for the
transthoracic electrical cardioversion of atrial fibrillation.
Additionally, increased efficacy with rectilinear biphasic
shocks is achieved with significantly less delivered current
than with monophasic shocks. The combination of increased
efficacy and decreased current requirements suggest that
rectilinear biphasic shocks may be the preferred method for
the transthoracic electrical cardioversion of atrial fibrillation.
Appendix
Investigators and Participating Institutions
Johns Hopkins University Medical Center, Baltimore, Md: Hugh
Calkins, MD (principal investigator), Rozann Hansford, RN; Uni-
TABLE 4. Univariate Analysis
Success Failure P
Shock waveform 0.005
Monophasic 79% 21%
Biphasic 94% 6%
Weight, kg 89Ϯ23 105Ϯ15 0.002
Duration of atrial fibrillation, days 143Ϯ408 613Ϯ1167 0.080
Left atrial size, cm 4.7Ϯ0.9 4.7Ϯ0.8 0.904
LV ejection fraction, % 49Ϯ15 48Ϯ12 0.922
Transthoracic impedance, ⍀ 75Ϯ17 87Ϯ12 0.005
TABLE 5. Multivariate Analysis
P
Adjusted RR*
(95% CIs)
Shock waveform 0.02 4.2 (1.3, 13.9)
Transthoracic impedance, ⍀ 0.005 0.64 (0.46, 0.90)†
Duration of AF, days 0.02 0.97 (0.96, 0.99)‡
RR indicates relative risk; CI, confidence interval; and AF, atrial fibrillation.
*The multivariate model included weight, duration of atrial fibrillation, left
atrial size, LV ejection fraction, transthoracic impedance, and shock waveform
used.
†per 10-⍀ increase in impedance; ‡per 30 days of AF.
1286 Circulation March 21, 2000
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6. versity of Michigan Medical Center, Ann Arbor, Mich: Bradley P.
Knight, MD (principal investigator), Fred Morady, MD; The New
York Hospital-Cornell Medical Center, New York, NY: Bruce B.
Lerman, MD (principal investigator), Kenneth M. Stein, MD, Steven
M. Markowitz, MD, Suneet Mittal, MD, David J. Slotwiner, MD,
Marc A. Scheiner, MD, Maliza Sarmiento, RN, MA, ANP, Mary
Wong, RN, MSN, ANP; MHSA Washington Hospital Center,
Washington, DC: Edward V. Platia, MD (principal investigator),
Jean Fenton, RN, MSN, Dulce Manno, RN; University of Pittsburgh
Medical Center, Pittsburgh, Pa: David Schwartzman, MD (principal
investigator), Doris Cavlovich, RN, BSN; Cleveland Clinic Founda-
tion, Cleveland, Ohio: Patrick J. Tchou, MD (principal investigator),
Donald R. Holmes, RN, MSN; and Duke University Medical Center,
Durham, NC: J. Marcus Wharton, MD (principal investigator),
Catherine Grill, RN, BSN.
Acknowledgments
This work was supported in part by grants from the National
Institutes of Health (RO1 HL-56139) and the Zoll Medical
Corporation.
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Mittal Monophasic vs Biphasic Shocks for Cardioversion 1287
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7. J. Tchou, Steven M. Markowitz, David J. Slotwiner, Marc A. Scheiner and Bruce B. Lerman
Suneet Mittal, Shervin Ayati, Kenneth M. Stein, David Schwartzman, Doris Cavlovich, Patrick
Versus Damped Sine Wave Monophasic Shocks
Transthoracic Cardioversion of Atrial Fibrillation: Comparison of Rectilinear Biphasic
Print ISSN: 0009-7322. Online ISSN: 1524-4539
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