(Circulation. 2000;102:2659.)
© 2000 American Heart Association, Inc.
Basic Science Reports |
Reduction of Atrial Defibrillation Threshold With an Interatrial Septal Electrode
From the Division of Cardiovascular Diseases, Department of Medicine, Department of Physiology, and Department of Biomedical Engineering, University of Alabama at Birmingham.
Correspondence to Raymond E. Ideker, MD, PhD, Volker Hall B140, 1670 University Blvd, Birmingham, AL 35294-0019. E-mail rei{at}crml.uab.edu
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Abstract |
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Background—The standard lead configuration for internal atrial defibrillation consists of a shock between electrodes in the right atrial appendage (RAA) and coronary sinus (CS). We tested the hypothesis that the atrial defibrillation threshold (ADFT) of this RAA
CS configuration would be
lowered with use of an additional electrode at the atrial septum
(SP).
Methods and Results—Sustained atrial fibrillation was induced in
8 closed-chest sheep with burst pacing and continuous pericardial
infusion of acetyl-ß-methylcholine. Defibrillation electrodes were
situated in the RAA, CS, pulmonary artery (PA), low right
atrium (LRA), and across the SP. ADFTs of RAACS and 4 other lead
configurations were determined in random order by use of a
multiple-reversal protocol. Biphasic waveforms of 3/1-ms duration were
used for all single and sequential shocks. The ADFT delivered energies
for the single-shock configurations were 1.27±0.67 J for RAACS and
0.86±0.59 J for RAA+CSSP; the ADFTs for the sequential-shock
configurations were 0.39±0.18 J for RAASP/CSSP, 1.16±0.72 J for
CSSP/RAASP, and 0.68±0.46 J for RAACS/LRAPA. Except for
CSSP/RAASP versus RAACS and RAACS/LRAPA versus
RAA+CSSP, the ADFT delivered energies of all of the configurations
were significantly different from each other
(P<0.05).
Conclusions—The ADFT of the standard RAACS configuration is
markedly reduced with an additional electrode at the atrial SP.
Key Words: defibrillation • atrium • electrophysiology
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Introduction |
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Electrical cardioversion remains a first-line therapy for atrial fibrillation (AF).1 2 Antiarrhythmic drugs and curative surgical and ablative therapies are still of limited efficacy, and their incidence of adverse effects is not insignificant.3 4 5 Because cardioversion with intrathoracic electrodes is more efficacious than transthoracic defibrillation6 and the implantable atrial defibrillator has been shown to be feasible,7 many recent investigations have focused on minimizing the energy requirements of internal cardioversion through novel waveforms or electrode configurations.8 9 10 11 12 Still, the most efficient cardioversion strategy clinically used, with biphasic waveforms and lead systems in which shock fields encompass both atria, requires shock strengths that are not sufficiently low to be tolerated by most patients without sedation.1 2 13 14 15
Atrial defibrillation may require a minimum potential gradient to be
generated by the shock throughout the atrial myocardium, as
does ventricular defibrillation throughout the ventricles.
The lowest-gradient areas, usually distant from the defibrillation
electrodes, are the areas from which earliest activations arise after
unsuccessful shocks.16 17 The region of earliest
activation, and presumably lowest gradient, with a right atrial
appendage–to–coronary sinus defibrillation configuration
(RAACS) is in the posterior left atrium.18 An electrode
configuration with an interatrial septal (SP) electrode
approximately midway between the RAA and CS electrodes should increase
the potential gradient in this region. The purpose of this study was to
determine whether the atrial defibrillation threshold (ADFT) could be
reduced by use of configurations with an atrial SP electrode.
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Methods |
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The use of experimental animals in this study was approved by the Institutional Animal Care and Use Committee at the University of Alabama at Birmingham. All studies were performed in accordance with the guidelines established in the "Position of the American Heart Association on Research Animal Use" adopted by the American Heart Association on November 11, 1984 (Circulation. April 1985).
Of 11 adult sheep, 8 completed the experimental protocol (body mass 41±6 kg, heart mass 217±8 g). Only the data from these 8 animals are reported.
Animal Preparation
As a preanesthetic agent, a 1-to-1 mixture of tiletamine and
zolazepam (8 to 10 mg/kg) was given intramuscularly. Approximately 10
minutes later, thiopental (2 to 6 mg/kg) was administered as a slow
intravenous bolus. The animal was laid on its back on a
fluoroscopy table, intubated, and placed on a volume-cycled ventilator
(tidal volume 15 to 20 mL/kg) with a 4% isoflurane/oxygen mixture at a
rate of 8 to 12 breaths per minute. The isoflurane concentration was
later decreased to 1.5% to 3.5% to maintain a deep surgical plane of
anesthesia. Ventilator settings were adjusted to maintain
blood gases within normal ranges. Lactated Ringer’s solution was
continuously infused with supplemental electrolytes as needed as
determined by serial blood gas and chemistry analyses every 30
to 60 minutes.
An 8F sheath was placed in the left femoral artery
percutaneously for continuous arterial
pressure monitoring. The animal was instrumented for lead II ECG and
esophageal temperature monitoring. A heated water blanket was used to
maintain body temperature at 
37°C. Neuromuscular blockade was
achieved with a 1-mg/kg succinylcholine chloride
intravenous bolus followed by an intravenous
drip (5 to 8 mg/min) for maintenance, depending on
neuromuscular tone.
Defibrillation Catheter Placement
All catheters were positioned transvenously under
fluoroscopic guidance. Through a jugular vein, a defibrillation lead
(Perimeter 7109, Guidant Corp) with a 6-cm-long coil electrode (Figure 1
) was situated in the distal CS with its
tip under the left atrial appendage (Figure 2). Care was taken not to place this lead
in the persistent superior vena cava, which is present in this
species. A modified quadripolar catheter (Mansfield EP-Boston
Scientific Corp) with a 4-cm-long coil electrode 1 cm proximal to the
catheter tip (Figure 1) was positioned in the RAA through the
left femoral vein (Figure 2). The bipolar tip of this catheter
was used for burst pacing to induce AF. Two other catheters, each with
a 4-cm-long coil electrode, were placed in the pulmonary artery
(PA) and lower right atrium (LRA). The PA electrode was positioned with
50% of the electrode in the main PA and half in the left PA. The
LRA electrode was positioned with 50% of the electrode in the LRA
and half in the inferior vena cava.
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A custom-made 6-cm coil electrode with its distal end 3 cm from the
catheter tip (Figure 1
) served as the interatrial SP electrode.
It was situated through a transseptal procedure. An 8F Mullins sheath
was advanced into the right atrium through the right femoral vein over
a 0.038-in guidewire. Then, a Brockenbrough needle replaced the
guidewire and was displaced through the atrial SP, usually under left
anterior oblique projection. Left atrial
catheterization was confirmed by measurement of oxygen
saturation of blood withdrawn through the needle and with contrast
injection into the left atrium during fluoroscopy. A stiff 0.038-in
guidewire was positioned in the left atrium through the sheath, and the
Mullins sheath was withdrawn. Next, an 11F guide sheath was advanced
over the wire into the left atrium. After withdrawal of the dilator and
guidewire, the SP electrode was inserted into the left atrium through
the guide sheath. The tip of the SP electrode catheter was placed
against the lateral wall of the left atrial appendage. Approximately
two thirds of the electrode was in the left atrium and one third in the
right atrium (Figure 2). After the SP electrode was placed, 1000
U of heparin was given intravenously every hour.
A catheter (Endotak DSP, Guidant Corp) was inserted through the other jugular vein with its defibrillation electrodes in the right ventricle and superior vena cava, and a tip electrode in the right ventricle for ventricular pacing. A 3-wire subcutaneous array was inserted over the left side of the heart. In the event of ventricular tachyarrhythmias, these electrodes were used to rescue the animal.
Induction of Atrial Fibrillation
To allow AF to be maintained, acetyl-ß-methylcholine
chloride (Sigma Chemical Co) was continuously infused into the
pericardial space. The pericardial space was approached
percutaneously under fluoroscopic guidance with a
3-in-long 16-gauge needle from just inferior to the right
subxiphoid position with the animal turned 20° toward the right
side. When the needle was confirmed by contrast injection to be within
the pericardial space, a guidewire was gently inserted through it into
the pericardial space. The pericardial location for the guidewire was
confirmed by inability to move it outside the fluoroscopic image of the
heart silhouette. After removal of the needle, a 6F sheath was advanced
into the pericardial space over the wire. After flushing with
acetyl-ß-methylcholine chloride, a 4F pigtail catheter was inserted
through the sheath. Typically, the catheter tip was advanced near the
left atrium and the sheath was removed.
Acetyl-ß-methylcholine chloride solution (1 g/250 mL saline) was infused at a rate of 20 µL/min with a microinfuser.19 20 Burst pacing used to induce AF consisted of 2-ms stimuli delivered at intervals of 30 to 80 ms. AF was defined as irregular rapid atrial activity with an irregular ventricular response on the surface ECG. Blood pressure and heart rate were recorded before and 20 minutes after acetyl-ß-methylcholine chloride infusion.
Defibrillation Waveforms and Lead Configurations
Once AF was maintained for >10 minutes, the defibrillation
protocol was begun. Briefly, a monophasic, truncated-exponential
waveform was produced by a programmable defibrillator (HVS-02,
Ventritex, Inc) with a discharge capacitance of 150 µF. This
monophasic waveform was divided into a biphasic waveform by a set of
high-voltage, cross-point switches; for sequential shocks, 2 biphasic,
truncated-exponential waveforms were created with the use of an
additional set of cross-point switches.9 Each biphasic
waveform had a first-phase duration of 3 ms and a second-phase duration
of 1 ms. The interval between each phase of the biphasic waveforms and
between the 2 biphasic waveforms of sequential shocks was 0.02
ms.9 All phases of the waveforms exhibited decaying
voltage from a single capacitor, in which the trailing-edge voltage of
each preceding phase was equal to the leading-edge voltage of the
succeeding phase.
In each animal, the ADFTs of 5 test configurations (Table 1) were determined. Three
configurations that used the SP electrode were named A1, A2, and A3.
The 2 others were named B and C. The order of determining the ADFTs was
randomized as follows. The order among A, B, and C was initially
randomized, and then the order of A1, A2, and A3 (within A) was
randomized. ADFTs of the SP electrode configurations were measured
consecutively to obviate the need for repositioning this electrode.
During ADFT testing, passive electrodes not delivering any shock for
that configuration were removed. Shock delivery was synchronized to
right ventricular pacing at a cycle length of 250 to 400
ms, depending on the intrinsic ventricular rate during AF.
Shocks were delivered 20 ms after the eighth pacing pulse.
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Each ADFT was determined by a multiple-reversal method with an initial commended peak voltage of 100 V and step sizes of 40/20/10 V.9 If the initial shock failed, the next and subsequent shock voltages were increased by 40 V until a shock succeeded. After the first shock that successfully terminated AF, voltages of subsequent shocks were decreased by 20 V until a shock failed. Then shock voltages were increased by 10 V until a shock succeeded again. Conversely, if the initial shock succeeded, subsequent shock voltages were decreased by 40 V until a shock failed. Then shock voltages were increased by 20 V until a shock succeeded, after which shock voltages were decreased by 10 V until a shock failed again. The last successful shock of the third reversal was deemed the ADFT shock for that configuration. The ADFT characteristics for each configuration were derived from this ADFT shock. All test shocks were applied after AF was sustained for 1 minute. When a test shock failed, a rescue shock of 200 to 300 V was given. A 1- to 2-minute period of sinus rhythm was allowed before the next AF induction.
Data Acquisition
For each test shock, the leading-edge voltage and current
were recorded, and the impedance and delivered energy were computed
by a waveform analyzer (DATA 6100, Data
Precision).9 The stored energy for each shock was
calculated as CV2/2, in which C is the discharge
capacitance (150x10-6 F)
and V is the commended peak voltage of the shock. The ADFT leading-edge
voltage, current, impedance, and delivered and stored energies were
derived from the ADFT shock.
Postmortem Examination
After completion of the experimental protocol, euthanasia was
induced with an intravenous bolus of potassium chloride.
The chest was opened, and the location of the electrodes of the last
test configuration was confirmed by palpation through the heart walls.
The heart was then removed and weighed.
Statistical Analysis
Results are expressed as mean±SD. The overall effects of
the 5 test configurations on each ADFT characteristic and the impedance
differences of current pathways were tested by repeated-measures ANOVA.
Differences between the 5 configurations were tested by Duncan’s
multiple range test.21 A value of P<0.05 was
considered significant.
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Results |
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Reproducible, sustained AF was induced in all animals. The ventricular rates in sinus rhythm before and 20 minutes after administration of acetyl-ß-methylcholine chloride were similar (112±8 versus 109±11 bpm, respectively, P=NS). The drug significantly lowered the sinus-rhythm systolic and diastolic blood pressure, however (107±8 versus 84±7 and 83±4 versus 62±5 mm Hg, respectively). During AF, the ventricular rate was 131±36 (range 80 to 178) bpm. In 1 sheep with an unusually long sinus recovery time, temporary postshock atrial pacing was performed.
ADFT Leading-Edge Voltages
The ADFT leading-edge voltage of configuration A2 was
significantly lower than each of the other 4 configurations (Figure 3). The ADFT leading-edge voltage of
configuration A1 was significantly lower than that of configurations A3
and B, but not C. The ADFT leading-edge voltage of configuration B was
significantly higher than each of the other 4 configurations.
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ADFT Leading-Edge Currents
The ADFT leading-edge current of configuration A2 was
significantly lower than that of A1, A3, and B and trended lower than
that of C (Figure 4). The ADFT
leading-edge current of configuration C was significantly lower than
that of configurations A1, A3, and B. The ADFT leading-edge current of
configuration A1 was significantly higher than each of the other
configurations.
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Configuration Impedances
Impedances of the same current pathway in different test
configurations were not significantly different. The impedance of the
RAA+CSSP current pathway was lower than that of all of the other
pathways tested (Table 2). The impedance
of CSSP was significantly lower than that of RAASP, and the
impedances of CSSP and RAASP were both significantly lower than
that of RAACS. The impedance of LRAPA was significantly lower
than that of RAACS.
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ADFT Shock Energy
Configuration A2 had a significantly lower ADFT delivered energy
than each of the other 4 test configurations (Figure 5). Configuration C had significantly
lower ADFT energy than that of configurations A3 and B and trended
lower than that of A1. The ADFT delivered energy of configuration C was
50±9% lower than that of configuration B. Configuration A1 had
significantly lower ADFT energy than configurations A3 and B (by
18±52% and 37±15%, respectively). The difference in ADFT delivered
energy between configurations A3 and B was not significant. The ADFT
delivered energies for each animal are shown in Figure 5B. On
each animal, the ADFT delivered energy of configuration A2 was lower
than that of configuration B. The configuration A2 ADFT delivered
energies of all 8 animals were lower than the configuration B mean ADFT
delivered energy, as well.
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The ADFT stored energies of configurations A1, A2, A3, B, and C were 1.32±0.88, 0.55±0.24, 1.66±0.94, 2.42±1.18, and 0.98±0.61 J, respectively. Except for A1 versus A3, A1 versus C, and A2 versus C, the ADFT stored energies for all of the test configurations were significantly different for each other.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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This study demonstrates that, in a sheep model of sustained AF, atrial defibrillation configurations that used an additional electrode at the interatrial SP required significantly lower energy than the standard RAA
CS configuration. The ADFT delivered energy of
RAA+CSSP was 0.86±0.59 J, 37±15% lower than that of RAACS
(1.27±0.67 J), and the ADFT delivered energy of the sequential-shock
configuration RAASP/CSSP was 0.39±0.18 J, 68±8% lower than
that of RAACS.
Previous experimental and clinical studies found the most efficient
simple single-shock configuration to be RAACS.22 23
This is the most common configuration for in-hospital internal
cardioversion and is the standard configuration used by the first
stand-alone implantable atrial defibrillator.7 With this
RAACS configuration, ADFTs in humans without a significant history
of AF are 1.5 to 2.5 J and are significantly greater in patients with
chronic AF.1 24 25 26 27 Unfortunately, shocks of this
magnitude are uncomfortable to unsedated patients; although a
"discomfort threshold" has not been clearly defined with this or
any other shock configuration, it appears that shocks need to be well
below 1 J to be well tolerated in most
patients.1 2 13 14 15
Cooper and colleagues9 have reported ADFTs <1 J in
a sheep model using a sequential, 2-current-pathway configuration. In
this study, the RAAdistal CS/PAproximal CS ADFT (0.36±0.13 J)
was significantly lower than that of the standard single-shock
RAAdistal CS configuration (1.29±0.26 J). In humans, a related
sequential-shock configuration, RAAdistal CS/left subclavian
veinproximal CS, was tested and found to have lower ADFTs than
RAAdistal CS (2.0±0.4 versus 5.1±1.8 J), as
well.27
In the present study, the ADFT of RAACS/LRAPA is similar to
the RAAdistal CS/PAproximal CS configuration studied by Cooper
and colleagues. We used an electrode in the LRA near the ostium of the
CS instead of one in the proximal CS because our CS catheter lacked an
electrode at the CS ostium. In the present study, the
RAACS/LRAPA ADFT (0.68±0.46 J) was 50±9% lower than that of
the RAACS configuration (1.27±0.67 J). In the study by Cooper et
al, the RAAdistal CS/PAproximal CS configuration exhibited an
ADFT energy 74% lower than that of RAAdistal CS. Thus, the
RAACS/LRAPA configuration did not exhibit quite the relative
reduction in ADFT compared with the control RAACS configuration as
the analogous configuration tested in the study by Cooper et
al.11 Still, the RAASP/CSSP ADFT, the most
efficacious sequential configuration tested with the SP electrode in
this study, was not only 68±8% lower than the standard RAACS
configuration but also 36±15% lower than the RAACS/LRAPA
configuration.
In our model, reversing the order of the sequential shocks from
RAASP/CSSP to CSSP/RAASP greatly increased the ADFT. The
impedance of the RAASP pathway was 46 
, whereas that of the
CSSP pathway was 35 (Table 2), which might be attributed
to the facts that (1) the RAA electrode (4 cm) was shorter than the CS
electrode (6 cm) and (2) the distance between the SP and CS electrodes
was shorter than that between the SP and RAA electrodes. When the
larger first shock of the sequential stimulus was delivered to the
pathway with higher impedance, probably encompassing a larger mass of
atrial tissue, and the smaller second shock was delivered to the
pathway with lower impedance, the ADFT was lower. This is
consistent with the concept that defibrillation requires a
minimum potential gradient throughout the entire atrial
myocardium.
In the present study, the atrial SP electrode was placed through a
transseptal procedure with most of the electrode situated near the high
left atrial SP and the smaller portion near the low right atrial SP.
This electrode was between the RAA and CS electrodes near the posterior
left atrial wall, where the earliest activations after unsuccessful
RAACS shocks have been reported to appear.18 This SP
electrode was far from the sinus and atrioventricular
nodes and remained firmly fixed in location throughout each study.
Study Limitations
The study was performed in sheep with acute AF maintained with
acetyl-ß-methylcholine chloride. Therefore, the results cannot be
extrapolated directly to patients with AF. Furthermore, the SP
electrode used in this study is not currently clinically acceptable,
because it carries the risk of thrombus and embolism and may be
problematic to extract.
Clinical Implications
As the population ages and the incidence of AF concomitantly
rises, the clinical application of atrial cardioversion becomes
broader. One of the prime detriments to internal atrial defibrillation
is the fact that the intensity of shocks required to successfully
cardiovert patients is uncomfortable. If a wholly right-sided SP
electrode can be developed that does not damage the sinus and
atrioventricular nodes, these data suggest a means for
reducing atrial defibrillation energy requirements.
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Acknowledgments |
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This study was supported in part by National Institutes of Health grant HL-42760, the Whitaker Foundation, and Guidant Corp.
Received March 17, 2000; revision received June 15, 2000; accepted June 21, 2000.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
-
Murgatroyd FD, Slade AKB, Sopher SM, et
al. Efficacy and tolerability of transvenous low energy
cardioversion of paroxysmal atrial fibrillation in humans. J
Am Coll Cardiol. 1995;25:1347–1353.[Abstract]
-
Lévy S, Ricard P, Gueunoun M, et al. Low-energy
cardioversion of spontaneous atrial fibrillation: immediate and
long-term results. Circulation. 1997;96:253–259.
[Abstract/Free Full Text]
-
Nattel S, Hadjis T, Talajic M. The treatment of atrial
fibrillation: an evaluation of drug therapy, electrical modalities and
therapeutic considerations. Drugs. 1994;48:345–371.[Medline]
[Order article via Infotrieve]
-
Coplen SE, Antman EM, Berlin JA. Efficacy and safety
of quinidine therapy for maintenance of sinus rhythm after
cardioversion: a meta-analysis of randomized control trials.
Circulation. 1990;82:1106–1116.
[Abstract/Free Full Text]
-
Cox JL, Boineau JP, Schuessier RB, et al.
Five-year experience with the MAZE procedure for atrial fibrillation.
Ann Thorac Surg. 1993;56:814–824.[Abstract]
-
Alt E, Ammer R, Schmitt C, et al. A comparison of
treatment of atrial fibrillation with low-energy intracardiac
cardioversion and conventional external cardioversion. Eur
Heart J. 1997;18:1796–1804.
[Abstract/Free Full Text]
-
Wellens HJ, Lau CP, Luderitz B, et al. Atrioverter: an
implantable device for the treatment of atrial fibrillation.
Circulation. 1998;98:1651–1656.
[Abstract/Free Full Text]
-
Cooper RAS, Wallenius ST, Smith WM, et al. The effect
of phase separation on biphasic waveform defibrillation. Pacing
Clin Electrophysiol. 1993;16:471–482.[Medline]
[Order article via Infotrieve]
-
Cooper RAS, Smith WM, Ideker RE. Internal
cardioversion of atrial fibrillation: marked reduction in
defibrillation threshold with dual current pathways.
Circulation. 1997;96:2693–2700.
[Abstract/Free Full Text]
-
Krum D, Hare J, Mughal K, et al. Optimization of
shocking lead configuration for transvenous atrial
defibrillation. J Cardiovasc Electrophysiol. 1998;9:998–1003.[Medline]
[Order article via Infotrieve]
-
Tomassoni G, Newby KH, Kearney MM, et al. Testing
different biphasic waveforms and capacitances: effect on atrial
defibrillation threshold and pain perception. J Am Coll
Cardiol. 1996;28:695–699.[Abstract]
-
Harbinson MT, Allen JD, Imam Z, et al. Rounded
biphasic waveform reduces energy requirements for transvenous catheter
cardioversion of atrial fibrillation and flutter. Pacing Clin
Electrophysiol. 1997;20:226–229.[Medline]
[Order article via Infotrieve]
-
Jung J, Heisel A, Fires R, et al. Tolerability of
internal low-energy shock strengths currently needed for endocardial
atrial cardioversion. Am J Cardiol. 1997;80:1489–1490.[Medline]
[Order article via Infotrieve]
-
Zipes DP, Jackman WM, Heger JJ, et al. Clinical
transvenous cardioversion of recurrent life-threatening
ventricular tachyarrhythmias: low energy
synchronized cardioversion of ventricular
tachycardia and termination of ventricular
fibrillation in patients using a catheter electrode. Am
Heart J. 1982;103:789–794.[Medline]
[Order article via Infotrieve]
-
Nathan AW, Bexton RS, Spurrell RAJ, et al. Internal
transvenous low energy cardioversion for the treatment of cardiac
arrhythmias. Br Heart J. 1984;52:377–384.
[Abstract/Free Full Text]
-
Wharton JM, Wolf PD, Smith WM, et al. Cardiac potential
and potential gradient fields generated by single, combined, and
sequential shocks during ventricular defibrillation.
Circulation. 1992;85:1510–1523.
[Abstract/Free Full Text]
-
Shibata N, Chen PS, Dixon EG, et al. Epicardial
activation following unsuccessful defibrillation shocks in dogs.
Am J Physiol. 1988;255:H902–H909.
[Abstract/Free Full Text]
-
Cooper RAS, KenKnight BH. The role of waveforms
and lead configurations for internal atrial cardioversion.
Herzschr Elektrophys. 1998;9:1–7.
-
Fotuhi PC, Cooper RA, Sreenan CM, et al. Can early
timed internal atrial defibrillation shocks reduce the atrial
defibrillation threshold? Pacing Clin Electrophysiol. 1999;22:1179–1185.[Medline]
[Order article via Infotrieve]
-
Sih HJ, Berbari EJ, Zipes DP. Epicardial maps of atrial
fibrillation after linear ablation lesions. J Cardiovasc
Electrophysiol. 1997;8:1046–1054.[Medline]
[Order article via Infotrieve]
-
Montgomery DC. Design and analysis of
experiments. 3rd ed. New York, NY: John Wiley and Sons;
1991:72–76.
-
Cooper RA, Alferness CA, Smith WM, et al. Internal
cardioversion of atrial fibrillation in sheep. Circulation. 1993;87:1673–1686.
[Abstract/Free Full Text]
-
Saksena S, Prakash A, Mangeon L, et al. Clinical
efficacy and safety of atrial defibrillation using biphasic shocks and
current nonthoracotomy endocardial lead configurations. Am J
Cardiol. 1995;76:913–921.[Medline]
[Order article via Infotrieve]
-
Heisel A, Jung J, Neuzner J, et al. Low-energy
transvenous cardioversion of atrial fibrillation using a single atrial
lead system. J Cardiovasc Electrophysiol. 1997;8:607–614.[Medline]
[Order article via Infotrieve]
-
Lau CP, Lok NS. A comparison of transvenous atrial
defibrillation of acute and chronic atrial fibrillation and the effect
of intravenous sotalol on human atrial defibrillation
threshold. Pacing Clin Electrophysiol. 1997;20:2442–2452.[Medline]
[Order article via Infotrieve]
-
Lévy S, Ricard P, Lau C, et al. Multicenter low
energy transvenous atrial defibrillation (XAD) trial results in
different subsets of atrial fibrillation. J Am Coll
Cardiol. 1997;29:750–755.[Abstract]
-
Cooper RA, Plumb VJ, Epstein AE, et al. Marked
reduction in internal atrial defibrillation thresholds with
dual-current pathways and sequential shocks in humans.
Circulation. 1998;97:2527–2535.
[Abstract/Free Full Text]
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