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From the Department of Cardiothoracic Surgery, University of Regensburg,
Regensburg, Germany.
Correspondence to Dr Andreas Liebold, Klinik für Herz-, Thorax-, und herznahe Gefäßchirurgie, Klinikum der Universität Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany. E-mail andreas.liebold{at}klinik.uni-regensburg.de
Methods and Results—Epicardial defibrillation wire
electrodes were placed at the left and right atria during open heart
surgery in 100 consecutive patients (age 65±9 years; male to female
ratio 67:23). Electrophysiological studies
performed postoperatively revealed a test shock (0.3 J) impedance of
96±12
Conclusions—Atrial defibrillation with temporary epicardial wire
electrodes can be performed safely and effectively in patients after
cardiac operations. The shock energy required to restore sinus rhythm
is low. Thus, patients can be cardioverted without
anesthesia.
Numerous studies of perioperative pharmacological
prophylaxis of atrial tachyarrhythmias after open heart
surgery have been published.7 8 9 However,
prophylactic treatment either failed to significantly
reduce the incidence of AF or had considerable side effects.
Established treatment of AF consists of the administration of a variety
of antiarrhythmics. Electrical transthoracic cardioversion
under general anesthesia is performed when AF results in
hemodynamic instability.
A new method of internal electrical cardioversion that uses epicardial
wire electrodes with low shock energies was developed in a canine
model.10 11 Clinical trials confirmed that
low-energy atrial defibrillation via endocardial electrodes placed in
the coronary sinus and the right atrial appendage is possible
in humans.12 13
This is the first clinical study on the feasibility of internal
atrial defibrillation with low-energy shocks in patients after open
heart surgery with temporary epicardial wire electrodes.
The patients underwent surgery in a standardized manner with
cardiopulmonary bypass and cold crystalloid cardioplegia.
Eighty-nine patients underwent CABG alone or in combination with aortic
valve replacement (n=4), left ventricular
aneurysmectomy (n=1), or resection of a lung tumor (n=1). Eight
patients underwent isolated valve replacement (aortic, n=7; mitral,
n=1). One patient each underwent surgery to replace the ascending
aorta, excise a left atrial myxoma, or resect a left ventricular
aneurysm.
Defibrillation wire electrodes (TADPole; InControl Inc) were
placed at the epicardium of the left and right atria. The stainless
steel wires were polyurethane-coated, except the distal 10 cm
(defibrillation electrode). In the proximal part, the electrode was
bipolar and contained a 5-mm ring electrode that allowed bipolar
sensing and pacing (pacing electrode). The tip was connected to a
needle for direct suture to the epicardium with 5 to 6 intramural
stitches. The right atrial electrode was implanted encircling an area
of the free right atrial wall between superior and inferior
venae cavae, and the left atrial electrode was secured encircling the
space between the AV groove and the left upper and lower
pulmonary veins. Thus, the bulk of the atrial muscle mass was
located between the 2 circles of the wire electrodes (Figure 1
On arrival in the intensive care unit, the pacing threshold and
impedance, as well as P- and R-wave amplitudes, were measured with a
pacing system analyzer (ERA 20; Biotronik GmbH). Biatrial
monophasic and biphasic test shocks of 0.3 J were delivered, and the
shock impedance was determined with an external programmer (Ventak ECD;
Cardiac Pacemakers Inc).
After surgery, all patients were continuously monitored during their
entire hospital stay for the development of AF by use of a telemetric
ECG monitoring system (Sirenet E 2513; Siemens Medicals Systems). No
prophylactic antiarrhythmic drugs were administered.
In the event of AF, patients were immediately connected to an external
defibrillator (Life Pak 10; Physio Control Corp) via a defibrillation
interface module (InControl Inc) to apply R-wave synchronous monophasic
shocks with very low energies (0.6 to 10.8 J). The first shock
delivered to every treated patient had an energy of 2 J. If
unsuccessful, the shock energy was increased stepwise (from 3 to 4 to 6
J) up to 10.8 J. If multiple shocks were applied in an awake patients,
sedatives (midazolam 2 to 5 mg IV) and analgesics (piritramide 2 to 5
mg IV) were given on patient request.
The treatment was termed primarily successful if AF was successfully
converted to SR (Figure 2
Before hospital discharge, the wire electrodes were removed by simple
transcutaneous retraction. After extraction, the wires were checked for
completeness. For patients who underwent surgery for valve replacement,
anticoagulation with warfarin was started on postoperative day 3. The
extraction technique and timing were the same for all patients
regardless of anticoagulation therapy.
Data are presented as mean±SD.
Of the 100 patients studied, 23 (23%) developed AF during their
postoperative course. The onset of AF occurred at a mean of 2.1±1.3
days postoperatively.
Two patients had self-limiting episodes of AF that converted to SR
spontaneously before electrical cardioversion. Another case of AF was
treated medically because the patient removed the defibrillation wires
himself in a state of temporary neurological impairment.
The remaining 20 patients were treated by internal atrial
defibrillation. In 16 patients (80%), AF was successfully converted to
SR with a mean shock energy of 5.2±3 J.
ERAF occurred in 8 patients. Four patients converted to SR within 48
hours of receiving antiarrhythmic medication. The other 4 patients with
ERAF were successfully cardioverted with a mean shock energy of 9.1±3
J after 48 hours of receiving antiarrhythmic medication. Five patients
experienced multiple episodes of AF (2 experienced 2 episodes; 1
experienced 3 episodes; and 1 experienced 6 episodes). LRAF was
terminated by single shocks with the same energy as the first
successful shock in all patients. The interval between multiple
episodes of LRAF ranged from 16 hours to 7 days. The latest onset of an
LRAF episode occurred in a 76-year-old patient 17 days after aortic
valve replacement. She was cardioverted with a 6-J shock and maintained
SR until hospital discharge.
In total, 35 episodes of spontaneous AF were treated by internal atrial
defibrillation, with a success rate of 88% (31/35).
Most cardioversions was performed in the cardiac surgical ward without
anesthesia. Only 6 of the 20 electrically treated patients
(30%) required sedation or analgesia. No general
anesthesia was used.
The wires were removed at a mean interval of 5.7±1.9 days
postoperatively by simple transcutaneous traction. No patient left the
hospital with the wires in place. No complications related to the
extraction of the wires (in particular, no bleeding) were observed.
Cerebrovascular accidents after open heart surgery are more common in
patients with AF.3 14 15 Creswell et
al3 reported that postoperative AF increased the
risk of postoperative stroke from 1.4% to 3.3%
(P<0.0005). Others found a significantly higher combined
incidence of stroke and transient ischemic attacks in patients
with AF after CABG (60% versus 18%, respectively;
P<0.0005).15 Moreover, the
development of AF after open heart surgery prolongs the hospital stay
and increases the costs of
treatment.2 3 5 15 16
Knowledge of the pathophysiology of AF after open heart surgery
is incomplete. Thus, antiarrhythmic medication aimed at slowing the
ventricular rate with a variety of drugs, including
digitalis, ß-blockers, and calcium channel antagonists,
is usually prescribed. Other antiarrhythmics such as quinidine,
propafenone, procainamide, disopyramide,
amiodarone, and sotalol are frequently used to restore SR.
These drugs, however, carry the risk of potentially serious side
effects. Quinidine, the antiarrhythmic most commonly used to treat AF,
has been shown to lead to a 3-fold increase in unadjusted mortality
rate of treated patients compared with control
subjects.17
Usually, transthoracic cardioversion is only used when SR
cannot be restored by other means or when control of the
ventricular rate is insufficient.
The feasibility of internal electrical cardioversion of atrial
tachycardias has been shown in
animal18 19 and clinical
studies.12 13 20 21 Using a canine sterile
pericarditis model, Ortiz et al11 demonstrated
that atrial defibrillation could be accomplished by low-energy shocks
delivered through epicardial wire electrodes.
Temporary pacing leads are routinely used after open heart surgery. The
electrical properties of the wire electrodes used in the present
study included both bipolar atrial sensing and pacing, as well as
biatrial defibrillation. Adequate sensing and secure pacing were
achieved in both atria. The mean lead impedance during test shock
application with this system was significantly higher than that
reported by Schmitt et al21 using transvenous
leads in 25 patients after failed transthoracic
cardioversion. These findings correspond to the results of Ortiz et
al,11 who compared epicardial wire electrodes
with transvenous electrodes in dogs. The higher impedance of epicardial
electrodes probably reflects the inclusion of more atrial musculature
within the electrical field between the electrodes. In contrast to
Cmolik et al10 and Ortiz et
al,11 who used a straight lead configuration, we
placed the electrodes uniformly in an O-shaped manner. The straight
configuration bears the risk of lead dislodgement and consecutive loss
of capture. Furthermore, we intended to use all 10 cm of the
defibrillation electrode to obtain the maximal shock impedance. From an
electrical point of view, the O-shaped configuration should be
preferred because higher shock impedance means less shock energy.
Although our method is more time-consuming, we felt comfortable with a
stable position and optimal electrical values.
The primary goal of this study was to investigate the safety and
efficacy of epicardial cardioversion in patients after cardiac surgery.
We demonstrated a primary success rate of 80% and an overall success
rate of 88% with energy as low as 5.2±3 J. Because this is the first
study in humans that used epicardial defibrillation electrodes to treat
postoperative AF, no data are available in the literature to compare
the energy required for successful cardioversion. In transvenous
cardioversion of chronic AF,12 20 21 similar
energies were used to restore SR. In the present study, most
patients (70%) did not request sedation or analgesia.
A high incidence of ERAF was an important observation in the
present study. We cannot determine whether concomitant
antiarrhythmic medication is helpful in maintaining SR after electrical
cardioversion on the basis of our data. Further studies are required to
clarify this issue.
We conclude that atrial defibrillation with temporary epicardial
wire electrodes can be performed effectively without
anesthesia in patients after open heart surgery. Easy
placement and uncomplicated removal of the wires, as well as a quick
and safe atrial shock application, are advantages of the system we
used. Because the shock intensity needed to defibrillate the atria is
low, cardioversion is well tolerated by patients and can be performed
in the ward. Thus, internal atrial defibrillation is a valuable tool in
patients with AF after open heart surgery.
Received January 21, 1998;
revision received April 6, 1998;
accepted April 20, 1998.
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
Low-Energy Cardioversion With Epicardial Wire Electrodes: New Treatment of Atrial Fibrillation After Open Heart Surgery
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background—Atrial fibrillation (AF)
is the most common arrhythmia after open heart surgery.
Traditional treatment with a range of antiarrhythmic drugs and
electrical cardioversion is associated with considerable side effects.
The aim of this study was to examine the feasibility and efficacy of
low-energy atrial defibrillation with temporary epicardial
defibrillation wire electrodes. 
(monophasic) and 97±13 (biphasic). During their
hospital stay, AF occurred in 23 patients (23%) at 2.1±1.3 days
postoperatively. Internal atrial defibrillation was performed in 20
patients. Of these patients, 80% (16/20) were successfully
cardioverted with a mean energy of 5.2±3 J. Early recurrence
of AF (
60 seconds after defibrillation) developed in 8 patients. Five
patients had multiple episodes of AF. In total, 35 episodes of AF were
treated, with an 88% success rate. Only 6 patients (30%)
required sedation. No complications were observed with shock
application or with lead extraction.
Key Words: defibrillation • electrical stimulation • atrium • cardioversion
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Atrial
tachyarrhythmias constitute the most common
arrhythmia after open heart surgery. The incidence varies
between 26% and 41%.1 2 3 4 5 6 In recent years, the
reported incidence has increased.2 3 5 Atrial
fibrillation (AF) has been associated with a high incidence of
postoperative strokes, ventricular arrhythmias,
hemodynamic deterioration, and the need for a permanent
pacemaker.3 5
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
The study was approved by the institutional review committee.
One hundred consecutive patients with a stable sinus rhythm (SR)
scheduled for open heart surgery with cardiopulmonary bypass
were enrolled. All patients gave their informed consent. Patients with
permanent pacemakers, chronic AF, and conduction disorders were
excluded. Patient characteristics are given in the
Table
.
View this table:
[in a new window]
Table 1. Patient Characteristics ). A third epicardial electrode for
temporary use (TME 63-Z; Sulzer-Osypka Inc) was sutured to the anterior
wall of the right ventricle to ensure R-wave synchronization of atrial
cardioversion. The electrodes were brought out through the skin and
secured with a suture.
View larger version (24K):
[in a new window]
Figure 1. Two views of human heart showing epicardial
defibrillation wire electrodes in place. Distal 10 cm of wire
electrodes is represented by an interrupted line forming an
O-shaped surface area at right and left atria, respectively. SVC
indicates superior vena cava; IVC, inferior vena cava; RAA,
right atrial appendage; Ao, Aorta; PA, pulmonary artery; PV,
pulmonary veins; and CS, coronary sinus. ). Early
recurrent AF (ERAF) was defined as recurrence of AF within 60
seconds of successful cardioversion. In the case of ERAF, patients were
medically treated depending on their preoperative medication. If
patients were receiving ß-blockers, AF was treated with
sotalol; otherwise, it was treated with verapamil.
If AF persisted >48 hours, a second attempt of internal defibrillation
was made. Late recurrent episodes of AF (LRAF) were also treated by
means of atrial defibrillation.
View larger version (15K):
[in a new window]
Figure 2. Sample of surface ECG lead II obtained during
successful internal atrial defibrillation with a 3-J monophasic shock
delivered through the epicardial defibrillation wire electrodes.
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
Placement of the epicardial defibrillation electrodes added
3.9±1.7 minutes to the operating time. The mean pacing threshold was
2.1±2 V in the right atrium and 1.9±1.7 V in the left atrium. Right
and left atrial P-wave amplitudes were 2.3±1.4 and 2.5±1.6 mV,
respectively. The mean biatrial lead impedance was 95.5±12 for
monophasic test shocks and 97.2±13 for biphasic test shocks.
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
Although AF after open heart surgery generally carries a favorable
prognosis, hemodynamic deterioration and systemic
embolization may ensue. Hemodynamic instability is more
common in patients with poor left ventricular function
(ejection fraction <30%), in whom postoperative AF is more likely to
occur.2 5
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
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