Surgical treatment of permanent atrial fibrillation during cardiac surgery using monopolar and bipolar radiofrequency ablation.

Abstract

Permanent atrial fibrillation (pAF) is a serious problem in cardiac surgery: An incidence of 3.5% among all patients scheduled for open heart surgery, 9.8% in heart valve cases and 45.6% among patients with severe rheumatic mitral valve (MV) disease was observed in our institution. Our experience with radiofrequency (RF) ablation procedures to treat pAF in these cases is reported.
Since February 2001 monopolar endocardial RF ablation procedures creating two encircling isolation lesions around the left and the right pulmonary veins (LPVs, RPVs) and a connection line between both were performed in patients with pAF concomitant to heart valve surgery. Since March 2003 bipolar RF ablation was used as an adjunct to CABG surgery. Amiodarone was given for 3 months after surgery.
Sixty-two patients with pAF underwent surgical ablation procedures and primary valve (mitral: n=45; aortic: n=13; aortic+mitral: n=1; LA-diameter 55.6+/-7.3 mm) or CABG surgery (n=3). Follow-up was performed at 3, 6, 9, 12, 18 and 24 months; 75% had stable sinus rhythm (SR) at late follow-up. Almost 90% of the patients with a preoperative LA-diameter of <56 mm had SR.
Isolation of the PVs using RF ablation procedures in combination with amiodarone therapy represents a safe and efficient option to cure pAF in patients undergoing open heart surgery.

Full text

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www.ipej.org 93
Original Article
Surgical treatment of permanent atrial fibrillation during
cardiac surgery using monopolar and bipolar
radiofrequency ablation
Stephan Geidel*, Jorg Ostermeyer*, Michael Lass*, Sigrid Boczor†, Karl-Heinz Kuck†
*Department of Cardiac Surgery and †Department of Cardiology, AK St.Georg,
Lohmuhlenstraße 5, 20099 Hamburg, Germany.
Address for correspondence: Dr. Stephan Geidel, MD, Cardiac Surgeon, Department of Cardiac
Surgery AK St. Georg Hamburg, Germany. Email: StGeidel@aol.com
Abstract
Objective: Permanent atrial fibrillation (pAF) is a serious problem in cardiac surgery: An
incidence of 3.5% among all patients scheduled for open heart surgery, 9.8% in heart valve cases
and 45.6% among patients with severe rheumatic mitral valve (MV) disease was observed in our
institution. Our experience with radiofrequency (RF) ablation procedures to treat pAF in these
cases is reported.
Methods: Since February 2001 monopolar endocardial RF ablation procedures creating two
encircling isolation lesions around the left and the right pulmonary veins (LPVs, RPVs) and a
connection line between both were performed in patients with pAF concomitant to heart valve
surgery. Since March 2003 bipolar RF ablation was used as an adjunct to CABG surgery.
Amiodarone was given for 3 months after surgery.
Results: Sixtytwo patients with pAF underwent surgical ablation procedures and primary valve
(mitral: n=45; aortic: n=13; aortic+mitral: n=1; LA-diameter 55.6±7.3 mm) or CABG surgery
(n=3). Follow-up was performed at 3, 6, 9, 12, 18 and 24 months; 75% had stable sinus rhythm
(SR) at late follow-up. Almost 90% of the patients with a preoperative LA-diameter of <56mm
had SR.
Conclusion: Isolation of the PVs using RF ablation procedures in combination with amiodarone
therapy represents a safe and efficient option to cure pAF in patients undergoing open heart
surgery.


Keywords: Atrial fibrillation; atrial fibrillation surgery; radiofrequency ablation; arrhythmia
surgery; heart valve surgery; maze surgery; bipolar radiofrequency ablation.
Introduction
In cardiac surgery strategies to treat permanent atrial fibrillation (pAF) effectively are of
greatest interest because pAF is a frequent problem that substantially deteriorates the
prognosis1,2,3. The data concerning the incidence of pAF following the classification of the
ACC/AHA/ESC Practice Guidelines4 that had been documented to persist for a period of at least
6 months among all patients scheduled for open heart surgery in our institution between
February 2001 and April 2003 are outlined in Table 1.
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Stephan Geidel, Jorg Ostermeyer, Michael Lass, Sigrid Boczor, Karl-Heinz Kuck, 94
“Surgical treatment of permanent atrial fibrillation during cardiac surgery using monopolar
and bipolar radiofrequency ablation”

Since Cox has demonstrated that AF can be definitely eradicated5, efforts were made to
achieve alternative and particularly less complex methods using surgical catheter ablation
techniques during cardiac surgery. A broad spectrum of these methods has been presented
recently6,7,8,9,10,11,12,13,14. Our experience with radiofrequency (RF) ablation procedures to treat
pAF during open heart surgery is reported.
Material and methods
Etiology of heart valve disease was assessed by clinical history, intraoperative valve
examination and histological analysis. Patients hospitalized for heart valve surgery with pAF
(>6months) underwent combined intraoperative AF treatment with monopolar RF ablation.
Since March 2003 a bipolar RF ablation procedure was performed in CABG cases with pAF.
Patients with any other form of AF (intermittent or pAF <6months), emergency operation, severe
reduced left ventricular function (EF<25%), acute bacterial endocarditis, cachexia [Body Mass
Index (BMI) <24], severe intracavitary thrombosis or extreme left atrial size were excluded (LA
diameters of >72mm were assessed to be our limit for the procedure).
Surgical procedure
Heart valve cases
The surgical procedure has been described detailed elsewhere15. To create endocardial
RF ablation lesions two almost identical systems were used: either the Thermaline® device or
(since 01/02) the Cobra® device (both Boston Scientific Corporation, San Jose, USA).
Monopolar RF ablation was performed using 100W RF power for 120 sec, the local temperature
was set at 70°C. The first lesion line completed the isolation of the right pulmonary veins
(RPVs) from the inferior to the superior RPV using the left atriotomy. Isolation of the left
pulmonary veins (LPVs) was performed with a semicircular ablation line close to the inferior,
and another one around the superior LPV. These were connected by a transverse lesion across

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Stephan Geidel, Jorg Ostermeyer, Michael Lass, Sigrid Boczor, Karl-Heinz Kuck, 95
“Surgical treatment of permanent atrial fibrillation during cardiac surgery using monopolar
and bipolar radiofrequency ablation”
the posterior wall of the LA (Fig.1 A). Arrangements to avoid thermic esophageal injury were:
(1) cachectic patients were excluded, (2) a dry compress was passed behind the LA before
delivery of RF energy, (3) the transesophageal echocardiogram (TEE) probe was removed
during the ablation procedure, (4) a flexible ablation probe was used and adapted to the tissue
without pressure, (5) local temperature was set at 70°C and (6) monopolar RF ablation was
performed precisely under direct view during conventional open heart valve surgery only.
CABG cases
The bipolar AtriCure device (AtriCure Inc., Cincinnati, USA) was used for an almost
identical lesion pattern (Fig.1 B). The device consists of a hand piece, a footswitch, connecting
cables and an ablation and sensing unit (ASU) that (1) delivers RF energy while simultaneously
measuring the tissue conductance and (2) uses a temperature sensing mechanism (range of 45 -
55°C). During ablation the tissue is impacted between two jaws of the hand piece and energy is
delivered by footswitch. The ablation was finished when the ASU monitor indicated that the
tissue conductance was at least 3 sec below 2.5 Millisiemens. After start of cardiopulmonary
bypass isolation of the RPVs and the LPVs was performed by grasping the adjacent atrial tissue.
Then a purse-string suture with a tourniquet was set at the posterior wall of the LA. The distal
jaw was inserted through a small incision in direction of the LPVs and RF ablation was
performed after clamp-closure, then the distal jaw was inserted in direction of the RPVs and the
connection line was completed (Fig. 1B).

Fig. 1 Ablation schemes. LAA, left atrial appendage; LPVs, left pulmonary veins; RPVs, right
pulmonary veins; MV, mitral valve.
Perioperative management, follow-up and statistical analysis
The perioperative management has been described detailed elsewhere15. Standard 12-
lead electrocardiogram (ECG) and transthoracic echocardiogram (TTE) were routinely
performed on admission (evaluation of LA diameter) and before discharge. Administration of
amiodarone was started before end of cardiopulmonary bypass and given for 3 months after
surgery. Early recurrence of AF was DC cardioverted after saturation with amiodarone. Patients
with CABG, mitral valve (MV) repair or bioprosthesis got cumarine for 3 months, patients with
mechanical valves lifelong anticoagulation. All patients were restudied 3, 6, 9, 12, 18 and 24
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Stephan Geidel, Jorg Ostermeyer, Michael Lass, Sigrid Boczor, Karl-Heinz Kuck, 96
“Surgical treatment of permanent atrial fibrillation during cardiac surgery using monopolar
and bipolar radiofrequency ablation”
months after surgery by standard 12-lead ECG and clinical examination. Quantitative
preoperative and operative data were normally distributed and described by arithmetic mean ±
standard deviation; qualitative distributed data were presented as absolute frequencies. For pAF
and sinus rhythm (SR) the relative frequency among all patients and some subgroups were
calculated. Qualitative characteristics were compared using the exact Fisher Chi-Square-Test.
All p-values were two-tailed and interpreted nominal that is not adjusted for multiple
comparisons. P-values <0.05 were considered to be statistically significant. Analysis was
performed with SPSS for Windows 11.5.1.
Results
Heart valve cases
Fifty-nine patients underwent surgical pAF ablation procedures associated with primary
valve operations (Table 2). From these patients 45 had MV, 13 AV and 1 AV+MV surgery; 13
were excluded. The main group suffered from rheumatic heart valve disease (39/59). Mean LA
diameter was 55.6±7.1mm, 32 patients had a small (<56mm) and 27 patients a large LA
(>56mm).There were two cases of hospital mortality (3.4%; 1 cardiac, 1 non-cardiac). Mean
follow-up time up to April 2003 was 14.1 ± 9.9 months (Table 3). One-year-survival was
91.7%; late mortality was related to cancer disease (n=2) and sudden death (n=1). At late follow-
up approximately 75% of all patients and almost 90% of those with a preoperative LA-diameter
of <56mm were in stable SR. Early postoperative recurrence of AF during the first 3 months
(32/59) was DC cardioverted in 13 of 25 cases, 6 turned to SR spontaneously later. Preoperative
duration of AF was not predictive for long term results.
CABG cases
In 3 bipolar RF ablation cases (Table 2) no severe complication occurred. At end of
surgery 2 patients were externally paced in DDD-mode, one was in SR. Early postoperative
return of AF was DC cardioverted in 1 of 2 cases; 2 of 3 patients left the hospital in SR.
Discussion
Rationale of surgical practices to treat pAF
Reliable and effective treatment strategies for pAF are of greatest interest in cardiac
surgery because pAF causes two times higher rates of death, five times higher risk of stroke,
reduced cardiac output and the need of systemic anticoagulation with the danger of bleeding1-3.
The incidence among patients scheduled for open heart surgery is particularly high among heart
valve cases and of special importance in MV disease15. That is why most of the recently reported
surgical AF ablation data were observed following heart valve (particularly MV) surgery6,-14.
The permanent form of AF is one of two AF-types (permanent and intermittent) and normally
the final mode in which non-permanent AF cumulates4: patients with pAF have atrial fibrillation
all of the time without any episode of SR. The variant clinical presentations of permanent and
intermittent AF have unfortunately caused heterogeneous nomenclatures in different countries
with currently used misleading terms (chronic, paroxysmal or persistent AF) and the resulting
difficulty to compare the success-rates
During the past years mainly three different energy sources have been favoured for
surgical practice to create atrial lesions to cure these AF-types; RF energy has been established
for variant treatment strategies and became the most widely used energy source for AF surgery8-
12. The use of microwave13,14 and cryoablation6 has been described alternatively. In these
investigations8-12 RF energy was used without exception in monopolar fashion for endocardial
or/and epicardial ablation techniques with more or less comparable and successful results.
However, two theoretical deficiencies remain with the application of monopolar RF energy: (1)
of different groups.
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Stephan Geidel, Jorg Ostermeyer, Michael Lass, Sigrid Boczor, Karl-Heinz Kuck, 97
“Surgical treatment of permanent atrial fibrillation during cardiac surgery using monopolar
and bipolar radiofrequency ablation”
transmurality of the created lesions is not definitely guaranteed and (2) rare but fatal
complications because of too deep lesions have occurred16,17. Experiences with possibly reliable
bipolar RF ablation techniques that guarantee lesion transmurality and continuity and definitely
bar extra-cardiac tissue injury are therefore of great interest.
Table 2: Preoperative and operative data (n=62)

*including adjustment of the equipment and a precise adaption of the probe to the
tissue (Thermaline / Cobra) and preparation of the PVs (Atricure); deg,
degenerative MV disease; bio, bioprosthesis; mech, mechanical valve.
Many surgeons who used ablation techniques in the past followed more or less closely
the principles of the Maze procedure which are PV isolation, reduction of atrial size and block of
re-entrant circuits by complex incisions8,9,11,12. An ideal lesion pattern should combine (1) slight
invasiveness, (2) simplicity, (3) high reproducibility and (4) saving of time with excellent
success rates in almost all cases. The question if such a lesion pattern is actually applied in
practice must be answered negative. The mechanisms of AF initiation and maintenance
obviously vary and are connected with individual electrophysiological and pathological atrial
Indian Pacing and Electrophysiology Journal (ISSN 0972-6292), 3(3): 93-100 (2003)