Indian Pacing Electrophysiol. J. 2003;3(3):93
Surgical treatment of permanent atrial
fibrillation during cardiac surgery using monopolar and bipolar
radiofrequency ablation
Stephan Geidel*, Jörg
Ostermeyer*, Michael Lass*, Sigrid Boczor**, Karl-Heinz Kuck**
*Department of Cardiac Surgery
and **Department of Cardiology, AK St.Georg, Lohmühlenstraße
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.
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 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 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.
*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.
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 bleeding1,2,3. 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) surgery6,7,8,9,10,11,12,13,14. 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 of different groups.
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 surgery8,9,10,11,12.
The use of microwave13,14
and cryoablation6 has been described
alternatively. In these investigations8,9,10,11,12
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)
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.
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 tissue changes in cases with AF and
particularly pAF18,19,20. It is possible that individual patients with
pAF probably need individual surgical ablation procedures. The relevant
questions are: (1) does a lesion pattern exist which can be recommended
as a basis and can be completed easily according to the individual
pathological or electrophysiological substrate and (2) can patients be
defined who need specific additional ablation procedures?
Referring to this Haissaguerre has described an important
pathophysiologic finding: he demonstrated that the initiation of AF
originates from rapidly
firing foci predominantly located inside the PVs21.
According to that the concept was developed that isolation of the PVs
creating transmural encircling RF ablation lesions around the LPVs and
the RPVs should be a sufficient basis for surgical ablation procedures.
To save LA
function and to bar potential generation of foci the maze pattern of
multiple
incisions was reduced to a short connection line between both. During
valve
surgery RF ablation was performed from the endocardial side with direct
view on the atrial tissue to guarantee continuity of the lesions. A new
bipolar RF approach was recently used in primary CABG cases with pAF as
an endocardial proceeding would have been of obvious disadvantage
because of greater invasiveness and prolonged aortic cross clamping
time in these cases. Amiodarone was normally given to reduce
postoperative recurrence of AF22.
Evaluation of the results
Our results conform to basic experiences of other research 5,21,23,24:
AF wavelets sustained by foci located inside the PVs were blocked by
the created lesions, the described antiarrhythmic protection supported
SR22 during the unstable initial stage,
which
was approximately 3 months. Early recurrence of AF after ablation
surgery
obviously occurred due to the fact that the refractory period of the
atrium
was still shortened. In the case of AF recurrence DC cardioversion was
still recommended, so the influence on the long-term results must be
further clarified. Our data indicate that the preoperative LA size is
of significant
concern for the success of the described method. However, it remains
uncertain
whether the LA size itself is the critical issue. It can be expected
that
rather cellular, structural morphologic and in parallel
electrophysiological
changes of the atrial tissues are more marked in cases with progressive
enlargement and hypertrophy of the atria18,19,20; this electrical and
anatomic
atrial remodeling is supposed to be the reason for what has been
decscribed
as AF begats AF25. It must be conceded
that
an additional effect may be that in cases with small LA the encircling
lesions
possibly encompassed larger portions of the LA in comparison to its
overall
size than in patients with large LA; in that cases re-entrant circuits
in the LA tissue could be interrupted more frequently. Besides LA
reduction
has been described to be of advantage for restoring SR in patients with
chronic AF and large LA following MV surgery26.
Even if our patients were approximately a decade older compared to
patients of other studies [9,10] surgery was tolerated well,
particularly no case of esophageal injury16,17 was observed. Also confirmed was the increase
of SR during the following months after surgery8,9,10,11. It
can be suggested that a 3 months administration of amiodarone is
appropriate but should be handled flexible. The described procedures
are of slight invasiveness and easy to
perform. The lesion pattern can be created with monopolar RF energy and
with a bipolar approach as well. However, it will have to be shown, if
the results with bipolar RF energy are as encouraging as the described
data
in valve patients. As for MV surgery the LA has to be opened anyhow we
continue to recommend for the present an endocardial ablation technique
for
these patients.
Limitations
For rhythm evaluation only 12-lead ECG was used. We consider to
complete
the follow-up data by performing a 24-hour-ECG registry to assess the
possibility of nonpermanent AF. The data were not evaluated under
randomized conditions.
Conclusion
We suppose that the described concept provides a successful treatment
of
pAF in patients undergoing open heart surgery; it fulfils all demands
of
an effective and easy to handle method. It simplifies the treatment of
pAF and can be recommended in patients undergoing cardiac surgery. The
advantages compared to other techniques are: (1) the procedure is easy
to practice and (2) atrial tissue trauma is extremely slight. Our data
indicate that particularly in patients with small LA restoration of
stable SR in 90% of the cases can be achieved.
References
1.
Benjamin EJ, Wolf PA, D’ Agostino RB,
Silbershatz H,
Kannel WB, Levy D. Impact of atrial fibrillation on the risk of death:
the Framingham Heart Study. Circulation 1998; 98:946-952.
2.
Jessurun UR, van Hemel NM, Kelder
JC, Elbers S, de la Riviere AB, Defauw JJ, Ernst JM. Mitral valve
surgery and atrial fibrillation: Is atrial fibrillation surgery also
needed? Eur J Cardiothorac Surg 2000;17:530-537.
3.
Morris JJ Jr, Entman M, North WC, Kong Y,
McIntosh H. The changes in cardiac output with reversion of atrial
fibrillation to sinus rhythm. Circulation 1995;31:670-678.
4.
ACC/AHA/ESC
Guidelines for the management of patients with atrial fibrillation:
Executive summary. A report of the American College of
Cardiology/American Heart Association Task Force on Practice Guidelines
and the European Society of Cardiology Committee for Practice
Guidelines and Policy Conferences (Committee to Develop Guidelines for
the management of patients with atrial fibrillation. Circulation
2001;104:2118-2150.
5.
Cox JL, Schuessler RB, Lappas DG,
Boineau
JP. An 8 _ year clinical experience with surgery for atrial
fibrillation.
Ann Thorac Surg 1996; 224:267-275.
6.
Chen MC, Gou GBF, Chang JP, Yeh KH, Fu M:
Radiofrequency and cryoablation of atrial fibrillation in patients
undergoing
valvular operations. Ann Thorac Surg. 1998; 65:1666-1672.
7.
Sueda T, Nagata H, Oriashi K, Morita S, Okada
K, Sueshiro M, Hirai S, Matsuura Y. Efficacy of a simple left atrial
procedure for chronic atrial fibrillation in mitral valve operations.
Ann Thorac Surg
1997;63:1070-1075.
8.
Pasic M, Bergs P, Müller P, Hofmann M,
Grauhan O, Kuppe H, Hetzer R. Intraoperative radiofrequency maze
ablation for atrial fibrillation: The Berlin modification. Ann Thorac
Surg 2001;72:1484-91
9.
Benussi
S, Pappone C, Nascimbene S, Oreto G, Caldarola A, Stefano PL, Casati V,
Alfieri O. A simple way to treat chronic atrial fibrilation during
mitral
valve surgery: the epicardial radiofrequency approach. Eur J
Cardiothorac
Surg 2000;17:524-529.
10.
Melo
J, Andragao P, Neves J, Ferreira M, Timoteo A, Santiago T, Ribeiras R,
Canada M. Endocardial and epicardial radiofrequeny ablation in the
treatment
of atrial fibrillation with a new intraoperative device. Eur J
Cardio-thorac Surg 2000;18:182- 186.
11.
Khargi
K, Kuschkowitz F, Deneke T, Lemke B, Haardt H, Müller KM,
Laczkovics. Cooled-tip-radiofrequency ablation is a distinct different
technique to treat chronic atrial fibrillation. A prospective study
including 138 patients. Thorac Cardiovasc Surg 2003;51,Suppl 1:S52.
12.
Hornero
F, Montero JA, Canovas S, Bueno M. Biatrial radiofrequency ablation for
atrial fibrillation: epicardial and endocardial surgical approach.
Interactive
Cardiovascular and Thoracic Surgery 2002;1:72-77.
13.
Knaut
M,
Tugtekin SM, Gulielmos V. Microwave ablation as an additional procedure
for treatment of permanent atrial fibrillation in patients with
cardiosurgical
disease. Thorac Cardiovasc Surg 2003;51,Suppl 1,S51.
14.
Schütz A, Schulze C, Sarvanakis C, Platzer
H,
Kilger E, Lamm P, Wildhirt SM, Reichert B. Subendocardial microwave
ablation in the treatment of chronic permanent atrial fibrillation.
Thorac Cardiovasc Surg 2003;51,Suppl 1,S52.
15.
Geidel S, Lass M, Boczor S, Kuck
KH, Ostermeyer J: Surgical treatment of permanent atrial fibrillation
during heart valve surgery. Interactive Cardiovascular and Thoracic
Surgery 2003; 2: In print.
16.
Mohr
FW, Doll N, Falk V, Walther T, Hindricks G, Kottkamp H. Curative
treatment of atrial fibrillation: acute and midterm results of
intraoperative radiofrequency ablation of atrial fibrillation in 150
patients. Read at the Eighty-first Annual Meeting of The American
Association of Thoracic Surgery, May 7, 2001.
17.
Gillinov AM, Pettersson G, Rice TW. Esophageal injury during
radiofrequency ablation for atrial fibrillation. J Thorac Cardiovasc
Surg 2001;122:1239-40.
18.
Li D, Fareh S, Leung TK, Nattel S. Promotion of atrial
fibrillation by heart failure in Dogs. Atrial remodeling of a different
sort. Circulation 1999;100:87-95.
19. Goette A. Staack T,
Röcken
C, Arndt M, Geller JC, Huth C, Ansorge S, Klein HU, Lendeckel U.
Increased
expression of extracellular signal-regulated kinase and
angiotensin-converting
enzyme in human atria during atrial fibrillation. JACC 2000;
35:1669-1677.
20. Kawara T,
Derksen
R, de Groot JR, Coronel R, Tasseron S, Linnenbank AC, Hauer RNW,
Kirkels H, Janse MJ, de Bakker JMT. Activation delay after premature
stimulation in chronically diseased human myocardium relates to the
architecture of interstitial fibrosis. Circulation 2001;104:3069-3075.
21. Haissaguerre M, Jais P, Shah DC, Takahashi A, Hocini M,
Quiniou G, Garrigue S, Le Mouroux A, Le Metayer P, Clementy J.
Spontaneus initiation of atrial fibrillation by ectopic beats
originating from the pulmonary veins. N Engl J med 1998;339: 659-666.
22.
Roy
D,
Talajic M, Dorian P, Connolly S, Eisenberg MJ, Green M, Kus T, Lambert
J, Dubuc M, Gagne P, Nattel S, Thibault B. Amiodarone to prevent
recurrence
of atrial fibrillation. N Engl J Med 2000;342:913-920.
23.
Moe GK: On the multiple wavelet hypothesis of atrial
fibrillation. Arch Int Pharmacodyn Ther 1962;140:183-188.
24.
Allessie M,
Lammers WJEP, Bunke FI, Hollen J. Experimental evaluation of Moe’s
multiple wavelet hypothesis of atrial fibrillation. In: Zipes D, Jalife
J, eds. Cardiac Electrophysiology and Arrhythmias. New York: Cruno and
Straiton 1985;265-275.
25.
Wijffels MCEF, Kirchhof CJHJ, Doland R et al. Atrial
fibrillation begets atrial fibrillation. Circulation 1995 ;92
:1954-1968.
26. Jansz P, Bennetts J, Wilson M, Spratt P,
Farnsworth A. Restoration of sinus rhythm following mitral valve
surgery with left atrial reduction in patients with chronic atrial
fibrillation. Abstract 38, Annual Scientific Meeting of the Society of
Cardiothoracic Surgeons of
Great Britain and Ireland, 2003.
