Five-year
follow-up report: box lesion radiofrequency ablation procedure for
atrial fibrillation under video-assisted thoracoscope.
Abstract
Objective: Radiofrequency ablation procedure has been applied to the
treatment of atrial fibrillation (AF), while limited articles referred
its long-time efficacy. The objective of this study was to report the
initial five-year follow-up of a novel mini-invasive procedure for
epicardial ablation applied in our center.
Methods: 31 patients with symptomatic atrial fibrillation were
consecutively enrolled in our study, which had unsuccessful drug therapy
or endocardial ablation or were intolerant to antiarrhythmic drugs. The
surgery performance included 3 5-12 mm holes on each side of the chest
wall. A bipolar radiofrequency device guided by navigators was applied
for the electrical isolation of pulmonary veins and the posterior wall
of left atrium. And a surgical stapler was used to excise the left
atrial appendage.
Results: The procedure was successfully performed in every patient, and
its median time was 115 minutes. No death, conversion to sternotomy or
thoracotomy, phrenic paralysis, stroke, pneumonia, transfusion, or
pacemaker insertion occurred. Postoperatively, 5 patients underwent
electrical cardioversion and returned to sinus rhythm remaining beyond
the discharge. 29 enrolled patients fulfilled the five-year follow up,
and the arrhythmia-free survival rates after one epicardial procedure
were 62.9%, 55.9%, 52.42% and 45.4% at 1, 2, 3, and 5 years
respectively.
Conclusion: Despite the sharp decrease of 21 percent in the second 6
month, the initial five-year survival rate of the applied procedure is
acceptable and comparable with that of hybrid ablation. And this shared
procedure is one of the reported procedures least time-consumptive and
harmful.
Keywords: Atrial fibrillation, epicardial ablation, minimally invasive
surgery
Key clinical message: we report the initial five-year follow-up of a
novel mini-invasive procedure for epicardial ablation for the treatment
of atrial fibrillation. The initial five-year survival rate is
acceptable and comparable with that of hybrid ablation. And this shared
procedure has the advantages of shorter operation time and less surgical
trauma.
Introduction
Atrial fibrillation (AF) is the most common arrhythmia and complicated
with thrombosis, atrial pumping dysfunction and stroke. As the
pharmacological treatment of AF is not always effective and sometimes
intolerable, the surgical management comes necessarily. The COX-Maze III
procedure described by Cox and his colleagues and developed with new
ablation sources realizing the commendable efficacy of surgical
intervention. Despite incorporating this golden procedure for
concomitant AF with valvular disease, the pursuit of less invasive
techniques treating AF especially the lone AF never fade. As mechanism
research highlight the stimuli from pulmonary veins (PVs) and posterior
wall of left atrium, catheter ablation is first introduced by
cardiologist and finally amended as PVs circular isolation and extra
linear lesion electrically blocking the posterior wall. However, the
general results of catheter-based ablation techniques used for lone AF
are relatively disappointing, as the arrhythmia-free survival rate at 5
years is less than 30%.
Epicardial ablation also named as video-assisted thoracoscopic surgery
(VATS) was reported in 2005, and this minimally invasive procedure
allows AF management through surgical approach on beating hearts.
Encouraged by this technique, cardiac surgeons are more willing to deal
with AF. According to the Society of Thoracic Surgeons Adult Cardiac
Surgery Database, from 2005 to 2010 stand-alone surgical ablations
increased significantly from 552 to 1041 cases and the off-CPB procedure
as the majority has better performance in avoiding stroke, renal
failure, reoperation for bleeding and other complications. As the
techniques evolving, there are other 2 minimally invasive ablation
procedures for AF introduced as hybrid ablation by Pison et al in 2012
and minimally invasive COX-Maze procedure by Ad et al in 2013
respectively. In this study, we implicate one of the epicardial
procedures as the least invasive and time saving method to share our
single center experience.
Materials and Methods
Patient Selection
31 patients with symptomatic atrial fibrillation were consecutively
enrolled in our study. The inclusion criteria were along with our
previously published article as (1) recurrent AF, and (2) AF refractory
to antiarrhythmic drugs, while the excluded criteria were: (1) previous
pulmonary and cardiac surgery, (2) underlying cardiovascular or
pulmonary diseases other than AF, (3) atrial thrombi or persistent left
superior vena cava, for which preoperative transthoracic echocardiograph
and computed tomography (CT) scan were made. Actually, every enrolled
patient was also allocated to lung function test and coronary
angiographic analysis checking whether there was any need for
extra-deposition. And following the Heart Rhythm Society, European Heart
Rhythm Association, and European Cardiac Arrhythmia Society consensus
statement they were all classified into paroxysmal, persistent, and
longstanding persistent AF. Our study was approved by Clinical Research
and Biomedical Ethical Committee of West China Hospital Sichuan
University.
Surgical Procedure
The procedure has been described earlier and will briefly be reviewed
here[1]. The patients assumed the supine position with both upper
arms dorsiflexed 15° to make bilateral chest walls be exposed completely
and were intubated with double-lumen endotracheal tubes under the
induction of general anesthesia. As a start, since the right lung
deflated, a 5-mm trocar was introduced into the fourth intercostal space
in the anterior axillary line for CO2 insufflation at approximately 8 to
12mmHg. And we also constructed other two 5-mm ports respectively in the
third and fifth intercostal space at the anterior axillary line.
Subsequently, the 12-mm port as working port was transformed from the
first 5-mm port. To open the right-sided pericardial sac, a lesion
paralleling to the phrenic nerve was made from the superior vena cava
(SVC) to the inferior vena cava (IVC) about 2 cm anterior. When
pericardium was open, the transverse and oblique sinuses were exposed by
blunt dissection, through which each Cardioblate Navigator (Medtronic,
Minneapolis, MN, USA) could be put respectively. In the next, the
ventilation of the right lung was restored, while its left counterpart
was deflated. Through the left corresponding ports, the left-sided
pericardium was opened to unveil the tips of two navigators, which then
were attached to jaws of the Cardioblate Gemini-s bipolar radiofrequency
isolator (Medtronic, Minneapolis, MN, USA) .The radiofrequency ablation
started from the left side and moved forward to the right side,
fulfilling the continuous box lesion which isolated the pulmonary veins
and posterior left atrial wall completely. At last, a single 28-French
chest tube was placed in each pleural space through the most inferior
ports and the patient was transferred to the intensive care unit for
recovery (Fig. 1, 2).
Rhythm Control and Anticoagulation Management
Continuous cardiac rhythm monitoring was sustained for another 48hours
and then replaced by daily 12-lead electrocardiograms. While for
patients with recurrent AF and postoperative Af (atrial flutter),
electrical cardioversion was applied. Amiodarone the suggested
Antiarrhythmic drugs (AAD) was generally implicated postoperatively and
recommended as discontinued 3months after the operation only if the
sinus rhythm remained. Similarly, the warfarin could be stopped after 3
months as if the thromboembolic risk is low, which was started from
postoperative day 2 targeting the INR range from 1.5 to 2.5 (an
experience of our center).
Follow-up
All patients were followed-up at post-operation 1 month, 3 months, 6
months, 1 year, 3 years and 5 years and for each time 24h Holter
Monitoring was performed, so as to patients with normal ECG but
AF-relating symptoms. Long term success was defined as freedom from
AF/Af/AT (atrial tachycardia) recurrences following the 3-month blanking
period through a minimum of 36-month follow-up from the date of the
ablation procedure in the absence of Class I and III antiarrhythmic drug
therapy according to 2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus
statement on catheter and surgical ablation of atrial fibrillation. And
among the enrolled patients, 29 patients fulfilled the video-assisted
thoracoscopic ablation and the follow-up of five years.
Statistical analysis
Normal values were expressed as mean ± standard deviation (SD),
non-normal values as median and IQR, and categorical variables as
percentages. The Mantel-Haenszel Chi-Square was employed to establish
differences among groupings. Statistical analysis was performed using
SPSS release 22.0. P values less than 0.05 were considered significant.
Results
Baseline Characteristics
Baseline characteristics were presented in table 1. Among the 31
enrolled patients, 20 patients had paroxysmal AF, 8 patients had
persistent AF and the left 3 had long-standing persistent AF. The median
follow-up duration was 60 months (range, 2 to 384 months). And the mean
left atrial diameter of patients with paroxysmal AF was 39.06 ±4.45, and
there was no significant difference when compared to 41.6 ±3.80 of
patients with none-paroxysmal AF(P=0.14). AADs were not that effective
or intolerable to all patients. And previous transcatheter endocardial
ablation was documented with 5 patients with recurrent AF.
Perioperative data
The epicardial ablation was successfully performed in every patient. And
the median procedure time was 115 minutes. Actually, the procedure time
would decrease as the more familiar the performing surgeon getting, and
the shortest documented time was 45minutes obtained in the later
practice. No death and conversion to sternotomy or thoracotomy occurred
intraoperation. And no phrenic paralysis, stroke, pneumonia,
transfusion, or pacemaker insertion was documented either. Electrical
conversion was performed as patients with recurrent AF or emerging AFL
after the operation during the hospital stay turning out to be
effective. The overall hospital-stay time ranged from 5 to 12 days with
the median as 8(Table 2).
Arrhythmia-free Survival After One Procedure
During the postoperative hospital-stay, 5 patients underwent electrical
cardioversion and returned to sinus rhythm(SR), which remained until
discharge. As the follow-up settled above and the loss of 2 patients
both at month 6, the arrhythmia-free survival rates after one epicardial
procedure were 62.9%, 55.9%, 52.42% and 45.4% at 1, 2, 3, and 5
years respectively (Fig 3). As early studies described the distinct
efficiencies of epicardial ablation for different patients, the survival
rates of paroxysmal AF and non-paroxysmal AF patients were shown in
Figure 4. With these data, we found that the peak recurrence time of
this procedure occurred in the second six months after operation, during
this period the overall survival rate decreased by almost 21%.
Discussion
Given the previously published data, the annual count of stand-alone
surgical procedures performed in STS documented medical centers are
doubled in 2010 when compared to that of 5 years ago. And since first
reported in 2005, epicardial ablation has been widely accepted and
conducted for its evident safety and promising efficacy. In our
research, with the implication of Cardioblate Navigators (Medtronic,
Minneapolis, MN, USA) and Cardioblate Gemini-s bipolar radiofrequency
isolator (Medtronic, Minneapolis, MN, USA) we are able to apply smaller
ports and further minimalize the invasiveness of the operation.
During the 15 years practicing of epicardial ablation, many remarkable
improvements are made, one of which worth being highlighted is the
evolving of the lesion set. Early research based on catheter ablation
indicates that besides PVI, extra linear lesions in the posterior wall
of left atrium are essential for the maintenance of sinus rhythm after
endocardial ablation in patients with permanent AF, left atrial
dilatation and valvular heart disease. And in early studies about
epicardial ablation, as technology limits the primary lesion set
including separated circulating isolation of the left and right PVs have
avoided these essential linear lesions intentionally or unintentionally.
Then followed with subsequent addition of roof line and dispensable
inferior line, while there are three main obstacles remained when
completing the mitral annulus connecting lesion through thoracoscopic
approach at the sites corresponding to cox-maze III set: (1) the
non-visibility of posterior wall of left atrium in the hollow space
behind it; (2) the inevitable risk damaging the circumflex coronary
artery; (3) the possible result of incomplete lesion as the coronary
sinus the dissatisfactory epicardial mark may be up to 13mm away from
the mitral annulus. Edgerton et al. re-orients the mitral annulus
connecting lesion to the doom of the left atrium from the left fibrous
trigone at the anterior mitral valve annulus to the roof line together
with the mentioned epicardial lesions described as the Dallas lesion
set. In our study as formerly described, the symmetric lesions performed
oppositely but combined forming the continuous isolation of the PVs and
main portion of posterior left atrium wall, and in our later practice
the additional mitral annulus connecting line has been performed.
Many researchers reproach the recovered pulmonary vein conduction
accounting for the recurrence of Ata after PVs isolation, which is
caused by incomplete and non-transmural ablation lines. They also
advocate the importance of electrophysiology confirmation after the
ablation procedure ensuring the endpoint as bidirectional conduction
block and non-inducibility of atrial fibrillation, which leads to the
promising ATa episode free rate without AAD reaching ninety percent for
the mean follow-up duration of six months. Although endocardial mapping
has been widely accepted by catheter ablation, it’s impossible to
realize under the non-heparinized circumstances during the epicardial
surgical procedure. Actually, in early trial of epicardial ablation,
many testing techniques for complete conduction block have been applied
but denied as their insensitivity when mapping epicardial. The situation
doesn’t change until Lockwood and his colleagues suggest separate narrow
probe with small closely spaced bipolar electrodes rather than larger
ones primarily designed for RF ablation. Then it becomes possible to
analyze the potentials of sites on the opposite side of and close to the
lesion line, and they also report the astonishing twenty-one percent
(3/14) of complete block after the first set of RF application. In other
words, the reported survival rates of early studies have been
underestimated, so as ours. And the early recurrence defined as
recurrent AF/AFL/AT within three months of ablation is not rare in our
study (16.13%), which also indicates the reconduction and residual
gaps.
Then referring the ablation of ganglionated plexus which along with
other mechanisms orchestrates the AF initiating and atrial autonomic
remodeling, even though basic research underlines its central role
during the procession of AF, there has always been limited evidence
supporting this strategy. And it is reported that in animal model the
ganglionated plexus activity could recover 4 weeks after the selective
ablation. Moreover, the efficacy and safety of ganglionated plexus
ablation for patients with persistent AF, enlarged left atrium or failed
catheter ablation has been completely denied as the republished data of
AFACT study. And for now, ganglionated plexus ablation is no longer
embraced by major lesion set, despite occasional mention.
Compared to other reported techniques for surgical epicardial ablation,
besides the bipolar radiofrequency source there are prominent advantages
in our performed procedure. During the operation, the lesion site
settled as the routs the navigators getting through and later confirmed
when isolator dock in taking the linear motion guided by navigators. The
ingenious set of symmetric lesion and subtle combination of Cardioblate
Navigators (Medtronic, Minneapolis, MN, USA) and Cardioblate Gemini-s
bipolar radiofrequency isolator (Medtronic, Minneapolis, MN, USA)
realize the isolation of PVs and most portion of posterior left atrial
wall while the procedure is still quite reproducible. And meanwhile the
procedural exclusion of jaw switching simplifies the operation and
avoids the possible damage made around PVs. Actually, the benefits of
alone linear motion come more, as it enables the application with
smaller ports resulting in procedure less invasive and time-consumptive.
113 m4inutes as mean operation time is far more promising than the given
figures of other reported epicardial ablation techniques without
mapping. And the more familiar performing surgeon gets with the
procedure, the more time saving would it be. We compared the documented
29 cases splitting them in to the earlier 15 and the subsequent 14
finding that the mean operation time declines from 135 ±25 minutes to
91±24 minutes.
Hybrid ablation combines epicardial ablation, endocardial mapping and
catheter ablation first 1111111introduced by Pison and his colleagues
was imposed as with higher efficiency for its advantage of selective
linear lesion making, especially the one connected to mitral isthmus.
However, in most studies the long-term performance of hybrid ablation
fails the expectation sharing the long-term success rate with epicardial
ablation as around forty-five percent when the follow up extends to five
years. Actually, no substantial improvements have been made with the
tinsel inclusion of catheter-based mapping and ablation when compared to
epicardial ablation following Dallas lesion set and incorporating
epicardial mapping. And there is the extra need for catheter induction
doing more harm and prolonging the operation, as well as full
hepatization that would increase the risk of bleeding leading to
transfusion or even conversion to median sternotomy or re-exploration,
letting alone radiation, contrast medium and extra financial cost.
The less invasiveness or higher effectiveness is a debating topic among
physicians, as it’s never easy to reach an equilibrium point. Even
though early researchers have proven the limited value of right atrial
lesions, a relatively new procedure including these lesions accepted as
minimally invasive named as the endocardial Cox-Maze procedure is
supported by many researchers. Despite the elaborate and ingenious
design for lesion-making, it is difficult to explain the differences
between the minimally invasive COX-MAZE IV procedure and traditional
surgical ablation after median sternotomy, as frequent suture and
puncture, full heparinization, cardiopulmonary bypass, aortic cross
clamp, and incision on the left atrium are all implicated during the
procedure. And for now, the follow up of one or two years suggests one
nose winning of minimally invasive CMIV procedure, while there are still
limited articles addressing its long-term efficiency, which could never
reach 75% the 5-year success rate after one traditional COX-MAZE
procedure with trauma of comparative scale.
In this study, the overall five-year arrhythmia-free survival rate after
one procedure is 45.43% in accord with Zheng et al. One evident
shortcoming of this procedure is the absence of electrophysiological
confirmation of bidirectional block of the lesions, which may partially
lead to the instant postoperative recurrence. Without epicardial
mapping, the operational success could be overestimated while the
long-term efficacy would be underestimated. And one study including
periprocedural confirmation of ablation lesions obtains enhanced 1-year
efficacy of epicardial ablation with 86% one-procedure success
rate[2]. Another possible shortcoming would be the incomplete
isolation of the posterior wall of left atrium. As the symmetric lesion
set circles parts of the posterior wall into the isolation area, there
are remaining sources of reentry wavelets at large. And the linear
lesion connecting the mitral isthmus is later incorporated. Thus,
besides the initial five-year experience elucidated there are still jobs
to do figuring out the long-time efficacy of epicardial ablation with
lesions also isolating the posterior wall of left atrium and
perioperatively confirmed by mapping techniques. Anyway, for now the
long-term result is way less than satisfactory so as other techniques,
and there is no such consensus of standardized procedure for lone AF
management. Therefore, it’s essential for status quo informing the
patients with all procedures in detail even the traditional invasive
surgery, which should also include the causing trauma and long-time
efficacy.
There are limitations in this study. First, the limited number of
enrolled patients in our center from 2011 to 2013 may increase the
selection bias. Second, also due to the small sample size, further
analysis of recurrence and complication events is impossible. Finally,
ATa episodes could flee from monitoring of Holter tests let along daily
ECG.
Conclusion
In summary, the applied mini-invasive epicardial surgical procedure is
acceptable in the long term as the five-year survival rate reaches
45.4%. And this shared procedure has the advantages of shorter
operation time and less surgical trauma. Therefore, the epicardial
ablation is quite recommendable for medical intervention of atrial
fibrillation especially the lone one.
Abbreviations
AAD: anti-arrhythmia drugs; AF: atrial fibrillation; AFL: atrial
flutter; AT: atrial tachycardia; CPB: cardiopulmonary bypass; CT:
computed tomography; ECG: electrocardiography; EF: ejection fraction;
INR: International normalized ratio; IPVS: Inferior pulmonary veins;
LAD: left atrial diameter; NPAF: none-paroxysmal atrial fibrillation;
PAF: paroxysmal atrial fibrillation; PVI: pulmonary veins isolation;
PVs: pulmonary veins; VATS: video-assisted thoracoscopic surgery; SPVs:
superior pulmonary veins
Yupeng Ji±†, Li He, Zeyi Cheng, Jun Shi, Lulu Liu,
Yingqiang Guo*
*Corresponding Author: Guo Ying Qiang, MD, Department of Cardiovascular
Surgery, West China Hospital, Sichuan University, 36th Guoxue Road,
Chengdu, 610041, Sichuan, People’s Republic of China. Email Address:
drguoyq@hotmail.com
†First Authors:
Yupeng Ji, MD, Department of Cardiovascular Surgery, Sichuan University
West China Hospital, Chengdu Sichuan China
Li He, MD, Department of Cardiovascular Surgery,
Sichuan
University West China Hospital, Chengdu Sichuan China
These two authors contribute equally to this research.
Other Authors:
Zeyi
Cheng, MD, Department of Cardiovascular Surgery, Sichuan University West
China Hospital, Chengdu Sichuan China
Jun Shi, MD, Department of Cardiovascular Surgery, Sichuan University
West China Hospital, Chengdu Sichuan China
Lulu Liu, MD, Department of Cardiovascular Surgery, Sichuan University
West China Hospital, Chengdu Sichuan China
Author contribution
All authors sufficiently contributed in the intellectual content, review
of literature, and analysis of data. Each author has reviewed the final
version of the manuscript and approves it for publication.
Conflicts of Interest: Dr Yingqiang Guo and other authors have no
financial or personal relationship with individuals or institutions that
would inappropriately influence this work. And this research is not
supported by any funding.
References
1. Guo Q, Zhu D, Bai Z et al : A Novel “Box Lesion” Minimally
Invasive Totally Thoracoscopic Surgical Ablation for Atrial
Fibrillation: Initial Report of 14 Cases. Annals Academy of
Medicine Singapore 2014, 43(12):1-7.
2. Krul SP, Driessen AH, van Boven WJ et al : Thoracoscopic
video-assisted pulmonary vein antrum isolation, ganglionated plexus
ablation, and periprocedural confirmation of ablation lesions: first
results of a hybrid surgical-electrophysiological approach for atrial
fibrillation. Circ Arrhythm Electrophysiol 2011, 4(3):262-270.