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Ann Thorac Surg 2007;83:1724-1730
© 2007 The Society of Thoracic Surgeons
Caynak, MDDepartment of Cardiac Surgery, Florence Nightingale Hospital, Istanbul, Turkey
Accepted for publication December 6, 2006.
* Address correspondence to Dr Akpinar, Department of Cardiac Surgery, Florence Nightingale Hospital, Abide’i Hurriyet Cad, No. 290 
ili, Istanbul, Turkey (Email: belhanakpinar{at}gmail.com).
| Dr Akpinar discloses a financial relationship with Medtronic.
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Abstract |
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Methods: Between April 2004 and February 2006, 26 drug-resistant and symptomatic lone atrial fibrillation patients (18 permanent, 8 paroxysmal) underwent an irrigated radiofrequency ablation procedure using the Cardioblate ablation system (Medtronic, Minnesota). There were 16 men and 10 women with a mean age of 55 ± 11 years. Mean duration of atrial fibrillation was 34.2 ± 18.9 months. All patients underwent a bilateral thoracoscopic procedure in which both pulmonary veins were ablated with an atrial cuff using an off-pump epicardial approach. The conduction block was assessed by pacing the pulmonary veins after each ablation. Sixteen patients underwent endoscopic stapling of the left atrial appendage.
Results: There were no hospital deaths. All procedures were completed as planned without any conversions to sternotomy. There were no major complications. Follow-up was complete at 6 months, and 80% of the patients were in sinus rhythm (paroxysmal: 100%, permanent: 72%). Of the patients with permanent atrial fibrillation, 85% had regained their atrial transport function. No major thromboembolic event was observed during the follow-up period.
Conclusions: The video-assisted bilateral pulmonary vein isolation technique was safe and effective. It was curative for paroxysmal atrial fibrillation patients and effective for permanent atrial fibrillation cases. This technique may find wider application if accumulating data further support these findings.
| This article has been selected for the open discussion forum on the CTSNet Web Site: http://www.ctsnet.org/sections/newsandviews/discussions/index.html
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Atrial fibrillation (AF) is the most common sustained cardiac rhythm disturbance and is associated with significant morbidity and mortality [1]. A substantial proportion of patients with AF have no detectable heart disease, and the term "lone AF" applies to patients younger than 60 years of age with no clinical or echocardiographic evidence of cardiopulmonary disease [1, 2] . Although these patients have a favorable prognosis with respect to thromboembolism and mortality, over time they move out of the lone AF category owing to aging or to development of cardiac abnormalities, and their risks of thromboembolism and mortality rise [1, 3] . Achieving and maintaining sinus rhythm could result in improvement of symptoms, lower stroke risk, improved quality of life, and lower mortality risk for these patients [4].
The surgical maze procedure is recognized as the most effective treatment of AF; however, the acceptance of this technique for patients with lone AF has not been universal because of its invasive nature [5]. As a consequence, catheter ablation has emerged as the second preferred line of therapy, after drugs, to cure patients with symptomatic lone AF [1, 6] . On the other hand, several surgical epicardial approaches using minimally invasive techniques have been introduced into clinical practice to compete with catheter ablation, and a wide variety of less invasive modifications are under investigation [7, 8] . Recently, there have been studies showing the feasibility of performing totally endoscopic or robotically enhanced pulmonary vein isolation on the beating heart in patients with lone AF [9]. The application of such minimally invasive technology can be an attractive therapeutic alternative for patients with symptomatic lone AF if the safety and efficacy of these techniques can be established.
This paper aims to review our experience using a video-assisted thoracoscopic approach for the treatment of patients with intractable lone AF. The procedure uses a bipolar irrigated radiofrequency ablation device that is applied epicardially through small incisions on the beating heart. The primary endpoint of this paper is to ascertain the safety and feasibility of this approach, and the secondary endpoint is to evaluate early results in terms of restoring sinus rhythm.
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Material and Methods |
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There were 16 male and 10 female patients, and ages ranged between 29 and 68 years (mean, 55.8 ± 11.2). Eighteen patients had permanent AF, and 8 patients were diagnosed with paroxysmal AF. The definition of paroxysmal and permanent AF was made in accordance with the American Heart Association, American College of Cardiology, and European Society of Cardiology (AHA/ACC/ESC) guidelines [1]. Duration of AF ranged between 8 and 79 months (mean, 34 ± 19). The clinical characteristics and risk factors of the patient group are shown in Table 1. Eleven patients were on amiodarone therapy preoperatively, and 26 patients were receiving at least one antiarrhythmic medication. All patients were under anticoagulation therapy with coumadine before the procedure.
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Ablation Device
The ablation is performed using a bipolar irrigated ablation device (Cardioblate BP-2, Cardioblate LP; Medtronic, Minneapolis, Minnesota). The system consists of a power generator and a bipolar clamp with irrigation. An algorithm allows the device to deliver the energy necessary to complete a transmural lesion and at the same time gives the surgeon a transmurality feedback. The radiofrequency energy is delivered through a bipolar clamp, which also provides irrigation. The conduction block is checked after each application using a pacing device (Detect; Medtronic) designed for minimally invasive procedures.
Surgical Technique
The patient lies supine on the operating table with both arms at his or her side. A towel is placed longitudinally under the spine. General anesthesia is administered with a double-lumen endotracheal tube for single lung ventilation. Transesophageal echocardiographic monitoring is performed during the entire procedure.
Right pulmonary vein ablation
The table is turned slightly to the left side.The procedure begins with a 5-cm right thoracic incision at the third intercostal space, between the anterior and mid axillary lines that serves as the working port. A soft tissue retractor (Cardiovations; Ethicon, Somerville, New Jersey) is placed for visualization without spreading the ribs. The right lung is deflated. A 10-mm trocar is introduced from the third intercostal space between the mid and posterior axillary lines. A zero-degree camera is introduced through this port. A second port is introduced in the sixth intercostal space mid axillary line. This port serves for the CO2 line to assist in resorptive atelectasis.The pericardium is opened 2 cm above and parallel to the phrenic nerve from the reflection of the pericardium to the superior vena cava (SVC) and down to the diaphragm. Pericardial stay sutures are pulled and anchored through the skin for traction to assist in the visualization of the pulmonary veins. Blunt dissection with endoscopic dissectors is performed under the left atrium between the right inferior pulmonary vein and the inferior vena cava to enter the oblique sinus. Blunt dissection is also performed under the SVC and to provide access to the transverse sinus. A Dietrich (Aeusclap, Germany) clamp with a long shaft is introduced through the working port to complete the gentle dissection at the oblique sinus.
A DLP 8-mm wire-guided sump (Medtronic) is then introduced into the chest through the working port and passed into the oblique sinus beneath the right pulmonary veins. While the sump is gently pushed toward the transverse sinus, the SVC is pushed downward, and the edge of the sump is extracted through the transverse sinus. The guidewire is withdrawn, and the edge of the sump is rerouted under the SVC with a long right angle clamp, completing a secure path beneath the right pulmonary veins. The bipolar clamp is then introduced through the working port, the edge of the sump is cut, and the lower jaw of the clamp is placed and secured at the end of the sump. The sump is now used to guide the lower jaw of the BP-2 clamp behind the right pulmonary veins while the upper jaw passes in front of the veins. The DLP sump is removed, and after the position of the jaws is confirmed, ablation is performed (Fig 1). The curve of the jaw is always directed toward the left atrium. Usually one to two applications are enough to create a conduction block, and the conductivity is evaluated by pacing the pulmonary veins using the Detect pacing system. At the end of the procedure, two atrial pacing electrodes are placed, a 20-mm chest tube is introduced through one of the port holes, the right lung is reinflated, and incisions are closed.
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At this stage, the shaft of the apical suction device (Starfish NS; Medtronic) is introduced through a separate port in the subxyphoid area and advanced toward the operation field. The apical suction cup is attached to the shaft, applied on the left ventricle, and used to maneuver the apex slightly toward the right side of the patient (Fig 2). This maneuver facilitates the exposure of the pulmonary veins. The dissection starts by dividing the ligament of Marshall and continues around the left superior pulmonary vein using endoscopic dissectors. A similar dissection is performed around the left inferior pulmonary veins by applying slight traction on the pericardium and by peeling the pericardium from the pulmonary veins. After this, the DLP sump is passed beneath the left pulmonary veins, and the pulmonary veins are secured. The sump is used to guide the lower jaw of the bipolar clamp under the pulmonary veins, and the ablation is performed in a similar fashion to the right side (Fig 3). The conductivity is evaluated once more with the Detect system. The pericardium is closed, and a 20-mm chest tube is inserted through one of the port holes. The left lung is inflated, and the incisions are closed in a similar fashion.
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Postoperative Antiarrhythmic Management
All patients continued to receive amiodarone for 6 months after the operation. The antiarrhythmic management protocol has been explained in detail previously [10].
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Results |
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Evaluation of the Rhythm Status
Follow-up period ranged between 6.2 and 11.3 months (mean, 8.1 ± 2.8). The closing interval was 6.2 months; that is, follow-up was complete for all 26 patients at the end of this period.
Patients with paroxysmal AF
Two of 8 patients in this group were in AF before the operation. Both were converted to sinus rhythm postoperatively, so all 8 patients with paroxysmal AF were in sinus rhythm after the surgical procedure. At discharge, 1 patient was in AF. During telemetric follow-up in the hospital, 3 of 8 patients (36%) experienced atrial arrhythmias and episodes of AF. At 3- and 6-month controls, all patients (100%) were in sinus rhythm.
Patients with permanent AF
Ten of 18 patients (55%) were in sinus rhythm at the end of the surgical procedure. Telemetric follow-up during the hospital stay revealed that 6 of the 10 patients (60%) who were in sinus rhythm suffered from atrial arrhythmias and episodes of AF. At 3 months, 12 of 18 patients (67%) were in sinus rhythm. At 6 months, 13 of 18 (72%) had regained sinus rhythm (Fig 4).
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Antiarrhythmic and coumadine therapy
Antiarrhythmic drugs were discontinued for patients who were in sinus rhythm at 6 months. Coumadine treatment was evaluated according to the patient risk factors for stroke (AHA/ACC/ESC guidelines), presence of atrial transport function, and ligation of the LAA. Nine patients of 21 who were in sinus rhythm continued to receive coumadine because they had other risk factors for stroke, but the medication was discontinued in the remaining 12 cases (57%) after 6 months according to the criteria mentioned above.
Atrial transport
Atrial transport function was evaluated by transesophageal echocardiography and magnetic resonance imaging in patients who were in sinus rhythm at 6 months. Atrial transport was regained in 83% of permanent AF cases. No pulmonary vein stenosis was detected during the magnetic resonance imaging evaluation.
Cardioversion
Electrical cardioversion was not attempted for patients who remained in AF after the surgical procedure and was reserved for patients who were still in AF at the end of 3 months. It is our observation that electrical cardioversion is not very helpful during the first couple of months after ablation, and the rate of conversion to AF is high.
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Comment |
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Percutaneous ablation techniques, which have become the second line strategy to cure patients with lone AF, carry certain disadvantages. Major complications such as pulmonary vein stenosis, thromboembolism, and atrioesophageal fistula have been reported in more than 6% of cases, and a need for a second or third procedure is not uncommon [16, 17]. These limitations have led to the development of new minimally invasive surgical techniques for lone AF treatment. These can be divided into two groups: (1) the "micromaze" technique; and (2) video-assisted thoracoscopic left and right pulmonary vein isolation.
The micromaze technique consists of creating a box lesion around four pulmonary veins using endoscopic or robotic instruments. Usually, microwave energy is used for this purpose. Favorable results have been published using microwave energy to create a box lesion around the pulmonary veins utilizing endoscopic techniques [7, 8]. A single (right-sided) or bilateral endoscopic approach can be taken; however, the right-sided–only approach has the disadvantage of not dealing with the LAA. The technique seems to be safe and fairly reproducible with good results [18]. However, some reports have proven the difficulty of producing transmural lesions constantly with microwave energy on the beating heart, resulting in gaps in the ablation line. The circulating blood with its cooling effect and the epicardial fat are believed to have an important negative effect on producing transmural lesions, and that has raised concern on the long-term results of this technique [4, 18, 19].
The second technique is video-assisted thoracoscopic left and right pulmonary vein isolation using bilateral small thoracic incisions or ports. During this operation, both pulmonary veins are isolated with the neighboring left atrial tissue epicardially on a beating heart using bipolar clamps delivering radiofrequency energy.
The interest in pulmonary vein isolation alone was aroused by the report in 1998 by Haissaguerre and colleagues [20], who showed that most paroxysmal AF originated in the pulmonary veins. Bilateral pulmonary vein isolation through two small thoracic incisions was first reported by Wolf and coworkers [21]. A dry bipolar radiofrequency system was used in that series, and the authors reported a 91% freedom from AF at the end of 3 months in a series that consisted mostly of patients with paroxysmal AF [21].
A similar video-assisted approach with some variations was used in our series. An irrigated radiofrequency system was used instead of a dry one to create transmural lesions around the pulmonary veins. The theoretical advantage of irrigated radiofrequency systems is that saline irrigation facilitates energy flow, allowing heat to move deeper into the tissue to create full cell death without any collateral damage [22]. Although it may not be a prerequisite to create transmural lesions, it is clear that lesions must create a conduction block to treat AF, and in this series, the Detect system has been very useful in checking the conductivity through a small incision.
The initial surgical results with pulmonary vein isolation in patients with permanent AF undergoing concomitant procedures have been disappointing [23, 24]. For patients with lone AF, the results of pulmonary vein isolation still remain to be defined. As opposed to pulmonary vein isolation with concomitant disease, there have been some reports indicating favorable results in this group [18, 20]. Today, it is a generally accepted concept that pulmonary vein isolation can be curative in patients with paroxysmal AF; however, this procedure is not as effective for patients with permanent AF [23, 24]. It has been shown that additional ablation lines are needed, and the Cox-maze III operation is the ideal procedure in patients with permanent AF [24].
Unfortunately, it is not possible at this stage to perform the interatrial connecting lesions or the left atrial isthmus lesion without the support of cardiopulmonary bypass, and this is one of the shortcomings of current minimally invasive techniques. To address this issue, a hybrid approach has been proposed for patients with permanent AF in which the pulmonary vein isolation can be performed surgically using minimally invasive techniques and the interatrial lesions can be addressed using percutaneous methods. Serious complications have occurred in the past with catheter ablation while creating ablation lines along the roof of the left atrium and the mitral valve annulus, however, and such risks must be kept in mind before embracing a hybrid procedure [16, 17]. Probably, new imaging systems combined with navigation systems and probably different energy sources will be needed to perform these additional lines on the beating heart through a minimally invasive approach.
The exclusion of the LAA is regarded as one of the main advantages of surgery over percutaneous techniques [25]. Our approach in this series was guided by anatomical and technical concerns. The LAA was isolated with a stapler in 16 cases. In the remaining 12 cases, we refrained from this maneuver either because the LAA was too small and there was no anatomical neck or because the tissue was too fragile. Care should be exercised to avoid traumatic grasping of the LAA during the stapling procedure. Isolation of the LAA is considered an integral part of the procedure and may represent an advantage over available medical management and catheter-based ablation procedures by decreasing the patient’s risk of stroke. Nevertheless, this decision should be based on patient anatomy, and a tailored approach is warranted.
The minimally invasive bilateral epicardial pulmonary vein isolation technique described above was safe and effective. There were no major procedure-related complications. Overall, 80% of the patients were in stable sinus rhythm at 6 months (100% paroxysmal, 72% permanent); and 88.5% of the patients in sinus rhythm had regained atrial transport function. Creating transmural lesions, being able to assess the conduction block, and isolating a relatively large left atrial tissue together with the pulmonary veins may have contributed to these favorable results. The role of autonomic ganglia on AF pathogenesis is a relatively new but exciting topic. These ganglia are known to be located in the fat tissue around the pulmonary veins and around the Marshall ligament. The surgical dissection of the fat tissue in this area might have affected the ganglia, but as detailed electrophysiologic mapping was not done, it was not possible to evaluate this. Postoperative atrial flutter, which can be seen in as many as 15% of patients, was not observed in this series. Although the reason for that is unclear, the low number of patients is a limitation to further comment on this issue. Antiarrhythmic therapy was discontinued for all patients with sinus rhythm after 6 months (80%). The decision to discontinue coumadine was based on the criteria mentioned previously, and coumadine could be discontinued for 12 of 21 patients (57%).
Our current knowledge suggests that there is no one universal ablation line for all AF patients. Most of the less invasive methods aimed at treating AF are currently focused on pulmonary vein isolation simply because of technical difficulties when faced with doing more. While it is well accepted that pulmonary vein isolation and LAA exclusion can be curative for paroxysmal AF, the results are less optimal for patients with permanent AF, and that has been our experience as well. The technique described above should be seen as an early attempt toward a totally off-pump endoscopic maze procedure. Improvement in current technology that will enable us to perform additional off-pump interatrial lesions and isolate the LAA through small ports safely will further improve results. Only time and accumulating experience will tell which minimally invasive procedure is more effective and should be the treatment of choice for patients with symptomatic lone AF. In the meantime, our results suggest that a minimally invasive approach that is safe and effective may be considered as an alternative to catheter ablation for patients with intractable lone AF rather than a procedure of last resort.
Study Limitations
The number of patients is low, and the follow-up time is rather short. Only 24-hour Holter monitoring could be done to evaluate a stable sinus rhythm at 3 and 6 months; clearly, a 48-hour evaluation would have been better, but was not possible. The duration of preoperative AF was rather short in some patients, and that could have played a role in the favorable outcomes in terms of rhythm restoration. Furthermore, the washout effect of antiarrhythmic drugs may not have been completed during the rhythm evaluation, and that also could have contributed to the favorable outcomes.
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References |
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TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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ndr O. Intraoperative saline irrigated radiofrequency modified maze procedure for atrial fibrillation Ann Thorac Surg 2002;74(Suppl):1301-1306.This article has been cited by other articles:
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  S. C. Lall, K. V. Foyil, S.-I. Sakamoto, R. K. Voeller, J. P. Boineau, R. J. Damiano Jr., and R. B. Schuessler Pulmonary vein isolation and the Cox maze procedure only partially denervate the atrium. J. Thorac. Cardiovasc. Surg., April 1, 2008; 135(4): 894 - 900. [Abstract] [Full Text] [PDF]
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