© 2014 Wiley Periodicals, Inc.

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Thoracoscopic Radiofrequency Ablation for Lone Atrial Fibrillation: Box-Lesion Technique Marek Pojar, Ph.D.,* Jan Vojacek, Ph.D.,* Ludek Haman, Ph.D.,y Petr Parizek, Ph.D.,y Nedal Omran, M.D.,* Martin Vobornik, M.D.,* and Jan Harrer, Ph.D.* *Department of Cardiac Surgery, Charles University in Prague, Faculty of Medicine and University Hospital in Hradec Kralove, Hradec Kralove, Czech Republic; and y1st Department of Cardiovascular Medicine, Charles University in Prague, Faculty of Medicine and University Hospital in Hradec Kralove, Hradec Kralove, Czech Republic ABSTRACT Background: We report the feasibility and outcomes of box-lesion ablation technique to treat stand-alone atrial fibrillation (AF). Methods: There were 41 patients with a mean age of 57.6 W 8.0 years who underwent bilateral totally thoracoscopic ablation of symptomatic paroxysmal AF (n = 24; 58.5%), persistent AF (n = 9; 22.0%), or long-standing persistent AF (n = 8; 19.5%). The box-lesion procedure included bilateral pulmonary vein and left atrial posterior wall ablation using irrigated bipolar radiofrequency with documentation of conduction block. Results: There were no intra- or perioperative ablation-related complications. There was no operative mortality, no myocardial infarction, and no stroke. Skin-to-skin procedure time was 119.5 W 23.7 minutes and the postoperative average length of stay was 7.4 W 2.5 days. At discharge, 38 patients (93%) were in sinus rhythm. Median follow-up time was 641 days (ranges, 185–1636 days). At six months postsurgery, 31 patients of 41 (76%) were free from AF without the need of antiarrhythmic drugs. One-year success rate was 73% (off antiarrhythmic drugs). Eight patients (19.5%) underwent catheter reablation. Thirty-six patients (90%) were in sinus rhythm at six months after the last performed ablation (surgical ablation or catheter reablation). At 12 months follow-up, 61% patients discontinued oral anticoagulant therapy. Conclusion: The thoracoscopic box-lesion ablation procedure is a safe, effective, and minimally invasive method for the treatment of isolated (lone) AF. This procedure provided excellent short-term freedom from AF. doi: 10.1111/jocs.12409 (J Card Surg 2014;29:757–762) Atrial fibrillation (AF) is the most common chronic arrhythmia in the world, affecting 1% of the population, including nearly 5 million persons in the European Union.1,2 AF is associated with increased mortality and increased risk of stroke, heart failure, and dementia.3,4 There are several approaches to the treatment of AF. Antiarrhythmic drugs (AADs) have limited efficacy in maintaining sinus rhythm and might have serious adverse effects.5 Endocardial ablation of AF has emerged as an option for treating AF. The finding of focal AF with the foci in the pulmonary veins introduced

Conflict of interest: The authors acknowledge no conflict of interest in the submission. Grant sponsor: MH CZ—DRO (UHHK); Grant number: 00179906; Grant sponsor: Research programme PRVOUK; Grant number: P37/ 04 Address for correspondence: Nedal Omran, M.D., Department of Cardiac Surgery, University Hospital, Sokolska 581, 500 05 Hradec Kralove, Czech Republic. Fax: þ420-495-833-026; e-mail: nidal81@ gmail.com

by Haı¨ssaguerre et al.6 led to the introduction of focal pulmonary vein ablation into clinical practice. Later, a combination of pulmonary vein isolation and AF substrate modification has yielded promising results, mainly in patients with paroxysmal AF. However, the endocardial approach has variable results with single ablation success ranging from 16% to 84%.7,8 In addition to catheter ablation, surgical techniques are effective in the treatment of AF. There is rapid progress toward minimizing the invasiveness of surgical ablation of AF. The increasing availability of minimally invasive techniques makes a surgical approach more appealing, especially because of its superior capacity to create transmural lesions.2 Patients with ‘‘lone’’ AF, that is AF in the absence of underlying heart disease, represent a special subgroup of AF patients.9 The minimally invasive (video-assisted) surgical approach is a very promising method for the treatment of patients with lone AF. The ‘‘box-lesion’’ technique is usually used, whereby a box lesion around pulmonary veins isolates not only the veins but also the

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posterior left atrial wall, which contains AF triggers in many patients. Gillinov et al.10 reported that adding a connecting line between the two pairs of isolated veins enhanced the chances of relief from AF. The aim of this paper was to report our experience with a minimally invasive thoracoscopic approach employing irrigated radiofrequency box-lesion ablation of AF and to establish the feasibility and outcomes of this box-lesion ablation technique to treat lone AF. MATERIALS AND METHODS Patient population The Institutional Review Board approved the study and individual consents were obtained from the patients. Patients requiring nonpharmacologic treatment of AF and patients with a preference for minimally invasive surgery and/or earlier failure of catheter pulmonary vein isolation were eligible for the study. According to the guidelines, only patients who had failed to maintain sinus rhythm when using at least one AAD for symptomatic AF were included. Definition of paroxysmal AF, persistent AF, and long-standing persistent AF (LSPAF), success and failure of ablation, and follow-up monitoring were based on the HRS/ EHRA consensus statement for catheter and surgical ablation of AF.7 Before surgery, all patients underwent clinical examination, 12-lead electrocardiogram (ECG), chest radiography, and coronary angiography if aged 40 years or older. The possibility of underlying heart disease was excluded by transthoracic or esophageal echocardiography. No patients had undergone a previous cardiac operation. Preoperative management Oral anticoagulant therapy was discontinued three days before surgery and replaced by low-molecular weight heparin when the international normalized ratio value was less than 2.0. AAD were continued during hospital admission. Before surgery transesophageal echocardiogram was performed to exclude thrombus in the left atrial appendage (LAA). Surgical technique The procedures were performed under general anesthesia with the trachea intubated using a doublelumen endotracheal tube for selective lung ventilation. The entire procedure was performed on the beating heart without the use of extracorporeal circulation. The patient was placed in the supine position with both arms alongside the body and slightly below table level. A towel roll or inflatable pressure bag was placed under the right and left shoulder enabling rotation of the patient’s chest. The procedure started on the right side. After right lung deflation, three ports were introduced into the pleural cavity at positions that correspond to a triangle. The port for the camera (11 mm) was introduced into the fifth intercostal space at the midaxillary line. The second port (5 mm, working port) was placed

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into the fourth intercostal space in the anterior-axillary line and the third port (11 mm working port) was placed into the sixth intercostal space in the anterior-axillary line. Lung collapse was facilitated by continuous carbon dioxide insufflation into the pleural cavity at 8–10 mmHg. Visualization was accomplished with a 10.0 mm 0degree endoscope. On the right side, the pericardium was widely opened at 1.5–2.0 cm anterior to the phrenic nerve. Pericardial retraction sutures were used to aid visualization. Blunt dissection was performed to open the oblique and transverse sinus. Flexible Gemini-s guides (Medtronic, Inc., Minneapolis, MN, USA) were passed through the transverse and oblique sinus. Prior to ablation, electrical testing of the threshold for capture of the atria with pulmonary vein electrical stimulation was measured. Following this, the left side approach was established. Three ports were introduced into the left pleural cavity in a similar fashion to the right pleural cavity, except that the left ports were placed more posteriorly. The pericardium on the left side was opened just below the phrenic nerve. The flexible guides were retrieved out of the left thorax. The Gemini-s (Medtronic, Inc.) was attached to the end of the guides outside the left chest. Using the guides, the Gemini-s was inserted across the left pulmonary veins and the left atrium. The left part of the box lesion was performed. The clamp was closed proximal to the confluence of the pulmonary veins and the radiofrequency energy for ablation was applied. After the first ablation, the radiofrequency clamp was opened and placed approximately 3–5 mm away from the first ablation line. Four ablation lines were placed on each side. The aim was to create four parallel lines at the atrial cuff. The right pulmonary vein ablation lines were completed through the right-sided ports. At this time complete box lesion was obtained. Conduction block was then confirmed by pacing distally to the ablation line from inside the ‘‘box.’’ If conduction block was not achieved after the first radiofrequency application additional radiofrequency applications were given until pulmonary vein conduction block occurred. The pericardium was closed on the right side. Intercostal analgesic blockade was applied. A single chest drain was inserted through the scope site on each side of the chest and the wounds were closed and dressed in a standard manner. If the patient was in AF and did not convert to sinus rhythm during the ablation procedure, an attempt was made to restore sinus rhythm using external cardioversion. The LAA was closed by an endoscopic stapling device with a no-knife stapling cartridge (Ethicon Endosurgery, Somerville, NJ, USA) in one patient, and was occluded using an epicardial clip (AtriCure, Inc., West Chester, OH, USA) in another patient. Occlusion of the LAA was indicated in patients with the history of stroke and previous signs of thrombus formation inside the appendage, which disappeared at the time of operation. Postoperative care and clinical follow-up Postoperative management of pharmacologic therapy was conducted according to a standardized protocol.

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Until discharge, patients were monitored by telemetry and standard 12-lead ECG recordings. All patients were discharged on both antiarrhythmic and anticoagulant therapy. AAD were continued for at least three months after surgery and were then withdrawn in patients who maintained sinus rhythm. Electrical cardioversion was attempted for patients who remained in persistent AF one month after the surgical procedure. Warfarin was administered one day following drain removal with a target international normalized ratio of 2–3. Anticoagulant therapy was withdrawn after six months if the Holter ECG monitoring showed a sinus rhythm, if patient had a low thromboembolic risk, and CHADS2 score was 30 seconds on any ECG record or 24-hour Holter ECG monitoring or longer monitoring.

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TABLE 1 Baseline Characteristics Age (years) Male (men) BMI Paroxysmal AF Persistent AF Long-standing persistent AF Duration of preoperative AF (months) LA diameter (mm) Previous catheter ablation NYHA class Prior stroke or TIA CHADS2 score 0 CHADS2 score 1 CHADS2 score 2 and more

57.6  8.0 31 (75.6%) 30.3  4.9 24 (58.5%) 9 (22.0%) 8 (19.5%) 61.6  49.8 (7.0–240.0) 45.3  5.9 5 (12.2%) 1.3  0.6 7 (17.1%) 11 (26.8) 19 (46.3%) 11 (26.8%)

AF, atrial fibrillation; BMI, body mass index; CHADS2, congestive heart failure, hypertension, age 75, diabetes mellitus, stroke; LA, left atrium; NYHA, New York Heart Association; TIA, transient ischemic attack.

paroxysmal AF, nine (22.0%) had persistent AF, and eight (19.5%) had LSPAF. The duration of AF was 61.6  49.8 months (range, 7–240 months). Patient clinical characteristics are presented in Table 1. Of the 41 patients, five patients (12.2%) had undergone prior catheter ablation. The left atrial dimension was 45.3  5.9 mm. The duration of postoperative hospital stay was 7.4  2.5 days. Our practice is to discharge patients with INR ratio of 2–3, and this strategy could have prolonged the length of hospital stay. Procedure details The mean procedure time was 119.5  23.7 minutes. There were no operative complications and no need for conversion to sternotomy. The duration of stay in the intensive care unit was 24.0  7.1 hours. Follow-up

Statistical analysis Perioperative data were obtained by prospective review of the patient’s hospital record. Follow-up information was obtained from comprehensive questionnaires and telephone interviews with the patient’s personal physician. Continuous variables are expressed as mean  standard deviation for normal values, and as median (range) for non-normal values. Categorical data are given as percentages.

RESULTS Patient characteristics Between May 2009 and September 2013, 41 patients with symptomatic lone AF that was resistant to antiarrhythmic therapy underwent bilateral thoracoscopic radiofrequency ablation using the Gemini-S ablation system (Medtronic, Inc.). There were 31 men (75.6%) and 10 women (24.4%) with a mean age of 57.6  8.0 years. Twenty-four patients (58.5%) had

At discharge, 38 patients were in sinus rhythm. Follow-up data were collected for all 41 patients (100%). The median follow-up time was 641 days (range, 185–1636 days). Thirty-three patients (80%) had a follow-up period of 1 year. End-points The primary end-point was reached in 24 of 33 (73%) patients. These patients were free from AF, atrial flutter, and atrial tachycardia without the use of AAD after 12 months from the surgical procedure. Patients who underwent catheter reablation were also excluded as a failure. One-year success rates were 81% (17/21) in paroxysmal AF, 67% (4/6) in persistent AF and 50% (3/6) in LSPAF patients (Fig. 1). In eight patients (19.5%), a follow-up catheter ablation was performed because of paroxysmal AF in five patients or macro-reentry atrial tachycardia in three patients. The box lesion was complete in three of the patients with postoperative paroxysmal AF and in one

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90 Succes rate off AAD (%)

80

76

83

81

78

73

70 60

67

50

50

50 All patients

40

Paroxysmal AF

30

Persistent AF

20

LSPAF

10 0

6 months (n=41)

12 months (n=33)

Follow-up (months)

Figure 1. Success rate after the surgical ablation in patients without antiarrhythmic drugs. (AF, atrial fibrillation; AAD, antiarrhythmic drugs; LSPAF, long-standing persistent atrial fibrillation).

patient with macro-reentry atrial tachycardia. Linear ablation and substrate ablation was performed in these patients. In patients with incomplete box lesion, reisolation of the box lesion was performed and linear as well as substrate ablation was added if necessary. Six of eight patients (75%) who underwent catheter reablation remained in sinus rhythm. The main place of the gap in the box lesion was on the posterior left atrial wall at the connection of the left and right ablation lines. Thirty-six of 40 patients (90%) reached the secondary end-point (23/24 paroxysmal AF, 8/9 persistent AF, 5/7 LSPAF). These patients were free from AF, atrial flutter, or atrial tachycardia without the use of AAD six months from the last ablation (surgical ablation or catheter reablation). One patient was followed for less than six months from the catheter reablation. Oral anticoagulant therapy was discontinued in 61% patients at 12 months follow-up. After minimally invasive AF ablation and a blanking period of three months, 31 of 41 (76%) patients were in sinus rhythm according to at least 24-hour Holter ECG monitoring or longer monitoring. At six months from the surgical procedure, 76% patients (20/24 paroxysmal AF, 7/9 persistent AF, 4/8 LSPAF) were free from AF, atrial flutter, and atrial tachycardia without the use of AAD. Adverse events There were no hospitalization-related deaths. One patient (2.4%) experienced diaphragmatic dysfunction, which resolved three months after the surgical procedure. No patient experienced a postoperative myocardial infarction, transient ischemic attack, cerebrovascular accident, reoperation for bleeding, port site infection or required the implantation of a permanent pacemaker. No patient required blood transfusions. One patient (2.4%) had postoperative pleural effusion that was treated by uncomplicated thoracocentesis. DISCUSSION The optimal therapy of paroxysmal AF and persistent AF remains undecided. None of the currently available approaches provide complete abolition of the arrhythmia. The aim of surgical treatment of AF is to restore sinus rhythm and normal systolic function of the left

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atrium. The Cox-Maze III operation, which was introduced into clinical practice in 1987, is still considered the gold standard for the surgical treatment of AF. Cox et al.11 has reported success rates of more than 95% in patients undergoing the Cox-Maze III procedure. However, the complexity and mortality associated with the cut-and-sew maze procedure has limited its acceptance among cardiac surgeons. Alternative energy sources have been developed to replace the traditional incisions and sutures of the standard CoxMaze procedure. Radiofrequency, microwave, ultrasound energy or cryothermia are used in Cox-Maze IV procedures and are promising tools in minimally invasive AF therapy. In a special subgroup of patients with AF and without heart disease, referred to as lone AF patients, the minimally invasive technique has been used since 2005, when Wolf et al.5 reported the first successful minimally invasive ablation of AF. Irrigated bipolar radiofrequency devices effectively produce transmural lesions on the beating heart.12 The bipolar application of radiofrequency energy achieves better transmurality of the ablation lines than the unipolar application.13,14 An additional benefit of bipolar ablation is that current density is confined to the tissue between the two electrodes on the jaws. This limits thermal energy spread and minimizes the risk of collateral tissue injury, which has been reported while using unipolar catheters. Additionally, bipolar RF devices have the capability of providing immediate feedback on the transmurality. When the conductance through the tissue falls below a threshold value, a transmural lesion is achieved. In the surgeries reported here, we used saline-irrigated radiofrequency. The irrigation of the electrodes allows the thermal energy to penetrate deeper in to the tissue, achieving deeper transmural lesions. Atrial tachyarrhythmias in the postablation period are most commonly caused by incomplete and nontransmural lesions. The procedure we performed was safe and effective in the intermediate follow-up period. Our approach avoids the need for a sternotomy or rib-spreading thoracotomy. The epicardial approach enables this procedure to be performed on a beating heart, avoiding the need for cardiopulmonary bypass and its associated complications. Other potential benefits include autonomic ganglia ablation and ligament of Marshall dissection.15 Finally, the ability to exclude the LAA may further decrease the incidence of the thromboembolic events. It may, in the future, represent an advantage over available medical management and catheter ablation procedures. There is increasing concern about the poor efficacy of simply pulmonary vein isolation for the treatment of persistent AF and LSPAF. From the literature the more extensively performed left atrial ablation the more is the probability to restore and to maintain sinus rhythm in patients undergoing surgical ablation.16 The box-lesion approach used in this study results in wide isolation of the pulmonary veins and the posterior part of the left atrium. Lee et al.17 stated that the left atrial posterior wall is one of the most important sources of AF in dilated atria. Voeller et al. reported a significant 48% decrease in the incidence of early postoperative atrial

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tachyarrhythmia in patients with isolation of the entire posterior left atrium instead of only pulmonary vein ablation. The freedom from AF at three months after the procedure was higher in the box-lesion group (p ¼ 0.028).18 In a study conducted by Minakata et al.,19 the use of a box-lesion and coronary sinus ablation were independent predictors of the maintenance of sinus rhythm at six months after ablation (p ¼ 0.011) and in a study performed by Damiano et al.,20 the failure to isolate the posterior left atrial wall was a predictor of recurrence of AF (p ¼ 0.022). The box-lesion procedure performed without the lesion across the left atrial isthmus can lead to postablation atrial flutter. A connecting lesion to the mitral valve annulus can be accomplished across the dome of the left atrium within the transvers sinus, as reported by Edgerton at al.21 in the ‘‘Dallas lesion set.’’ However, this lesion across the dome of the left atrium to the left fibrous trigone divides Bachmann’s bundle and can lead to severe intra-atrial conduction delay, thus eliminating all left atrial transport function.16 The success rate at six months after the last ablation, surgical, or catheter, without the AAD was 90%. Of the study group, 61% patients were free of oral anticoagulant therapy at 12 months follow-up. These results are comparable to results of other groups that used bipolar radiofrequency ablation. Doty and Clayson22 reported in the Galaxy study freedom from AF at 12 months in 90% and 80% for paroxysmal and persistent AF. Bauer et al.23 reported the presence of sinus rhythm without AAD in 65% of patients at six months and 78% of patients at one year after surgery. On the other hand, Pruitt et al.24 used the microwave energy for ablation and reported that only 42% of patients were in sinus rhythm at the end of follow-up (mean follow-up duration, 23 months). In accordance with other studies, we found that the proportion of patients free from AF without AAD at six months post-surgery was higher among paroxysmal AF patients (83%) than persistent AF (78%) or LSPAF (50%). These results could be explained by the limitation of the ablation lines on the epicardial surface. In addition, the absence of the left isthmus line and ablation of the coronary sinus could lead to lower success in patients with persistent AF. The box lesion is the gold standard of minimally invasive surgical ablation and is now considered as an accepted strategy in the hybrid approaches. In the last few years, there has been a tendency for increased collaboration between electrophysiologists and surgeons in the therapy of AF. Hybrid procedures that combine surgical and catheter ablation to overcome the shortcomings of these two approaches and combine their advantages are a novel concept in the treatment of AF. Hybrid procedures are usually performed simultaneously in a hybrid operating theatre or as a two-stage procedure where the surgical ablation and healing period is followed by the electrophysiological study and catheter ablation in the left or right atrium.25 Recently, Krul et al.26 presented a singlesession success rate of 86% for hybrid procedures. Mahapatra et al.27 have published their experience with surgical and endocardial ablation carried out in two

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sequential steps for the treatment of persistent AF and LSPAF, and reported a success rate of 86.7% after a mean follow-up of 20.7  4.5 months.27 Kurfirst et al.28 published similar results when applying the two-stage hybrid approach for the management of patients with chronic AF, reporting a success rate as high 90%.28 This study has some limitations. These results may not be generalized as they were observed in a single surgeon experience. The small patient population and the short follow-up do not allow us to draw definite conclusions. Larger series with long-term follow-up are needed. Another limitation of this study is that 60% patients from the study group had paroxysmal AF and only 40% patients had persistent AF. Therefore, we reported results also for group of patients with paroxysmal AF and persistent AF. Another limitation of this study is that LAA was occluded only in two patients. Oral anticoagulant therapy thus could not be discontinued early in our patients. Finally, we report results after only six months from the last ablation (surgical ablation or catheter reablation after the previous surgical ablation). In these patients, longer follow-up is needed especially in light of the catheter ablation results that show steep failure rate after the first year of follow-up. REFERENCES 1. Go AS, Hylek EM, Phillips KA, et al: Prevalence of diagnosed atrial fibrillation in adults: National implications for rhythm management and stroke prevention: The AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) study. JAMA 2001;285:2370–2375. 2. Speziale G, Bonifazi R, Nasso G, et al: Minimally invasive radiofrequency ablation of lone atrial fibrillation by monolateral right minithoracotomy: Operative and early followup results. Ann Thorac Surg 2010;90:161–167. 3. Ott A, Breteler MM, de Bruyne MC, et al: Atrial fibrillation and dementia in a population-based study. The Rotterdam study. Stroke 1997;28:316–321. 4. Stewart S, Hart CL, Hole DJ, et al: A population-based study of the long-term risks associated with atrial fibrillation: 20-Year follow-up of the Renfrew/Paisley study. Am J Med 2002;113:359–364. 5. Wolf RK, Schneeberger EW, Osterday R, et al: Videoassisted bilateral pulmonary vein isolation and left atrial appendage exclusion for atrial fibrillation. J Thorac Cardiovasc Surg 2005;130:797–802. 6. Haı¨ssaguerre M, Jaı¨s P, Shah DC, et al: Electrophysiological end-point for catheter ablation of atrial fibrillation initiated from multiple pulmonary venous foci. Circulation 2000;101:1409–1417. 7. Calkins H, Kuck KH, Cappato R, et al: 2012 HRS/EHRA/ ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, end-points, and research trial design. Europace 2012;14:528–606. 8. Weerasooriya R, Khairy P, Litalien J, et al: Catheter ablation for atrial fibrillation: Are results maintained at 5 years of follow-up? J Am Coll Cardiol 2011;57:160–166. 9. Gelsomino S, La Meir M, Luca` F, et al: Treatment of lone atrial fibrillation: A look at the past, a view of the present and a glance at the future. Eur J Cardiothorac Surg 2012;41:1284–1294.

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10. Gillinov AM, Bhavani S, Blackstone EH, et al: Surgery for permanent atrial fibrillation: Impact of patient factors and lesion set. Ann Thorac Surg 2006;82:502–513. 11. Cox JL, Schuessler RB, D’Agostino HJ Jr, et al: The surgical treatment of atrial fibrill: III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg 1991;101:569–583. 12. Melby SJ, Gaynor SL, Lubahn JG, et al: Efficacy and safety of right and left atrial ablations on the beating heart with irrigated bipolar radiofrequency energy: A long-term animal study. J Thorac Cardiovasc Surg 2006;132:853–860. 13. Bugge E, Nicholson IA, Thomas SP: Comparison of bipolar and unipolar radiofrequency ablation in an in vivo experimental model. Eur J Cardiothorac Surg 2005;28:76–80. 14. Prasad SM, Maniar HS, Schuessler RB, et al: Chronic transmural atrial ablation by using bipolar radiofrequency energy on the beating heart. J Thorac Cardiovasc Surg 2002;124:708–713. 15. Edgerton JR, Jackman WM, Mack MJ: Minimally invasive pulmonary vein isolation and partial autonomic denervation for surgical treatment of atrial fibrillation. J Interv Card Electrophysiol 2007;20:89–93. 16. Cox JL: The longstanding, persistent confusion surrounding surgery for atrial fibrillation. J Thorac Cardiovasc Surg 2010;139:1374–1386. 17. Lee SH, Tai CT, Hsieh MH, et al: Predictors of nonpulmonary vein ectopic beats initiating paroxysmal atrial fibrillation: Implication for catheter ablation. J Am Coll Cardiol 2005;46:1054–1059. 18. Voeller RK, Bailey MS, Zierer A, et al: Isolating the entire posterior left atrium improves surgical outcomes after the Cox Maze procedure. J Thorac Cardiovasc Surg 2008;135: 870–877. 19. Minakata K, Yunoki T, Yoshikawa E, et al: Predictors of success of the modified maze procedure using radiofrequency device. Asian Cardiovasc Thorac Ann 2011;19: 33–38.

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20. Damiano RJ Jr, Schwartz FH, Bailey MS, et al: The Cox Maze IV procedure: Predictors of late recurrence. J Thorac Cardiovasc Surg 2011;141:113–121. 21. Edgerton JR, Jackman WM, Mahoney C, et al: Totally thorascopic surgical ablation of persistent AF and longstanding persistent atrial fibrillation using the ‘‘Dallas’’ lesion set. Heart Rhythm 2009;6:S64–S70. 22. Doty JR, Clayson SE: Surgical treatment of isolated (lone) atrial fibrillation with Gemini-S Ablation and Left Atrial Appendage Excision (GALAXY procedure). Innovations (Phila) 2012;7:33–38. 23. Bauer M, Hetzer R: Video-assisted thoracoscopic surgical treatment of lone atrial fibrillation. Multimed Man Cardiothorac Surg 2009;2009: mmcts.2008.003848. 24. Pruitt JC, Lazzara RR, Ebra G: Minimally invasive surgical ablation of atrial fibrillation: The thoracoscopic box lesion approach. J Interv Card Electrophysiol 2007; 20:83–87. 25. La Meir M, Gelsomino S, Lorusso R, et al: The hybrid approach for the surgical treatment of lone atrial fibrillation: One-year results employing a monopolar radiofrequency source. J Cardiothorac Surg 2012;7:71. 26. 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 surgicalelectrophysiological approach for atrial fibrillation. Circ Arrhythm Electrophysiol 2011;4:262–270. 27. Mahapatra S, LaPar DJ, Kamath S, et al: Initial experience of sequential surgical epicardial-catheter endocardial ablation for persistent and long-standing persistent atrial fibrillation with long-term follow-up. Ann Thorac Surg 2011;91:1890–1898. 28. Kurfirst V, Mokracek A, Bulava A, et al: Two-staged hybrid treatment of persistent atrial fibrillation: Short-term singlecentre results. Interact Cardiovasc Thorac Surg 2014;18:451–456.

Thoracoscopic radiofrequency ablation for lone atrial fibrillation: box-lesion technique.

We report the feasibility and outcomes of box-lesion ablation technique to treat stand-alone atrial fibrillation (AF)...
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