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Surgical and Hybrid Ablation of Atrial Fibrillation
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Heart, Lung and Circulation (2017) xx, 1–7 1443-9506/04/$36.00 http://dx.doi.org/10.1016/j.hlc.2017.05.114
Surgical and Hybrid Ablation of Atrial Fibrillation Reece A. Davies, [4_TD$IF]MBBS (Hons), B. AppSc (Pthy) (Hons) a,c*, Saurabh Kumar, MBBS, PhD, FRACP b[,5_TD$IF] Richard B. Chard, MBBS (Hons), BDS (Hons), FRACS, FCSANZ a,c, Stuart P. Thomas, BMed, PhD, FRACP b,c a
Department of Cardiothoracic Surgery, Westmead Hospital, Sydney, NSW, Australia Department of Cardiology, Westmead Hospital, Sydney, NSW, Australia Faculty [6_TD$IF]of Medicine, University of Sydney, Sydney, NSW, Australia
b c
Atrial fibrillation (AF) is the most common arrhythmia in humans and is known to be associated with an increased risk of stroke, dementia, heart failure and mortality. Non-pharmacological therapy with ablation [8_TD$IF] using either surgical or percutaneous techniques is recommended in drug refractory AF. Early attempts to devise procedures to ablate AF and restore sinus rhythm culminated with the Cox-Maze procedure, the first truly successful procedure. Since then, ablation surgery has been conducted predominately as a concomitant procedure. The Cox Maze procedure is complex and technically demanding and has, therefore, been extensively modified with new techniques for creating the linear ablation lines, new lesion sets, minimally invasive surgical techniques and most recently hybrid surgical-catheter ablation techniques. Surgical ablation techniques result in a marked reduction in atrial fibrillation when compared to conventional therapy with only a small increase in procedural risk. However, further research is required to more accurately quantify those benefits and to determine the optimal lesion sets, specific to the underlying arrhythmia mechanism and the optimal energy sources for ablation. Keywords
Atrial fibrillation Surgical ablation Cox Maze
Introduction Atrial fibrillation (AF) is a common medical condition, with studies showing it is currently affecting over five million people in the United States and projections of its prevalence increasing to over 12 million by 2030 [1]. Atrial fibrillation is a risk factor for other diseases, such stroke and heart failure, and is associated with an increased risk of death even after controlling for concomitant diseases [2]. Initial attempts at surgical ablation for AF extend back to the 1980s, and include left atrial isolation and the Corridor procedure; however it wasn’t until 1987 and the development of the Cox-Maze procedure that success with surgical ablation was reliably achieved [3]. Despite its reliability, the traditional Cox-Maze procedure was a technically challenging operation requiring sternotomy, cardiopulmonary bypass and extensive suture lines. This has led to attempts to replicate its outcomes with a
procedure that is less technically demanding and potentially less invasive [4].
Indications The Heart Rhythm Society Task Force on Catheter and Surgical Ablation of Atrial Fibrillation (2012) released an expert consensus statement that included indications for surgical AF ablation [5]. They recommended that surgical ablation should be considered as an additional procedure in all patients with symptomatic AF, with or without trial of antiarrhythmic drugs, in cases where these patients were already scheduled to undergo cardiac surgery for other indications. This represents a Class IIa indication for paroxysmal, persistent and long-standing persistent AF failing antiarrhythmic drugs and paroxysmal and persistent
*Corresponding author at: Department of Cardiothoracic Surgery, Westmead Hospital, Cnr Hawkesbury and Darcy Roads, Westmead NSW 2145, Australia., Email: [email protected] © 2017 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Davies RA, et al. Surgical and Hybrid Ablation of Atrial Fibrillation. Heart, Lung and Circulation (2017), http://dx.doi.org/10.1016/j.hlc.2017.05.114
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AF prior to a trial of antiarrhythmic drugs. It is a Class IIb indication for long-standing persistent AF prior to a trial of antiarrhythmic drugs. The Taskforce also reported that surgical ablation may be considered as a stand-alone procedure in patients who have failed antiarrhythmic drugs and who have either failed catheter ablation or who prefer surgery over catheter ablation (Class IIb indication). Stand-alone surgical ablation in patients who haven’t trialled antiarrhythmic drugs was not recommended (Class III indication). In 2016, the European Society of Cardiology (ESC), in collaboration with the European Association for Cardiothoracic Surgery, released guidelines for the management of AF [6]. In relation to the ablation of AF, they recommended catheter or surgical ablation should be considered for symptomatic control in all cases of persistent or long-standing persistent AF that is refractory to antiarrhythmic drugs (Class IIa indication). They also recommended that minimally invasive pulmonary vein isolation (PVI) should be considered where catheter ablation failed in symptomatic AF, and Maze surgery should be considered in refractory symptomatic AF or post ablation AF to reduce symptoms (Class IIa indications). In patients undergoing cardiac surgery, they recommended that Maze surgery should be considered in symptomatic patients with AF (class IIa) and may be considered in asymptomatic patients in AF (Class IIb). The ESC AF guidelines also proposed that AF surgery and extensive ablations should be discussed by an ‘Atrial Fibrillation Heart Team’ comprising a cardiologist with expertise in antiarrhythmic drug therapy, an interventional electrophysiologist and a cardiac surgeon with expertise in AF surgery.
Surgical Techniques The Cox-Maze III procedure uses a ‘cut and sew’ incision technique to create a ‘maze’ pathway from the sinoatrial node to the atrioventricular node. This allows activation of the
myocardium through corridors created by [9_TD$IF]incisions and anatomical obstacles. This approach reduces the contiguous muscle mass preventing activation of a larger area of atrial myocardium that may allow a re-entry circuit to perpetuate [7,8]. The Maze procedure is underpinned by the concept of the ‘multiple wavelet’ hypothesis of AF, which proposes that large re-entry circuits can only occur in situations where there is an adequate mass of conducting myocardium, slowed conduction velocities, and shortened refractory periods [9]. The lesions in the Cox-Maze III involve excision of the left and right atrial appendages, suture lines between the superior vena cava (SVC) and inferior vena cava (IVC) and between the IVC and tricuspid valve in the right atrium, suture lines isolating the pulmonary veins and posterior left atrium and a suture line from the mitral valve to the pulmonary veins [5]. Due to the complexity of the Cox-Maze III, it has had limited uptake and attempts have been made to simplify it to make it more accessible. One such approach is the Cox-Maze IV (Figure 1A and B), wherein the majority of the lesions from the Cox-Maze III are replaced with ablation lesions from energy sources [10]. The Cox Maze IV aims to reduce the procedural complexity and shorten procedural time by reducing the time required to create atrial lesions, potentially allowing the use of minimally invasive approaches, such as via minithoracotomy [11]. Increasing understanding of the pathophysiology of AF, in particular its origins, which are frequently in the pulmonary veins, has led to proposals of further modifications and simplifications to the technique. These have included leftsided Maze procedures [12,13] and procedures that purely isolate the pulmonary veins (PVI) [14] (Figure 2). The intent of these procedures is to prevent the trigger sites of AF from communicating electrically with remaining atrial tissue, therefore preventing the initiation of AF. Other modifications of the original Cox-Maze procedure have focussed on alternate energy sources to create the lesions. Although a manual incision may be the ideal method
Figure 1 Lesion set for Cox-Maze IV: A- Left-sided lesions. B- Right-sided lesions.
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Figure 3 Intraoperative picture of cryoablation being used in a Star procedure. Cryo probe marked with (*). Figure 2 Bipolar Radiofrequency ablation for Pulmonary Vein Isolation.
for the creation of durable, permanent atrial lesions, the procedural morbidity associated with such an approach motivated the pursuit for alternate energy sources. However, a major compromise to a potential reduction in procedural complexity and duration is a risk of incomplete atrial lesion formation and, thus, recurrence of organised atrial arrhythmias due to re-entry in and around gaps within the ablation lines that may require additional percutaneous catheter ablation procedures [15]. Progress in the techniques employed to create linear lesions has partly been driven by the desire to create durably transmural lesions similar to those achieved by linear incision of the atria. The energy sources explored included radiofrequency ablation, cryoablation and microwave ablation [16]. The Cox-Maze IV is an example of this, with the majority of the lesion lines replaced with radiofrequency and cryoablation (Figure 3) enabling less complex and shorter operations [10,17]. The advent of alternative energy sources has enabled minimally invasive techniques, such as Video Assisted Thoracoscopic Surgery (VATS), to be developed for use in standalone operations for AF [18,19] and with concomitant minimally invasive cardiac surgery [20], typically applying epicardial lesions such as radiofrequency PVI.
Surgical Outcomes Concomitant Procedures Surgical ablation of AF is most commonly performed in patients undergoing cardiac surgery for other reasons, with this category of procedure accounting for just under 95% of all surgical ablations for AF in the United States between 2005 and 2010 [21]. Of the 11% of patients undergoing cardiac surgery in that period who also presented with AF, approximately 40% had a concomitant surgical ablation. This percentage, however,
varied widely depending on the primary operation, with 61.5% of patients in AF undergoing mitral valve surgery receiving an ablation compared with 33.9% of those undergoing an aortic valve replacement (AVR) and 27.5% undergoing coronary artery bypass grafts (CABG) [21]. In 2016 the Cochrane Collaboration performed a systematic review and meta-analysis of 22 randomised control trials (RCT) of patients undergoing concomitant cardiac surgery, exploring outcomes of surgical AF ablation procedures versus control groups receiving no ablation [22]. They found no significant difference in 30-day mortality (3.1% for ablation vs 2.3% for control; RR 1.25[95% confidence interval: 0.71–2.20]) or all-cause mortality (7% vs 6.6%; RR 1.14 [0.81–1.59]). They found that patients who underwent AF ablation were significantly more likely to be free from AF, atrial flutter or atrial tachycardia at three months compared to controls, both without the use of antiarrhythmic drugs (51.0% vs 24.1%; RR 2.04 [1.63–2.55]) and with antiarrhythmic drugs (60.1% vs 24.4%; RR 2.46 [2.16–2.80]). However, they reported a significantly greater rate of pacemaker implantation in patients who had undergone AF ablation (6.9% vs 4.1%; RR 1.69 [1.12–2.54]). There was no significant difference in the stroke rate (3.87% vs 3.74; RR 1.05 [0.60–1.83]). The authors cautioned about the validity of their results due to most studies being small with significant sources of bias, leading to most of their conclusions to be assessed as low to moderate quality evidence. They were unable to comment on the relative effectiveness of different lesion sets. The two largest studies in the Cochrane review, and the only studies with over 200 patients, were by Gillinov et al. in 2015 [23] and Budera in 2012 [24]. Gillinov et al. [23] randomised 260 patients requiring mitral valve surgery who also presented with persistent or long-standing persistent AF into two groups: AF ablation or no ablation. The ablation group was further randomised to either PVI or bi-atrial Maze. They reported that significantly more patients were free from AF on 72-hour Holter monitoring at both 6
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and 12 months after AF ablation (63.2% vs 29.4%; p < 0.001) with no significant differences between bi-atrial Maze and PVI (61.0% vs 66.0%; p = 0.60). There were no significant differences in one-year mortality between groups (6.8% vs 8.7%; p = 0.55) however ablation was associated with significantly greater rates of pacemaker implantation at 12 months (21.5% vs 8.1%; p = 0.01). They found no significant difference in stroke rate at one year (3% vs 1.6%; p = 0.43). Budera et al. [24] randomised 224 patients undergoing valve and/or coronary surgery with atrial fibrillation (at least two episodes in the preceding six months) to left atrial ablation with left atrial appendage ligation versus a control receiving no arrhythmia ablation. They found significantly greater sinus rhythm with no AF on a 24-hour Holter monitor at 12 months in the ablation group (60.2% vs 35.5%; p = 0.002). However, this benefit was restricted to patients with long-standing persistent AF preoperatively (53.2% vs 13.9%; p < 0.001) with no significant difference in patients in paroxysmal or persistent AF preoperatively. They reported no significant difference at 12 months in either all-cause mortality (16.2% vs 17.4%; p = 0.80), stroke (2.7% vs 4.3%; p = 0.319) or pacemaker implantation (9.9% vs 13.0%; p = 0.512). Local Australian experience by Rahman et al. (2010) [25] reported a case series of 57 patients using the STAR ablation procedure[10_TD$IF][. The STAR procedure is a biatrial linear lesion set, using cryoablation to make the lesions in this study. The lesions on the left are from the inferior posterior mitral annulus to and around the left and right pulmonary veins and on the right between the SVC and IVC, to the coronary sinus and then to the tricuspid annulus. They found an 81% freedom for AF recurrence at 12 months, 3.5% mortality out to 24 months and 21% requiring pacemaker implantation. Several studies have attempted to measure quality of life (QoL) changes due to concomitant AF ablation surgery. Gillinov et al. [23] found a significantly improved rating of subjective AF symptoms at least daily (19.8% vs 45.2%; p < 0.001), but this study wasn’t blinded and found no significant differences in the other QoL measurements (SF-12 or NYHA). Jessurun et al. 2003 [26] compared the randomised addition of the Cox-Maze III ‘cut and sew’ technique to mitral valve surgery, and found no significant difference on the SF36 QoL questionnaire between patients receiving the CoxMaze procedure and those that didn’t. Van Breugel at al. 2010 [27] randomised patients undergoing coronary and/or valve surgery with the intervention group additionally receiving left atrial epicardial ablation. They found no difference between groups on the SF-36 questionnaire or the MFI-20 questionnaire, however on the EuroQoL classification there was a significantly greater deterioration at 12 months in the ‘Pain and Discomfort’ subscale in the control group compared to the ablation group. Chernyavskiy et al. 2016 [28], in a study undertaken on patients undergoing CABG, compared a modified mini-Maze procedure versus PVI versus CABG alone. They found significant improvements for the miniMaze procedure compared to CABG alone at two years in the categories of ‘Physical Functioning’ (73.6 vs 60; p = 0.02),
‘Role- Physical’ (65.7 vs 41.7; p = 0.024), ‘General Health’ (65.3 vs 52.8; p = 0.04) and ‘Role- Emotional’ (75.2 vs 51.1; p = 0.03). The PVI group was not significantly improved compared to CABG in any domain and was significantly worse in ‘Bodily Pain’. Thus, studies have generally not shown any consistent QoL improvements with the addition of surgical AF ablation to the planned procedure.
Stand-alone Procedures Although surgical ablation for AF is much less frequently performed as a stand-alone procedure compared to its use as a concomitant procedure [21], the initial report of the CoxMaze procedure was as a stand-alone procedure, and was successful in providing freedom for atrial fibrillation in all 22 patients at three months [7]. The open sternotomy, ‘cut and sew’ Cox-Maze III procedure has been used as a stand-alone procedure for the treatment of AF in some centres, with reports showing 95.9% freedom from atrial fibrillation at long-term follow-up with no significant difference in success rate compared to patients who had the Cox-Maze III performed as concomitant procedure (97.5% freedom from AF) [29]. However, it is important to note the differences in the rigour of follow-up which account for some variations in reported rates of freedom from AF. These differences and those relating to patient selection make the interpretation of reported results from single centre observational studies difficult. Due to the invasiveness of a median sternotomy, efforts have been made to reduce the invasiveness of stand-alone surgical ablation of AF. This has been assisted by the introduction of alternative energy sources for ablation, reducing the need for ‘cut and sew’ incisions. One approach to this has been via a right anterior mini-thoracotomy, with a case series of 41 patients having a Maze procedure with cryoablation on cardiopulmonary bypass (CBP) performed via this approach, showing 87.2% being in sinus rhythm at six months, no perioperative mortality, and a new pacemaker implantation rate of 10.8%. Alternative energy sources have also allowed epicardial surgical ablations, avoiding the use of CPB and potentially allowing totally thoracoscopic procedures. A 2015 systematic review of cases series and one RCT, found a rate of 72% for sinus rhythm at 12 months without the use of antiarrhythmic drugs in patients undergoing stand-alone epicardial ablation and a perioperative mortality rate of 0.5%, with 61.5% of studies using a totally thoracoscopic approach and the rest using either mini-thoracotomies or a mixture of both [4]. The RCT included in that review compared thoracoscopic epicardial PVI and left atrial appendage excision to percutaneous catheter PVI [30]. They found freedom from AF at 12 months without antiarrhythmic drugs was significantly greater with surgical compared with catheter ablation (65.6% vs 36.5; p = 0.0022) and there were no periprocedural deaths in either group, however surgical ablation came at significant risk of other adverse events, such as bleeding, pneumothorax, infection, stroke or pericardial effusion (23.0% vs 3.2%; p = 0.001).
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Comparison of Bi-atrial and Left Atrial Only Ablation A systematic review and meta-analysis by Phan et al. in 2015 [12], which didn’t include Gillinov et al. 2015 [23] but included two other RCTs along with cohort studies, compared bi-atrial vs left atrial only ablations in patients with AF undergoing cardiac surgery. Due to the lack of randomisation in the majority of the studies, the patients undergoing biatrial ablations were more likely to have permanent/persistent AF (88.6% vs 69%; p < 0.00001) and less likely to have paroxysmal AF (11.5% vs 31.4%; p < 0.00001) than patients undergoing only left sided ablation. There were no significant differences in cross clamp times between groups, however the bi-atrial group had significantly longer CPB time by 16 minutes (p = 0.0002). Freedom from atrial fibrillation at 12 months was greater in the bi-atrial group compared to left atrial only (77.8% vs 71.1%; p = 0.02). They found similar rates of sinus rhythm at discharge between bi-atrial and left atrial ablations (70.0% vs 74.7%; p = 0.21) however, there were greater rates of sinus rhythm for bi-atrial ablation in the studies reporting rhythms at six months (four studies; 74% vs 64%; p = 0.03) and 12 months (four studies; 77% vs 70%; p = 0.005). In the four studies reporting results at greater than 12 months, there was, again, no significant difference between the techniques. There were no significant differences in 30-day mortality between bi-atrial and left atrial ablation (4.1% vs 2.2%; p = 0.14) but there was a significantly greater rate of pacemaker implantation with bi-atrial ablation (7.0% vs 5.4%; p = 0.008). This review suggests that bi-atrial ablation may potentially be slightly more effective than left atrial only ablation at the cost of a greater rate of pacemaker implantation; however, there is a potential for significant biases in this review due the preponderance of non-randomised studies, significant differences in the type of AF preoperatively between groups and the heterogeneity of surgical techniques, leaving the answer to this question open to further research. Other potential reasons for a pacemaker postoperatively include underlying conductive system disease or sinus node dysfunction unmasked by the return to sinus rhythm or damage to the conductive system or its blood supply associated with the concomitant procedure.
Comparison of Energy Sources Multiple methods have been used to create electrically insulating linear lesions, from ‘cut and sewing’ to cryoablation, RF ablation and microwave ablation, however, there has been very limited head-to-head research comparing their relative efficacies. Phan et al. in 2015 [16] performed a systematic review and Bayesian network meta-analysis looking at the various techniques. Using a rank probability analysis, they found sinus rhythm beyond 12 months was similar between ‘cut and sew’, RF and microwave ablation, which all performed better than cryoablation. The traditional ‘cut and sew’ method ranked worse compared to the other techniques in terms of mortality, but was associated with significantly less stroke risk than microwave ablation, and
exhibited a trend towards less risk of pacemaker implantation compared to the other techniques. However, the authors regarded these results with caution due to the lack of direct comparisons between techniques. These comparisons are limited by variations in patient selection, the procedure performed, experience with the new technology and the rigour of follow-up. Together these factors limit our capacity to draw meaningful conclusions from the data available.
Hybrid Procedures In an attempt to improve outcomes for atrial fibrillation ablation, approaches combining surgical (usually epicardial) and catheter-based ablation have been proposed. The technique with the largest reported studies involves using both thoracoscopic surgical epicardial ablations combined with catheter-based conduction block testing and endocardial lesions during the same procedure. Pison et al. in 2014 [31] reported a case series using this technique on 78 patients. They reported an 87% success rate in obtaining sinus rhythm with no AF/flutter greater than 30 seconds on Holter monitoring off antiarrhythmic drugs at the end of follow-up of at least 12 months. However, they reported 13% of these patients in sinus rhythm required a subsequent catheter based ablation after their original hybrid procedure to obtain this result. They reported no mortalities or requirements for CPB and 1% reoperation rate for bleeding and 2% rate of pacemaker implantation. Gehi et al. [32] in 2013, reported a series of 101 patients undergoing a hybrid ablation, with the surgical ablation being performed pericardioscopically via a subxyphoid incision. They reported a rate of 66.3% freedom from AF at 12 months after a single procedure, which increased to 70.5% after repeat ablations, with 37% being on antiarrhythmic drugs. They had a 2% early postoperative mortality rate, 2% reoperation rate for bleeding and 2% had a pericardial tamponade. An alternative approach to performing hybrid ablation has been to perform a surgical ablation first, with a sequential catheter-based procedure at a later interval to assess the efficacy of the original ablation and perform additional ablations as required. Mahapatra et al. in 2011 [33] reported a case series of 15 patients in persistent AF having failed at least one antiarrhythmic drug and at least one catheter ablation. They performed a thoracoscopic epicardial ablation, then around four days later, the patients underwent a catheter-based procedure for endocardial ablations followed by an attempt to induce AF, which was further ablated as necessary. They were compared to a matched cohort of 30 patients who underwent additional catheter ablations instead. They reported, at a mean follow-up interval of 20.7 months, that patients experienced freedom from AF at a rate of 87.6% off antiarrhythmic drugs and 93.3% with antiarrhythmic drugs (compared with 53.3% and 56.7% respectively for the repeat catheter ablation group). They reported no complications in the hybrid ablation patients. Sequential procedures were also trialled by Muneretto et al. in 2012 [34] in a case series of 36 patients who had failed at least one antiarrhythmic drug.
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These patients then underwent right thoracosopic epicardial ablation followed by electrophysiological study 30 days post operation, during which 66.1% of patients required catheter ablations. They reported, after a mean follow-up of 30 months, that 77.7% of patients were in sinus rhythm and off antiarrhythmic drugs, rising to 91.6% with the use of antiarrhythmics. There were no complications.
Conclusion Surgical and hybrid ablation are two techniques available in the management of atrial fibrillation, in particular in symptomatic patients who have failed more conservative management options. Since their inception 30 years ago, techniques have progressed allowing for shorter and less invasive procedures, which are potentially more reproducible and hence more widely available. Surgical AF ablation in patients undergoing cardiac surgery for other reasons offers good outcomes in terms of rhythm control in exchange for a relatively minimal increase in operative time and risk, and we feel should be strongly considered for all patients undergoing cardiac surgery who present in AF. For patients who have failed antiarrhythmic drug therapy and/or catheter ablation, stand-alone surgical ablations offer a modality with relatively good rates of success, and with modern minimally invasive techniques have much less impact on the patient compared to the original Maze procedures. Hybrid surgical and catheter ablation is another option that has evolved within the last decade. Such approaches would be best accomplished in experienced centres currently until familiarity with the techniques grows. However, there is a relative lack of large, good quality randomised trials in the area of surgical and hybrid AF ablation, especially in the comparison of different techniques and ablation technologies. The optimal pattern of lesions beyond simple isolation of the pulmonary veins for patients with varying types of AF and underlying structural heart disease is unknown. There is also a need for more rigorous heart rhythm monitoring protocols in future studies. As with transcatheter ablation, it has been difficult to demonstrate a benefit for additional lesions beyond PVI, even for patients with persistent and long-standing persistent AF. The best outcomes are likely to be associated with achieving the goal of reliable electrical isolation of the pulmonary veins and possibly the posterior left atrium. The residual questions relating to these procedures represent an important area for future research to guide practice and fully establish the indications for surgical and hybrid ablation amongst the options for the management of atrial fibrillation.
Disclosures The authors report no external sources of funding for this study.
Acknowledgements The authors wish to thank Les Ashbourne for preparing the illustrations (Figures 1 and 2) in this manuscript.
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new intraoperative endocardial radiofrequency ablation procedure for atrial fibrillation. Journal of the American College of Cardiology 2000;35 (2):442–50. Phan K, Xie A, Kumar N, Wong S, Medi C, La Meir M, et al. Comparing energy sources for surgical ablation of atrial fibrillation: a Bayesian network meta-analysis of randomized, controlled trials. Eur J Cardiothorac Surg 2015;48(2):201–11. Gaynor SL, Diodato MD, Prasad SM, Ishii Y, Schuessler RB, Bailey MS, et al. A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation. J Thorac Cardiovasc Surg 2004;128(4):535–42. Wolf RK, Schneeberger EW, Osterday R, Miller D, Merrill W, Flege Jr JB, et al. Video-assisted bilateral pulmonary vein isolation and left atrial appendage exclusion for atrial fibrillation. J Thorac Cardiovasc Surg 2005;130(3):797–802. Yilmaz A, Van Putte BP, Van Boven WJ. Completely thoracoscopic bilateral pulmonary vein isolation and left atrial appendage exclusion for atrial fibrillation. J Thorac Cardiovasc Surg 2008;136(2):521–2. Akpinar B, Guden M, Sagbas E, Sanisoglu I, Ozbek U, Caynak B, et al. Combined radiofrequency modified maze and mitral valve procedure through a port access approach: early and mid-term results. Eur J ?A3B2 re 3j?Cardiothorac Surg 2003;24(2):223–30. Ad N, Suri RM, Gammie JS, Sheng S, O’Brien SM, Henry L. Surgical ablation of atrial fibrillation trends and outcomes in North America. J Thorac Cardiovasc Surg 2012;144(5):1051–60. Huffman MD, Karmali KN, Berendsen MA, Andrei AC, Kruse J, McCarthy PM, et al. Concomitant atrial fibrillation surgery for people undergoing cardiac surgery. Cochrane Database Syst Rev 2016;8:CD011814. Gillinov AM, Gelijns AC, Parides MK, DeRose Jr JJ, Moskowitz AJ, Voisine P, et al. Surgical ablation of atrial fibrillation during mitral-valve surgery. N Engl J Med 2015;372(15):1399–409. Budera P, Straka Z, Osmancik P, Vanek T, Jelinek S, Hlavicka J, et al. Comparison of cardiac surgery with left atrial surgical ablation vs. cardiac surgery without atrial ablation in patients with coronary and/ or valvular heart disease plus atrial fibrillation: final results of the PRAGUE-12 randomized multicentre study. Eur Heart J 2012;33 (21):2644–52. Rahman NM, Chard RB, Thomas SP. Outcomes for surgical treatment of atrial fibrillation using cryoablation during concomitant cardiac procedures. Ann Thorac Surg 2010;90(5):1523–7.
[26] Jessurun ER, van Hemel NM, Defauw JJ, Brutel De La Riviere A, Stofmeel MA, Kelder JC, et al. A randomized study of combining maze surgery for atrial fibrillation with mitral valve surgery. J Cardiovasc Surg (Torino) 2003;44(1):9–18. [27] Van Breugel HN, Nieman FH, Accord RE, Van Mastrigt GA, Nijs JF, Severens JL, et al. A prospective randomized multicenter comparison on health-related quality of life: the value of add-on arrhythmia surgery in patients with paroxysmal, permanent or persistent atrial fibrillation undergoing valvular and/or coronary bypass surgery. J Cardiovasc Electrophysiol 2010;21(5):511–20. [28] Chernyavskiy A, Kareva Y, Pak I, Rakhmonov S, Pokushalov E, Romanov A. Quality of Life after Surgical Ablation of Persistent Atrial Fibrillation: A Prospective Evaluation. Heart, Lung and Circulation 2016;25(4):378– 83. [29] Prasad SM, Maniar HS, Camillo CJ, Schuessler RB, Boineau JP, Sundt 3rd TM, et al. The Cox maze III procedure for atrial fibrillation: long-term efficacy in patients undergoing lone versus concomitant procedures. J Thorac Cardiovasc Surg 2003;126(6):1822–8. [30] Boersma LV, Castella M, van Boven W, Berruezo A, Yilmaz A, Nadal M, et al. Atrial fibrillation catheter ablation versus surgical ablation treatment (FAST): a 2-center randomized clinical trial. Circulation 2012;125 (1):23–30. [31] Pison L, Gelsomino S, Luca` F, Parise O, Maessen JG, Crijns HJGM, et al. Effectiveness and safety of simultaneous hybrid thoracoscopic and endocardial catheter ablation of lone atrial fibrillation. Annals of Cardiothoracic Surgery 2014;3(1):38–44. [32] Gehi AK, Mounsey JP, Pursell I, Landers M, Boyce K, Chung EH, et al. Hybrid epicardial-endocardial ablation using a pericardioscopic technique for the treatment of atrial fibrillation. Heart Rhythm 2013;10(1): 22–8. [33] Mahapatra S, LaPar DJ, Kamath S, Payne J, Bilchick KC, Mangrum JM, 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(6):1890–8. [34] Muneretto C, Bisleri G, Bontempi L, Curnis A. Durable staged hybrid ablation with thoracoscopic and percutaneous approach for treatment of long-standing atrial fibrillation: A 30-month assessment with continuous monitoring. The Journal of Thoracic and Cardiovascular Surgery 2012;144(6):1460–5.
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[3_TD$IF]REVIEW
Heart, Lung and Circulation (2017) xx, 1–7 1443-9506/04/$36.00 http://dx.doi.org/10.1016/j.hlc.2017.05.114
Surgical and Hybrid Ablation of Atrial Fibrillation Reece A. Davies, [4_TD$IF]MBBS (Hons), B. AppSc (Pthy) (Hons) a,c*, Saurabh Kumar, MBBS, PhD, FRACP b[,5_TD$IF] Richard B. Chard, MBBS (Hons), BDS (Hons), FRACS, FCSANZ a,c, Stuart P. Thomas, BMed, PhD, FRACP b,c a
Department of Cardiothoracic Surgery, Westmead Hospital, Sydney, NSW, Australia Department of Cardiology, Westmead Hospital, Sydney, NSW, Australia Faculty [6_TD$IF]of Medicine, University of Sydney, Sydney, NSW, Australia
b c
Atrial fibrillation (AF) is the most common arrhythmia in humans and is known to be associated with an increased risk of stroke, dementia, heart failure and mortality. Non-pharmacological therapy with ablation [8_TD$IF] using either surgical or percutaneous techniques is recommended in drug refractory AF. Early attempts to devise procedures to ablate AF and restore sinus rhythm culminated with the Cox-Maze procedure, the first truly successful procedure. Since then, ablation surgery has been conducted predominately as a concomitant procedure. The Cox Maze procedure is complex and technically demanding and has, therefore, been extensively modified with new techniques for creating the linear ablation lines, new lesion sets, minimally invasive surgical techniques and most recently hybrid surgical-catheter ablation techniques. Surgical ablation techniques result in a marked reduction in atrial fibrillation when compared to conventional therapy with only a small increase in procedural risk. However, further research is required to more accurately quantify those benefits and to determine the optimal lesion sets, specific to the underlying arrhythmia mechanism and the optimal energy sources for ablation. Keywords
Atrial fibrillation Surgical ablation Cox Maze
Introduction Atrial fibrillation (AF) is a common medical condition, with studies showing it is currently affecting over five million people in the United States and projections of its prevalence increasing to over 12 million by 2030 [1]. Atrial fibrillation is a risk factor for other diseases, such stroke and heart failure, and is associated with an increased risk of death even after controlling for concomitant diseases [2]. Initial attempts at surgical ablation for AF extend back to the 1980s, and include left atrial isolation and the Corridor procedure; however it wasn’t until 1987 and the development of the Cox-Maze procedure that success with surgical ablation was reliably achieved [3]. Despite its reliability, the traditional Cox-Maze procedure was a technically challenging operation requiring sternotomy, cardiopulmonary bypass and extensive suture lines. This has led to attempts to replicate its outcomes with a
procedure that is less technically demanding and potentially less invasive [4].
Indications The Heart Rhythm Society Task Force on Catheter and Surgical Ablation of Atrial Fibrillation (2012) released an expert consensus statement that included indications for surgical AF ablation [5]. They recommended that surgical ablation should be considered as an additional procedure in all patients with symptomatic AF, with or without trial of antiarrhythmic drugs, in cases where these patients were already scheduled to undergo cardiac surgery for other indications. This represents a Class IIa indication for paroxysmal, persistent and long-standing persistent AF failing antiarrhythmic drugs and paroxysmal and persistent
*Corresponding author at: Department of Cardiothoracic Surgery, Westmead Hospital, Cnr Hawkesbury and Darcy Roads, Westmead NSW 2145, Australia., Email: [email protected] © 2017 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.
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AF prior to a trial of antiarrhythmic drugs. It is a Class IIb indication for long-standing persistent AF prior to a trial of antiarrhythmic drugs. The Taskforce also reported that surgical ablation may be considered as a stand-alone procedure in patients who have failed antiarrhythmic drugs and who have either failed catheter ablation or who prefer surgery over catheter ablation (Class IIb indication). Stand-alone surgical ablation in patients who haven’t trialled antiarrhythmic drugs was not recommended (Class III indication). In 2016, the European Society of Cardiology (ESC), in collaboration with the European Association for Cardiothoracic Surgery, released guidelines for the management of AF [6]. In relation to the ablation of AF, they recommended catheter or surgical ablation should be considered for symptomatic control in all cases of persistent or long-standing persistent AF that is refractory to antiarrhythmic drugs (Class IIa indication). They also recommended that minimally invasive pulmonary vein isolation (PVI) should be considered where catheter ablation failed in symptomatic AF, and Maze surgery should be considered in refractory symptomatic AF or post ablation AF to reduce symptoms (Class IIa indications). In patients undergoing cardiac surgery, they recommended that Maze surgery should be considered in symptomatic patients with AF (class IIa) and may be considered in asymptomatic patients in AF (Class IIb). The ESC AF guidelines also proposed that AF surgery and extensive ablations should be discussed by an ‘Atrial Fibrillation Heart Team’ comprising a cardiologist with expertise in antiarrhythmic drug therapy, an interventional electrophysiologist and a cardiac surgeon with expertise in AF surgery.
Surgical Techniques The Cox-Maze III procedure uses a ‘cut and sew’ incision technique to create a ‘maze’ pathway from the sinoatrial node to the atrioventricular node. This allows activation of the
myocardium through corridors created by [9_TD$IF]incisions and anatomical obstacles. This approach reduces the contiguous muscle mass preventing activation of a larger area of atrial myocardium that may allow a re-entry circuit to perpetuate [7,8]. The Maze procedure is underpinned by the concept of the ‘multiple wavelet’ hypothesis of AF, which proposes that large re-entry circuits can only occur in situations where there is an adequate mass of conducting myocardium, slowed conduction velocities, and shortened refractory periods [9]. The lesions in the Cox-Maze III involve excision of the left and right atrial appendages, suture lines between the superior vena cava (SVC) and inferior vena cava (IVC) and between the IVC and tricuspid valve in the right atrium, suture lines isolating the pulmonary veins and posterior left atrium and a suture line from the mitral valve to the pulmonary veins [5]. Due to the complexity of the Cox-Maze III, it has had limited uptake and attempts have been made to simplify it to make it more accessible. One such approach is the Cox-Maze IV (Figure 1A and B), wherein the majority of the lesions from the Cox-Maze III are replaced with ablation lesions from energy sources [10]. The Cox Maze IV aims to reduce the procedural complexity and shorten procedural time by reducing the time required to create atrial lesions, potentially allowing the use of minimally invasive approaches, such as via minithoracotomy [11]. Increasing understanding of the pathophysiology of AF, in particular its origins, which are frequently in the pulmonary veins, has led to proposals of further modifications and simplifications to the technique. These have included leftsided Maze procedures [12,13] and procedures that purely isolate the pulmonary veins (PVI) [14] (Figure 2). The intent of these procedures is to prevent the trigger sites of AF from communicating electrically with remaining atrial tissue, therefore preventing the initiation of AF. Other modifications of the original Cox-Maze procedure have focussed on alternate energy sources to create the lesions. Although a manual incision may be the ideal method
Figure 1 Lesion set for Cox-Maze IV: A- Left-sided lesions. B- Right-sided lesions.
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Figure 3 Intraoperative picture of cryoablation being used in a Star procedure. Cryo probe marked with (*). Figure 2 Bipolar Radiofrequency ablation for Pulmonary Vein Isolation.
for the creation of durable, permanent atrial lesions, the procedural morbidity associated with such an approach motivated the pursuit for alternate energy sources. However, a major compromise to a potential reduction in procedural complexity and duration is a risk of incomplete atrial lesion formation and, thus, recurrence of organised atrial arrhythmias due to re-entry in and around gaps within the ablation lines that may require additional percutaneous catheter ablation procedures [15]. Progress in the techniques employed to create linear lesions has partly been driven by the desire to create durably transmural lesions similar to those achieved by linear incision of the atria. The energy sources explored included radiofrequency ablation, cryoablation and microwave ablation [16]. The Cox-Maze IV is an example of this, with the majority of the lesion lines replaced with radiofrequency and cryoablation (Figure 3) enabling less complex and shorter operations [10,17]. The advent of alternative energy sources has enabled minimally invasive techniques, such as Video Assisted Thoracoscopic Surgery (VATS), to be developed for use in standalone operations for AF [18,19] and with concomitant minimally invasive cardiac surgery [20], typically applying epicardial lesions such as radiofrequency PVI.
Surgical Outcomes Concomitant Procedures Surgical ablation of AF is most commonly performed in patients undergoing cardiac surgery for other reasons, with this category of procedure accounting for just under 95% of all surgical ablations for AF in the United States between 2005 and 2010 [21]. Of the 11% of patients undergoing cardiac surgery in that period who also presented with AF, approximately 40% had a concomitant surgical ablation. This percentage, however,
varied widely depending on the primary operation, with 61.5% of patients in AF undergoing mitral valve surgery receiving an ablation compared with 33.9% of those undergoing an aortic valve replacement (AVR) and 27.5% undergoing coronary artery bypass grafts (CABG) [21]. In 2016 the Cochrane Collaboration performed a systematic review and meta-analysis of 22 randomised control trials (RCT) of patients undergoing concomitant cardiac surgery, exploring outcomes of surgical AF ablation procedures versus control groups receiving no ablation [22]. They found no significant difference in 30-day mortality (3.1% for ablation vs 2.3% for control; RR 1.25[95% confidence interval: 0.71–2.20]) or all-cause mortality (7% vs 6.6%; RR 1.14 [0.81–1.59]). They found that patients who underwent AF ablation were significantly more likely to be free from AF, atrial flutter or atrial tachycardia at three months compared to controls, both without the use of antiarrhythmic drugs (51.0% vs 24.1%; RR 2.04 [1.63–2.55]) and with antiarrhythmic drugs (60.1% vs 24.4%; RR 2.46 [2.16–2.80]). However, they reported a significantly greater rate of pacemaker implantation in patients who had undergone AF ablation (6.9% vs 4.1%; RR 1.69 [1.12–2.54]). There was no significant difference in the stroke rate (3.87% vs 3.74; RR 1.05 [0.60–1.83]). The authors cautioned about the validity of their results due to most studies being small with significant sources of bias, leading to most of their conclusions to be assessed as low to moderate quality evidence. They were unable to comment on the relative effectiveness of different lesion sets. The two largest studies in the Cochrane review, and the only studies with over 200 patients, were by Gillinov et al. in 2015 [23] and Budera in 2012 [24]. Gillinov et al. [23] randomised 260 patients requiring mitral valve surgery who also presented with persistent or long-standing persistent AF into two groups: AF ablation or no ablation. The ablation group was further randomised to either PVI or bi-atrial Maze. They reported that significantly more patients were free from AF on 72-hour Holter monitoring at both 6
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and 12 months after AF ablation (63.2% vs 29.4%; p < 0.001) with no significant differences between bi-atrial Maze and PVI (61.0% vs 66.0%; p = 0.60). There were no significant differences in one-year mortality between groups (6.8% vs 8.7%; p = 0.55) however ablation was associated with significantly greater rates of pacemaker implantation at 12 months (21.5% vs 8.1%; p = 0.01). They found no significant difference in stroke rate at one year (3% vs 1.6%; p = 0.43). Budera et al. [24] randomised 224 patients undergoing valve and/or coronary surgery with atrial fibrillation (at least two episodes in the preceding six months) to left atrial ablation with left atrial appendage ligation versus a control receiving no arrhythmia ablation. They found significantly greater sinus rhythm with no AF on a 24-hour Holter monitor at 12 months in the ablation group (60.2% vs 35.5%; p = 0.002). However, this benefit was restricted to patients with long-standing persistent AF preoperatively (53.2% vs 13.9%; p < 0.001) with no significant difference in patients in paroxysmal or persistent AF preoperatively. They reported no significant difference at 12 months in either all-cause mortality (16.2% vs 17.4%; p = 0.80), stroke (2.7% vs 4.3%; p = 0.319) or pacemaker implantation (9.9% vs 13.0%; p = 0.512). Local Australian experience by Rahman et al. (2010) [25] reported a case series of 57 patients using the STAR ablation procedure[10_TD$IF][. The STAR procedure is a biatrial linear lesion set, using cryoablation to make the lesions in this study. The lesions on the left are from the inferior posterior mitral annulus to and around the left and right pulmonary veins and on the right between the SVC and IVC, to the coronary sinus and then to the tricuspid annulus. They found an 81% freedom for AF recurrence at 12 months, 3.5% mortality out to 24 months and 21% requiring pacemaker implantation. Several studies have attempted to measure quality of life (QoL) changes due to concomitant AF ablation surgery. Gillinov et al. [23] found a significantly improved rating of subjective AF symptoms at least daily (19.8% vs 45.2%; p < 0.001), but this study wasn’t blinded and found no significant differences in the other QoL measurements (SF-12 or NYHA). Jessurun et al. 2003 [26] compared the randomised addition of the Cox-Maze III ‘cut and sew’ technique to mitral valve surgery, and found no significant difference on the SF36 QoL questionnaire between patients receiving the CoxMaze procedure and those that didn’t. Van Breugel at al. 2010 [27] randomised patients undergoing coronary and/or valve surgery with the intervention group additionally receiving left atrial epicardial ablation. They found no difference between groups on the SF-36 questionnaire or the MFI-20 questionnaire, however on the EuroQoL classification there was a significantly greater deterioration at 12 months in the ‘Pain and Discomfort’ subscale in the control group compared to the ablation group. Chernyavskiy et al. 2016 [28], in a study undertaken on patients undergoing CABG, compared a modified mini-Maze procedure versus PVI versus CABG alone. They found significant improvements for the miniMaze procedure compared to CABG alone at two years in the categories of ‘Physical Functioning’ (73.6 vs 60; p = 0.02),
‘Role- Physical’ (65.7 vs 41.7; p = 0.024), ‘General Health’ (65.3 vs 52.8; p = 0.04) and ‘Role- Emotional’ (75.2 vs 51.1; p = 0.03). The PVI group was not significantly improved compared to CABG in any domain and was significantly worse in ‘Bodily Pain’. Thus, studies have generally not shown any consistent QoL improvements with the addition of surgical AF ablation to the planned procedure.
Stand-alone Procedures Although surgical ablation for AF is much less frequently performed as a stand-alone procedure compared to its use as a concomitant procedure [21], the initial report of the CoxMaze procedure was as a stand-alone procedure, and was successful in providing freedom for atrial fibrillation in all 22 patients at three months [7]. The open sternotomy, ‘cut and sew’ Cox-Maze III procedure has been used as a stand-alone procedure for the treatment of AF in some centres, with reports showing 95.9% freedom from atrial fibrillation at long-term follow-up with no significant difference in success rate compared to patients who had the Cox-Maze III performed as concomitant procedure (97.5% freedom from AF) [29]. However, it is important to note the differences in the rigour of follow-up which account for some variations in reported rates of freedom from AF. These differences and those relating to patient selection make the interpretation of reported results from single centre observational studies difficult. Due to the invasiveness of a median sternotomy, efforts have been made to reduce the invasiveness of stand-alone surgical ablation of AF. This has been assisted by the introduction of alternative energy sources for ablation, reducing the need for ‘cut and sew’ incisions. One approach to this has been via a right anterior mini-thoracotomy, with a case series of 41 patients having a Maze procedure with cryoablation on cardiopulmonary bypass (CBP) performed via this approach, showing 87.2% being in sinus rhythm at six months, no perioperative mortality, and a new pacemaker implantation rate of 10.8%. Alternative energy sources have also allowed epicardial surgical ablations, avoiding the use of CPB and potentially allowing totally thoracoscopic procedures. A 2015 systematic review of cases series and one RCT, found a rate of 72% for sinus rhythm at 12 months without the use of antiarrhythmic drugs in patients undergoing stand-alone epicardial ablation and a perioperative mortality rate of 0.5%, with 61.5% of studies using a totally thoracoscopic approach and the rest using either mini-thoracotomies or a mixture of both [4]. The RCT included in that review compared thoracoscopic epicardial PVI and left atrial appendage excision to percutaneous catheter PVI [30]. They found freedom from AF at 12 months without antiarrhythmic drugs was significantly greater with surgical compared with catheter ablation (65.6% vs 36.5; p = 0.0022) and there were no periprocedural deaths in either group, however surgical ablation came at significant risk of other adverse events, such as bleeding, pneumothorax, infection, stroke or pericardial effusion (23.0% vs 3.2%; p = 0.001).
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Comparison of Bi-atrial and Left Atrial Only Ablation A systematic review and meta-analysis by Phan et al. in 2015 [12], which didn’t include Gillinov et al. 2015 [23] but included two other RCTs along with cohort studies, compared bi-atrial vs left atrial only ablations in patients with AF undergoing cardiac surgery. Due to the lack of randomisation in the majority of the studies, the patients undergoing biatrial ablations were more likely to have permanent/persistent AF (88.6% vs 69%; p < 0.00001) and less likely to have paroxysmal AF (11.5% vs 31.4%; p < 0.00001) than patients undergoing only left sided ablation. There were no significant differences in cross clamp times between groups, however the bi-atrial group had significantly longer CPB time by 16 minutes (p = 0.0002). Freedom from atrial fibrillation at 12 months was greater in the bi-atrial group compared to left atrial only (77.8% vs 71.1%; p = 0.02). They found similar rates of sinus rhythm at discharge between bi-atrial and left atrial ablations (70.0% vs 74.7%; p = 0.21) however, there were greater rates of sinus rhythm for bi-atrial ablation in the studies reporting rhythms at six months (four studies; 74% vs 64%; p = 0.03) and 12 months (four studies; 77% vs 70%; p = 0.005). In the four studies reporting results at greater than 12 months, there was, again, no significant difference between the techniques. There were no significant differences in 30-day mortality between bi-atrial and left atrial ablation (4.1% vs 2.2%; p = 0.14) but there was a significantly greater rate of pacemaker implantation with bi-atrial ablation (7.0% vs 5.4%; p = 0.008). This review suggests that bi-atrial ablation may potentially be slightly more effective than left atrial only ablation at the cost of a greater rate of pacemaker implantation; however, there is a potential for significant biases in this review due the preponderance of non-randomised studies, significant differences in the type of AF preoperatively between groups and the heterogeneity of surgical techniques, leaving the answer to this question open to further research. Other potential reasons for a pacemaker postoperatively include underlying conductive system disease or sinus node dysfunction unmasked by the return to sinus rhythm or damage to the conductive system or its blood supply associated with the concomitant procedure.
Comparison of Energy Sources Multiple methods have been used to create electrically insulating linear lesions, from ‘cut and sewing’ to cryoablation, RF ablation and microwave ablation, however, there has been very limited head-to-head research comparing their relative efficacies. Phan et al. in 2015 [16] performed a systematic review and Bayesian network meta-analysis looking at the various techniques. Using a rank probability analysis, they found sinus rhythm beyond 12 months was similar between ‘cut and sew’, RF and microwave ablation, which all performed better than cryoablation. The traditional ‘cut and sew’ method ranked worse compared to the other techniques in terms of mortality, but was associated with significantly less stroke risk than microwave ablation, and
exhibited a trend towards less risk of pacemaker implantation compared to the other techniques. However, the authors regarded these results with caution due to the lack of direct comparisons between techniques. These comparisons are limited by variations in patient selection, the procedure performed, experience with the new technology and the rigour of follow-up. Together these factors limit our capacity to draw meaningful conclusions from the data available.
Hybrid Procedures In an attempt to improve outcomes for atrial fibrillation ablation, approaches combining surgical (usually epicardial) and catheter-based ablation have been proposed. The technique with the largest reported studies involves using both thoracoscopic surgical epicardial ablations combined with catheter-based conduction block testing and endocardial lesions during the same procedure. Pison et al. in 2014 [31] reported a case series using this technique on 78 patients. They reported an 87% success rate in obtaining sinus rhythm with no AF/flutter greater than 30 seconds on Holter monitoring off antiarrhythmic drugs at the end of follow-up of at least 12 months. However, they reported 13% of these patients in sinus rhythm required a subsequent catheter based ablation after their original hybrid procedure to obtain this result. They reported no mortalities or requirements for CPB and 1% reoperation rate for bleeding and 2% rate of pacemaker implantation. Gehi et al. [32] in 2013, reported a series of 101 patients undergoing a hybrid ablation, with the surgical ablation being performed pericardioscopically via a subxyphoid incision. They reported a rate of 66.3% freedom from AF at 12 months after a single procedure, which increased to 70.5% after repeat ablations, with 37% being on antiarrhythmic drugs. They had a 2% early postoperative mortality rate, 2% reoperation rate for bleeding and 2% had a pericardial tamponade. An alternative approach to performing hybrid ablation has been to perform a surgical ablation first, with a sequential catheter-based procedure at a later interval to assess the efficacy of the original ablation and perform additional ablations as required. Mahapatra et al. in 2011 [33] reported a case series of 15 patients in persistent AF having failed at least one antiarrhythmic drug and at least one catheter ablation. They performed a thoracoscopic epicardial ablation, then around four days later, the patients underwent a catheter-based procedure for endocardial ablations followed by an attempt to induce AF, which was further ablated as necessary. They were compared to a matched cohort of 30 patients who underwent additional catheter ablations instead. They reported, at a mean follow-up interval of 20.7 months, that patients experienced freedom from AF at a rate of 87.6% off antiarrhythmic drugs and 93.3% with antiarrhythmic drugs (compared with 53.3% and 56.7% respectively for the repeat catheter ablation group). They reported no complications in the hybrid ablation patients. Sequential procedures were also trialled by Muneretto et al. in 2012 [34] in a case series of 36 patients who had failed at least one antiarrhythmic drug.
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These patients then underwent right thoracosopic epicardial ablation followed by electrophysiological study 30 days post operation, during which 66.1% of patients required catheter ablations. They reported, after a mean follow-up of 30 months, that 77.7% of patients were in sinus rhythm and off antiarrhythmic drugs, rising to 91.6% with the use of antiarrhythmics. There were no complications.
Conclusion Surgical and hybrid ablation are two techniques available in the management of atrial fibrillation, in particular in symptomatic patients who have failed more conservative management options. Since their inception 30 years ago, techniques have progressed allowing for shorter and less invasive procedures, which are potentially more reproducible and hence more widely available. Surgical AF ablation in patients undergoing cardiac surgery for other reasons offers good outcomes in terms of rhythm control in exchange for a relatively minimal increase in operative time and risk, and we feel should be strongly considered for all patients undergoing cardiac surgery who present in AF. For patients who have failed antiarrhythmic drug therapy and/or catheter ablation, stand-alone surgical ablations offer a modality with relatively good rates of success, and with modern minimally invasive techniques have much less impact on the patient compared to the original Maze procedures. Hybrid surgical and catheter ablation is another option that has evolved within the last decade. Such approaches would be best accomplished in experienced centres currently until familiarity with the techniques grows. However, there is a relative lack of large, good quality randomised trials in the area of surgical and hybrid AF ablation, especially in the comparison of different techniques and ablation technologies. The optimal pattern of lesions beyond simple isolation of the pulmonary veins for patients with varying types of AF and underlying structural heart disease is unknown. There is also a need for more rigorous heart rhythm monitoring protocols in future studies. As with transcatheter ablation, it has been difficult to demonstrate a benefit for additional lesions beyond PVI, even for patients with persistent and long-standing persistent AF. The best outcomes are likely to be associated with achieving the goal of reliable electrical isolation of the pulmonary veins and possibly the posterior left atrium. The residual questions relating to these procedures represent an important area for future research to guide practice and fully establish the indications for surgical and hybrid ablation amongst the options for the management of atrial fibrillation.
Disclosures The authors report no external sources of funding for this study.
Acknowledgements The authors wish to thank Les Ashbourne for preparing the illustrations (Figures 1 and 2) in this manuscript.
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