The Cox-Maze procedure: What lesions and why

Abstract

Central MessageIn a successful Maze, all lesions must be fully transmural, the entirety of the posterior LA must be isolated, and the LAA must be excluded. In a successful Maze, all lesions must be fully transmural, the entirety of the posterior LA must be isolated, and the LAA must be excluded. The Cox-Maze procedure (CMP) is the most effective treatment for atrial fibrillation (AF). Despite this, many patients with AF undergoing cardiac surgery for other pathologies are not offered a concomitant CMP, whereas other patients with lone AF are not offered surgical intervention at all.1Mehaffey J.H. Krebs E. Hawkins R.B. Charles E.J. Tsutsui S. Kron I.L. et al.Variability and utilization of concomitant atrial fibrillation ablation during mitral valve surgery.Ann Thorac Surg. 2021; 111: 29-34Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar Part of the original reticence to perform the CMP lay in the technical complexity of the “cut-and-sew” Maze (ie, the CMP III), in which multiple incisions were made in both atria to create conduction block. The introduction of radiofrequency (RF) and cryoablation devices has made the latest iteration of the CMP—the CMP-IV—not only technically simpler but also more time efficient, thereby decreasing cardiopulmonary bypass (CPB) times and procedural morbidity and mortality.2Weimar T. Schena S. Bailey M.S. Maniar H.S. Schuessler R.B. Cox J.L. et al.The Cox-Maze procedure for lone atrial fibrillation: a single-center experience over 2 decades.Circ Arrhythm Electrophysiol. 2012; 5: 8-14Crossref PubMed Scopus (183) Google Scholar However, the number of CMPs performed today still falls short of the number of patients who would benefit from this procedure. It has been estimated that approximately one-third of patients undergoing mitral valve surgery who have a history of AF do not receive the CMP.1Mehaffey J.H. Krebs E. Hawkins R.B. Charles E.J. Tsutsui S. Kron I.L. et al.Variability and utilization of concomitant atrial fibrillation ablation during mitral valve surgery.Ann Thorac Surg. 2021; 111: 29-34Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar This is despite multiple societies' recommendations for the management of AF, including a class 1A recommendation from the Society of Thoracic Surgery.3Badhwar V. Rankin J.S. Damiano Jr., R.J. Gillinov A.M. Bakaeen F.G. Edgerton J.R. et al.The Society of Thoracic Surgeons 2017 clinical practice guidelines for the surgical treatment of atrial fibrillation.Ann Thorac Surg. 2017; 103: 329-341Abstract Full Text Full Text PDF PubMed Scopus (322) Google Scholar Lingering hesitancy to perform the CMP is in part due to surgeon inexperience and lack of comfort, but may also be due to a lack of understanding of the foundational concepts of the Maze and an unfamiliarity with the location and function of each individual lesion. This article aims to provide a clear description of the biatrial lesion set and the importance of the individual lesions. We aim to do this in 3 parts: (1) a description of the goals of the CMP; (2) a description of the criteria required for successful lesions; and (3) a description of each lesion and its importance/function. We will end with a brief discussion of the various ablation modalities available with which to make Maze lesions. This is not a step-by-step description of how to perform the Maze. Our group has published multiple articles describing our operative technique in detail, both via sternotomy (Video 1) and via right minithoracotomy (Video 2).4MacGregor R.M. Khiabani A.J. Damiano R.J. The surgical treatment of atrial fibrillation via median sternotomy.Oper Tech Thorac Cardiovasc Surg. 2019; 24: 19-37Abstract Full Text Full Text PDF Scopus (6) Google Scholar,5Robertson J.O. Saint L.L. Leidenfrost J.E. Damiano Jr., R.J. Illustrated techniques for performing the Cox-Maze IV procedure through a right mini-thoracotomy.Ann Cardiothorac Surg. 2014; 3: 105-116PubMed Google Scholar Instead, our goal is to enable a conceptual understanding of the electrical rationale for a biatrial CMP. The major goal of the CMP is termination of AF and restoration of normal sinus rhythm. A secondary goal is the excision or exclusion of the left atrial appendage (LAA) to prevent strokes, the most dreaded complication of AF. The intended hemodynamic outcomes are (1) restoration of the atrial kick with subsequent improvement in cardiac output and amelioration of heart failure, and (2) cessation of stagnant blood flow in the fibrillating left atrium (LA) that serves as a nidus for thromboemboli. The core tenet of the CMP is that a pattern of lesions made in both atria block the conduction of aberrant electrical impulses, both by isolating arrhythmogenic foci and by interrupting micro- and macro-reentrant circuits, thereby preventing sustained AF. The ultimate effect is to create a constrained pathway through which electrical impulses travel from the sinoatrial node complex (SAN) to the atrioventricular node (AVN) and activate the majority of atrial tissue with the crucial exception of the posterior LA (including the region of the pulmonary veins [PVs]). The posterior LA is isolated in its entirety given this area's propensity for developing arrhythmogenic foci. There are specific criteria a lesion must meet to consistently and reproducibly block electrical conduction. Even if all lesions of the CMP are made, if each individual lesion does not meet these criteria, the CMP as a whole may be incomplete and ineffective. Fortunately, these criteria are straightforward and are as follows:1.Each lesion must be transmural throughout its entirety. Our laboratory and others have shown that even a very small gap in a lesion can allow conduction of aberrant electrical impulses.6Melby S.J. Lee A.M. Zierer A. Kaiser S.P. Livhits M.J. Boineau J.P. et al.Atrial fibrillation propagates through gaps in ablation lines: implications for ablative treatment of atrial fibrillation.Heart Rhythm. 2008; 5: 1296-1301Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar Furthermore, these small gaps may actually be proarrhythmic given that they often result in slow conduction of these impulses, increasing the likelihood of maintaining reentrant circuits.2.Each lesion must originate from or end in tissue that is not electrically conductive. Electrically nonconductive tissue can either be another lesion or tissue that is natively nonconductive such as a valve annulus or vena cava. This is necessary to block conduction, particularly of the rotors and micro- and macro-reentrant circuits that may be needed to sustain AF. Lesions that are not anchored on at least one side by electrically nonconductive tissue can actually serve as a nidus for reentrant circuits that can rotate around the lesions creating atypical atrial flutters.7Gillette P.C. Kugler J.D. Garson Jr., A. Gutgesell H.P. Duff D.F. McNamara D.G. et al.Mechanisms of cardiac arrhythmias after the Mustard operation for transposition of the great arteries.Am J Cardiol. 1980; 45: 1225-1230Abstract Full Text PDF PubMed Scopus (125) Google Scholar We will handle the latter criteria first: where to place your lesions and why. The complete biatrial CMP lesion set is described next: management of the LAA, isolation of the posterior LA, completion of the LA lesion set, and the right atrial (RA) lesion set, with numbering in parentheses corresponding to Figure 1. By ordering the lesion sets and their descriptions in this manner, we aim to focus on the conceptual importance of each lesion/set of lesions and how the final pattern of ablation lines in the biatrial CMP restricts electrical wavefronts to prevent arrhythmias. Of note, this is different from the order in which we create these lesions intraoperatively, which is dictated primarily by the practicalities of anatomy and operative approach. A brief description of our operative procedure (ie, a list of the lesions in the order in which we create them intraoperatively) is shown in Table E1. The management of the LAA is essential to performing a CMP. Most important, because the majority of thromboembolic strokes in patients with AF originate in the LAA, removal of the LAA significantly decreases the risk of stroke or systemic embolism. This has been observed both in retrospective case series and prospective, randomized trials.8Whitlock R.P. Belley-Cote E.P. Paparella D. Healey J.S. Brady K. Sharma M. et al.Left atrial appendage occlusion during cardiac surgery to prevent stroke.N Engl J Med. 2021; 384: 2081-2091Crossref PubMed Scopus (238) Google Scholar,9Pet M. Robertson J.O. Bailey M. Guthrie T.J. Moon M.R. Lawton J.S. et al.The impact of CHADS2 score on late stroke after the Cox maze procedure.J Thorac Cardiovasc Surg. 2013; 146: 85-89Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar In our experience, we have found either excision or application of an epicardial exclusion device (AtriClip, AtriCure Inc) to be the most effective means of eliminating the LAA. Unfortunately, stapler exclusion, oversewing, and ligation have had reasonably high failure rates.10Squiers J.J. Edgerton J.R. Surgical closure of the left atrial appendage: the past, the present, the future.J Atr Fibrillation. 2018; 10: 1642Crossref PubMed Google Scholar,11Lee R. Jivan A. Kruse J. McGee Jr., E.C. Malaisrie S.C. Bernstein R. et al.Late neurologic events after surgery for atrial fibrillation: rare but relevant.Ann Thorac Surg. 2013; 95: 126-132Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar The appendage clip has had promising intraoperative and late success rates of both complete LAA occlusion and safety.12Ailawadi G. Gerdisch M.W. Harvey R.L. Hooker R.L. Damiano Jr., R.J. Salamon T. et al.Exclusion of the left atrial appendage with a novel device: early results of a multicenter trial.J Thorac Cardiovasc Surg. 2011; 142 (1009.e1): 1002-1009Abstract Full Text Full Text PDF PubMed Scopus (185) Google Scholar,13Emmert M.Y. Puippe G. Baumuller S. Alkadhi H. Landmesser U. Plass A. et al.Safe, effective and durable epicardial left atrial appendage clip occlusion in patients with atrial fibrillation undergoing cardiac surgery: first long-term results from a prospective device trial..Eur J Cardio Thorac Surg. 2014; 45: 126-131Crossref PubMed Scopus (94) Google Scholar In our hands, and in either minimally invasive or beating-heart applications, clipping the LAA is the most reasonable approach. Whether the LAA is excised or clipped, it is important to leave no stump, because residual LAA tissue (in communication with the LA) has been shown to be prothrombotic.14Al-Saady N.M. Obel O.A. Camm A.J. Left atrial appendage: structure, function, and role in thromboembolism.Heart. 1999; 82: 547-554Crossref PubMed Scopus (498) Google Scholar Even in the absence of a stump, the LAA exclusion line if not properly anchored in electrically nonconductive tissue can still serve as a nidus for a flutter circuit.7Gillette P.C. Kugler J.D. Garson Jr., A. Gutgesell H.P. Duff D.F. McNamara D.G. et al.Mechanisms of cardiac arrhythmias after the Mustard operation for transposition of the great arteries.Am J Cardiol. 1980; 45: 1225-1230Abstract Full Text PDF PubMed Scopus (125) Google Scholar Given this, we also create a lesion from the excluded LAA to the left PV lesion (as described next), connecting the LAA exclusion to the electrically excluded posterior LA. This is the single most important part of the CMP (Figure 2). The posterior LA, including the PVs, has consistently been identified as important to both the initiation and maintenance of AF. Catheter-based electrophysiologic studies have shown that between 87% and 96% of ectopic atrial foci in patients with AF are located within this region.15Haissaguerre M. Jais P. Shah D.C. Takahashi A. Hocini M. Quiniou G. et al.Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins.N Engl J Med. 1998; 339: 659-666Crossref PubMed Scopus (6519) Google Scholar,16Lin W.S. Tai C.T. Hsieh M.H. Tsai C.F. Lin Y.K. Tsao H.M. et al.Catheter ablation of paroxysmal atrial fibrillation initiated by non-pulmonary vein ectopy.Circulation. 2003; 107: 3176-3183Crossref PubMed Scopus (613) Google Scholar Moreover, our data have shown that without complete isolation of the posterior LA, the remainder of the CMP lesions only lead to a 33% freedom from recurrent atrial tachyarrhythmias at 5 years.17Henn M.C. Lancaster T.S. Miller J.R. Sinn L.A. Schuessler R.B. Moon M.R. et al.Late outcomes after the Cox maze IV procedure for atrial fibrillation.J Thorac Cardiovasc Surg. 2015; 150 (1178.e1-2): 1168-1176Abstract Full Text Full Text PDF PubMed Scopus (103) Google Scholar A complete box electrically isolates the whole posterior LA by encompassing the entirety of the PVs and most, if not all, of the posterior LA tissue between the PVs. The term “pulmonary vein isolation” (PVI) is inconsistently used, but in the context of surgical ablation most commonly refers to creating 2 separate ablation lesions—one around the left-sided PVs, one around the right-sided PVs—that are not connected to each other. This results in electrical isolation of the left and right PVs, but does not isolate any of the rest of the posterior LA between the PVs (Figure 3). When so defined, has been shown to be an treatment for AF, with success rates no different ablation but with randomized with surgical this A. T.J. R.J. J.J. et of surgical ablation for paroxysmal and early atrial Arrhythm Electrophysiol. 2018; PubMed Scopus Google M. D. J. et ablation for atrial fibrillation: long-term of the randomized 2019; PubMed Scopus Google Scholar Our data on an incomplete box also the of given the 33% of atrial freedom patients who all had M.C. Lancaster T.S. Miller J.R. Sinn L.A. Schuessler R.B. Moon M.R. et al.Late outcomes after the Cox maze IV procedure for atrial fibrillation.J Thorac Cardiovasc Surg. 2015; 150 (1178.e1-2): 1168-1176Abstract Full Text Full Text PDF PubMed Scopus (103) Google Scholar The role for the box isolation as a lesion has not been because no clinical has this A lesion connecting the box to the mitral which is electrically be This has been the and is to prevent both and atypical LA S. Hocini M. M. S. et al.Left atrial lesions are required for successful treatment of atrial J. 2008; PubMed Scopus Google Scholar The sinus be at this the latter is not the sinus can aberrant electrical to LA flutter around the mitral A. R. M. atrial flutter originating in the sinus after radiofrequency ablation of atrial Electrophysiol. PubMed Scopus Google Scholar The goal of the lesion set is to create a complete line of block from the vena to the vena and this line to the natively nonconductive tissue of the and the annulus to the right atrial appendage not the or (Figure There is to the importance of the the in the initiation and maintenance of atrial flutter as as D.C. P. M. S. Takahashi A. Hocini M. et of the atrial flutter in the right PubMed Scopus Google Schuessler R.B. Damiano Jr., R.J. et of epicardial in with atrial fibrillation PubMed Scopus Google Scholar We have shown that to one-third of AF originate in the Schuessler R.B. Damiano Jr., R.J. et of epicardial in with atrial fibrillation PubMed Scopus Google Scholar Moreover, the late results of surgical ablation have been shown after biatrial lesion M.C. Lancaster T.S. Miller J.R. Sinn L.A. Schuessler R.B. Moon M.R. et al.Late outcomes after the Cox maze IV procedure for atrial fibrillation.J Thorac Cardiovasc Surg. 2015; 150 (1178.e1-2): 1168-1176Abstract Full Text Full Text PDF PubMed Scopus (103) Google Scholar discussion of the for a is the of this particularly in to performing a biatrial CMP in with other cardiac and is on surgeon experience and It is important to that the 2 for after a biatrial CMP are sinus and complete heart block after a CMP is most secondary to intraoperative that during a concomitant that not due to the CMP The CMP does not any ablation in the of the is most at and by the CMP. The of with and of AF. the we have found that approximately of our patients with approximately of these patients for and the other for A.J. R.M. J.L. Sinn L.A. Maniar H.S. et al.The long-term outcomes and of the Cox-Maze IV procedure for atrial fibrillation.J Thorac Cardiovasc Surg. Full Text Full Text PDF PubMed Scopus Google Scholar We do not or function all patients have which are or patients have had time to from There is a high of early due to and we at least 5 a The right have a in to the of the and is transmural and is electrically We only perform a right via a When performing the CMP via a right we create all right-sided lesions through The vena lesions a line that is to the and that the and lesions are made as posterior and as to to the the and the by the lesions must the vena to the vena line in its entirety and in electrically nonconductive This connecting line the lesions to the electrically tissue of the annulus first of the and This a ablation and is important for the of atrial F.G. M. A. J.L. ablation of the vena valve in atrial J Cardiol. Full Text PDF PubMed Scopus Google Scholar This lesion the line of block the connecting the annulus to the This of macro-reentrant circuits around the and may be particularly important in patients with to allow for of this lesion is via a small at the of the We create a final lesion from the of the the the side of the to the for this lesion is via the small for lesion We will the criteria for a successful CMP throughout the entirety of the lesion. We will how this can be with our ablation either a or Cox-Maze lesion must be transmural throughout its entirety. This can be by any of the techniques in isolation or in surgical and It is our practice to a of these with each of the 3 to specific lesions to of the procedure. 3 modalities are effective if is with an However, this is the most technically and we its to only is required to to the of the Our right as an and an ablation lesion. We make our left to to the posterior experience in our laboratory has shown that the only devices that create transmural lesions are (as to and a more of as in A.J. R.M. J.L. S.J. et radiofrequency ablation on how to transmural Thorac Surg. Full Text Full Text PDF PubMed Scopus Google M.R. S.J. M. M. Schuessler R.B. Damiano Jr., R.J. of a novel for atrial ablation in a Thorac Surg. 2017; Full Text Full Text PDF PubMed Scopus (6) Google Scholar to the of the atria and for the right and left PV lesions that can be by within the as a of LA tissue as around the of the PV from the of the 2 of atrial an around each set of PVs and is not necessary as the and connecting lesions and will all tissue between the PVs the 2 box lesions in Figure 3). However, we the PVs in this because it is to do so on the heart on but This in for to PV isolation and function of the A novel device has been to the it to perform the entirety of the LA box exclusion with a single application and without the LA. Our laboratory has found that the AtriCure Inc) transmural lesions in a M. S. S.J. et of a novel radiofrequency an PubMed Scopus (2) Google Scholar However, are no available data on the clinical of this can be via a and can be to a lesion the epicardial or of the has been shown to be most effective on from the D. J. of tissue and experience in the treatment of Cardiovasc 1999; PubMed Scopus Google Scholar This is due to the of blood the needed to transmural in to the of epicardial In a beating-heart in which the posterior LA box epicardial cryoablation in of the box lesions were fully S. A. J.P. T. et and pulmonary vein isolation with epicardial cryoablation in a beating-heart Thorac Cardiovasc Surg. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar We make the majority of our CMP lesions we do a to lesions to both valve This is primarily to the risk of to the valve (as via does not or the it around R.M. S.J. Schuessler R.B. Damiano R.J. for the surgical treatment of atrial 2019; PubMed Scopus (6) Google Scholar We the in this region given the in to the valve due to the of the atrioventricular and the of in this R.M. S.J. Schuessler R.B. Damiano R.J. for the surgical treatment of atrial 2019; PubMed Scopus (6) Google Scholar It is important to that is to on the R.M. S.J. Schuessler R.B. Damiano R.J. for the surgical treatment of atrial 2019; PubMed Scopus (6) Google Scholar We in this region on the heart blood in to the epicardial around the the from is used, it is that the surgeon the of their must be each of these devices to consistently transmural lesions. Our laboratory that each lesion be without the tissue in between to of A.J. R.M. J.L. S.J. et radiofrequency ablation on how to transmural Thorac Surg. Full Text Full Text PDF PubMed Scopus Google Scholar our practice is to perform each lesion 2 to 3 with each lesion without and the between each It is also important to all is the between each set of a When any of it is important to tissue and tissue that between the 2 such as or or will prevent transmural lesion cryoablation a single application of 3 for devices and 2 for S. A. J.P. T. et and pulmonary vein isolation with epicardial cryoablation in a beating-heart Thorac Cardiovasc Surg. 2008; Full Text Full Text PDF PubMed Scopus Google R.M. S.J. Schuessler R.B. Damiano R.J. for the surgical treatment of atrial 2019; PubMed Scopus (6) Google Scholar The to be in with atrial tissue its is an so if are any gaps between the and the the that will that and lead to The CMP is the most effective treatment for AF, but is in We performing a complete biatrial Maze in the majority of patients undergoing cardiac surgery who have a history of AF and are surgical a electrophysiologic must that all lesions are fully transmural, and that all lesions both or end in electrically The LAA and the entirety of the posterior LA (including the PV and the must be excluded. Surgeons must the specific of device they to to create transmural lesions and their technique are to meet these criteria and the of this effective surgical this would make a impact for patients with AF, not only by sinus and the risk of stroke but also by long-term A.J. R.M. J.L. Sinn L.A. Maniar H.S. et al.The long-term outcomes and of the Cox-Maze IV procedure for atrial fibrillation.J Thorac Cardiovasc Surg. Full Text Full Text PDF PubMed Scopus Google Scholar

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