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The longstanding, persistent confusion surrounding surgery for atrial fibrillation

2010; Elsevier BV; Volume: 139; Issue: 6 Linguagem: Inglês

10.1016/j.jtcvs.2010.02.027

1097-685X

James L. Cox,

Cardiac electrophysiology and arrhythmias

The surgical treatment of atrial fibrillation (AF) persists in being a confusing topic, despite the fact that surgeons have been able to treat this entity successfully for more than 2 decades. Much of the confusion stems from electrophysiologic concepts that have arisen from observations made after catheter ablation, where the interventional electrophysiologists do not know the precise location, length, depth, or width of their lesions. In addition, the lack of a physiologically based classification system that is meaningful for patients undergoing interventional therapy for AF, the indiscriminant use of unproven lesion patterns, the inability to create transmural and contiguous ablative lesions reliably, the lack of agreement regarding what constitutes a surgical failure, and the lack of a standard means of assessing postoperative results have all contributed to the current state of confusion. Some surgeons are now questioning the validity of treating AF surgically in the case of patients who are already entering the operating room for other cardiac surgery, such as mitral valve repair. Gammie and associates1Gammie J.S. Haddad M. Milford-Beland S. Welke K.F. Ferguson Jr., T.B. O'Brien S.M. et al.Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database.Ann Thoracic Surg. 2008; 85: 914-915Abstract Full Text Full Text PDF PubMed Scopus (170) Google Scholar recently reviewed the Society of Thoracic Surgeons National Cardiac Database and reported that of 67,389 patients with AF who underwent surgery for other cardiac problems only 38% underwent a concomitant surgical procedure for AF, including 52% of those undergoing mitral valve surgery, 28% of those undergoing aortic valve surgery, and 24% of those undergoing isolated coronary artery bypass grafting (CABG). This disappointing performance was seen despite the publication of multiple studies from around the world confirming the ability of a variety of concomitant surgical procedures to eliminate AF.2Blomström-Lundqvist C. Johansson B. Berglin E. Nilsson L. Jensen S.M. Thelin S. et al.A randomized double-blind study of epicardial left atrial cryoablation for permanent atrial fibrillation in patients undergoing mitral valve surgery: the SWEDish Multicentre Atrial Fibrillation study (SWEDMAF).Eur Heart J. 2007; 28: 2902-2908Crossref PubMed Scopus (104) Google Scholar, 3Myrdko T. Sniezek-Maciejewska M. Rudziński P. Myć J. Lelakowski J. Majewski J. Efficacy of intra-operative radiofrequency ablation in patients with permanent atrial fibrillation undergoing concomitant mitral valve replacement.Kardiol Pol. 2008; 66: 932-940PubMed Google Scholar, 4Chen M.C. Chang J.P. Chen Y.L. Surgical treatment of atrial fibrillation with concomitant mitral valve disease: an Asian review.Chang Gung Med J. 2008; 31: 538-545PubMed Google Scholar, 5von Oppell U.O. Masani N. O'Callaghan P. Wheeler R. Dimitrakakis G. Schiffelers S. Mitral valve surgery plus concomitant atrial fibrillation ablation is superior to mitral valve surgery alone with an intensive rhythm control strategy.Eur J Cardiothorac Surg. 2009; 35: 641-650Crossref PubMed Scopus (73) Google Scholar, 6Chevalier P. Leizorovicz A. Maureira P. Carteaux J.P. Corbineau H. Caus T. et al.Left atrial radiofrequency ablation during mitral valve surgery: a prospective randomized multicentre study (SAFIR).Arch Cardiovasc Dis. 2009; 102: 769-775Crossref PubMed Scopus (46) Google Scholar, 7Kim J.B. Yun T.J. Chung C.H. Choo S.J. Song H. Lee J.W. Long-term outcome of modified maze procedure combined with mitral valve surgery: analysis of outcomes according to type of mitral valve surgery.J Thorac Cardiovasc Surg. 2010; 139: 111-117Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar Most authorities believe that concomitant AF surgery is indicated not only for patients with AF who are undergoing mitral valve surgery8Alfieri O. Benussi S. Mitral valve surgery with concomitant treatment of atrial fibrillation.Cardiol Rev. 2000; 8: 317-321Crossref PubMed Scopus (12) Google Scholar, 9Gillinov A.M. Ablation of atrial fibrillation with mitral valve surgery.Curr Opin Cardiol. 2005; 20: 107-114Crossref PubMed Scopus (35) Google Scholar, 10Gehi A.K. Adams D.H. Filsoufi F. The modern surgical management of atrial fibrillation.Mt Sinai J Med. 2006; 73: 751-758PubMed Google Scholar but also for patients with AF who are undergoing CABG or aortic valve surgery.11Geidel S. Ostermeyer J. Lass M. Geisler M. Kotetishvili N. Aslan H. et al.Permanent atrial fibrillation ablation surgery in CABG and aortic valve patients is at least as effective as in mitral valve disease.Thorac Cardiovasc Surg. 2006; 54: 91-95Crossref PubMed Scopus (30) Google Scholar Ridding the patient of AF at the time of mitral valve, aortic valve, or coronary artery surgery has been documented to cause no increased surgical risk12Ad N. Cox J.L. The significance of atrial fibrillation ablation in patients undergoing mitral valve surgery.Semin Thorac Cardiovasc Surg. 2002; 14: 193-197Abstract Full Text PDF PubMed Scopus (10) Google Scholar yet results in multiple benefits relative to leaving these patients in AF postoperatively. The benefits include not only a better quality of life13Forlani S. De Paulis R. Guerrieri Wolf L. Greco R. Polisca P. Moscarelli M. et al.Conversion to sinus rhythm by ablation improves quality of life in patients submitted to mitral valve surgery.Ann Thorac Surg. 2006; 81: 863-867Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar but also less postoperative morbidity,14Ngaage D.L. Schaff H.V. Mullany C.J. Barnes S. Dearani J.A. Daly R.C. et al.Influence of preoperative atrial fibrillation on late results of mitral repair: is concomitant ablation justified?.Ann Thorac Surg. 2007; 84: 434-442Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar lower incidences of thromboembolic events and valve-related complications,15Fukunaga S. Hori H. Ueda T. Takagi K. Tayama E. Aoyagi S. Effect of surgery for atrial fibrillation associated with mitral valve disease.Ann Thorac Surg. 2008; 86: 1212-1217Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar, 16Itoh A. Kobayashi J. Bando K. Niwaya K. Tagusari O. Nakajima H. et al.The impact of mitral valve surgery combined with maze procedure.Eur J Cardiothorac Surg. 2006; 29: 1030-1035Crossref PubMed Scopus (55) Google Scholar improvement in the commonly associated problem of tricuspid regurgitation,17Kim H.K. Kim Y.J. Kim K.I. Jo S.H. Kim K.B. Ahn H. et al.Impact of the maze operation combined with left-sided valve surgery on the change in tricuspid regurgitation over time.Circulation. 2005; 112: I14-I19PubMed Google Scholar, 18Stulak J.M. Schaff H.V. Dearani J.A. Orszulak T.A. Daly R.C. Sundt 3rd, T.M. Restoration of sinus rhythm by the Maze procedure halts progression of tricuspid regurgitation after mitral surgery.Ann Thorac Surg. 2008; 86: 40-45Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar and improved patient survival.16Itoh A. Kobayashi J. Bando K. Niwaya K. Tagusari O. Nakajima H. et al.The impact of mitral valve surgery combined with maze procedure.Eur J Cardiothorac Surg. 2006; 29: 1030-1035Crossref PubMed Scopus (55) Google Scholar, 19Louagi Y. Buche M. Eucher P. Schoevaerdts J.C. Gerard M. Jamart J. et al.Improved patient survival with concomitant Cox Maze III procedure compared with heart surgery alone.Ann Thorac Surg. 2009; 87: 440-446Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar Indeed, the surgical literature of the past decade leaves no doubt that the concomitant surgical treatment of AF associated with other cardiac surgery should increase in the future. The current lack of aggressiveness in treating AF with concomitant surgical procedures has other consequences. For example, it is uncommon for surgeons to perform stand-alone operations for AF. The usual explanation for this is, "My referring cardiologist won't refer these patients." There are likely several reasons for the lack of referrals, but 2 stand out: (1) stand-alone surgical procedures are not referred because many surgeons do not even routinely treat AF with a concomitant cardiac surgical procedure, and (2) most contemporary surgical techniques are left-sided procedures, and although they may be fairly effective as concomitant procedures for AF, they are not nearly so effective when applied as stand-alone procedures for AF. Indeed, the stand-alone surgical results with left-sided procedures may be no better than those attained by catheter ablation. Because these procedures are obviously more invasive, why should cardiologists be expected to refer their patients with AF to surgeons if they cannot expect to see a significant improvement in outcome? The term atrial fibrillation is a clinical diagnosis that is based on the findings of an irregular P wave and an irregularly irregular QRS complex on the standard limb-lead electrocardiogram. The clinical diagnosis of AF reveals little, however, about the underlying electrophysiologic events that are actually occurring in the atria. For example, the electrocardiographic findings of AF can be caused by a single unstable macro-reentrant circuit in either atrium, by 2 simultaneous macro-reentrant circuits in a single atrium, by a single macro-reentrant circuit in each atrium, or by as many as 6 simultaneous macro-reentrant circuits (Figure 1).20Lewis T. Drury A.N. Iliescu C.C. Further observations upon the state of rapid re-excitation of the auricles.Heart. 1921; 8: 311-340Google Scholar, 21Garrey W.E. Auricular fibrillation.Physiol Rev. 1924; 4: 215-250Google Scholar, 22Allessie M.A. Bonke F.I. Schopman F.J. Circus movement in rabbit atrial muscle as a mechanism of tachycardia. III. The "leading circle" concept: a new model of circus movement in cardiac tissue without the involvement of an anatomical obstacle.Circ Res. 1977; 41: 9-18Crossref PubMed Scopus (766) Google Scholar, 23Allessie M.A. Lammers W.J. Bonke F.I. Hollen J. Experimental evaluation of Moe's multiple wavelet hypothesis of atrial fibrillation.in: Zipes D.P. Jalife J. Cardiac electrophysiology and arrhythmias. Grune & Stratton, Orlando (FL)1985: 265-275Google Scholar AF is either paroxysmal or nonparoxysmal. Individual episodes of paroxysmal AF (PAF) depend on focal atrial triggers for their induction; once induced, however, the individual episodes are sustained by self-perpetuating macro-reentrant circuits in the atrium until they spontaneously terminate. Haïssaguerre and associates24Haïssaguerre M. Jaïs 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 (5930) Google Scholar and others25Lee S.H. Tai C.T. Hsieh M.H. Tsao H.M. Lin J.Y. Chang S.L. et al.Predictors of non–pulmonary vein ectopic beats initiating paroxysmal atrial fibrillation: implication for catheter ablation.J Am Coll Cardiol. 2005; 46: 1054-1059Abstract Full Text Full Text PDF PubMed Scopus (164) Google Scholar have demonstrated that the focal triggers that induce PAF are in and around the pulmonary vein (PV) orifices in approximately 90% of patients. By definition, all AF that does not occur sporadically is nonparoxysmal AF, which includes the subcategories of persistent, longstanding persistent, permanent, chronic, continuous, or any other arbitrary designation that refers to AF that is not paroxysmal (Figure 2) . Because the term nonparoxysmal AF is cumbersome and unfamiliar to most surgeons, however, the remainder of this discussion will refer to all nonparoxysmal AF as chronic AF (CAF). Whereas PAF depends on atrial triggers for its induction, CAF requires no such triggers because it does not need to be repeatedly induced. CAF occurs because the self-perpetuating macro-reentrant circuits (drivers) in the atria that spontaneously terminate in patients with PAF no longer terminate; thus, the AF becomes nonparoxysmal or chronic. These macro-reentrant drivers can occur virtually anywhere in either atrium and are usually at least 5 cm in diameter, not 1 to 2 cm in diameter or smaller as implied in such prominent publications as the Heart Rhythm Society/European Heart Rhythm Association/European Cardiac Arrhythmia Society Expert Consensus Statement.26Calkins H. et al.European Heart Rhythm Association (EHRA)European Cardiac Arrhythmia Society (ECAS)American College of Cardiology (ACC)American Heart Association (AHA)Society of Thoracic Surgeons (STS)HRS/EHRA/ECAS Expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation.Heart Rhythm. 2007; 4 (Erratum in: Heart Rhythm. 2009;6:148): 816-861Abstract Full Text Full Text PDF PubMed Scopus (1049) Google Scholar The presence of these self-perpetuating macro-reentrant drivers, and the fact that they are physically large rather than focal, is the reason that PV isolation alone will not cure CAF and why it is necessary to add strategically placed linear lesions in these patients. Arrhythmia surgeons deal almost exclusively with AF that arises secondary to some type of left heart problem, usually mitral valve disease but also aortic valve disease, ischemic heart disease, or left heart failure. This AF is frequently referred to as concomitant AF, but it is more accurate to think of it as secondary AF that is treated with a concomitant surgical procedure. A few arrhythmia surgeons also treat patients with AF that is not associated with another cardiac problem severe enough to warrant surgery. This is commonly referred to as stand-alone AF, but it is more accurate to think of it as primary AF that is treated with a stand-alone surgical procedure. Before performing concomitant surgery for AF, all patients should be classified as having either secondary PAF or secondary CAF (Figure 3). Before performing stand-alone surgery for AF, all patients should be classified as having either primary PAF or primary CAF. Both primary and secondary PAF are caused by focal triggers that are usually located in or near the PV orifices, and both therefore can be treated successfully with PV isolation. Surgeons are rarely referred patients with primary PAF, because satisfactory results can be attained by catheter ablation in these cases. Because secondary PAF occurs frequently in patients undergoing other cardiac surgery, however, concomitant surgical PV isolation is a commonly used procedure.27Gillinov A.M. Bakaeen F. McCarthy P.M. Blackstone E.H. Rajeswaran J. Pettersson G. et al.Surgery for paroxysmal atrial fibrillation in the setting of mitral valve disease: a role for pulmonary vein isolation?.Ann Thorac Surg. 2006; 81: 19-28Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar Although this would seem to be appropriate for all patients with secondary PAF, PV isolation alone can be quite arrhythmogenic, especially in patients with enlarged or diseased left atria, in which setting atypical left atrial flutter (Figure 4) is a frequent postoperative occurrence. Atypical left atrial flutter is characterized by a long reentrant circuit formed around the PV-isolating lesions in which the electrical impulse travels along the left atrial isthmus between the inferior PVs and the mitral annulus, through the atrial septum, around the anterior left atrium above the mitral annulus, and then in the lateral left atrium beneath the orifice of the left atrial appendage. If a patient is undergoing surgery for mitral valve disease in which the left atrium is already opened it is therefore advisable, even for secondary PAF, to go ahead with a complete left atrial maze III lesion pattern, which usually adds less than 15 minutes to the operative procedure. The right atrial maze III lesions can then be added during the rewarming phase without extending the operative time. In patients with secondary PAF who are undergoing aortic valve surgery or CABG, however, where a left atriotomy is not otherwise required, it is reasonable to perform a simple epicardial PV isolation. Although both primary and secondary CAF depend on the presence of macro-reentrant drivers for their maintenance, there are critical electrophysiologic differences between the two that can doom a surgeon's stand-alone practice for AF if they are ignored. The critical difference relates to the number of macro-reentrant circuits that can occur in the right atrium under various clinical conditions. These differences explain why satisfactory results can often be attained in patients undergoing concomitant surgery28Ninet J. Roques X. Seitelberger R. Deville C. Pomar J.L. Robin J. et al.Surgical ablation of atrial fibrillation with off-pump, epicardial, high-intensity focused ultrasound. Results of a multicenter trial.J Thorac Cardiovasc Surg. 2005; 130: 803-809Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar, 29Groh M.A. Binns O.A. Burton 3rd, H.G. Ely S.W. Johnson A.M. Ultrasonic cardiac ablation for atrial fibrillation during concomitant cardiac surgery: Long-term clinical outcomes.Ann Thorac Surg. 2007; 84: 1978-1983Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar but not stand-alone surgery, despite identical lesion pattern and energy source.30Klinkenberg T.J. Ahmed S. Ten Hagen A. Wiesfeld A.C. Tan E.S. Zijlstra F. et al.Feasibility and outcome of epicardial pulmonary vein isolation for lone atrial fibrillation using minimal invasive surgery and high intensity focused ultrasound.Europace. 2009; 11: 1624-1631Crossref PubMed Scopus (37) Google Scholar The durations of the local refractory periods in atrial tissue determine the physical size of local macro-reentrant circuits.31Cox J.L. Boineau J.P. Schuessler R.B. Kater K.M. Lappas D.G. Five-year experience with the maze procedure for atrial fibrillation.Ann Thorac Surg. 1994; 56: 814-824Abstract Full Text PDF Scopus (413) Google Scholar Areas of the atrium with shorter refractory periods can harbor smaller macro-reentrant circuits, whereas areas with longer refractory periods can harbor only larger macro-reentrant circuits. The refractory periods in the left atrium are normally shorter than those in the right atrium,32Lammers W.J. Schalij M.J. Kirchhof C.J. Allessie M.A. Quantification of spatial inhomogeneity in conduction and initiation of reentrant atrial arrhythmias.Am J Physiol. 1990; 259: H1254-H1263PubMed Google Scholar so macro-reentrant circuits that form in the left atrium are usually smaller than those in the right atrium (Figure 1, C). In fact, because of its relatively long refractory periods, the normal right atrium is capable of harboring only a single large macro-reentrant circuit, the classic atrial "flutter wave" that traverses the cavotricuspid isthmus.32Lammers W.J. Schalij M.J. Kirchhof C.J. Allessie M.A. Quantification of spatial inhomogeneity in conduction and initiation of reentrant atrial arrhythmias.Am J Physiol. 1990; 259: H1254-H1263PubMed Google Scholar, 33Cox J.L. Boineau J.P. Schuessler R.B. Kater K.M. Lappas D.G. Surgical interruption of atrial reentry as a cure for atrial fibrillation.in: Olsson S.B. Allessie M.A. Campbell R.W. Atrial fibrillation: mechanisms and therapeutic strategies. Futura Publishing, Armonk (NY)1994: 373-404Google Scholar Thus to choose the appropriate surgical approach for each patient, one must take into account not only the type of AF present but also the clinical statuses of both the right and left atria. Because the right atrium may not be affected by left heart problems, such as mitral or aortic valve disease, ischemic heart disease, or left heart failure, the normal right atrium in these patients is still capable of supporting only a single macro-reentrant circuit, the right atrial flutter wave (Figure 5). Thus the macro-reentrant drivers responsible for the secondary CAF in such patients reside predominantly in the left atrium, and concomitant AF surgical procedures confined to the left atrium therefore can have a relatively high success rate in such patients. After strictly left-sided concomitant procedures, however, approximately 10% of these patients will have postoperative atrial flutter originating from the right atrium.34Benussi S. Pappone C. Nascimbene S. Oreto G. Caldarola A. Stefano P.L. et al.A simple way to treat chronic atrial fibrillation during mitral valve surgery: the epicardial radiofrequency approach.Eur J Cardiothorac Surg. 2000; 17: 524-529Crossref PubMed Scopus (162) Google Scholar Some surgeons therefore add a right atrial "flutter lesion" to their concomitant left-sided surgical procedures. Others choose to ignore the possibility of postoperative atrial flutter from the right atrium and let their cardiologists treat it with catheter ablation should it occur. Either approach is reasonable. If the right atrium is enlarged or stretched as a result of the left heart problem, it may become large enough to support two simultaneous macro-reentrant circuits (Figure 6). In that case, concomitant AF procedures confined to the left atrium will fail because the postoperative persistence of multiple macro-reentrant circuits in the enlarged right atrium can still cause AF postoperatively. Thus although concomitant left-sided AF procedures are generally fairly effective for secondary CAF, if there is any hint of right atrial involvement, the patient should have the full set of maze III lesions applied in the right atrium as well as in the left atrium. This is perhaps the most frequent reason for recurrent AF after strictly left-sided concomitant AF procedures for the treatment of CAF secondary to mitral valve disease. Moreover, the addition of a right atrial flutter lesion would have no effect whatsoever on the occurrence of postoperative AF in these patients, because that lesion is only effective for atrial flutter coming from the right atrium. Because it is not always possible to know whether the right atrium is affected by the left heart problems in these patients, even when looking directly at the right atrium during surgery, and because it takes only about 10 minutes and no additional pump time to perform the right atrial lesions of the maze III lesion set, it seems prudent to add the right-sided lesions in all patients undergoing combined mitral valve and AF surgery. This is especially true in view of the fact that, unlike the right atrial flutter lesion, the right atrial maze III lesions prevent both AF and atrial flutter that might arise postoperatively in the right atrium. If the associated surgical procedure is aortic valve replacement or CABG, the best results for secondary CAF would be attained by performing a full biatrial maze III lesion pattern. Because that set currently requires a left atriotomy for proper performance, however, the decision of whether to add the biatrial procedure or perform some other lesser procedure is at the surgeon's discretion. A word of caution is warranted here. The right atrial cavotricuspid flutter lesion ablates right atrial flutter but not right AF, whereas the right atrial maze lesions ablate both. It is never acceptable, however, to perform both the right atrial cavotricuspid flutter lesion and the right atrial maze lesions in the same patient. This combination of lesions actually isolates the lower third of the right atrial free wall (Figure 7), and that is the site of origin of the normal sinus rhythm impulse during heart rates less than 60 beats/min.35Boineau J.P. Canavan T.E. Schuessler R.B. Cain M.E. Corr P.B. Cox J.L. Demonstration of a widely distributed atrial pacemaker complex in the human heart.Circulation. 1988; 77: 1221-1237Crossref PubMed Scopus (229) Google Scholar Thus if the heart rate normally drops below that level, say when a patient is asleep, there may be no primary mechanism for generating a sinus rhythm if the lower third of the right atrium has inadvertently been isolated. I was wrong for several years in believing that a properly performed stand-alone left atrial maze III lesion set without the right atrial maze III lesions would cure primary CAF at the same rate that it cured secondary CAF when performed as a concomitant procedure.28Ninet J. Roques X. Seitelberger R. Deville C. Pomar J.L. Robin J. et al.Surgical ablation of atrial fibrillation with off-pump, epicardial, high-intensity focused ultrasound. Results of a multicenter trial.J Thorac Cardiovasc Surg. 2005; 130: 803-809Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar, 36Cox J.L. NASPE history: cardiac surgery for arrhythmias.Pacing Clin Electrophysiol. 2004; 27: 1-17Crossref PubMed Scopus (29) Google Scholar, 37Cox J.L. The role of surgical intervention in the management of atrial fibrillation.Tex Heart Inst J. 2004; 31: 257-265PubMed Google Scholar Clinical experience eventually demonstrated that after a stand-alone left-sided procedure for primary CAF, the recurrence rate of AF could be 50% or more.30Klinkenberg T.J. Ahmed S. Ten Hagen A. Wiesfeld A.C. Tan E.S. Zijlstra F. et al.Feasibility and outcome of epicardial pulmonary vein isolation for lone atrial fibrillation using minimal invasive surgery and high intensity focused ultrasound.Europace. 2009; 11: 1624-1631Crossref PubMed Scopus (37) Google Scholar Clearly, AF surgical procedures that are confined to the left atrium fail much more often when they are used as stand-alone procedures to treat primary CAF than when they are used as concomitant procedures to treat secondary CAF. This dramatic difference in surgical results was the observation that established unequivocally that there was a critical difference in the electrophysiologic mechanisms underlying secondary CAF and primary CAF. It is important to recognize that primary CAF arises de novo in an otherwise grossly normal heart, or at least in a heart that has no obvious clinical cause for the AF (mitral, aortic, or ischemic disease). Why? One reason is that in patients with primary CAF, the right atrium may have abnormally short refractory periods, meaning that their corresponding right atrial macro-reentrant circuits can be smaller than normal.38Haïssaguerre M. Wright M. Hocini M. Jaïs P. The substrate maintaining persistent atrial fibrillation.Circ Arrhythm Electrophysiol. 2008; 1: 2-5Crossref PubMed Scopus (36) Google Scholar Thus, unlike the situation in the normal right atrium, multiple macro-reentrant drivers can reside simultaneously within the normal-appearing right atrium in patients with primary CAF (Figure 8). Clearly, a stand-alone AF surgical procedure confined to the left atrium, with or without addition of a right atrial flutter lesion, would fail in such patients because of the postoperative persistence of the multiple macro-reentrant drivers in the right atrium. Indeed, a sure way to preclude the development of a viable clinical practice treating primary CAF with stand-alone surgical procedures is to use procedures that are confined to the left atrium! In 1998, Haïssaguerre and associates24Haïssaguerre M. Jaïs 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 (5930) Google Scholar published their seminal article demonstrating for the first time that most episodes of AF are induced by focal triggers in and around the PV orifices. This article led to an explosion of industry involvement in the field, with the introduction of multiple new energy sources incorporated into surgical devices that were designed primarily for encircling the PVs.28Ninet J. Roques X. Seitelberger R. Deville C. Pomar J.L. Robin J. et al.Surgical ablation of atrial fibrillation with off-pump, epicardial, high-intensity focused ultrasound. Results of a multicenter trial.J Thorac Cardiovasc Surg. 2005; 130: 803-809Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar, 39Wolf R.K. Schneeberger E.W. Osterday R. Miller D. Merrill W. Flege Jr., J.B. et al.Video-assisted bilateral pulmonary vein isolation and left atrial appendage exclusion for atrial fibrillation.J Thorac Cardiovasc Surg. 2005; 130: 797-802Abstract Full Text Full Text PDF PubMed Scopus (267) Google Scholar, 40Melo J. Adragão P. Neves J. Ferreira M.M. Pinto M.M. Rebocho M.J. et al.Surgery for atrial fibrillation using radiofrequency catheter ablation: assessment of results at one year.Eur J Cardiothorac Surg. 1999; 15: 851-855Crossref PubMed Scopus (144) Google Scholar, 41Knaut M. Spitzer S.G. Karolyi L. Ebert H.H. Richter P. Tugtekin S.M. et al.Intraoperative microwave ablation for curative treatment of atrial fibrillation in open heart surgery—the MICRO-STAF and MICRO-PASS pilot trial. MICROwave Application in Surgical Treatment of Atrial Fibrillation. MICROwave Application for the Treatment of Atrial Fibrillation in Bypass-Surgery.Thorac Cardiovasc Surg. 1999; 47: 379-384Crossref PubMed Google Scholar, 42Dörschler K. Müller G. The role of laser in cardiac surgery.Thorac Cardiovasc Surg. 1999; 47: 385-387Crossref PubMed Google Scholar This simultaneous introduction of 2 variables into the surgical treatment of AF, new energy sources and new lesion patterns, directly violated a cardinal rule of scientific investigation, which demands that all variables in an experiment be controlled save the one being evaluated. The violation of this simple but basic scientific principle preordained the massive confusion that we now face in trying to interpret the reason for surgical failures. Are they due to the inadequacy of the energy source or to inappropriate lesion sets? With two variables having been introduced simultaneously some 10 to 12 years ago, it is i