Editor's Note: This article is based on Weimar T., et al. The Cox-Maze Procedure for Lone Atrial Fibrillation: A Single-Center Experience Over 2 Decades. Circ Arrhythm Electrophysiol 2012; 5:8-14.

Introduction

In 1987, Dr. Jim Cox introduced the Maze procedure at Washington University after extensive experimental work. The procedure was designed to disrupt the existing and potential macro re-entrant circuits that were thought to be the cause of atrial fibrillation (AF) and direct the electrical wave front down a “maze" of pathways from the SA node to the AV node and throughout the atria.⁽¹⁾ Although there was considerable clinical interest in the 1990s, the operation was complex, invasive, required techniques that were unfamiliar to most cardiac surgeons, and was only regularly adopted by a handful of surgeons. Nevertheless, reports of freedom from AF (albeit reported using early standards, not with the quality of monitoring we would expect today), and most importantly, freedom from late stroke were high.^{(2, 3)}  In 2002, modification of the original Cox-Maze "cut-and-sew" procedure was initiated using newly available bipolar radiofrequency clamps to create many of the lesions, and supplementing others with cryoablation. Therefore, the operation required less extensive atrial incisions, could be performed faster, and was more easily applied concomitant to other open-heart surgery. This report summarizes the findings over two decades for the stand-alone Maze procedure using the two different procedures.⁽⁴⁾

Methods

From April 1992 through October 2012, 212 consecutive patients underwent the Cox-Maze procedure. Of these, 112 had the classic "cut-and-sew" technique and 100 patients received the “Cox-Maze IV” procedure (using bipolar radiofrequency) since 2002. The lesion set in both procedures included isolation of all four pulmonary veins, and a lesion to the mitral valve annulus (typically performed at least in part with cryoablation), excision of the left atrial appendage, a right atriotomy with ablation lines into the superior vena cava and into the inferior vena cava, and lesions to the tricuspid valve annulus at two locations from the right atriotomy. Both operations required cardiopulmonary bypass and aortic cross clamp for the left atrial portion of the procedure.

Postoperative care was standardized in both and included regular follow-up appointments including EKG monitoring. Importantly, 24-hour Holter monitoring or pacemaker interrogation was not introduced until 2006 when new follow-up guidelines were established.⁽⁵⁾ Late recurrence was defined as any episode of atrial tachycardia that lasted greater than 30 seconds. Any patient requiring an interventional procedure after three months postoperatively was deemed permanent failure. Patients were only considered to be a success if they were free of both atrial fibrillation and free of antiarrhythmic drugs (class I or III). 

Results

The mean age was 53.5 +/- 10.4 years (upper age 77), 78% were males, and the median duration of preoperative atrial fibrillation was 6.0 years (interquartile range 2.9 to 11.5 years). Paroxysmal atrial fibrillation was present in 48% and persistent or long-standing persistent in 52%. Twenty percent of patients had had previous catheter ablation failure. Fourteen percent of patients had had prior TIA or stroke.

The 30-day mortality was 1.4% (n = 3), 1.8% for cut-and-sew Maze, 1% for Maze IV. The major complication rate was 10% for the Cox-Maze III, and 1% (one stroke) for the Cox-Maze IV. 

The median follow-up was 5.9 years for the Cox-Maze III. Freedom from atrial fibrillation off antiarrhythmic drugs was 83% with no difference whether there was paroxysmal or long-standing persistent or persistent AF. One late stroke occurred in a patient who was not on anticoagulation. Eighty-six percent of patients were off anticoagulation therapy with warfarin. Of the Cox-Maze IV patients, the median follow-up was only 1.0 years. Freedom from atrial fibrillation off antiarrhythmic drugs was 82% at 12 months. There were no late strokes. Seventy-four percent of patients were free of anticoagulation with warfarin.

Conclusion

The results of the two procedures are similar, but the Cox-Maze IV had lower bypass and crossclamp times and lower perioperative morbidity.

Perspective

Catheter ablation is now becoming the standard of care for many patients who are symptomatic, young, intolerant of medications, and who want an invasive alternative to ongoing medical therapy.⁽⁶⁾ However, catheter ablation fails in many patients, and for highly symptomatic patients a surgical procedure is another option. The Cox-Maze III operation is a very successful operation, which has a very low freedom from stroke rate in multiple series.^{(3, 7, 8)} Of the surgical options, many still consider this the gold standard and have shown better results than with radiofrequency or other technology used to create the ablation lines,(9, 10) as these are not always transmural ablation lines.

The results of the original Cox-Maze are difficult to analyze today because the use of holter monitors, pacemaker interrogation, implantable monitoring devices, were not routine and therefore the results most likely overestimate the success. The results of the Cox-Maze IV are more rigorous and withstand the standards of reporting today, but surprisingly in this report, the median follow-up was only 1.0 years with data reported up to two years, even though the surgery series began in 2002 and more intensive monitoring in 2006.

The field is moving to even less invasive surgical procedures, frequently as a "hybrid" with electrophysiologists ready to perform staged hybrid procedures later, or occasionally even at a single setting.⁽¹¹⁾ These experiences are also small and single-center, but some appear encouraging.^{(12, 13)} One surgical approach employs bilateral thoracotomies and also includes excision or closure of the left atrial appendage. Bilateral pulmonary vein isolation can be performed and other limited lesions followed by catheter ablation. Another even much less invasive approach is right side port access to create a box lesion, the left atrial appendage is left alone, and later catheter ablation is added.^{(14, 15)} The challenge of these procedures has been to employ technology on a beating heart from the epicardium and still create reliably transmural lesions. Also, surgeons must be familiar with the anatomy and the techniques to avoid possible complications that can lead to bleeding, myocardial infarction, or even esophageal disruption. Furthermore, these procedures are anatomically based, not mapping based as the EP procedures typically are. The advantage of the hybrid procedure is that triggers outside of the box lesion can be identified and eliminated after the bulk of the posterior left atrium and pulmonary veins have been electrically isolated.

Dr. Jim Cox will always be recognized as a pioneer in the interventional therapy of atrial fibrillation. His procedure still is employed by several of us who have extensive experience with it, and we still use the cut-and-sew procedure for patients with a very dilated left atrium to reduce the size. However, the invasive nature of the procedure is being supplanted by more focused, less invasive procedures that are better tolerated by patients. The Cox-Maze IV is a step towards that goal from the original procedure, but as a stand-alone therapy for lone atrial fibrillation, it is unlikely that another 20 years will find us still doing this procedure.

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References

1. Cox, J.L., et al., The surgical treatment of atrial fibrillation. II. Intraoperative electrophysiologic mapping and description of the electrophysiologic basis of atrial flutter and atrial fibrillation. J Thorac Cardiovasc Surg 1991; 101:406-26.
2. Cox, J.L., N. Ad, and T. Palazzo, Impact of the maze procedure on the stroke rate in patients with atrial fibrillation. J Thorac Cardiovasc Surg 1999; 118:833-40.
3. Handa, N., et al., Outcome of valve repair and the Cox maze procedure for mitral regurgitation and associated atrial fibrillation. J Thorac Cardiovasc Surg 1999; 118: 628-35.
4. Weimar, T., et al., The cox-maze procedure for lone atrial fibrillation: a single-center experience over 2 decades. Circ Arrhythm Electrophysiol 2012; 5:8-14.
5. Calkins, H., et al., 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; 4:816-61.
6. Calkins, H., et al., 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. J Interv Card Electrophysiol 2012; 33:171-257.
7. McCarthy, P.M., et al., The Cox-Maze procedure: the Cleveland Clinic experience. Semin Thorac Cardiovasc Surg 2000; 12:25-9.
8. Schaff, H.V., et al., Cox-Maze procedure for atrial fibrillation: Mayo Clinic experience. Semin Thorac Cardiovasc Surg 2000; 12:30-7.
9. McCarthy, P.M., et al., Where does atrial fibrillation surgery fail? Implications for increasing effectiveness of ablation. J Thorac Cardiovasc Surg 2010; 139:860-7.
10. Stulak, J.M., et al., Superiority of cut-and-sew technique for the Cox maze procedure: comparison with radiofrequency ablation. J Thorac Cardiovasc Surg 2007; 133:1022-7.
11. Sales, V.L. and P.M. McCarthy, Minimally invasive surgery for atrial fibrillation. Tex Heart Inst J 2010; 37:660-1.
12. Edgerton, J.R., et al., Totally thorascopic surgical ablation of persistent AF and long-standing persistent atrial fibrillation using the "Dallas" lesion set. Heart Rhythm 2009; 6:S64-70.
13. Beyer, E., R. Lee, and B.K. Lam, Point: Minimally invasive bipolar radiofrequency ablation of lone atrial fibrillation: early multicenter results. J Thorac Cardiovasc Surg 2009; 137:521-6.
14. Boersma, L.V., et al., Atrial fibrillation catheter ablation versus surgical ablation treatment (FAST): a 2-center randomized clinical trial. Circulation 2012; 125:23-30.
15. Muneretto, C., et al., Durable staged hybrid ablation with throrascopic and percutaneous approach for treatment of long standing atrial fibrillation: Results at 30 months assessed with continuous monitoring, in American Assocation of Thoracic Surgery 2012 Annual Meeting. 2012: San Francisco, CA.

Keywords: Atrial Appendage, Atrial Fibrillation, Cardiopulmonary Bypass, Mitral Valve, Myocardial Infarction, Pulmonary Veins, Stroke, Tachycardia, Tricuspid Valve, Vena Cava, Inferior, Warfarin

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