Research on the Surgical Treatment of Atrial Fibrillation

For more than 20 years, Washington University School of Medicine has been a leader in research on the surgical treatment of atrial fibrillation (AF). In 1987, researchers at the medical school led by James Cox, MD, developed a surgical cure for AF called the Cox-Maze procedure. The operation was designed to interrupt the multiple macroreentrant circuits in the atria believed to be responsible for AF. The procedure proved extremely effective – with a high success rate and virtual elimination of late stroke – and since has become the gold standard for the surgical treatment of AF.

More recent studies by the Division of Cardiothoracic Surgery at Washington University School of Medicine support more widespread use of the Cox-Maze procedure for treatment of AF in combination with other heart procedures. In addition, researchers have been active in efforts to simplify the Cox-Maze procedure, which is technically very challenging for cardiac surgeons to perform. In the modified procedure, surgical incisions are replaced with bipolar radiofrequency ablation lines. Studies have shown this procedure is safe and effective in controlling AF.

Early Research

• In 1985, Cox, then chairman of the Division of Cardiothoracic Surgery at Washington University School of Medicine, and his coworkers described for the first time a series of experiments attempting to cure AF in a canine model.¹ After a number of experiments, it was found that a single long incision across both atria and down into the septum cured AF. This “atrial transsection” procedure prevented the induction and maintenance of AF or atrial flutter in every canine treated.²
• Extensive experimental investigation under the leadership of Cox led to the introduction of the Maze procedure in 1987.^2-4 The Cox-Maze procedure was designed to interrupt any and all macro-reentrant circuits that potentially might develop in the atria, thereby preventing atrial fibrillation. The operation involved creating a myriad of incisions across both the right and left atria. The surgical incisions were placed so that the sinoatrial (SA) node could direct the spread of the sinus impulse throughout both atria. This significantly decreased the risk of thromboembolism and stroke.⁵

Cox-Maze Combined with Other Heart Procedures

• A study by the Division of Cardiothoracic Surgery at Washington University School of Medicine compared the long-term outcomes of 112 patients who underwent the Cox-Maze III procedure (the final modification of the “cut-and-sew” procedure, considered the gold standard) alone versus 86 who underwent the Cox-Maze III procedure along with other heart procedures (the most common were mitral valve repair, mitral valve replacement and coronary artery bypass grafting [CABG]) during a 13-year period. Overall, 96.6 percent of patients were free of atrial fibrillation at follow-up of 5.4 years. The authors concluded that the Cox-Maze III procedure has “equivalent operative risk and long-term efficacy in patients undergoing both lone operations and concomitant procedures.”⁶
• A second study by the division also suggested a more widespread use of the Cox-Maze III procedure in patients undergoing other heart procedures.⁷

Ablation Technology

• Although the Cox-Maze III procedure is very effective in curing AF, it has not been widely adopted because it is technically very challenging to perform and requires prolonged cardiopulmonary bypass. After extensive benchmark testing of bipolar radiofrequency ablation technology in the Washington University basic science laboratory, scientists concluded that this technology was as effective as the cut-and-sew lesions of the original Cox-Maze procedure.⁸
• In the October 2004 issue of the Journal of Thoracic and Cardiovascular Surgery, Ralph Damiano, Jr., MD, and his colleagues in the Division of Cardiothoracic Surgery, described a modified Cox-Maze III procedure with bipolar radiofrequency energy and its results in 40 consecutive patients. Nineteen had a lone Maze procedure, and 21 had the procedure in combination with another heart operation (mitral valve repair or replacement, CABG or CABG and a mitral valve repair). A little over 90% of patients followed for six months still had healthy heart rhythms. Meanwhile, the cross-clamp times were much shorter for the modified procedure. The study concluded that RF ablation is safe and can effectively replace the surgical incisions of the Cox-Maze III procedure.
• A second study of 130 patients who underwent a Cox-Maze procedure using bipolar radiofrequency energy (100), a limited Cox-Maze procedure (seven) or pulmonary vein isolation alone (23) was published in the October 2006 issue of the Annals of Surgery. The patients undergoing these ablation-assisted procedures were compared with a historical group of patients undergoing the Cox-Maze III procedure at Washington University School of Medicine and Barnes-Jewish Hospital.⁶ Ninety-one percent of patients who underwent the Cox-Maze IV procedure (the operation using radiofrequency energy) were free of AF at 12-month follow-up compared with 99% of Cox-Maze III patients. The authors concluded that bipolar radiofrequency is an effective and safe technology for the surgical treatment of atrial fibrillation.¹⁰
• A third study by the Division of Cardiothoracic Surgery at Washington University School of Medicine compared 154 patients who had the Cox-Maze III procedure and 88 who had the Cox-Maze IV procedure over a 13-year period. The study found there was no significant difference in intensive care unit and hospital stay, 30-day mortality, permanent pacemaker placement, early atrial tachyarrhythmias (rapid irregular heartbeat), late stroke or survival. Freedom from recurrence of AF was greater than 90% in both groups at one year. The authors concluded that the use of bipolar radiofrequency ablation has simplified the Cox-Maze procedure, making it suitable for virtually all patients with AF undergoing other cardiac surgery.¹¹