Because of the limitations of medical therapy for atrial fibrillation, there was a strong interest in the non-pharmacological treatment of the disease in the 1980s and 1990s, which led to the development of various catheter-based and surgical techniques. Although many of these techniques were not successful in addressing all of the effects of AF, they helped physicians gain fundamental knowledge of the mechanism of AF and laid a foundation for the development of the Cox-Maze procedure.
Three surgical procedures developed in the early 1980s – the left atrial isolation procedure, catheter ablation of the AV node-His bundle complex and corridor procedure – attempted to isolate and confine AF to a certain region of the atria, preventing it from spreading its effects to the ventricles. None of these procedures were targeted to cure the AF itself.
In 1985, James Cox, MD, and his group at Washington University School of Medicine and Barnes-Jewish Hospital described, for the first time, a series of experiments that attempted to cure AF in a canine model. 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 atrial fibrillation or atrial flutter in every canine treated.
Unfortunately, this procedure was effective but not curative in its clinical application. It soon became apparent that the surgical cure of AF would require a more complete understanding of the fundamental electrophysiological mechanisms of the illness.
Development of the Cox-Maze Procedure
Extensive experimental investigation under the leadership of Dr. Cox led to the introduction of the Maze procedure in 1987. The Cox-Maze procedure was designed to interrupt any and all macro-reentrant circuits that might potentially develop in the atria, thereby eliminating the chaotic web of electric impulses that spread throughout the atria and preventing flutter or fibrillation. Essentially, surgeons make small, strategically placed incisions in the atria. The incisions generate scar tissues that serve as barriers, trapping abnormal electric signals in a “maze” of barricades. Only one path remains intact, guiding impulses to their correct destination. In contrast to the earlier procedures, the Maze procedure successfully restored both atrioventricular synchrony and a regular heartbeat, thus significantly decreasing the risk of thromboembolism and stroke. It also allowed all of the atrial myocardium (middle muscular layer of the heart wall) to be activated, resulting in preservation of atrial transport function in most patients.
During the operation, the pulmonary veins also are completely isolated. This has proven to be fortuitous as the importance of the pulmonary veins in the initiation of AF has become more appreciated in recent years. The left atrial appendage (LAA) is either sewn closed or completely removed during surgery. This is performed because the LAA is a common source of clot development and serves to greatly reduce the risk of stroke in this population.
The original Maze procedure performed in the 1980s was modified because of the increased incidence of pacemaker implantation. However, the second Maze procedure proved to be very difficult technically to perform. It was therefore modified again to become the Maze-III procedure, also known as the Cox-Maze III procedure today.
The Cox-Maze procedure became the gold standard for the surgical treatment of AF. In a long-term study of patients who had the Cox-Maze procedure at Barnes-Jewish Hospital, 97 percent of patients at late follow-up were free of the disease. Although other institutions have experienced good results, our group has achieved the best long-term results in the world. Our team also has taught surgeons from around the world how to perform this operation.
Modified Cox-Maze Procedure Using Bipolar Radiofrequency Energy
Despite its proven effectiveness, the Cox-Maze III procedure did not gain widespread acceptance. Few cardiac surgeons were willing to add the procedure to a coronary revascularization or valve procedure because of its complexity and technical difficulty. In an attempt to simplify the operation and make it more accessible to the average surgeon, groups around the world have replaced the incision of the traditional cut-and-sew Cox-Maze III procedure with linear lines of ablation. These linear lines of ablation are created using a variety of energy sources including radiofrequency energy, microwave, cryoablation, laser and high-frequency ultrasound.
The development of these new ablation technologies has revolutionized the surgical treatment of AF by taking a technically difficult and time-consuming operation and making it easy for all cardiac surgeons to perform. Today, most patients with chronic AF undergoing open heart surgery are offered a modified Maze procedure as part of the operation. Another advantage of ablation technologies is the promise of development of less-invasive procedures for AF via a small incision or port.
At Washington University, bipolar radiofrequency energy has been used successfully to replace most of the surgical incisions of the Cox-Maze III procedure. The current procedure incorporates lesions identical to those of the Cox-Maze III procedure, and has been named the Cox-Maze IV procedure. Clinical data have shown that this modified operation has significantly shortened the operative time while maintaining the high success rate of the traditional cut-and-sew Cox-Maze III procedure.