The Historical Perspective of the Cox Maze III
Dr. James L. Cox is rightly credited for his pioneering methodical work developing a treatment for atrial fibrillation (AF): identifying the magnitude of the clinical problem, studying the mechanisms of AF in his laboratory, developing an operative solution in the animal model, then successfully introducing the operation into clinical practice in 1987. The operation became widely recognized as the “Cox-Maze Procedure”. The operation creates a “maze” of pathways in the atria starting at the SA node and the electrical wavefront travels through the pathway to activate both atria and the AV node. The left atrial appendage was also excised to decrease the stroke burden. The original Cox-Maze procedures were performed with multiple incisions, and small targeted cryolesions at the mitral and tricuspid annuli and on the coronary sinus. But the operation was complex and only adopted at a handful of centers. In 2001 bipolar radiofrequency (RF) clamps became commercially available to facilitate creation of transmural ablation lines. The goal of the RF clamps was to make the operation faster and safer than “cut and sew” procedures, to preserve transmural lesions (never in doubt with cut and sew!), and to spread adoption.
The Cox- Maze operation was originally performed with reusable cryoablation equipment, but several iterations of disposable flexible cryoprobes were developed which allow good contact free of gaps along curved atrial surfaces and thus created long transmural lesions. Many other technologies including unipolar RF, bipolar cryoablation clamps, high intensity focused ultrasound, microwave, and lasers were also used to create the ablation lines; most of these devices were discarded due to inconsistent transmural lesions. Many types of operations have been performed as “stand-alone” AF treatments, but due to the inconsistent results, morbidity of the procedures relative to catheter ablation, and lack of enthusiasm in the electrophysiology community, none of them have become widely successful. Likewise various “lesions sets”, including the Cox Maze IV using bipolar RF, were designed to standardize the approach and make the operation more efficient. While improved in some ways compared to the original cut and sew Cox-Maze III operation, adoption is still relatively low and training, coaching, and proctoring are needed to achieve proficiency. At Northwestern we’ve developed a more efficient operation using only cryoablation lesions that is easy to understand, is routinely applied in almost 100% of our concomitant mitral operations in patients with preexisting AF, and over 60% of coronary artery bypass and aortic valve operations. So, more than 30 years after the first Maze operations were performed, adding AF ablation concomitant to other cardiac operations has been widely studied in multiple randomized trials and shown to be effective at greatly reducing AF compared to untreated controls; several database, multicenter, and matched single center studies have shown that it improves late survival; and perioperative risks for AF treated patients are not increased (or perhaps even decreased) compared to untreated AF patients. Furthermore, for standalone treatment of long standing and persistent AF patients, a recent randomized trial documented an approximately 20% improvement in effectiveness for a hybrid surgical and catheter ablation approach compared to catheter ablation alone. These evolutions stem from the seminal work of Dr. Cox, who joins Dr. Norman Shumway as the pioneer of heart transplantation and Dr. Alain Carpentier who invented and refined the field of valve repair, as one of the most influential heart surgeons in the history of cardiac surgery.
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