Evolution of Maze Surgery
The history of maze surgery began in 1992 with the advent of the Cox-Maze III procedure. The Cox-Maze III was the first operation designed to cure atrial fibrillation, and maintain both the normal synchrony between the atria and ventricles, as well as the normal responsiveness of heart rate to exercise. Thus, the patient could resume an excellent quality of life without the need for warfarin or anti-arrhythmia drugs.
At that time, current understanding of the mechanism of atrial fibrillation consisted of the "multiple wavelet" theory. This understood atrial fibrillation as a random circular current traversing the atria in a rapid, disorganized movement. The Cox-Maze III was therefore designed with two principles in mind:
- First, a series of incisions in the atria were made to create a defined corridor for the impulse of conduction to travel from the sinoatrial node (the origin of the heartbeat) to the atrioventricular node, where ventricular contraction is initiated. This corridor would ensure normal atrioventricular synchrony, but deny access to any abnormal wavelets outside the pathway.
- Second, the incisions in the atria resulted in the creation of multiple isolated compartments, resulting in an electrical "debulking" of the atria. It was hypothesized that about 2.5 cm of contiguous atrium was needed to sustain the wavelets atrial fibrillation. The compartmentalization of the atria thus eliminated the substrate necessary for atrial fibrillation to propagate.
Limitations in This Technique
The Cox-Maze III procedure, either in its original form or the "minimally invasive" variant, required an open-chest approach and access to the interior of the heart on cardiopulmonary bypass, the heart-lung machine to maintain circulation while the heart is stopped. While very effective in restoring normal sinus rhythm, the procedure was highly invasive and technically fairly complex, and was associated with not insignificant morbidity rates.
These issues limited the popularity of the operation for otherwise healthy patients with lone atrial fibrillation, and spurred the development of alternative energy sources to reduce the invasiveness of the operation. These alternative energy sources were designed to replace the incisions in the atria of the Cox-Maze III, thereby delivering the same effect of compartmentalizing the atria without the need for endocardial access, leading to truly minimally invasive approaches.
Developments in Maze Surgery
In the years that followed, many different products utilizing a variety of energy sources (laser, high-frequency ultrasound, cryothermy, etc.) became available, touting the ability to create the same effect of the Cox-Maze incisions with less invasiveness. Countless operations were devised, all sharing the moniker "maze," with highly inconsistent treatment of the key anatomy, and even more inadequate verification of the techniques employed. Not surprisingly, these operations, although less invasive than the Cox-Maze III, were substantially less effective in treating atrial fibrillation. With no standardization amongst these so-called "Maze" procedures, patient outcomes were disappointing, and the reputation of surgical therapy of atrial fibrillation waned
Mini-Maze
In 2003, Dr. Randall Wolf developed the "Wolf Mini-Maze," representing an important step forward in anti-arrhythmia surgery. The operation addressed two of the four mechanisms now known to cause atrial fibrillation - the junction of the pulmonary veins with the left atrium, and the epicardial autonomic ganglia - in addition to closing the left atrial appendage for stroke prevention.
Most importantly, this operation was the first to verify both of these critical endpoints in real time. Amazingly, no previous maze operation had included intraoperative verification of its endpoints as a standard part of the procedure. Moreover, access for the operation consisted of a 4 to 6 inch incision between the ribs on each side of the chest, in addition to several other port incisions, without the need for cardiopulmonary bypass. Thus, Dr. Wolf is credited for the advent of a reproducible, less invasive operation which consistently achieves its basic endpoints.
However, as the understanding of atrial fibrillation grew to include the left atrium as an independent source, the limitations of the Wolf Mini-Maze became clear, particularly in managing persistent atrial fibrillation. The Mini-Maze, in fact, omits any treatment of the left atrium, thereby reducing its effectiveness in patients with advanced atrial fibrillation. Furthermore, while the technique required less invasive incisions than the Cox-Maze III, it still involved cutting through a significant amount of muscle tissue, elevating patient discomfort and morbidity rates. Even worse, incisions needed for visualization hampered access to the key anatomy needed to treat all of the sources of atrial fibrillation in the heart. Therefore, the two objectives of minimal access and the comprehensiveness of the anti-arrhythmia procedure appeared to remain in conflict.
Building on prior developments in maze surgery, the five-box thoracoscopic maze procedure has been devised as a more effective surgical approach with higher success rates. If you would like more information about surgical options for treating atrial fibrillation, request a phone consultation with Dr. John Sirak or call his appointment phone at (614) 366-7414.