The mini-maze procedures are cardiac surgery procedures intended to cure atrial fibrillation (AF), a common disturbance of heart rhythm. They are procedures derived from the original maze procedure developed by James Cox, MD.
The origin of the mini-maze procedures: The Cox maze procedure
James Cox, MD, and associates developed the "maze" or "Cox maze" procedure, an "open-heart" cardiac surgery procedure intended to eliminate atrial fibrillation, and performed the first one in 1987. "Maze" refers to the series of incisions arranged in a maze-like pattern in the atria. The intention was to eliminate AF by using incisional scars to block abnormal electrical circuits (atrial macroreentry) that AF requires. This required an extensive series of endocardial (from the inside of the heart) incisions through both atria, a median sternotomy (vertical incision through the breastbone) and cardiopulmonary bypass (heart-lung machine; extracorporeal circulation). A series of improvements were made, culminating in 1992 in the Cox maze III procedure, originally a cut-and-sew procedure, but later performed with cryosurgical lesions. In 2002 Maze IV was first used combining bipolar radiofrequency clamps with linear cryoprobes. Cox-Maze IV is now considered to be the "gold standard" for effective surgical cure of AF, but the results are institution dependent. It was quite successful in eliminating AF, but had drawbacks as well. The Cox maze III is sometimes referred to as the "Traditional maze", the "cut and sew maze", or simply the "maze".
Minimally invasive epicardial surgical procedures for AF (minimaze) Efforts have since been made to equal the success of the Cox maze III while reducing surgical complexity and likelihood of complications. During the late 1990s, operations similar to the Cox maze, but with fewer atrial incisions, led to the use of the terms "minimaze", "mini maze" and "mini-maze", although these were still major operations. A primary goal has been to perform a curative, "maze-like" procedure epicardially (from the outside of the heart), so that it could be performed on a normally beating heart, without cardiopulmonary bypass. Until recently this was not thought possible; as recently as 2004, Dr. Cox defined the mini-maze as requiring an endocardial approach:
"In summary, it would appear that placing the following lesions can cure most patients with atrial fibrillation of either type: pulmonary vein encircling incision, left atrial isthmus lesion with its attendant coronary sinus lesion, and the right atrial isthmus lesion. We call this pattern of atrial lesions the "mini-maze Procedure" ... None of the present energy sources—including cryotherapy, unipolar radiofrequency, irrigated radiofrequency, bipolar radiofrequency, microwave, and laser energy—are capable of creating the left atrial isthmus lesion from the epicardial surface, because of the necessity of penetrating through the circumflex coronary artery to reach the left atrial wall near the posterior mitral annulus. Therefore, the mini-maze procedure cannot be performed epicardially by means of any presently available energy source." Although Dr. Cox's 2004 definition specifically excludes an epicardial approach to eliminate AF, he and others pursued this important goal, and the meaning of the term changed as successful epicardial procedures were developed. In 2002 Saltman performed a completely endoscopic surgical ablation of AF and subsequently published their results in 14 patients. These were performed epicardially, on the beating heart, without cardiopulmonary bypass or median sternotomy. Their method came to be known as the minimaze or microwave minimaze procedure, because microwave energy was used to make the lesions that had previously been performed by the surgeon's scalpel. Shortly thereafter, Randall K. Wolf, MD and others developed a procedure using radiofrequency energy rather than microwave, and different, slightly larger incisions. In 2005, he published his results in the first 27 patients. This came to be known as the Wolf minimaze procedure. Today, the terms "minimaze", "mini-maze", and "mini maze" are still sometimes used to describe open heart procedures requiring cardiopulmonary bypass and median sternotomy, but more commonly they refer to minimally invasive, epicardial procedures not requiring cardiopulmonary bypass, such as those developed by Saltman, Wolf, and others. These procedures are characterized by:
No median sternotomy incision; instead, an endoscope and/or "mini-thoracotomy" incisions between the ribs are used. No cardiopulmonary bypass; instead, these procedures are performed on the normally beating heart. Few or no actual incisions into the heart itself. The "maze" lesions are made epicardially by using radiofrequency, microwave, or ultrasonic energy, or by cryosurgery. The part of the left atrium in which most clots form (the "appendage") is usually removed, in an effort to reduce the long-term likelihood of stroke.
Microwave minimaze Completely Endoscopic Microwave Ablation of Atrial Fibrillation on the Beating Heart Using Bilateral Thoracoscopy: The microwave minimaze requires three 5 mm to 1 cm incisions on each side of the chest for the surgical tools and the endoscope. The pericardium is entered, and two sterile rubber tubes are threaded behind the heart, in the transverse and oblique sinuses. These tubes are joined, then used to guide the flexible microwave antenna energy source through the sinuses behind the heart, to position it for ablation. Energy is delivered and the atrial tissue heated and destroyed in a series of steps as the microwave antenna is withdrawn behind the heart. The lesions form a "box-like" pattern around all four pulmonary veins behind the heart. The left atrial appendage is usually removed.
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