User:Jamesmcclelland/minitest
Minimaze procedures are minimally invasive cardiac surgical procedures that may cure atrial fibrillation (AF), a common disturbance of heart rhythm. Minimaze refers to "mini" versions of the original Maze procedure.
History of Surgical Procedures for Cure of AF
The Cox-Maze Procedure
James Cox, MD, developed the original "Maze" or "Cox-Maze" procedure, an open-heart surgical procedure to eliminate atrial fibrillation, during the 1980's and performed the first one in 1987 (1). “Maze” refers to the series of incisions made in the upper chambers of the heart, which are arranged in a maze-like pattern. These incisions were intended to stop AF by blocking the irregular electrical activity by the scars of the incisions, although they may work by other methods as well. This procedure required a median sternotomy (an incision through the breastbone), cardiopulmonary bypass (heart-lung machine), and an extensive series of incisions through both atria (upper chambers of the heart). It met with success, but had complications as well. A series of improvements were made, culminating in the Cox Maze III procedure in 1992. The Cox Maze III procedure has long been considered the “gold standard” for effective surgical cure of AF, and now, when the Maze procedure is discussed, it is usually the Cox Maze III that is meant. This procedure goes by other names, including the “Traditional Maze” or the “Cut and Sew Maze”, and others.
A great deal of effort has since been made to equal or exceed the success of the original Cox Maze III, while reducing the complexity and likelihood of complications. Fewer incisions on the heart and smaller incisions through the chest led to the use of terms such as “mini-maze”, “minimaze”, and “mini maze” for these procedures. These terms were first used in 1999 in an article entitled "Midterm results after the mini-maze procedure" (2). It referred to a procedure similar to the original Cox-Maze III (it required cardiopulmonary bypass, a median sternotomy, and endocardial incisions), but with fewer incisions on the heart. In 2004, Dr. Cox also defined the “Mini-Maze” procedure in a similar way, requiring incisions from the inside of the heart, hence requiring cardiopulmonary bypass. His definition specifically excluded all currently available minimally invasive surgical procedures for atrial fibrillation:
“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.” (3)
The Advent of Minimally Invasive Surgical Procedures for AF
The meaning of the "mini-maze" terms changed as the procedures themselves changed. In 2002 Saltman performed a completely endoscopic surgical ablation of AF (4) and went on to publish a series of 14 patients (5). These were performed epicardially, using microwave energy, without cardiopulmonary bypass or median sternotomy, and came to be known as the minimaze or microwave minimaze procedure.
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 (6). 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 are more commonly they refer to the minimally invasive procedures including those that that Saltman and Wolf developed. These procedures are characterized by:
1. No median sternotomy incision; instead, endoscopes or “mini-thoracotomy” incisions are used between the ribs.
2. No cardiopulmonary bypass (heart-lung machine); instead, these procedures are performed on the normally beating heart.
3. Few or no actual incisions into the heart itself. The "maze" lesions are made epicardially (from the outside of the heart) by heating the tissue using radiofrequency, microwave, or ultrasonic energy, or by freezing the tissue.
4. The part of the left atrium in which most clots form (the “appendage”) is removed, which may reduce the long-term likelihood of stroke.
Currently Available Types of Minimaze Procedures
Microwave minimaze
Completely Endoscopic Microwave Ablation of Atrial Fibrillation on the Beating Heart Using Bilateral Thoracoscopy: The microwave minimaze requires 3 one centimeter incisions on each side of the chest. The pericardial space is entered, and two sterile rubber tubes are threaded behind the heart. These are used to guide the microwave energy source to the appropriate region to begin ablation. The microwave source is long and flexible; it is manuevered to the appropriate sites, energy is delivered, and the atrial tissue heated and destroyed. The left atrial appendage is usually removed. (4, 5)
Wolf minimaze
Video-assisted Bilateral Epicardial Bipolar RF Pulmonary Vein Isolation and Left Atrial Appendage Excision: The Wolf MiniMaze requires 2 one centimeter and 1 five centimeter incisions on each side of the chest. These incisions allow the surgeon to maneuver the tools, view areas through a videoscope, and to see the heart directly. The right side of the left atrium is exposed first. The surgeon places clamp-like tool on the left atrium near the pulmonary veins, and ablation is performed by heating the atrial tissue between the jaws of the clamp, cauterizing the area, much like a catheter ablation. The clamp is removed. The nerves that cause AF (autonomic ganglia; ganglionated plexi) are in the area and are eliminated as well. In many institutions, a surgeon and an electrophysiologist work closely together to ensure that the ablation of conduction from the atrium to the pulmonary veins, and the gangionated plexi is complete.
Subsequently the left side of the chest is entered. The ligament of Marshall (an area known to cause AF in some patients) is removed. The surgeon then positions the clamp near the left sided pulmonary veins, and performs the ablation. Testing for elimination of conduction, and for elimination of activity of the ganglionated plexi, may be performed. (6)
HIFU minimaze
Surgical ablation of atrial fibrillation with off-pump, epicardial, high-intensity focused ultrasound: The HIFU minimaze is usually performed in conjunction with other cardiac surgery, such as mitral valve repair. An ultrasonic device is postioned epicardially, around the pulmonary veins, and intense acoustic energy is directed at the heart to destroy tissue. Ultrasonic energy is thought to be able to be directed precisely. (7)
Patient Selection
The minimaze procedures are an alternative to catheter ablation of AF. Patients are considered for minimaze procedures if they have moderate or severe symptoms and have failed medical therapy; asymptomatic patients are generally not considered. Those most likely to have a good outcome have paroxysmal (intermittent) AF, and have a heart that is relatively normal. Those with severely enlarged atria, markedly reduced heart pumping function, or severely leaking heart valves are much less likely to have a successful result; these procedures are not recommended for such patients. Previous open heart surgery provides technical challenges due to scarring on the outside of the heart but does not always preclude minimally invasive surgery.
Results
Consensus regarding success of the minimaze procedures has not been attained. Widely varying ways of reporting findings has made characterizing and comparing procedures difficult or impossible. Procedures continue to evolve rapidly, so direct comparisons with long follow-up do not accurately reflect current procedural methods. For the newer minimaze procedures, only relatively small and preliminary reports are available.
Perhaps the biggest problem in determination of procedural success rates is inconsistent methods of following patients to determine if atrial fibrillation has recurred. It has been clearly demonstrated that longer or more intensified follow-up identifies much more recurrent atrial fibrillation (ref), hence the more careful investigator may appear "less successful". With those caveats in mind, it can be said that successful elimination of atrial fibrillation can be attained in 50% to 99% of carefully selected patients.
References
1. The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. JL Cox, RB Schuessler, HJ D'Agostino Jr, CM Stone, BC Chang, ME Cain, PB Corr and JP Boineau. J Thorac Cardiovasc Surg. 1991 Apr;101(4):569-83. PMID 2008095
2. Midterm results after the mini-maze procedure. Zoltan A. Szalaya, W. Skwaraa, H.-F. Pitschnerb, I. Faudeb, W.-P. Klövekorna, Erwin P. Bauera. Eur J Cardiothorac Surg 1999;16:306-311. PMID 10554849
3. The Role of Surgical Intervention in the Management of Atrial Fibrillation. James L. Cox, MD. Tex Heart Inst J. 2004; 31(3): 257–265. PMID 15562846
4. A completely endoscopic approach to microwave ablation for atrial fibrillation. Saltman AE, Rosenthal LS, Francalancia NA, Lahey SJ. Heart Surg Forum. 2003;6(3):E38-41 PMID 12821436
5. The completely endoscopic treatment of atrial fibrillation: report on the first 14 patients with early results. Salenger R, Lahey SJ, Saltman AE. Heart Surg Forum. 2004;7(6):E555-8. PMID 15769685
6. Video-assisted bilateral pulmonary vein isolation and left atrial appendage exclusion for atrial fibrillation. Randall K. Wolf, MD, E. William Schneeberger, MD, Robert Osterday, PA, Doug Miller, MED, Walter Merrill, MD, John B. Flege, Jr, MD, A. Marc Gillinov, MD. PMID 16153931
7. Surgical ablation of atrial fibrillation with off-pump, epicardial, high-intensity focused ultrasound: Results of a multicenter trial. Jean Ninet, MD, Xavier Roques, MD, Rainald Seitelberger, MD, Claude Deville, MD, Jose Luis Pomar, MD, Jacques Robin, MD, PhD, Olivier Jegaden, MD, Francis Wellens, MD, Ernst Wolner, MD, Catherine Vedrinne, MD, PhD, Roman Gottardi, MD, Javier Orrit, MD, Marc-Alain Billes, MD, Drew A. Hoffmann, PhD, James L. Cox, MD, Gerard L. Champsaur, MD. J Thorac Cardiovasc Surg 2005;130:803 PMID 16153932
A more complete current listing of minimaze references can be obtained by this search at the Cardiothoracic Surgery Network.