Mini Maze Procedure (Surgical Ablation)
Not everyone with atrial fibrillation needs to have open-heart surgery. For these patients, the open-chest procedure may not make sense, especially because it typically takes longer to recover from an open-chest procedure compared to a minimally invasive (closed chest) procedure.
Fortunately, if you have just atrial fibrillation and no other heart issues, some cardiac surgeons can ablate heart tissue without opening the chest. This is often called the mini maze, although maze is not an accurate description of the procedure. In most cases, the surgeon doesn’t create a true maze as in the Cox maze III and IV procedures to keep electrical impulses on the appropriate path through the left and right atria in the heart. Instead, most mini maze procedures are performed only in the left atrium. The proper term for closed-chest ablation procedures is minimally invasive surgical ablation or thoracoscopic surgical ablation.
Minimally invasive surgical ablation takes only a few hours. In addition, it doesn’t require the large incisions in the sternum that are necessary for open-heart surgery. Thus, recovery is much shorter and easier, and most patients are afib-free afterward.
While patients with paroxysmal afib have been considered the best candidates for minimally invasive surgical ablation, recent enhancements have also yielded success for patients with persistent and longstanding persistent afib (sometimes referred to as chronic afib).
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Minimally Invasive Surgical Ablation Techniques
To get to the heart, the surgeon makes three or four small incisions on each side of the chest. Next, the surgeon places three to four ports (tubes) in these incisions. These ports are used to introduce surgical instruments, ablation devices, and a thoracoscope to enter the chest.
A thoracoscope (or mini camera) is placed in one of the ports so that the surgeon can see the patient’s internal organs and the location of surgical ablation devices and tools. This allows the surgeon to see the heart and where ablation lines are placed even though the chest remains closed. Because a thoracoscope is integral to closed-chest surgical ablation procedures, these are sometimes called video-assisted surgical ablation or thoracoscopic surgical ablation.
A surgical ablation energy source, such as radiofrequency or cryothermy, is used to scar the heart tissue. In this way, the surgeon can create a conduction block that isolates the pulmonary veins and stops the chaotic electrical signals from disrupting the heart. Minimally invasive surgical ablation is different from catheter ablation as it is performed on the outside of the heart, known as epicardial ablation. For catheter ablation, the electrophysiologist scars tissue inside the heart, known as endocardial ablation.
Some surgeons only perform pulmonary vein isolation in doing thoracoscopic surgical ablation procedures. At a minimum, this involves ablating the pulmonary veins and may include additional ablation along the roof of the left atrium or in other areas in the left atrium. Some surgeons call this type of ablation a “modified Maze.” However, this is an incorrect use of the term as ablation is only performed in the left atrium.
Since the ablation is on the surface of the heart, there is less risk that pulmonary vein stenosis will occur, as can happen in catheter ablation. Pulmonary vein isolation may be sufficient to stop atrial fibrillation in patients with paroxysmal afib.
Patients with persistent and longstanding persistent afib likely need more extensive ablation. These more severe forms of afib are characterized by changes in the atrial tissue and muscle (called substrate modification).
Two techniques, the Dallas Lesion Set and the Five Box Thoracoscopic Maze, have demonstrated solid success rates when treating persistent and longstanding atrial fibrillation. These techniques are described below.
To watch a video of a minimally invasive (mini maze) surgical ablation procedure, including the evolution of maze surgical ablation procedures, see Surgeon Discusses Evolution and Future of the Atrial Fibrillation Maze Procedure.
Dallas Lesion Set
In addition to pulmonary vein isolation, the Dallas Lesion Set includes additional lesion lines to connect the left superior pulmonary vein to the right superior vein. With other ablation lines, a triangle is created on the dome of the left atrium. A sensing pen is placed in the dome to confirm that conduction block has been achieved. High-frequency stimulation is used to identify the location of ganglionated plexi, which are then ablated. The left atrial appendage is also excluded.1
Six-month results of 10 patients with persistent afib showed 90% of patients to be free from atrial fibrillation. Of the 20 longstanding persistent afib patients treated, 75% were free of afib. However, some patients remained on antiarrhythmic drugs.2
Five Box Thoracoscopic Maze
This technique involves creating five electrically-isolated compartments in the left atrium. In addition to pulmonary vein isolation, the superior vena cava and coronary sinus are ablated. All of the ablations are enclosed within discrete but contiguous compartments. The integrity of each box—that is, whether afib has been isolated—is verified in real-time. This is done by using a pacing probe to confirm that electrical signals entering and exiting each compartment are “blocked.”3
Six-month results showed that 96.6% of patients, virtually all of whom had longstanding persistent afib, were free of atrial fibrillation and antiarrhythmic medication. At 13 months, 96.2% of patients remained in normal sinus rhythm and were off antiarrhythmic drugs.4
What’s important is that patients have a choice. Typically, catheter ablation is the first procedure considered for those with afib. However, if you prefer a minimally invasive surgical ablation approach, you have that option. Results of the FAST study (Atrial Fibrillation Catheter Ablation versus Surgical Ablation Treatment: A MultiCenter Randomized Clinial Trial) showed higher success rates for patients who had minimally invasive afib surgery after failing catheter ablation compared to patients who had a second catheter ablation.
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