The Mini-Maze procedure is a three pronged approach to convert patients to Normal Sinus Rhythm, eliminate the need for long term anti arrhythmic medication and reduce the potential for thromboembolic stroke such that patients can safely discontinue the use of coumadin. The three components include pulmonary vein isolation with communicating lesion set, vagal ganglionic mapping and ablation, and amputation of the left atrial appendage.
The mainstay of ablative arrhythmia procedures has been isolation of the pulmonary veins. This stems from the work of Cox as well as Haissaguerre which implicated the pulmonary veins as an ectopic focus of excitation. This is accomplished using the Atricure bipolar ablation device which reproducibly makes transmural complete linear lesions circumferentially around the pulmonary veins by burning a cuff of atrium. Pulmonary vein stenosis is essentially not possible since the ablation is made on the left atrium itself. Because of the use of bipolar energy, only the tissue within the jaws of the clamp is ablated and energy is not allowed to dissipate within the body. As a consequence, atrio-esophageal fistulas have not been reported. The risk of phrenic nerve injury is also significantly reduced because of the direct visualiztion which is afforded of this structure.
More recently Jackman has identified the importance of vagal tone as contributing to the excitation and facilitating ectopic foci to fire by lengthening the refractory period.
High freqency stimulation of the epicardial surface of the heart is used to map the location of the vagal ganglia which are then ablated using a bipolar pen. This generally results in an increase in resting heart rate and helps further maintain Normal Sinus Rhythm. In some patients, vagal tone is the primary physiologic trigger for paroxysmal Atrial Fibrillation. Continued work in this area will help to further elucidate the physiology of this mechanism.
It is felt that over 90% of thromboembolic strokes originate in the left atrial appendage. To deal with this reality amputation of the left atrial appendage is performed using an endolinear stapling device with TEE confirmation of exclusion of the appendage. Terminating the use of coumadin is a contentious issue. We obtain a CardioNet monitor for two weeks once the patient is off medication and then discontinue coumadin after at least 90 days in consultation with the patients physicians. There have currently been no CVA's off coumadin.
Who is a Candidate?
Any patient with Paroxysmal, Persistent or Chronic Atrial fibrillation who is symptomatic from their Atrial fibrillation, is intolerant of their medication, or who either does not desire or is unable to be anticoagulated. Patients who are not a candidate for catheter ablation due to body habitus or have failed prior catheter ablation are candidates for a surgical approach. The age range has been from 40 to 84. The patient must be willing to undergo surgery. Risks include bleeding, infection, possible cardiac injury. The surgery is minimally invasive, being performed both thoracoscopically and off pump. To date, there have been no conversions to sternotomy or requirement of cardiopulmonary bypass.
Postoperative length of stay is in the 3-4 day range and patients return to full activity within 2-3 weeks. The maor postoperative issues relate to pain and early dysrhythmia.
A combination of intercostal nerve block, use of On-Q catheters and Patient Controlled Analgesia (PCA) improves pain management.
Postop AFib: Almost all patients will leave the OR in Normal Sinus Rhythm. Most patients will have an episode of Atrial Fibrillation within the first few days postoperatively. This is common to both catheter and surgical approaches. By about 6-8 weeks most patients convert to NSR on their own. A small number may require cardioversion at this point in time. A very small number will have right sided Atrial Flutter unmasked and will need a flutter ablation on the right which can be very simply done in the EP lab.
Patients with severe COPD who are unable to tolerate single lung ventilation. Most patients do qualify.
Intraoperative Recording Strips
Pulmonary Vein Stenosis Due to Catheter Based Ablation - The Mini-Maze is intended to prevent this complication.
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McClelland et al., J Cardiovasc Electrophysiol, Vol. pp. 1-7
Wudel et al., 2008;85:34-38Ann Thorac Surg
Edgerton et al., J Interv Card Electrophysiol
Jackman - Circulation
Stollberger, et al. Pathophysiology of Left Atrial Appendage, Chest. 2003;124:2356-2362
Bettoni - Circulation - Vagal Tone and PAF
Gaynor - AF Predictors of Recurrence
Haissaguerre Paper NEJM
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