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Ann Thorac Surg 2006;81:1325-1331
© 2006 The Society of Thoracic Surgeons
Cardiac Surgical Associates MAZE Workgroup, Tampa-Saint Petersburg, Florida
Accepted for publication July 13, 2005.
* Address correspondence to Dr Pruitt, Cardiac Surgical Associates, St. Joseph's Medical Arts Building 2nd Floor, 3003 W. Dr. M. L. King Jr. Blvd., Tampa, FL 33607 (Email: jpruitt153{at}aol.com).
Presented at the Forty-first Annual Meeting of The Society of Thoracic Surgeons, Tampa, FL, Jan 24–26, 2005.
| Drs Pruitt and Lazzara disclose that they have a financial relationship with Guidant.
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Abstract |
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METHODS: Between August 2003 and October 2004, 50 drug-resistant, symptomatic atrial fibrillation patients underwent thoracoscopic or robotic-assisted off-pump epicardial microwave ablation with the FLEX 10 device (Guidant, Indianapolis, IN). There were 35 men (70.0%) and 15 women (30.0%), mean age 59.1 years ± 10.0 (range, 37-75 years). Mean duration of atrial fibrillation was 73.5 months ± 82.3 (range, 5-480 months). Thirty-three patients (66.0%) had intermittent atrial fibrillation and 17 (34.0%) continuous. Intermittent patients had pulmonary vein isolation whereas continuous patients had additional right and left atrial lesions performed. Forty-six patients (92.0%) had endoscopic stapling of the left atrial appendage.
RESULTS: There were no hospital deaths. Postoperative in-hospital complications were minimal with 2 patients (4.0%) experiencing diaphragmatic dysfunction. No patient required a permanent pacemaker implant. Mean postoperative length of stay was 3.7 ± 2.2 days. Cumulative follow-up was 335.8 patient months, mean 7.6 months (range, 2.0-15.9 months). There was 1 late death (2.0%). In 5 patients (10.0%) the MicroMaze operation and subsequent electrophysiology intervention failed and a Cox-Maze III operation was performed. Follow-up was 100% complete with 79.5% (35 of 44) patients in normal sinus rhythm.
CONCLUSIONS: Totally endoscopic closed-chest microwave ablation for treatment of intermittent and continuous atrial fibrillation is technically feasible and presents minimal risk to the patient. Initial results are impressive and demonstrate an enhanced quality of life and freedom from atrial fibrillation in drug-resistant symptomatic patients.
Atrial fibrillation (AF) is the most common form of arrhythmia encountered in today's clinical practice and is associated with increased morbidity and mortality. Over 2.2 million Americans are affected by AF [1] and approximately 160,000 new cases are identified each year [2]. It is present in 0.4% of the population and greater than 1.0% in individuals 60 years of age and over [3, 4] with an incidence of 9.0% occurring in octogenarians [5, 6].
Morbidities associated with AF include patient discomfort, anxiety, hemodynamic compromise and thrombolic complications [7–10]. Stroke continues to be the most lethal complication associated with AF, with an overall incidence of 5-7% per year [11]. The mortality of patients with AF is twice that of individuals in normal sinus rhythm (NSR) [12].
Major strides have been made in the medical and surgical treatment of AF. Drugs have been shown to induce chemical cardioversion, however, their failure rate at 2 years is as high as 60% [13]. Procedure times of 5-10 hours for percutaneous radiofrequency ablation [14, 15] and associated morbidities, including cardiac tamponade, stroke and pulmonary vein stenosis [16, 17] have detracted from the efficacy of the approach. The Cox-Maze III operation has demonstrated curative results for AF. While the Cox-Maze III operation has become the "gold-standard" for the surgical treatment of AF, this procedure has not been embraced by the cardiac surgical community since it is technically challenging and few surgeons across the country have become proficient with the "cut and sew" technique [18]. Its acceptance in patients with lone AF has not been universal.
The purpose of this study has been to devise a low-risk, closed-chest, off-pump, minimally invasive surgical approach to facilitate the rapid and effective treatment of AF. It seeks to define the safety, clinical benefits, efficiency and early outcomes of a minimally invasive thoracoscopic approach for the treatment of AF.
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Material and Methods |
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TopAbstractIntroductionMaterial and MethodsResultsCommentDiscussionAcknowledgmentsReferences |
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There were 35 men (70.0%) and 15 women (30.0%) between the ages of 37 and 75 years old, with a mean age of 59.1 ± 10.0 years. There were 33 patients (66.0%) with intermittent and 17 patients (34.0%) with continuous AF. Mean duration of AF in the present series was 73.5 ± 82.3 months and ranged from 5 to 480 months. Patient clinical characteristics are presented in Table 1.
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The MicroMaze operation utilizes a closed-chest bilateral thoracoscopic approach. The manubrial notch and xyphoid process are marked. The 5 or 10 mm camera ports are positioned midway between the manubrial notch and the xyphoid process at the mid-axillary line at the fourth intercostal space. Two triangles, 1 on the right side and the other on the left, are drawn on the patient's chest connecting the manubrial notch, the xyphoid process with the camera port sites. These triangular areas represent the visual fields for use with the thoracoscope. Two additional instrument ports (for a total of 3 ports on each side of the patient) are required and marked. A 5mm port is placed at the second intercostal space at the anterior axillary line and a 10mm port at the fifth to sixth intercostal space at the anterior axillary line. These 2 markings are outside of the thoracoscope visual field. The right and left side port placements are identical except that the left inferior-most port (12 mm) is placed more posteriorly to allow a stapling device to engage the base of the left atrial appendage (Figure 1). Following the marking procedure, the chest is prepped and draped and thoracoscopic camera holders (Karl Storz, Tuttlingen, Germany) are attached to the operating room table on each side of the patient.
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In patients with intermittent AF, a boxed lesion around all 4 pulmonary veins is created, as well as 1 from the box to the tip of the left atrial appendage (Figure 2). In patients with continuous AF, 2 right atrial lesions are also performed which include a caval to caval ablation line, and another up to the tip of the right atrial appendage (Figure 3). At the completion of the lesion set, endo-stapling of the left atrial appendage is performed with the endo-stapler (Ethicon, Somerville, NJ) with a no-knife stapling cartridge. The stapling cartridge is covered with SEAMGUARD (Gore, Flagstaff, AZ) to ensure hemostasis.
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Operative Data
The operation was performed thoracoscopically in 47 patients (94.0%) and robotic-assisted in 3 patients (6.0%). The lesion set created for the series is summarized in Table 2. The left atrial appendage was endoscopically stapled in 46 patients (92.0%). In 4 patients (8.0%) the left atrial appendage was not stapled for anatomic reasons. In 3 patients (6.0%) a minithoracotomy was performed intraoperatively to control bleeding. Figure 4
provides a graphic representation of the procedure times for the series. The mean duration for the procedure was 214.0 minutes and ranged from 71 minutes to 391 minutes.
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Data are presented as frequency distributions and simple percentages. Values of continuous variables are expressed as mean ± standard deviation. Analysis of discrete variables was accomplished by X2, the continuity-adjusted X2 analysis or a 2-tailed Fisher's exact test. Data collected were analyzed using the Number Cruncher Statistical Systems (NCSS; Kaysville, UT). A significant difference between measurements was defined as p 
0.05.
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Results |
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Patient Follow-Up
Follow-up data was collected for 50 patients (100.0%) discharged from the hospital and ranged from 2 to 15.9 months (mean, 7.6) with a cumulative follow-up of 335.8 patient-months. There was 1 (2.0%) late death. The patient was morbidly obese and had severe pulmonary disease at the time of the operation. The cause of death was undetermined. There were 5 patients (10.0%) where the MicroMaze procedure and subsequent EP intervention failed and a Cox-Maze III operation was performed. At follow-up, all 5 patients (100.0%) were free of AF as evidenced by ECG results. None of the patients during the follow-up experienced a major adverse cardiac event (MACE), eg, TIA, CVA, nonfatal MI or anticoagulation complication. The remaining 44 patients who underwent a MicroMaze procedure only or an additional catheter ablation constitute the clinical material for the remainder of the follow-up.
At last follow-up, 79.5% (35 of 44) patients were found by ECG to be in NSR. The results, by patient group, are presented in Table 3. A comparison by patient-group approached statistical significance (p = 0.053). There were 65.0% (13 of 20) patients with left atrial dimension of 4.5 cm who were in NSR. Moreover, there were 91.7% (22 of 24) patients with left atrial dimension of 
4.6 cm who were found to be in NSR. This difference approached statistical significance (p = 0.057). In 18.2% (8 of 44), a follow-up catheter ablation was performed for continued AF or atrial flutter after the MicroMaze operation. Following the ablative procedure, 75.0% (6 of 8) were free of AF as evidenced by ECG results.
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Quality of Life
At follow-up, a number of patients were clinically and functionally improved and free of AF. Patients were asked questions during the course of the follow-up concerning their perception of the MicroMaze operation and perceived health status. A significant 93.2% (41 of 44) patients indicated they had returned to their normal activities of daily living including full-time employment. Moreover, 81.8% (36 of 44) patients reported they were pleased with the outcome of their operation. A similar percentage 81.8% (36 of 44) patients felt the operation had been beneficial and allowed them to achieve an enhanced quality of life (QOL) as a part of the follow-up. Patients were asked to compare their current health status to that of 1 year ago. A significant number, 81.2% (36 of 44) patients stated they were "much" or "somewhat" better than 1 year ago, 13.6% (6 of 44) patients indicated they were "about the same" and 4.5% (2 of 44) patients reported being "somewhat" or "much" worse than 1 year ago.
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Comment |
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As technology continues to advance, the focus must be on the development of a minimally invasive operation for the treatment of both intermittent and continuous AF. The current limitations of such an operation must be recognized since the lesion sets created through this approach are incomplete. Omitted are the right atrial isthmus and the mitral annular lesions. Moreover, transmurality is not completely assured and there exists the potential for gaps in the ablation line.
Freedom from AF was documented in 80.6% (29 of 36) patients undergoing an isolated MicroMaze operation, as documented by ECG at follow-up. Eight patients who continued to experience AF or atrial flutter 3 months following the MicroMaze procedure were evaluated by the electrophysiologist to be considered for an ablative procedure. Six of the 8 patients (75.0%) were free of AF following the ablative procedure. The overall rate of freedom from AF in the series for minimally invasive procedures (MicroMaze + EP ablation) was 79.5% (35 of 44) patients. These outcomes demonstrate the benefits of a combined approach with the electrophysiologist in the treatment of AF. While these outcomes are encouraging, the freedom from AF is less than that reported with the Cox-Maze III operation [18, 19]. This is to be expected since all lesions cannot be treated with currently available minimally invasive technology. In our patients, those who continue to experience AF following minimally invasive procedures, an option is presented to undergo a Cox-Maze III operation.
On several occasions, the EP evaluation of a failed MicroMaze revealed that more than 1 area of electrical leak in the pulmonary vein box lesion is present. In 1 case, no box scar could be identified. The underlying reason for the lack of transmurality or skipped areas in some patients cannot be fully explained at present. Possible explanations may include: inadequate contact of the FLEX 10 with the left atrial tissue, presence of a thick left atrial wall, occurrence of high cardiac output causing loss of heat energy, or motion during the burning sequence. These factors, individually or collectively, may contribute to an inadequate burning process. A further understanding of these inherent limitations may enhance the outcome of the MicroMaze operation.
Patients with large left atria (4.5 cm) were found to be in NSR more often at follow-up than those with small left atria (4.6 cm). This finding approached statistical significance (p = 0.056) and may be explained on the basis that a large left atrium may provide a more favorable contour for contact with the FLEX 10 device. This could also explain why patients in continuous AF (who have large left atria) have relatively high success rates with the MicroMaze operation.
The acceptable morbidity and mortality experienced with the MicroMaze operation has been encouraging. The majority of patients has clearly realized clinical and symptomatic improvement and has indicated an enhanced QOL during this early phase. The occurrence of MACE in the present series has been nonexistent and no patient has required a permanent pacemaker. Pacemaker implants following the standard Cox-Maze III operation are reported as high as 20.0% [20].
During the operation, every attempt should be made to reduce potential respiratory complications secondary to possible phrenic nerve injury. Transient elevation of the right hemidiaphragm was documented in 4.0% (2 of 50) patients. Extreme vigilance is required during the operation to avoid contact with the phrenic nerve. Intraoperative bleeding complications were experienced in 6.0% (3 of 50) patients, who required a minithoracotomy for control. This most often occurs during endostapling of the left atrial appendage. Therefore, care should be exercised to avoid traumatic grasping of the left atrial appendage during the stapling procedure. Obliteration of the left atrial appendage is considered an integral part of the MicroMaze operation and may represent an advantage over available medical management and catheter-based ablation procedures by decreasing the patient's risk of stroke.
Operative times have shown a steady decline as a result of refinements in our techniques (Figure 4). The development of a specific guide catheter and other minimally invasive instrumentation should yield even greater improvements in operative times. Operative times of 2 hours or less have become a reality.
The significant (p = 0.001) reduction in the use of Amiodarone and Coumadin during the follow up period is important. Our protocol for discontinuance of medications has been to stop the use of antiarrhythmics at two months postprocedure if the patient is free from AF. Coumadin is discontinued at three months postprocedure if the patient continues to report freedom from AF.
In select groups of AF patients, QOL has been shown to be compromised [20] and particularly impaired in those with paroxysmal AF [21]. The present study has demonstrated that the MicroMaze operation has been perceived as a beneficial therapeutic intervention by a majority of patients. A significant number of patients are functionally and symptomatically improved and experiencing an enhanced QOL.
Continued technological advances will facilitate the minimally invasive treatment of AF. Clearly, an innovative therapeutic strategy utilizing minimally invasive technology is an effective and safe approach for the treatment of AF. When the minimally invasive approach fails, the Cox-Maze III operation remains an alternative. Long-term follow-up with definitive rhythm recordings over extended periods of time will clarify the benefits (or lack thereof) of the MicroMaze operation. Creating innovative ways to complete the full Cox-Maze III lesion set using a minimally invasive approach is a priority. The lesion set should be transmural and continuous (no skips). Methods to intraoperatively assess the integrity of the burns should be developed so any deficiency can be identified before the patient leaves the operating room.
Limitations of the Study
Despite the contributions of this study, several limitations must be addressed. This investigation represents an observational, clinical study and not a randomized trial. The relatively small sample size (N = 50) and brief duration of follow-up (mean, 7.5 months) is a limiting factor. Objective data derived from long-term (>48 hours) continuous rhythm monitoring was unavailable in the present study. Moreover, lack of specific information concerning EP ablative procedures performed by the electrophysiologist post-MicroMaze operation precludes determining what specific ablation therapies significantly influenced freedom from AF.
Comparison of outcomes using various approaches and operations for the treatment of AF is also difficult without standardized methods. Variations in lesion sets, energy sources, methods of follow-up, definition of end points etc., detract from the ability to derive meaningful conclusions from various studies.
Conclusions
As the population continues to age and the prevalence of AF increases, the potential for devastating complications will serve as a catalyst to continue developing improved minimally invasive techniques to more effectively treat lone AF. These preliminary clinical outcomes and patients perceived enhanced sense of well-being clearly suggest the value of a hybrid approach to the treatment of AF. The application of minimally invasive technology is an attractive therapeutic alternative for patients with lone AF.
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Discussion |
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Also, I was curious, you mentioned no MIs or cardiac events. Preoperatively do you evaluate these patients with a stress test or are they cathed, or do they have a cardiac history where they have already been evaluated?
Again, congratulations on a very nice presentation as well as the video.
DR PRUITT: Thank you very much. Our patients underwent an exercise stress test prior to this operation. We did not routinely catheterize these patients. In answer to your question about the intermittent A-fib patients and their medications, the majority was on medications, and we do have this information in our database. Virtually all of them were on anti-arrhythmic medications, although their A-fib was not being controlled.
DR TOMMIE MACK GRANGER (Alexandria, LA): Dr. Pruitt, I have two questions. One, have you correlated the failures of the procedure with the size of the left atrium, and could you comment on the use of cardioversion postoperatively and in the early post-op period?
DR PRUITT: Thank you very much. We actually did look at the correlation of left atrial size and EKG rhythm at rest. To our surprise, the larger left atria had more often normal sinus rhythm on EKG than the small atria. We have hypothesized that possibly contact issues of the device in the smaller left atria may have influenced this outcome. However, we really don't know the meaning of this finding. We had three patients with left atria greater than 6 cm, but very few were the monstrously huge left atria that are associated with poor outcomes.
As to the second question, initially in our study we did use cardioversion fairly frequently in the hospital to try to get people, particularly our continuous A-fib people—which, by the way, do not generally cardiovert during the ablation procedure. We are not seeing them convert to normal sinus rhythm like we see with the full Cox-Maze procedure. Initially, we were being fairly vigorous about trying to cardiovert these patients prior to discharge. We often will try cardioversion if the patient is from out of town, but we won't insist on this approach. We generally bring them back a month later and then cardiovert them. We are generally successful at that time.
DR WILLIAM SCHNEEBERGER (Cincinnati, OH): I have a question about your results. You used the word "perceived" concerning the patients post-op symptoms and you were obviously only doing "snapshot EKGs".
We have found in our patients who are monitored for a week continuously pre-operatively to assess their AF burden, that when they "perceive" intermittent atrial fibrillation, they are only really perceiving 50% of their episodes. Have you noticed that?
The final point is that in the post-op period, (during this time we monitor them continuously for 3 weeks) when they were "perceiving" atrial fibrillation, a number of them had flutter and some of them had paroxysmal atrial tachycardia, not atrial fibrillation.
DR PRUITT: Thank you for that question. I think that you are probably right. We used two ways to discern our freedom from atrial fibrillation and they are imperfect methods. I think long-term continuous rhythm monitoring is what is required and we have not done that in this study. This is a serious limitation. Patient perception in our study, however, did match EKG findings; at least when they said they perceived that they were in normal rhythm, they were in normal rhythm. But the fact that they are missing paroxysms of A-fib, I am sure that is true. Patients in this study were generally highly symptomatic. Part of our follow-up was to assess quality of life issues and whether they felt the operation was beneficial and whether they had fewer paroxysms than prior to surgery. Approximately 80% reported yes to all these factors-that is the operation was beneficial, they perceived fewer paroxysms, and had an improvement in the quality of their life compared to the previous year.
DR TAKASHI NITTA (Tokyo, Japan): Congratulations on the excellent data. We all understand that the goal of atrial fibrillation surgery is to prevent thromboembolism. We found that some of the patients after the limited lesion set still have atrial fibrillation. What do you think about a redo surgery to complete the maze procedure in the patients who still have atrial fibrillation after the limited surgery?
DR PRUITT: We have done five of those operations now and we do the full lesion set. We do not rely on any of the lesions that were previously placed during the MicroMaze procedure. We redo the complete operation. We do not just add the missing lesions.
DR NITTA: Did you open the sternum to do the surgery?
DR PRUITT: Yes, we do a complete sternotomy.
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= robotic-assisted; 
= Nonrobotic-assisted.)