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Ann Thorac Surg 2002;74:S1301-S1306
© 2002 The Society of Thoracic Surgeons
lhan Saniso
lu, MDaba
, MDa
a Department of Cardiovascular Surgery, Florence Nightingale Hospital, Istanbul, Turkey
b Department of Anesthesia, Kadir Has University, Florence Nightingale Hospital, Istanbul, Turkey
* Address reprint requests to Dr Akpinar, Florence Nightingale Hospital, Abide’i HÜrriyet Cad. No:290, 80220 
L, Istanbul, Turkey
e-mail: belh{at}turk.net
Presented at the Eighth Annual Cardiothoracic Techniques and Technologies Meeting 2002, Miami Beach, FL, Jan 23–26, 2002.
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Abstract |
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METHODS: During a period of 11 months, 62 patients with chronic atrial fibrillation who were having concomitant cardiac surgery underwent the procedure. The mean age of the patients was 52 ± 14 years. Patients underwent either a biatrial (group A; n = 39) or left atrial (group B; n = 23) procedure.
RESULTS: Two patients (3.2%) died early in the postoperative period. Three patients (4.8%) required reoperation for bleeding. One patient in group A (1.6%) received a permanent pacemaker. Patients in both groups were free of atrial fibrillation at the end of the procedure (group A: sinus 86.9%, pacemaker 13%; group B: sinus 90.5%, pacemaker 9.5%) (p > 0.05). At 1-month and longer-term follow-up, sinus rhythm was maintained in 92% and 95% of cases in group A, respectively, whereas this rate was 71% and 81% in group B (p > 0.05). Holter monitor surveillance revealed a higher rate of atrial fibrillation, atrial arrhythmias, and atrial flutter in group B (p < 0.05). Transthoracic echocardiography revealed improvement over time in left atrial transport function in both groups (p < 0.05).
CONCLUSIONS: The saline-irrigated radiofrequency modified Maze procedure was performed safely and efficiently. Both the left and biatrial procedures were successful in terms of restoring sinus rhythm during short-term follow-up. Long-term follow-up with more cases is needed to show the superiority of one method over the other.
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Introduction |
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| Dr Akpinar discloses that he has a financial relationship with Medtronic, Inc.
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Atrial fibrillation (AF) is a common arrhythmia that affects 0.4% of the general population and up to 10% of persons older than 65 years of age. More importantly, 60% of patients admitted for mitral valve surgery and up to 5% of patients undergoing coronary revascularisation are known to have chronic AF [1]. The Maze III procedure, described by Cox and colleagues [2], remains the gold standard for the surgical treatment of AF. The Maze III procedure is highly effective; however, it is an extensive and time-consuming technique, which precludes its widespread application. In an effort to reduce technical concerns with the procedure, a variety of other sources such as cryoablation, microwave, bipolar cautery, and radiofrequency (RF) have been used to create lesions similar to those used in the original "cut and sew" technique. Sie and colleagues [3] and Khargi and associates [4] were among the first to use the irrigated RF device to create lesions similar to those in the Maze III procedure, and they named it the "irrigated radiofrequency modified Maze procedure."
The aim of this study was to evaluate the effectiveness of this Saline-Irrigated RF System (Cardioblate, Medtronic Inc, Minneapolis, MN) for surgical treatment of AF, and to determine whether performing left-sided lesions alone would be as effective as performing the biatrial Maze procedure in eradicating AF.
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Material and method |
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The RF ablation system
The system consists of a power generator and a pen. The Medtronic Cardioblate surgical ablation pen is a hand-held, unipolar RF ablation device. The electrode tip is irrigated with saline that cools the tissue and provides a low-impedance path, which allows creation of deeper lesions with less damage to the surrounding tissue. Saline irrigation through nine tip openings conducts RF current away from the tip, creating a virtual electrode. The tip of the pen is slowly oscillated over the endocardial tissue during the procedure. The power generator can produce a power output ranging between 20 and 30 W, and a pump achieves irrigation (5 mL/min). The exact duration of application for each lesion varies according to tissue thickness, power setting, and irrigation rate. Higher power settings lead to increased generation of heat, allowing more rapid creation of deeper lesions. However, heating that is too rapid will result in boiling of intracellular fluid, which can cause damage to the tissue and create a so-called "tissue pop." Most of these pops are minor and do not require intervention, but larger pops may require suturing. We observed two cases of tissue pops in our experience, in which the left atrial tissue was repaired with 4-0 Prolene (Ethicon, Somerville, NJ) stitches. Throughout our experience, we used 25 W with an irrigation rate of 5 mL/min.
Surgical technique
After median sternotomy, cardiopulmonary bypass (CPB) was established in a standard fashion. Both vena cavae were cannulated for venous return. Antegrade and retrograde tepid (32°C) blood cardioplegia was used for myocardial protection.
Left-sided SIRFMM
After cardioplegic arrest, left atrial incision was performed through the interatrial groove. Both cavae were encircled with tapes for total CPB to have a dry field during ablation. A larger sling was used to go around the inferior vena cava; by using this sling, the heart was lifted and turned toward the surgeon to facilitate better exposure of the left atrial appendage (LAA). The LAA was either amputated and sutured afterward, or a circumferential radiofrequency lesion was created around its base and the orifice oversewn from inside the atrium. After the LAA was excised, an ablation line from the LAA to the left superior pulmonary vein was created. In addition to the incision in the interatrial groove, isolation of the right pulmonary veins was completed by a circular ablation line. The left pulmonary veins were encircled and a connecting line was performed between both islands of pulmonary veins, as near to the left atrial roof as possible to avoid injury to esophagus. An ablation line from the left pulmonary veins to the posterior mitral annulus was then performed with caution so as not to injure the circumflex coronary artery. Manipulation with the surgeon’s left index finger or administration of retrograde cardioplegia enabled the surgeon to locate the circumflex artery and to prevent injury during the procedure. In some cases, after placement of a surgical instrument in the coronary sinus from the right side to push up against the left atrial wall to locate where the coronary sinus ended on the left side, an ablation line from the middle of the mitral valve ablation line down toward the base of the atria was performed to prevent the reentry pathways moving between the atria through the coronary sinus (Fig 1).
After the left-sided Maze procedure, the LAA amputation site was sutured with a horizontal matrix suture technique using pericardial strip for reinforcement. Concomitant procedures were performed only after completing the left-sided ablation. The left-sided Maze procedure added 9 to 12 minutes to the original operation.
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Decision to perform left or biatrial procedure
The biatrial Maze procedure was applied in cases in which the right atrium had to be opened for a tricuspid valve inspection or an atrial septal defect, or if the patient formerly had an atrial flutter. Otherwise, the procedure was limited to the left side. We had two subgroups of patients: group A (n = 39) consisted of patients who underwent both the left and right-sided Maze procedure, whereas group B (n = 23) comprised patients who underwent only the left-sided Maze procedure.
Follow-up for the whole group ranged from 45 to 245 days (mean 104 days). All patients underwent 24 hours of Holter monitoring during their hospitalization. Atrial transport function was evaluated by transthoracic echocardiography at 1 and 6 months postoperatively.
Statistical analysis
Statistical analysis was performed using the Prisma program package, version 3 (BMDP, CA). Fisher’s exact test was used to evaluate differences in the patient groups. McNemar’s test was used to evaluate changes in a variable over time, and the unpaired t test was used for age comparison between two groups. A value of p less than 0.05 was considered to be statistically significant.
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Results |
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In group B, intraoperatively freedom from AF was also 100%. Six hours after the operation, 1 patient in this group urgently required reopening in the intensive care unit for sudden massive bleeding, which was due to partial disruption of the LAA suture line. The LAA amputation site was repaired and the patient recovered uneventfully.
Table 2 gives the rhythm status of patients during follow-up. Table 3 shows the Holter monitoring and atrial transport function.
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Atrial transport function was evaluated at 1 month (n = 59) and 6 months (n = 24) postoperatively using transthoracic echocardiography with Doppler analysis of mitral and tricuspid flows. There was no difference in right atrial transport function between groups A and B at 1 and 6 months postoperatively (p > 0.05) However, left atrial transport function improved over time in both groups (p < 0.05) (Table 3).
At the end of 1 month, the New York Heart Association functional class of patients in both groups had significantly improved (group A: 3.2 ± 0.6/1.8 ± 0.4; group B: 2.8 ± 0.5/2.0 ± 0.7; p < 0.05).
Postoperative considerations
The anticoagulation management protocol was the same as that applied for routine open heart surgery. Patients receiving mechanical valves continued to be treated with Coumadin (Du Pont Pharmaceuticals, Wilmington, DE). For patients who remained in sinus rhythm, the INR was kept around 2 for aortic valves and between 2.5 and 3 for mitral valves. Temporary pacing wires (atrial and ventricular) were routinely used for pacing or for overdriving the atrium when necessary.
As early postoperative arrhythmias may be caused my mechanisms other than chronic AF, patients were given 200 mg/d amiodarone on a routine basis for a period of three months. We do not favor early cardioversion for patients in postoperative AF and reserve this for patients who are still in AF after 3 months. Two patients in group B who were in AF 3 months postoperatively underwent cardioversion, but 1 patient remained in AF despite cardioversion. This patient continued to receive amiodarone.
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Comment |
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There have been recent reports of higher restoration of sinus rhythm with only a left-sided RF procedure. Pasic and colleagues [15] have recently published their modification of the Maze procedure. This is an RF Maze operation (Berlin modification) that is based on the principle of the left atrial part of the Maze III procedure combined with the method of isolation of the pulmonary veins. These investigators did not excise or exclude the LAA. The freedom from AF was 92% at 6 months postoperatively.
Isobe and colleagues [16] have recently reported their experience with a modification of the Maze III procedure in which they preserved both atrial appendages. By doing so they claim to improve atrial natriuretic peptide secretion, to retain atrial transport function, and to simplify the operation without decreasing its effectiveness against atrial fibrillation. They were able to restore sinus rhythm in 95.7% of patients. On the other hand, some researchers argue that LAA excision, even if not necessary to interrupt atrial macro reentry circuits, is important to avoid thrombus formation [6]. This is our view, as well.
Some proponents of the procedure involving the left-sided Maze only suggest that the procedure is less time consuming, that it eliminates the need for incisions in the right atrium, and that even if a patient develops atrial flutter after the operation, this problem can easily be managed by catheter ablation techniques [13, 14]. Although this may be true, a second procedure will increase the cost considerably; in addition, this option may not be available in all centers.
In an effort to reduce the number of incisions required for the Maze III procedure, Sie and colleagues [3, 17] have used SIRFMM procedure to create the majority of the required lesions. They reported freedom from AF of 98% ± 1.5% at 1 year. This rate dropped to 86% at 2 years and to 78% at 3 years. Although 83% of patients demonstrated right atrial transport, this rate was 77% on the left side at their last echocardiographic examination. Their series remain highly successful in terms of restoration of sinus rhythm and long-term results in comparison to other series using RF techniques. Khargi and associates [4] have compared the results of 60 patients undergoing mitral valve replacement (MVR) alone or MVR with the SIRFMM procedure, and concluded that at the end of 2 years, patients who underwent the SIRFMM procedure enjoyed a freedom from AF at a rate of 80% versus 20% in the MVR-alone group. We conducted a similar retrospective analysis and evaluated the data of 20 patients with chronic AF who had undergone a mitral valve procedure earlier. At the end of 1 month, only 1 patient was in sinus rhythm (5%). This was reported as 7% in a study published by Melo and associates [14]. The idea that some of these patients do convert to sinus rhythm irrespective of ablation, and that ablation may not be necessary, does not seem to be justified by the present data.
The saline-irrigated RF energy has some theoretical advantages over dry RF energy. The problem with the latter is the limitation of the depth that it can penetrate into the tissue [4, 17]. When using irrigated RF, the normal saline irrigation cools the surface temperature so that direct resistive heating is directed below the surface, resulting in a lesion of greater depth and in a higher chance of creating a transmural lesion [17]. Tissue injury due to excessive application of the cardioblate pen has been reported. This occurred in two cases in our series in which the injury could easily be repaired using 5-0 Prolene sutures. This can be kept to a minimum with experience. Three patients in our series were reopened for bleeding. All bleedings were associated with the LAA amputation site. In 1 patient, bleeding was due to partial disruption of the suture line. This complication occurred early in our experience when LAA amputation site was sutured before completion of the left-sided ablation. Because of the suspicion that such a complication may have been a result of damage to the suture line by RF heat waves, we changed our protocol so that amputation site was not sutured before the completion of left-sided RF ablation. As the LAA is a fragile tissue and as bleeding can still occur, another option is to ablate the LAA circumferentially within the left atrium, which was performed in 9 patients.
Whether a limited ablation procedure will restore sinus rhythm in the majority of patients with structural heart disease still remains to be investigated. Evidence collected so far suggests that the excellent results established by the Maze III procedure should not be compromised for the sake of simplifying the procedure.
Left atrial diameter or volume has been a concern for the success of the Maze procedure. It has been reported that patients with a left atrial diameter of more than 65 mm have lower conversion rates to sinus rhythm [13, 15, 18]. Our experience has also shown that patients with a very large atrium have a higher rate of reconversion to AF (although a statistical analysis was not performed), and perhaps a left atrial reduction procedure should be added to the operation.
Whatever technique is used, even with the Maze III procedure, an early AF rate of almost 35% is reported [6, 13]. This incidence ranged between 5.2% and 28.6% in our series. These early arrhythmias usually respond well to medical therapy and provide a solid basis for antiarrhythmic therapy after the operation. This early AF has been reported by other groups as well, and is explained by the late (3 to 6 months) healing process of the atrial lesions and by the inflammatory process associated with the procedure; and it may be for this reason that many researchers report higher success rates at 1 year [13, 15, 16].
Patients in both groups A and B had a 100% freedom from AF at the end of the operation, suggesting the efficacy of both approaches. Holter monitoring revealed a higher rate of atrial arrhythmias and of episodes of AF and flutter in group B (p < 0.05). In addition, during follow-up, more patients stayed in sinus rhythm in group A than in group B, although this is not statistically significant. For this reason, we preferred the biatrial Maze procedure during the later part of our experience to avoid the necessity for a second catheter ablation procedure for atrial flutter.
Limitations of the study
This is a preliminary report on our experience, and it has two major limitations. These are the relatively small number of patients in each group as well as the short-term follow-up. Nevertheless, we were able to demonstrate that the SIRFMM procedure is easy to perform and that it is safe and effective. Longer follow-up with a larger series will be necessary to determine which procedure (left-sided Maze, biatrial Maze, appendage-preserving operation, epicardial approach, etc) would be the choice in this group of patients. Until then, our current policy is to perform the biatrial SIRFMM procedure for patients with chronic AF who are undergoing concomitant cardiac surgery, because adding the right-sided ablation did not complicate the procedure and seemed to improve results in our series, despite the lack of statistical significance.
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