Ann Thorac Surg 2003;75:1490-1494
© 2003 The Society of Thoracic Surgeons
Original article: cardiovascular
Left atrial maze procedure: a useful addition to other corrective operations
Norihiro Kondo, PhDa,
Kenji Takahashi, MDa*,
Masahito Minakawa, MDa,
Kazuyuki Daitoku, MDa
a Department of Cardiovascular Surgery, Aomori Rousai Hospital, Aomori, Japan
Accepted for publication November 27, 2002.
* Address reprint requests to Dr Takahashi, Department of Cardiovascular Surgery, Aomori Rousai Hospital, 1 Minamigaoka, Shirogane, Hachinohe Aomori 031-0822, Japan.
e-mail: takaken{at}aomorih.rofuku.go.jp
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Abstract
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BACKGROUND: The left atrial maze procedure is performed to treat atrial fibrillation (AF), mainly in patients with mitral valve disease. In this study, we assessed the midterm results of this procedure and clinically analyzed predicting factors for postoperative persistent AF.
METHODS: From June 1997 to May 2001, the left atrial maze procedure was performed on 31 patients (29 with mitral valve disease and 2 lone AF). For purposes of analysis, patients were divided postoperatively into those with persistent atrial fibrillation (AF) and those with sinus rhythm (SR), except 2 patients who required pacemaker implantation for sinus node dysfunction. Over a follow-up period of more than 12 months, patients were compared based on their preoperative and intraoperative variables.
RESULTS: At discharge, the success rate was 89.7%. The midterm rates (total of 94.9 patient-years of follow-up) of sinus rhythm and freedom from AF were 72.4% and 79.3%, respectively. There were significant differences in duration of AF, voltage of f-wave at first precordial lead of electrocardiogram, and cardiothoracic ratio between the SR and AF groups.
CONCLUSIONS: Our midterm results suggest that the left atrial maze procedure is an effective alternative adjunct procedure for elective open heart surgery to treat AF, depending upon the patient’s clinical condition.
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Introduction
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Atrial fibrillation (AF), the most common sustained cardiac rhythm disturbance, increases in prevalence as populations age [1, 2] and is often associated with mitral valve disease. Hemodynamic impairment and thromboembolic events due to AF result in significant morbidity, mortality, and cost [2]. Cox and colleagues [3–6] developed the maze procedure for treating AF, and subsequently developed two improved versions of this operation, the maze II and maze III procedures. Kosakai and colleagues [7, 8] modified the maze procedure (Kosakai-maze procedure), and showed that it is effective in the treatment of chronic AF with mitral valve disease. Although the mortality rate of an isolated maze operation is less than 1%, mortality is higher when the procedure is combined with other types of operative repair [2]. Sueda and colleagues [9–11] and Imai and associates [12] performed a simple left atrial procedure (based on the modified left-side only maze operation) in patients with chronic AF associated with mitral valve disease. They found that their procedure was effective in curing AF with mitral valve disease. However, there have been few reports of midterm results of left atrial maze procedures [11–13]. We believe that the left atrial maze procedure is much simpler than other maze procedures, and have therefore performed the left atrial maze procedure since 1997. The aim of the present study was to obtain midterm results of this procedure for at least 12 months of follow-up.
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Material and methods
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Patients
Between June 1997, and May 2001, a total of 13 men and 18 women (age range 45 to 76 years, average age 59.8 years) underwent the left atrial maze procedure in our department. All patients had chronic AF refractory to medical treatment. The preoperative period of AF ranged from 3 to 300 months, with a mean of 77.3 months. Transthoracic echocardiography and chest roentgenography revealed left atrial dilatation and cardiomegaly, respectively, in all patients. Of the patients, 13 had mitral regurgitation, 12 mitral stenosis, and 4 mitral stenosis and regurgitation. Two patients were lone AF cases, both with repeated thromboembolism and thrombotic obstruction of the abdominal aorta. For these 2 patients, we performed the procedure with left atrial thrombectomy to reduce operative time. Five patients had aortic regurgitation, 8 tricuspid regurgitation, and 3 angina pectoris. Eight patients had a past history of cerebral infarction. Seven patients had undergone previous open heart surgery: 6 patients open mitral commissurotomy and 1 patient correction of atrial septal defect. The following concomitant mitral operations were performed at the time of the left-atrial maze procedure: mitral valve replacement, 20 patients; mitral annuloplasty, 3 patients; and open mitral comissurotomy, 6 patients. Other concomitant operations were as follows: aortic valve replacement, 4 patients; tricuspid annuloplasty, 7 patients; and coronary artery bypass, 3 patients. One patient with mitral regurgitation did not undergo mitral surgical intervention, as the leaflets were preserved and as his mitral regurgitation was trivial on preoperative transthoracic echocardiography.
Surgical procedure
The surgical procedure is depicted in Figure 1.
The patient was placed in the standard supine position. The procedure was performed under cardiopulmonary bypass with normothermia and warm blood cardioplegia. After initiation of cardiopulmonary bypass, a right-sided left atriotomy was made and extended to the left margin of the left pulmonary veins. Electrical isolation was performed with ablation between the upper and lower edge of the atriotomy encircling the orifices of the pulmonary veins. Isolation involved the left atrial appendage and encircling ablated line, left atrial appendage, and posterolateral part of the mitral annulus, lower atriotmy line, and middle part of the mitral annulus. Electrical isolation was performed with cryoablation (-60°C, for 2 minutes) in 30 patients and radiofrequency ablation (1500 W, 70°C, for 2 minutes) in 1 patient. After ablation, the planned operation for organic heart disease was performed. No further atriotomy was performed on the atrial septum or right atrium if it was not necessary to perform surgery on the tricuspid valve or annulus. All patients in this study underwent operation by the same surgeon and surgical team.
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Fig 1. Schema of maze left atrial procedure. Left part shows schema of atriotomy; right part shows schema of ablation. (IVC = inferior vena cava; LA = left atrium; LAA = left atrial appendage; MV = mitral valve; RA = right atrium; RIPV = right inferior pulmonary vein; RSPV = right superior pulmonary vein; SVC = superior vena cava.) Shaded areas indicate ablation.
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Postoperative follow-up
Patients whose chronic AF had disappeared by discharge were considered to be early success cases. After discharge, patients were followed-up by our clinic or their local cardiologist. Postoperative rhythm was evaluated with a 12-lead electrocardiogram. For the purpose of analysis, the patients were divided into two groups (the SR group and the AF group) retrospectively, based on their latest cardiac rhythm. Patients in the SR group had restored sinus rhythm. Patients in the AF group had recurrent sustained AF postoperatively or during the follow-up period. Two patients who required pacemakers for sinus node dysfunction were disregarded in this analysis.
Statistical analysis
Preoperative and intraoperative variables were compared between the SR group and AF group. All data are reported as mean ± standard deviation. We performed this analysis using StatView for Windows J5.0 (SAS Institute, Cary, NC). Continuous variables were compared using the nonparametric Mann-Whitney U test. Discrete variables were analyzed using the 
2 statistic test. Differences were considered to be statistically significant when the p value was less than 0.05.
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Results
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Operative procedure, mortality, and morbidity
All patients underwent the left atrial maze procedure. Operative time ranged from 188 to 450 minutes (279 ± 86 minutes). Aortic cross clamp time ranged from 60 to 220 minutes (109 ± 36 minutes). Total extracorporeal circulation time ranged from 94 to 257 minutes (146 ± 39 minutes). The left atrial maze procedure time ranged from 20 to 37 minutes (mean 30.6 ± 5.4 minutes). In all, 13 patients underwent surgery without blood transfusion, and 11 did not require postoperative blood transfusion. Two patients died of acute renal failure and low output syndrome (mortality 6.4%). Postoperative duration of hospitalization for patients other than the 2 fatalities ranged from 21 to 74 days (37.5 ± 18.4 days). The follow-up period ranged from 12 to 60 months (37.7 ± 15.0 months). None of the patients died or experienced cerebral thromboembolic complications in the follow-up period.
Recurrence of atrial fibrillation
In all patients, AF disappeared soon after the operation. Between 2 and 15 days after the operation, AF recurred in 18 patients, and sinus rhythm was restored in 15 patients with pharmacological or electrical defibrillation. Five patients received a pacemaker postoperatively because of sinus bradycardia or sinus node dysfunction. Of the 29 patients, 26 had restored sinus rhythm or were free of AF at discharge, for an early success rate of 89.7%. Of the 2 lone AF cases, 1 had restored sinus rhythm, and the other was free of AF but received a pacemaker because of sinus node dysfunction. In all, 21 patients with restored sinus rhythm had a clearly visible P wave on their electrocardiogram and underwent pulsed-wave Doppler examinations at discharge. An A wave was detected at the transmitral flow in 18 of these 21 patients (85.7%) and at the transtricuspid flow in all 21 patients (100%). Three patients developed AF after discharge. Two patients had recurrent AF 2 months after the operation, and 1 patient had recurrent AF 28 months after the operation. At midterm, of the 29 surviving patients, 23 (79.3%) were free of AF and 21 (72.4%) had sinus rhythm.
Postoperative medication
No patient was given special prophylactic medication postoperatively for the prevention of atrial fibrillation. Patients with atrial fibrillation during hospitalization were treated with antiarrhythmic agents in class I or IV of the Vaughan Williams classification. We then gradually decreased medication if the sinus rhythm became stable in our outpatient clinic. Warfarin was used in every case of concomitant mitral valve replacement or persistent AF.
Statistical analysis
By comparing the AF group to the SR group, we found that the predicting factors for postoperative persistent AF were long duration of AF, low-voltage f-wave at first precordial lead of electrocardiogram, and high cardiothoracic ratio. Data are given in Table 1.
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Comment
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During AF, loss of atrioventricular synchrony and atrial transport function decreases cardiac output, especially in patients with organic heart disease. Cox and colleagues [6, 15, 16] developed the maze procedure for treating AF, and they reported that it cured atrial fibrillation in nearly 100% of patients. Kosakai and associates [7, 8] reported a defibrillation rate of 84 to 86% for their modified maze procedure (Kosakai-maze procedure) for treatment of chronic AF with mitral valve disease. In several studies of modified maze procedures for AF with mitral valve disease, the defibrillation rate was approximately 80% [17–19]. The long operative time and cardiopulmonary bypass time are problematic when a complete or modified maze procedure is performed as a concomitant operation with standard open heart surgery. Sueda and colleagues [9–11] and Imai and associates [12] reported that a simple left atrial procedure was effective for treatment of chronic AF with mitral valve disease; AF was absent 3 years after the operation in 74.5% of patients. Kosakai [20] compiled data from a questionnaire about results of using the maze procedure to treat atrial fibrillation with mitral disease in Japan and found the following success rates: left atrial maze procedure, 73%; maze III procedure, 76%; and Kosakai-maze procedure, 74%. However, the number of patients who underwent the left atrial maze procedure was approximately one-sixth the number who underwent the maze III or Kosakai-maze procedure; there have been few reports of midterm results of the left atrial maze procedure. We have performed the left atrial maze procedure since 1997. This procedure very effectively restores sinus rhythm and atrial kick, whereas mitral valve surgery restores sinus rhythm in only about 20% of patients who have AF with mitral valve disease [7, 11]. We believe that the left atrial maze procedure has the advantages of short aortic crossclamp time and short cardiopulmonary bypass time, both of which help to reduce blood loss and surgical morbidity and mortality. However, this procedure can involve prolonged postoperative stay, for the following reasons. In cases in which paroxysmal AF occurred after the operation, the patient was observed for about 1 week after defibrillation. Postoperative rehabilitation was lengthy for cases in which cerebral infarction occurred before the operation. The postoperative stay was about 20 days for patients without paroxysmal AF, and this is comparable to postoperative stay for mitral valve surgery alone. The rationale of the left atrial maze procedure is based on electrophysiologic evidence that the left atrium acts as an electrical driving chamber in chronic AF with mitral valve disease [11]. Given the high probability that AF originates in the pulmonary veins and left atrial appendage, we performed atriotomy and ablation as shown Figure 1. Because we believe that the left atrial appendage is important for contraction of the left atrium [13, 14], we performed ablation without excision or oversewing in cases in which there was no thrombus in the left atrial appendage. Ablation of the left atrial posterior–inferior portion is important because it interrupts conduction and prevents postoperative atrial flutter [21]. Because of the possibility that superior pulmonary veins are involved in postoperative recurrence of AF, the right superior pulmonary vein was isolated individually. Electrophysiologic studies have shown that the pulmonary veins, especially superior pulmonary veins, are important sources of ectopic beats and initiate paroxysmal AF [22–24]. In the 2 lone AF cases in the present study, the AF disappeared, and we speculated that their AF originated in the left atrium (probably in the pulmonary vein). The following predicting factors of persistent postoperative AF have previously been reported: long duration of AF, low f-wave voltage at first precordial lead, high cardiothoracic ratio, larger left atrial size, and complications with severe tricuspid regurgitation [9, 12]. In the present study, in which the sample size was small, we found significant differences in AF duration, f-wave voltage, and cardiothoracic ratio between the SR and AF groups. With a larger sample size, yet more significant factors might be revealed. We believe that the duration of AF is especially important, and that other factors are the result of prolonged load and bilateral atrial degeneration. It has been reported that in cases in which supraventriclar arrhythmia persists after the maze operation, there is micro-reentry or acceleration of automaticity [11]. It is possible that AF can result in degenerated atrial muscle. Recent findings suggest that variations in right atrial conduction play an important role in immediate recurrence of AF in patients converted to sinus rhythm by internal cardioversion [25]. In our experience, in 5 of 6 unsuccessful left atrial maze operations, AF recurred within 2 months after surgery. Clarification of factors that affect recurrence at this early stage should help to improve the success rate. In such cases, AF may originate from the right atrium. Prior studies have demonstrated that the trigger of paroxysmal AF arises from areas other than the pulmonary veins in 6% to 10% of foci [22, 23]. After pulmonary vein isolation, AF recurrence results from recovery of atriopulmonary vein conduction [26]; specifically, recovery of atriopulmonary vein conduction may cause late recurrence of AF. Because of individual variation, the left atrial maze procedure is not necessarily appropriate in all cases in which there is degeneration. Therefore, detailed electrophysiological study and longer-term follow-up studies are needed.
In conclusion, midterm results of the left atrial maze procedure showed that the early favorable results had been maintained, and were comparable to results of other maze procedures, in cases of chronic AF with mitral valve disease. Although the indications for of the left atrial maze procedure are debatable, it appears to be an effective adjunct procedure for mitral valve surgery or left atrial thrombectomy in patients with AF. In order To clarify the indications for this procedure, we will perform longer-term follow-up studies and will continue to accumulate data.
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Acknowledgments
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We thank Shingen Owada, MD, for his valuable advice about the origin of AF, and Carlos Hartmann, MD, for his assistance in language editing.
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Abstract
Introduction
