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Ann Thorac Surg 2008;86:1409-1414. doi:10.1016/j.athoracsur.2008.06.064
© 2008 The Society of Thoracic Surgeons
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Original Articles: Adult Cardiac

Intermediate to Long-Term Results of Radiofrequency Modified Maze Procedure as an Adjunct to Open-Heart Surgery

Willem P. Beukema, MDa,*, Hauw T. Sie, MDb, Anand R. Ramdat Misier, MD, PhDa, Peter Paul H.M. Delnoy, MDa, Hein J.J. Wellens, MD, PhDa, Arif Elvan, MD, PhDa

a Department of Cardiology, Isala Klinieken, Zwolle, the Netherlands
b Department of Cardiothoracic Surgery, Isala Klinieken, Zwolle, the Netherlands

Accepted for publication June 11, 2008.

* Address correspondence to Dr Beukema, Department of Cardiology, Isala Klinieken, Groot Wezenland 20, Zwolle, 8011 JW, the Netherlands (Email: v.r.c.derks{at}isala.nl).


Adult cardiac surgery: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
Background: Of patients scheduled for elective open heart surgery, a substantial number of patients have preoperative atrial fibrillation (AF). The cut-and-sew Maze procedure and variant Maze procedures abolish AF in 45% to 95% during short- to intermediate-term follow-up. Limited data are available about maintenance of sinus rhythm during intermediate- to long-term follow-up. The objective of the present study was to assess the association between postoperative rhythm and mortality and stroke.

Methods: From November 1995 to November 2003, 258 patients with structural heart disease and permanent AF with a duration of longer than 12 months were scheduled for elective cardiac surgery and included in a registry. They underwent a radiofrequency modified Maze procedure as an adjunct to the open heart operation. Patients were followed in the outpatient clinic, and follow-up data were obtained from medical correspondence of attending physicians. For this paper, follow-up ended November 2006; however, patients are being followed in an ongoing registry.

Results: Two hundred fifty-eight patients (mean age, 68.1 ± 9.5 years) with permanent AF underwent cardiac surgical procedures and concomitant radiofrequency Maze surgery; 213 patients (82.5%) underwent more than one procedure. Mean duration of permanent AF was 66.6 ± 69.8 months (range, 16 to 96). Preoperatively, 82.9% of patients were in New York Heart Association class III. In-hospital mortality was 3.9% (10 patients), and during a mean follow-up of 43.7 ± 25.9 months (range, 27 to 114), 73 patients (28.3%) died. Left ventricular ejection fraction was normal in 44.6%, moderately decreased in 42.5%, and poor in 12.9% of patients. Sustained sinus rhythm, including atrial rhythm or an atrial-based paced rhythm was present in 69% of patients at 1 year, in 56% at 3 years, in 52% at 5 years, and in 57% of patients at the latest follow-up. Antiarrhythmic drugs were used by 64% of survivors who were free of atrial fibrillation. Oral anticoagulation therapy was taken by 99% of patients. Stroke was reported in 4 patients (1.6%).

Conclusions: The RF modified Maze procedure abolishes AF in the majority of patients with structural heart disease and longstanding permanent AF. Postoperative rhythm was not predictive of all-cause mortality, cardiac mortality, and stroke, neither in the whole group nor in the subgroups defined by preoperative left ventricular ejection fraction and New York Heart Association class. The stroke rate was very low in this group with longstanding AF.

Although as many as 50% of patients scheduled for mitral valve surgery have atrial fibrillation (AF), surgical correction of the underlying cardiac abnormality usually will not abolish AF [1–4]. Maze surgery using the cut-and-sew technique or alternative means of creating linear lesions of electrical block in both atria, results in sinus rhythm or an atrial rhythm in 44% to 95% of cases [5–11]. Permanent AF in the absence of rheumatic heart disease confers a fivefold increase in stroke risk, and AF in rheumatic heart disease has a 17-fold increase in stroke incidence [10–14]. Theoretically, the added value of the Maze procedure is to reestablish sinus rhythm, to restore atrioventricular synchrony, and to minimize the risk of thromboembolism. Limited data are available from the randomized studies about the association between sinus rhythm after the Maze procedure and the incidence of stroke, hemodynamics, and mortality [7].

A recent meta-analysis of clinical outcomes of Maze-related surgical procedures for medically refractory AF found successful restoration of sinus rhythm in the Maze group (80.7% versus 17.3%); however, it did not answer the questions of whether Maze-induced sinus rhythm is associated with lower long-term mortality and stroke and of which patients will benefit from this type of surgery [7].

This report on the intermediate-term to long-term follow-up of patients who underwent a RF modified Maze procedure as adjunctive surgery during an elective open heart operation aims to help answer these important questions.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
Patients
From November 1995 to November 2003, 258 patients with structural heart disease and permanent AF for at least 12 months who were scheduled for elective cardiac surgery were included in a registry. All patients consented to their data being registered and used for publication, as did the Board of Hospital Administrators. All patients underwent a RF Maze procedure as an adjunct to the primary surgery. Patients were followed in the outpatient clinic, and follow-up data were obtained from attending doctors. Follow-up ended November 2006. All available electrocardiograms for each patient starting at 6 months postoperatively and ending November 2006 were scored as showing sinus rhythm, atrial-based paced rhythm, atrial flutter/atrial tachycardia, or AF. Surface electrocardiogram atrial fibrillation wave (F wave) amplitude was determined. The F wave was scored according to the presence of a coarse (F-wave in lead V1 ≥ 1 mm) or fine (F-wave in lead V1 < 1 mm) F-wave on surface electrocardiogram.

Surgical and Radiofrequency Ablation Procedure
The RF modified Maze procedure was performed using a unipolar RF ablation device. Radiofrequency energy was used to create long continuous endocardial lesions under direct vision with a hand-held, cooled tip probe. The RF energy was administered by using a continuous sinusoidal unmodulated waveform of 500 kHz and delivered in a unipolar mode between the 4-mm tip electrode of a specially designed probe and a 10 x 6 cm external backplate electrode that was underneath the back of the patient. The ablation procedure was done in a bloodless operating field. For the first 173 patients, a custom-made RF probe with a saline irrigation system incorporated to cool the tip of the probe was used along with a HAT 200S generator (Sulzer-Osypka GmbH, Grenzach-Wyhlen, Germany). In 85 patients who had undergone surgery after November 2000, the cooled tip Cardioblate pen (Medtronic, Minneapolis, MN) was used. The tip of both types of RF probe was irrigated with saline at room temperature at a flow rate of 4 to 6 mL per minute. Application of energy was done by oscillating the probe back and forth with a standard setting of 25 to 30 Watts and a saline irrigation flow rate of 5 mL per minute.

All atrial incisions currently used in the Cox Maze procedure were replaced in our RF modification by endocardial linear ablation lines. The surgical procedure has been described in detail previously [11].

Preoperative Management
In the 258 patients enrolled in the study, ventricular rate control medication, namely, calcium-channel blockers or digoxin, or both, was allowed to continue until the day before surgery. Oral anticoagulant therapy (warfarin) for the prevention of thromboembolism secondary to chronic AF was discontinued 2 days before surgery. Beta-adrenergic blockers were continued.

Postoperative Management and Follow-Up
Early postoperative care, including anticoagulant management, was similar as for routine cardiac surgery. Cardiac rhythm was continuously monitored after surgery until stable rhythm returned. Temporary epicardial wires attached to the right ventricle as well as to the right atrium were used to pace the patient, to monitor the rhythm, or to overdrive the atrium. Postoperative atrial arrhythmias were treated with sotalol, 80 to 120 mg, or amiodarone, 200 mg, and combined with direct-current cardioversion if necessary. All patients were operated on in one institution and by the same surgeon (H.T.S.). After discharge, patients were seen in the outpatient clinic within 4 weeks, at 3 months and at 6 months after operation, or earlier when necessary. Antiarrhythmic drugs were tapered gradually after cardiac rhythm was considered stable. The presence of atrial contraction was documented by transthoracic and transesophageal Doppler echocardiography performed at 3 and 6 months after surgery and related to the presence of electrical activity in the surface electrocardiogram. After 6 months and for as long as 3 years, patient status was determined by screening records of outpatient visits and correspondence with referring physicians.

Statistical Analysis
All data are reported as mean and standard deviation. Analysis of variance was applied to compare effects over time and effects per time point. The arrhythmia-free survival curves were constructed by using the Kaplan-Meier method; differences between groups were investigated with the log-rank test. A confidence level of 95% was considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
Preoperative Data
Between November 1995 and November 2003, 258 patients (mean age, 68.1 ± 9.5 years; median, 70.1) with permanent AF for 12 months or longer underwent surgery (Table 1). Mean duration of permanent AF was 66.6 ± 69.8 months (median, 35; range, 12 to 396). Preoperatively, 82.9% of patients were in New York Heart Association (NYHA) class III and 5.0% were in class IV. Left ventricular (LV) ejection fraction (EF) was normal in 49.3%, moderately decreased in 37.3%, and poor (EF < 30%) in 13.4% of patients. The etiology of AF was mitral valve disease in the great majority of patients.


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  		Table 1 Clinical Characteristics of 258 Patients With Permanent Atrial Fibrillation (AF)
 
Operative Data
The 258 patients with permanent AF and with an AF duration of more than 12 months underwent a total of 592 cardiac surgical procedures and concomitant RF Maze surgery (Table 2). One hundred seventy patients (66%) underwent tricuspid valve surgery; 222 (86%) underwent mitral valve surgery as part of the surgical procedure; and 213 (82.5%) underwent multiple procedures. Extracorporeal circulation time and aortic cross-clamp time for the 258 patients were 226.4 ± 59.6 and 122.9 ± 44.3 minutes, respectively.


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  		Table 2 Operation Based on 258 Patients
 
Postoperative Data
For the 258 patients with AF for longer than 12 months, in-hospital mortality was 3.9% (10 patients); and during a mean follow-up of 43.7 ± 25.9 months (median, 40.4; range, 27 to 114), 73 patients (28.2%) died. Neither NYHA class nor LVEF was predictive of recurrent AF (Table 3). Sinus rhythm, atrial rhythm, or an atrial-based paced rhythm was present in 69% of patients at 1 year, in 56% at 3 years, in 52% at 5 years, and in 57% of patients at the latest follow-up (Fig 1). The presence of sinus rhythm did not influence cardiac mortality, total mortality (Fig 2), or stroke rate. Antiarrhythmic drugs were used by 67% of survivors who were free of AF (Table 4). Oral anticoagulation drugs were taken by 99% of patients. Stroke was reported in 4 patients (1.6%), 3 ischemic and 1 hemorrhagic. At the time of stroke, 2 patients were in sinus rhythm and 2 patients were in AF. All 4 patients were on oral anticoagulation therapy.


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  		Table 3 Comparison of Patients With Sustained Sinus Rhythm (SR) Versus Recurrent Atrial Fibrillation (AF)
 

Figure 1
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  		Fig 1. Freedom from atrial fibrillation or atrial flutter (AF/AFL) using the Kaplan-Meier actuarial curve. On the horizontal axis is shown the follow-up in days and number of patients at risk in each 365-day interval. (See text for details.)

 

Figure 2
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  		Fig 2. Actuarial survival curve for the study population with sustained sinus rhythm (SR) or recurrent atrial fibrillation (AF) after radiofrequency Maze procedure. On the horizontal axis is shown the follow-up in days and number of patients (Pts) at risk in each 365-day interval. (See text for details.)

 

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  		Table 4 Medication at Latest Follow-Up
 
Predictive Factors of Sinus Rhythm After RF Maze Procedure
Factors predictive of postoperative AF recurrence were duration of permanent AF, preoperative atrial fibrillation wave, and preoperative left atrial size (Fig 3). Underlying cardiac abnormality, NYHA class, LVEF, pulmonary artery pressure, mean pulmonary capillary wedge pressure, LV end-diastolic diameter, and LV end-systolic diameter were not predictive of postoperative AF (Table 3). Left atrial size decreased during follow-up in patients with sustained sinus rhythm, whereas LA size increased in case of recurrent AF (Table 5).


Figure 3
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  		Fig 3. The relationship between left atrial (LA) dimension and the rhythm outcome at the latest follow-up is shown. Percentage of patients (Pts) free from atrial fibrillation or atrial flutter (AF/AFL) is significantly lower for the patients with a left atrial dimension greater than 60 mm compared with the remaining groups with a left atrial dimension less than 60 mm (p = 0.008). (PSLAX = parasternal long axis view.)

 

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  		Table 5 Changes in Left Atrial (LA) Dimension After Radiofrequency Maze Procedure
 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
Main Findings
The present study of 258 patients who underwent a RF Maze procedure as concomitant to open heart surgery does not show a lower incidence of (cardiac) mortality or stroke among those with postoperative sinus rhythm. A potential benefit of postoperative sinus rhythm could not be observed in any subgroup. After 9 years of follow-up, 57% of patients were in sinus rhythm.

Maze Surgery for AF
Atrial fibrillation is present in as many as 50% of patients undergoing mitral valve surgery and will not be converted to sinus rhythm by only surgical correction of coexisting cardiac abnormalities [4–7]. The cut-and-sew Cox Maze procedure, however, abolishes AF in 74% to 97% of patients. There are two important questions: is the Maze procedure associated with better clinical outcome; and, if so, is this associated with post-Maze sinus rhythm. A lower stroke rate was observed for Maze versus non-Maze patients in matched cohorts. None of these studies, however, were randomized controlled trials [1–19]. Variant Maze procedures, namely, modifications of the lesion set of the Cox Maze III and the use of energy sources like RF, cryoablation, and microwave, have not been able to completely mimic the results of the cut-and-sew Maze with return of sustained sinus rhythm between 44% and 92% [12–25]. Short-term and intermediate-term sinus rhythm after classical Maze or variant Maze varies widely and is reported between 44% and 95%. However, none of the six randomized trials of Maze versus no-Maze showed clear benefit on mortality or stroke. Part of almost all surgical procedures is amputation of the left atrial appendage, and possibly this is a cause of lower incidence of stroke [11–30].

Preoperative Factors Predictive of Recurrent AF After RF Modified Maze Procedure and Postoperative Factors Associated With Sustained Sinus Rhythm
Knowledge of prognostic factors remains important for individual patient counseling. This study of 258 elderly patients with structural heart disease and permanent AF who underwent an open heart operation and concomitant RF Maze surgery found preoperative duration of AF, preoperative left atrial size, and preoperative F wave prognostic factors for recurrence of AF or sustained sinus rhythm after RF Maze surgery. Underlying cardiac abnormality, preoperative invasive hemodynamic factors, NYHA class, and LVEF were not predictive of postoperative rhythm. Our findings are in agreement with many other studies, although most often these studies included a much younger patient population [13–25].

Experimental AF causes changes in electrophysiologic properties of the atria, a process called electrical remodeling [31, 32]. In humans, duration of AF is also associated with perpetuation of the arrhythmia. Spontaneous or electrical conversion of AF to sinus rhythm is inversely related to duration of AF [33–35]. Duration of AF also is an independent predictor of left atrial size. In the clinical setting, left atrial size and AF are significantly and mutually related to each other. Many clinical investigations have recognized left atrial dilatation as a cause of AF. Left atrial dilatation may also be, on the other hand, a consequence of AF. Why preoperative atrial fibrillation wave (F wave) is a predictor for recurrence of AF is unknown. Some studies have shown a correlation between F-wave amplitude and left atrial size, and F-wave amplitude and rheumatic AF or nonvalvular AF; however, others have not corroborated these findings [36, 37]. In this study, atrial fibrillation wave, namely, F wave, was inversely associated with left atrial size. It is likely that a combination of the changes in atrial architecture caused by ageing, AF, and congestive heart failure play an important role.

Stroke Risk and RF Modified Maze Procedure
Atrial fibrillation is an independent risk factor for stroke and may play a role in 15% to 20% of all ischemic strokes. Annual stroke rate in nonrheumatic AF patients without oral anticoagulation therapy is 4.5%. It is assumed that a patient with rheumatic mitral valve disease has at least a 20% chance of having a clinically detectable systemic embolus during the course of the disease, and approximately 20% of patients with prosthetic valves have an embolic stroke by 15 years after valve replacement [28, 38]. The stroke rate in this registry was low: only 4 strokes (3 ischemic and 1 hemorrhagic) occurred after discharge, for an annual stroke rate of 0.61%. The explanation for that may be that the great majority of patients were taking oral anticoagulant drugs, whether in sinus rhythm or AF, and that in all patients, the left atrial appendage was amputated.

Surgical obliteration or amputation of the left atrial appendage may be a potentially valuable (additional) strategy for stroke prophylaxis [39, 40] and may, at least partially, explain the extremely low stroke rate in some studies of Maze surgery [28].

Limitations
A major limitation of all studies or registries of treatment of AF is that the burden of atrial arrhythmia can not reliably be determined unless an implantable device with a specific algorithm to detect atrial arrhythmia is used. Silent atrial fibrillation remains an important issue in the postoperative follow-up of these patients. Furthermore, quality of life issues need to be addressed. Limitations with using monopolar radiofrequency, microwave, or cryoenergy to treat AF are that it is not possible to verify transmurality of the linear lesions at the time of energy delivery. Electrical activity may still traverse nontransmural lesions created endocardially on the epicardial surface of the atrium or through gaps in the ablation lines. However, given that there is no real-time method to document complete conduction block, one may speculate on the importance of functional block in these ablation lesions on clinical outcome. The RF modified Maze, however, simplifies the classic cut-and-sew Maze operation with long-term results similar to those of other reports, as discussed in the previous section. The results of this observational study with a relatively large number of patients are from a single center performed by one surgeon, and multicenter studies are needed. Almost half of the patients are still taking antiarrhythmic drugs at latest follow-up because the decision to cease medication was at the discretion of referring physicians.

Conclusion
In conclusion, this report on the intermediate- to long-term follow-up of patients with structural heart disease and concomitant RF Maze surgery showed that postoperative sinus rhythm does not translate to reduction of mortality and stroke rate. The question whether Maze-induced sinus rhythm is equivalent to natural sinus rhythm remains to be answered. Longer follow-up and larger sample sizes are needed. Because of the good to excellent long-term survival of many surgical patients, however, a mortality benefit by adding Maze surgery will be hard to prove. At the present time, there is not enough evidence available for clinicians to answer the question of who will profit from Maze surgery and who will not.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

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