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Ann Thorac Surg 2003;76:1259-1263
© 2003 The Society of Thoracic Surgeons

Original article: cardiovascular

Atrial compartment operation for atrial fibrillation: to isolate the left atrium or not?

Huey-Ming Lo, MDa*, Fang-Yue Lin, MD, PhDb, Yung Zu Tseng, MDc

a Department of Internal Medicine, Tzu Chi General Hospital and Tzu Chi University, Hualien, Taiwan
b Departments of Surgery, National Taiwan University College of Medicine, Taipei, Taiwan
c Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan

Accepted for publication April 21, 2003.

* Address reprint requests to Dr Lo, Department of Internal Medicine, Shin Kong Wu Ho-Su Memorial Hospital, 95 Wen-Chang Road, Shih-Lin, Taipei 11, Taiwan
e-mail: moolool{at}ms.skh.org.tw


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 Conclusions
 References
 
BACKGROUND: The atrial compartment operation was designed to convert atrial fibrillation (AF) to sinus rhythm with intentional preservation of the electrical connection between adjacent atrial compartments. However, incidental left atrial isolation was observed in some patients. This study compared the long-term clinical outcomes of left atrial isolation for AF with those with right and left atrial connection.

METHODS: Twenty patients with mitral valve disease and chronic AF who underwent atrial compartment operation with successful sinus conversion were studied. Left atrial isolation was documented by local electrogram recording. When there were no signs of electrical connection between the left atrium and the rest of the heart, either during sinus rhythm or during stimulation from various atrial compartments, left atrial isolation was confirmed. All patients were followed by electrocardiogram and echocardiogram serial recordings. Clinical signs and symptoms of cardiac performance and thromboembolism were also examined.

RESULTS: Seven patients showed an isolated left atrium and 13 patients had electrical connection between the right and left atria. The age, gender, AF duration, and underlying disease were not different between the two groups of patients. During a mean follow-up period of 66 ± 15 months, none of the patients with left atrial isolation showed recurrence of AF, although one experienced paroxysmal atrial flutter. However, 8 of the 13 patients with right and left atrial connection experienced recurrent atrial flutter/fibrillation (6 atrial flutter and 5 AF) (p = 0.058). The propensity for recurrent atrial flutter/fibrillation in these patients may be related to the conduction delay between the two atrial compartments, measured at 142 ± 48 ms. At the end of the follow-up period, all patients with left atrial isolation remained in normal sinus rhythm without antiarrhythmic drugs. Of the patients who had right and left atrial connection, 2 developed sustained AF and 1 developed atrial flutter. Patients with left atrial isolation showed a decreased transmitral "A" flow compared with those with right and left atrial connection. Postoperative left atrial diameter and clinical functional class did not differ between patients with and without left atrial isolation. The incidence of embolization observed in both treatment groups did not differ significantly: 14% (1/7) in patients with left atrial isolation and 8% (1/13) in patients with right and left atrial connection (p > 0.05 between the groups).

CONCLUSIONS: Left atrial isolation confers a better arrhythmia outcome but at the expense of poorer mechanical performance as compared with preserved electrical connection between the two atria. Nonetheless, all patients remain at risk for systemic embolization. Therefore, modifications of current surgical incisions for AF are needed.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 Conclusions
 References
 
Atrial fibrillation (AF) is a common cardiac arrhythmia associated with increased morbidity and mortality. The mechanism of AF is very complicated and not clearly understood. Treatments for AF have been largely confined to medical control of ventricular rate. However, based on the observations of animal experiments, several surgical interventions have been developed and performed on selective patients with AF.

Left atrial isolation was originally designed for the treatment of refractory ectopic supraventricular tachycardia arising in the left atrium [1]. This procedure was subsequently performed in association with valvular surgery in mitral valve patients with chronic AF under the supposition that the enlarged left atrium was responsible for the AF [2]. Although a satisfactory percentage of patients were maintained in sinus rhythm at the end of the 24-month study period [2], long-term clinical outcomes such as AF recurrence, atrial mechanical function, and risk of embolization were not examined in this study.

Several other surgical procedures such as the corridor operation and the maze operation were also developed for the treatment of AF [3, 4]. Based on Moe's multiple wavelet hypothesis [5] and Allessie and colleagues' [6] observation of critical wavelet number, we designed an atrial compartment operation for converting AF to sinus rhythm in mitral valve patients [7]. In this operation, electrical connections between adjacent compartments were intentionally preserved in order to maintain a regular electrical and mechanical activity of the left atrium. However, patients with incidental left atrial isolation were observed [8].

In the present study, we compared the long-term clinical outcomes of patients with left atrial isolation with those with preserved right and left atrial electrical connection.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 Conclusions
 References
 
Patients
This study was conducted after approval by the Institutional Review Board. Twenty patients with mitral valve disease and chronic AF (for > 0.5 year) who underwent atrial compartment operation with successful sinus conversion were followed. Of the 20 patients, 12 were men and 8 were women, with a mean age of 49 years (range, 22 to 72 years). Based on electrophysiological studies, the patients were divided into two groups. One group consisted of patients with isolated left atrium (n = 7) and the other group consisted of patients who retained an electrical connection between the right and left atrium (n = 13). Patients' clinical characteristics are listed in Table 1.


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  		Table 1. Patient Profiles

 
Surgery
In addition to valvular surgery, a concomitant atrial two- or three-compartment operation was performed to convert AF to normal sinus rhythm. This surgical technique has been reported previously [7]. Specifically, a two-compartment operation comprises a horseshoe incision along the left side of the interatrial septum. The anterior and posterior ends of the incision near the mitral annulus are cryoablated from the endocardial sides. However, the atrial fibers behind the coronary sinus are left intact so that an electrical connection between the right and left atria could be preserved. A three-compartment operation comprises another atrial incision in addition to that of the two-compartment operation. The additional incision is placed at the crest of the right atrial appendage and extended anteriorly and inferiolaterally, parallel to the sulcus terminalis until 1 cm above the tricuspid annulus. The anterior end of the incision is then extended to the tricupid annulus and cryoablated.

Follow-up
After the operation, continuous electrocardiographic (ECG) monitoring and daily complete ECG recording were performed during the patients' stay in the surgical intensive care unit. Patients receiving mechanical valve replacement were administered warfarin after removal of the pericardial drainage tube. They were maintained on warfarin thereafter at an international normalized ratio (INR) of 1.5 to 2.5 times that of normal control. Patients with mitral valve plasty and sinus rhythm were not administered warfarin. Regular ECG and Holter and echocardiographic recordings were performed on all patients during the follow-up visits at the outpatient department. Special attention was paid to cardiac rhythm, atrial contractile function, and thromboembolic episodes in these patients.

Electrophysiological study
After a year or more postoperative, patients were subjected to electrophysiological studies. The methods of recording and stimulation were as previously reported [8]. Bipolar local recordings of the left atrium were achieved in the coronary sinus in 19 patients and in the left atrium through a patent foramen ovale in 1 patient. Left atrial isolation was defined as the absence of signs of electrical connection between the left atrium and the rest of the heart either during sinus rhythm or stimulation from various atrial compartments.

Statistical analysis
All results were expressed as mean ± SD. Student's t test, Fisher's exact test, and repeated measurements of analysis of variance were used for comparison between the two groups where applicable. A p value of less than 0.05 was considered statistically significant a priori.


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 Conclusions
 References
 
Electrophysiologic studies showed 7 patients to have an isolated left atrium and 13 patients to have an electrical connection between the right and left atria. Of the 7 patients with isolated left atrium, 5 had a quiescent left atrium, 1 showed a slow left atrial activity, and 1 had a left atrial flutter. Of the 13 patients who had sustained electrical connection between the atria, 12 exhibited prolonged conduction times ranging from 75 to 266 ms (mean, 142 ± 48 ms) from the high right atrium to the distal coronary sinus.

Baseline clinical profiles of patients in the two groups are shown in Table 1. No differences in the age, gender, AF duration, and underlying disease in the two groups of patients were observed. The underlying disease in both groups was mostly rheumatic valvular disease. The only difference between the two groups was a predominance of the three-compartment operation in the group with right and left atrial connection. This might reflect a learning effect because the three-compartment operation was modified from the two-compartment operation.

Arrhythmia outcome
During a mean follow-up period of 66 ± 15 months, none of the patients with left atrial isolation showed recurrence of AF. One patient had paroxysmal atrial flutter, 80 months after the operation. At the end of follow-up period, all 7 patients with left atrial isolation were in normal sinus rhythm, none of them was taking antiarrhythmic drugs, and none of them required a permanent pacemaker implantation (Table 2).


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  		Table 2. Clinical Outcomes

 
Eight of the 13 patients (61.5%, p = 0.058) who had right and left atrial connection experienced recurrent atrial flutter/fibrillation, 6 patients had atrial flutter, and 5 had AF, during a mean follow-up period of 60 ± 23 months. Of the 5 patients who had AF, 3 of them had AF recurrence in the early postoperative days, at 7 days (case 15), 2 weeks (case 8), and 4 months (case 13) after the operation, and 2 patients had AF recurrence at a later stage, at 45 months (case 14) and 61 months (case 12) after the operation. The early stage AF of the 3 patients was sustained for 3 days to 1 month. In 2 of these patients (cases 15 and 8), spontaneous reversion to sinus rhythm occurred, whereas in the third patient (case 13), sinus rhythm was attained after treatment with amiodarone. The 2 patients with late recurrence of AF were treated with amiodarone but their AF was sustained despite treatment. In the 6 patients who had recurrent atrial flutter, in 1 patient it subsided spontaneously (case 8), in 2 patients it was converted to sinus rhythm with overdrive pacing (case 13 and 19), in 1 patient it was terminated with radiofrequency catheter ablation (case 10), in 1 patient it was converted to sinus rhythm after cardioversion but recurred and then sustained despite amiodarone treatment (case 18), and in 1 patient it ended up as AF (case 14). Amiodarone was used in 6 of the 13 patients with right to left atrial connection for the treatment of recurrent atrial flutter and fibrillation but none of them required a permanent pacemaker implantation for sinus node dysfunction.

Hemodynamic outcomes
Before the operation, all patients had no transmitral "A" flow. After attaining sinus rhythm postoperatively, all patients with right and left atrial connection demonstrated a gradual increase in transmitral "A" flow, which leveled off after a year. On the other hand, all but 1 patient with left atrial isolation had no transmitral "A" flow postoperatively. Thus, patients with left atrial isolation showed a poorer left atrial contractile function compared with those with right and left atrial connection (Table 3). However, the left atrial diameter decreased after the operation in both groups of patients. As shown in Table 4, the preoperative left atrial diameter in patients with left atrial isolation was 53 ± 6 mm. This decreased to 44 ± 8 mm (p < 0.0001) 1 month after the operation and was maintained through to the end of the follow-up period. In patients with right and left atrial connection, a similar degree of decrease in left atrial diameter was noted after the operation (Table 3).


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  		Table 3. Postoperative Serial Changes in Transmitral "A" Flow Velocity

 

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  		Table 4. Changes in the Left Atrial Dimensions Before and After the Operation

 
There was no difference in the functional class of the patients in the two groups, as defined by The New York Heart Association. Of the 7 patients with left atrial isolation, 2 (29%) were in functional class I and 5 were in class II. Of the 13 patients with right and left atrial connection, 5 (38%) were in functional class I and 8 were in class II.

Embolization
There was no difference in the incidence of embolization in the two groups. Among patients with left atrial isolation, 3 had concomitant mitral valve replacement and were maintained with warfarin without embolization. But, 1 patient (14%) with mitral valve plasty had a stroke, 10 months after the operation despite being in sinus rhythm (case 6). This patient's local electrogram recording showed left atrial fluttering. All patients who had right and left atrial connection underwent concomitant valve plasty and were not maintained on warfarin. One patient (8%) had a stroke, which occurred at 72 months after the operation when she had AF recurrence (case 12).

At the end of follow-up period, there was no mortality in both groups of patients (Table 2).


   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
Conclusions
 References
 
An ideal treatment for AF should achieve the following goals: (1) restoration and maintenance of normal sinus rhythm; (2) recovery of atrial contractile function; and (3) reduction in thromboembolic events. However, pharmacological treatments for established AF usually fail to achieve these goals, especially the former two goals. Several surgical procedures such as left atrial isolation, corridor operation, and maze operation have been employed to treat patients with either chronic or paroxysmal AF. Although these surgical interventions resulted in satisfactory sinus conversion, a significant proportion of patients who underwent the maze and corridor procedures developed sinus node dysfunction. The preventive effect in thromboembolic attacks was also questioned in patients with left atrial isolation and corridor operation.

The atrial compartment operation was designed to convert chronic AF to normal sinus rhythm in mitral valve patients. In this operation, an anatomic connection of about 1 cm wide was preserved between adjacent compartments to serve as the electrical connection. However, left atrial isolation did occur after the operation. The isolated left atria were mostly quiescent in this study (5/7 = 71.4%). Only one out of seven atria (14.3%) showed a slow rhythm and one out of seven atria (14.3%) demonstrated atrial flutter. In previous studies, during the early postoperative period, the majority of the isolated left atria were reported to be in atrial fibrillation, 55.8% after left atrial isolation operation [2] and 66.7% after corridor operation (biatrial isolation) [3]. In contrast to the present study, only 12.7% of isolated atria after left atrial isolation operation [2] and 11.1% of isolated atria after corridor operation [3] were quiescent. The reasons for these differences in atrial rhythm between the present study and the previously reported studies are not known. But they may simply be due to the small sample sizes examined, or they may represent a time-dependent degeneration of the fibrillated atrium into total arrest.

Whether a preserved electrical connection between adjacent atria results in a better clinical outcome than atrial isolation has not been investigated before. In this long-term clinical outcome study, patients with left atrial isolation were found to have poorer left atrial mechanical performance than those with right to left atrial connection. However, clinical functional class and decreases in left atrial diameter were not different between the two groups. Both groups of patients were at risk for systemic embolization. Patients with right and left atrial connection were particularly at risk during AF recurrence.

The most striking contrast in the patients with and without left atrial isolation in this study was in their arrhythmogenecity. During the follow-up period, almost all of the patients with left atrial isolation were maintained in sinus rhythm without antiarrhythmic drug, whereas recurrent atrial flutter/fibrillation was commonly seen in patients with right and left atrial connection. The underlying mechanism for this difference is not clear, although it has been suggested that atrial size could be a major determinant for the initiation and maintenance of AF [9, 10]. In fact, the "effective" atrial mass in left atrial isolation is believed to be smaller than that in right to left atrial connection. This value, however, was not measured in the present study. Another possible underlying mechanism could be attributed to the conduction delay created by the incision in patients with right to left atrial connection. Similar to our study, an interatrial conduction delay was reported to likely predispose patients to atrial flutter/fibrillation in a study by Bayes de Luna and associates [11]. In addition, conduction delay may result in an impaired left atrial mechanical function when the left atrium and ventricle contract simultaneously [12].

Is it possible to make an atrial incision that is both effective in AF conversion and devoid of conduction delay? In our atrial compartment operation, the Bachmann bundle was incised, leading to almost all patients showing a severe conduction delay from the right to the left atria. Therefore, a modified incision that preserves the Bachmann bundle might be helpful in preventing interatrial conduction delay. The size of the "isthmus" connecting the adjacent atrial compartments may constitute another critical factor in determining the efficacy of AF conversion and intercompartmental conduction.

With the demonstration that ectopic foci in pulmonary veins can trigger paroxysms of AF [13], catheter ablation and surgical techniques have been developed to treat either paroxysmal or chronic AF [14, 15]. Kalil and associates reported that simple surgical isolation of pulmonary veins was effective in treating AF in mitral valve disease [16]. At the end of a 1-year follow-up period, 87.5% of the patients attained sinus rhythm with restored effective atrial mechanical function. Although the long-term clinical outcome of pulmonary vein isolation is not known, a better atrial mechanical function compared with left atrial isolation may be anticipated. In this sense, pulmonary vein isolation could be considered a better choice for AF surgery than left atrial isolation. Furthermore, if the risk of systemic embolization could be prevented by simple pulmonary vein isolation, then this operation could be an ideal treatment for selective patients with AF.

The major limitation of the present study was its small size. In addition, a large-scale clinical trial could not be undertaken because of ethical and technical considerations.


   Conclusions
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Conclusions
References
 
Although left atrial isolation confers better maintenance of sinus rhythm than preserved right to left atrial electrical connection, isolation is prone to mechanical dysfunction and carries the risk of systemic embolization. On the other hand, patients with right to left atrial connection who have a conduction delay are especially susceptible to recurrent atrial flutter/fibrillation and require supplemental antiarrhythmic drugs. Based on the results of this long-term outcome study, we suggest that a modified atrial incision is necessary to improve conduction between the right and left atria.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Conclusions
 References
 

  1. Williams J.M., Ungerleider R.M., Lofland G.K., et al. Left atrial isolation: new technique for the treatment of supraventricular arrhythmias. J Thorac Cardiovasc Surg 1980;80:373-380.[Abstract]
  2. Graffigna A., Pagani F., Minzioni G., et al. Left atrial isolation associated with mitral valve operations. Ann Thorac Surg 1992;54:1093-1098.[Abstract]
  3. Leitch J.W., Klein G., Yee R., et al. Sinus node-atrioventricular node isolation: long-term results with the "corridor"operation for atrial fibrillation. J Am Coll Cardiol 1991;17:970-975.[Abstract]
  4. Cox J.L., Boineau J.P., Schuessler R.B., et al. Five-year experience with the maze procedure for atrial fibrillation. Ann Thorac Surg 1993;56:814-823.[Abstract]
  5. Moe G.K. On the multiple wavelet hypothesis of atrial fibrillation. Arch Int Pharmacodyn 1962;140:183-188.
  6. Allessie M.A., Rensma P.L., Brugada J., Smeets J.L.R.M., Penn O., Kirchof C.J.H.J. Pathophysiology of atrial fibrillation. In: Zipes D.P., Jalife J., eds. Cardiac electrophysiology: from cell to bedside. Philadelphia: WB Saunders, 1990:548-559.
  7. Shyu K.G., Cheng J.J., Chen J.J., et al. Recovery of atrial function after atrial compartment operation for chronic atrial fibrillation in mitral valve disease. J Am Coll Cardiol 1994;24:392-398.[Abstract]
  8. Lo H.M., Lin F.Y., Lin J.L., et al. Electrophysiological properties in patients undergoing atrial compartment operation for chronic atrial fibrillation with mitral valve disease. Eur Heart J 1997;18:1805-1815.[Abstract/Free Full Text]
  9. Garrey W.E. The nature of fibrillary contraction of the heart: its relation to tissue mass and form. Am J Physiol 1914;33:397-414.[Free Full Text]
  10. Morillo C.A., Klein G.J., Jones D.L., et al. Chronic rapid atrial pacing: structural, functional and electrophysiologic characteristics of a new model of sustained atrial fibrillation. Circulation 1995;91:1588-1595.[Abstract/Free Full Text]
  11. Bayes de Luna A., Cladellas M., Oter R., et al. Interatrial conduction block and retrograde activation of the left atrium and paroxysmal supraventricular tachyarrhythmia. Eur Heart J 1988;9:1112-1118.[Abstract/Free Full Text]
  12. Lo H.M., Lin F.Y., Lin J.L., et al. Impaired cardiac performance relating to delayed left atrial activation after atrial compartment operation for chronic atrial fibrillation. PACE 1999;22:379-381.
  13. Haissaguerre M., Jais P., Shah D.C., et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998;339:659-666.[Abstract/Free Full Text]
  14. Kottkamp H., Hindricks G., Hammel D., et al. Intraoperative radiofrequency ablation of chronic atrial fibrillation: a left atrial curative approach by elimination of anatomic "anchor" reentrant circuits. J Cardiovasc Electrophysiol 1999;10:772-780.[Medline]
  15. Sueda T., Imai K., Orihashi K., Watari M., Okada K. Pulmonary vein orifice isolation for elimination of chronic atrial fibrillation. Ann Thorac Surg 2001;71:708-710.[Abstract/Free Full Text]
  16. Kalil R.A., Lima G.G., Leiria T.L.L., et al. Simple surgical isolation of pulmonary veins for treating secondary atrial fibrillation in mitral valve disease. Ann Thorac Surg 2002;73:1169-1173.[Abstract/Free Full Text]



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