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Ann Thorac Surg 1998;65:1666-1672
© 1998 The Society of Thoracic Surgeons
a Section of Cardiology, Department of Medicine, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China
b Section of Cardiovascular Surgery, Department of Surgery, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China
Accepted for publication January 30, 1998.
Address reprint requests to Dr Chen, Section of Cardiology, Chang Gung Memorial Hospital, 123, Ta Pei Rd, Niao Sung Hsiang, Kaohsiung Hsien 83305, Taiwan, Republic of China
| Abstract |
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Methods. Twelve patients undergoing mitral valve procedures were included in this study. Radiofrequency and cryoablation were applied to create lesions in both atria to simulate the classic maze operation.
Results. There were two surgical deaths. At the mean follow-up of 10.25 months for the remaining 10 patients; 6 were in sinus rhythm, 2 in atrial rhythm, 1 in paroxysmal atrial tachycardia, and 1 in atrial fibrillation. Doppler echocardiography at 6-month follow-up showed emergence of biatrial transport function in 3 patients and right atrial contractility in 8. At 12-month follow-up of 5 patients, Doppler echocardiography showed biatrial transport function in 3 and right atrial contractility in 4.
Conclusions. Our modified maze procedure during valvular operation is effective for achieving an acceptable success rate to restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation.
| Introduction |
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| Material and methods |
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Electrocardiography, Doppler echocardiography, and medications
After discharge, patients were followed monthly for adjustment of medication, evaluation of rhythm, and signs of myocardial ischemia. Early diastolic ventricular filling and filling by atrial contraction across the tricuspid and mitral valves were assessed by Doppler echocardiography 3, 6, and 12 months after operation. Anticoagulation with warfarin was used in all patients and discontinued only in patients when they showed atrial rhythm and documented atrial contraction after reparative operation.
| Results |
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Morbidity and mortality
There were two in-hospital deaths. One patient (patient 5), who had a normal preoperative coronary artery angiogram, had development of an acute inferior wall myocardial infarction postoperatively and died of massive cerebral infarction on the 17th day after operation while in atrial rhythm, despite no evidence of atrial thrombus by echocardiography. The other patient (patient 11) died of acute renal failure and heart failure 1 month after operation.
Postoperative cardiac rhythm
Immediately after operation, AF disappeared in 11 patients (92%) with 4 patients in sinus rhythm, 5 in atrial rhythm, and 2 in junctional rhythm. While recuperating in the hospital, 5 patients reverted to sinus rhythm from atrial rhythm (n = 2), junctional rhythm (n = 2), and AF (n = 1). However, 1 patient went back to AF from sinus rhythm and another patient developed junctional rhythm from atrial rhythm. At 1-month follow-up, one more patient went back to AF from sinus rhythm. This patients AF became persistent throughout the 12-month follow-up period and was the only patient treated with procainamide. At 6-month follow-up for the remaining 10 patients, the rhythms were sinus in 5 patients (50%), atrial in 2 (20%), paroxysmal left atrial tachycardia with a cycle length of 320 ms by electrophysiologic study in 1 (who refused transseptal approach for catheter ablation), typical counter-clockwise atrial flutter in 1 (who refused electrophysiologic study), and persistent AF in 1 (see Tables 1, 2). Of the 5 patients who had 12-month follow-up, 4 had sinus rhythm, including the patient who had AF again during hospitalization and reverted to atrial flutter for the following 6 months before returning to sinus rhythm at 9-month follow-up (Fig 3). The remaining 1 patient had persistent AF throughout the follow-up. Because of the small number of patients, we could not specifically address the issue of correlation between success rate and age, left atrial size, or AF duration.
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Functional class
At mean follow-up of 10.25 months (6 to 14 months) for the remaining 10 patients, the functional class improved to class I (n = 7) or II (n = 3).
| Comment |
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Comparison with previous reports
Cox and associates [11] developed the maze procedures to treat patients with a majority of lone AF and 99% of patients were free of AF. Kosakai and colleagues [18] modified Coxs maze procedures for patients with organic heart disease and 86% of patients were free of AF and atrial flutter. We used radiofrequency catheter ablation and cryoablation with modified maze procedures to obviate the need of extensive atrial incision to patients undergoing simultaneous valvular operation. In addition, pericardial patching was not necessary in our modified maze II procedure as there was no incision in the superior vena cava. Postoperative rhythms at 6-month follow-up were 80% in sinus or atrial rhythm. Five patients had 12-month follow-up, and the rhythms were sinus in 4 (80%). It has been known that the atrial pacemaker complex actually encompasses an area of 2 by 5 cm centering about the sinoatrial node [19]. In our study the modified maze procedure involved at least part of the pacemaker complex. This could contribute to the sinus node dysfunction observed in 7 patients (5 in atrial rhythm and 2 in junctional rhythm) immediately after operation. Similar results were also reported by Cox [11] and Kosakai [18] and their colleagues in humans. We have tried to avoid pacemaker injury by using either a maze II or III lesion pattern depending on the course of the sinus nodal arteries. Modification of the maze procedure that avoids damage to the atrial pacemaker complex and blood supply to the sinus node may reduce procedure-related sinus node dysfunction.
Feinberg and colleagues [10] demonstrated restoration of right atrial contraction in 83% and left atrial contraction in 61% of 46 patients after the maze procedure in their early experience. With a modified procedure (ie, the maze III), atrial transport functions were restored to 98% in the right and 94% in the left atria [11]. Kosakai and associates [18] reported restoration of right atrial transport in 88% and left atrial transport function in 73% with their modified maze procedure in 101 patients with organic heart disease. Thus, atrial transport function of the left atrium tends to recover less than that of the right atrium. We found a similar trend in our study. An A wave was detected in 80% for transtricuspid flow, but only in 30% of patients for transmitral flow at 6-month follow-up. At 12-month follow-up of 5 patients, 3 had biatrial and 4 had right atrial transport function. The reduced tendency of recovery of the left atrial contractile function could be attributed to more extensive lesions in the left atrium and interatrial conduction delay created by the maze procedure [11].
Reducing incidence of systemic embolism is one of the goals of restoring sinus rhythm from AF. However, in the studies by Cox [11] and Kosakai [18] and their co-workers, each had one transient ischemic attack during sinus rhythm after operation. This is conceivable because coexistence sinus rhythm and AF in a patient has been documented after the maze procedure [20] and the restoration of atrial transport function may lag behind after conversion of atrial flutter by pacing or electrical cardioversion [21]. One patient in our study died of massive cerebral infarction after mitral repair while in atrial rhythm, despite being under adequate anticoagulation with no evidence of atrial thrombus using transthoracic echocardiography. Although we could not exclude other possibilities, the cause of this patients death was most likely attributable to systemic embolization to the cerebral and coronary circulation, as the coronary angiogram was normal before operation. In addition, the time course was too short for it to be a result of coronary intimal hyperplasia at the site of cryoablation [22, 23]. Thus, systemic embolism can occur during the early postoperative period, although AF has been terminated.
In our study, the aortic cross-clamp time and cardiopulmonary bypass time were longer than those in the study by Kawaguchi and colleagues [14]. This was a result of valve repair using the Carpentier technique attempted in every patient. In average, this took 100 ± 20 minutes, and if failed, the mitral valve replacement was performed. However, our modified maze procedure took only 30.5 to 72 minutes (53.7 ± 14.5 minutes), including the mean left atrial ablation time of 29.5 minutes (21 to 36 minutes). The latter reflects a shorter ischemic time as compared with that in the series by Kosakai and associates [22]. With further refinement of the ablation catheter, the procedure time could be shortened and the risk of combining the maze procedure with valvular operation should be further reduced.
Blood loss was less in our study than in the study by Kawaguchi and colleagues [14] (365 ± 116 mL versus 1014 ± 513 mL). This could be attributed to less incision in our modified method. Thus, homeostasis may not be a critical problem using our modified maze procedure, even combined with valvular operation. This should be another impact of our modification. We wonder whether our method may avoid the complication related to cardiac tamponade reported by Cox [11] and Kosakai [18] and colleagues.
Study limitations
The first limitation of this study was that the atrial linear lesions created by radiofrequency energy were judged by discoloration. Because atrial electrograms were not recorded during the procedure, it was not certain whether the atrial discoloration represented a complete conduction block. However, the success rate of restoration of sinus or atrial rhythm was comparable with that of previous studies using a surgical approach. The mechanisms of AF have been postulated to involve single or multiple rapidly discharging foci [15, 24] or multiple wave front reentrant circuits [24]. Thus, the second limitation was the lack of mappings of AF to define the mechanisms. A mechanistic approach may allow a less extensive procedure but still achieve a high success rate [15, 16]. The third limitation was that this was a nonrandomized study in a small number of patients, making it difficult to compare with the classic surgical maze procedure. Further study with a larger number of patients should be conducted to confirm the feasibility of this method.
In conclusion, a combination of radiofrequency linear ablation and cryoablation simulating the maze procedure during valvular operation is feasible and effective for achieving an acceptable success rate to restore sinus rhythm and atrial transport function in patients with chronic AF.
| References |
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