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Eur J Cardiothorac Surg 1998;13:247-252
© 1998 Elsevier Science NL

Improved success rate of the maze procedure in mitral valve disease by new criteria for patients’ selection¹

The Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishiro-dai, Suita-city, Osaka 565, Japan

Received 29 September 1997; received in revised form 8 December 1997; accepted 16 December 1997.

Corresponding author. Tel.: +81 6 8335012; fax: +81 6 8727486; e-mail: jkobayas@hosp.ncvc.go.jp

	Abstract

Top Abstract Introduction Patients and methods Results Discussion References

 
Objective: We have carried out the maze procedure for atrial fibrillation (AF) as a combined operation with mitral valve surgery in a consecutive fashion until December 1994 (period 1). Therefore, the success rate in sinus rhythm conversion remained unsatisfactory. We have selected the patients according to arbitrarily decided new criteria since January 1995 (period 2), and examined the results prospectively. Methods: Between May 1992 and February 1997, we carried out the maze procedure in 220 patients as a combined operation with mitral valve surgery. During period 2, we carried out the maze procedure in 63 cases who satisfied all the new criteria (voltage of f-wave in V1 lead >0.1 mV, cardiothoracic ratio (CTR) <70%, LA dimension <70 mm), and 37 patients out of these criteria. Success was defined as sinus rhythm restoration without sick sinus syndrome. Results: There were 4 hospital deaths (1.8%) and 4 late deaths (1.8%). Success rate was significantly (P=0.0089) higher in period 2 (82%) than in period 1 (65%). Success rate was significantly higher in patients within criteria than out of criteria both in period 1, period 2, and total (77 versus 48%, P=0.018; 90 versus 66%, P=0.004, and 83 versus 55%, P=0.0001). Conclusion: The maze procedure is highly reliable when combined with mitral valve surgery if patients are selected properly.

Key Words: Atrial fibrillation • Maze procedure • Mitral valve disease

	Introduction

Top Abstract Introduction Patients and methods Results Discussion References

 
Atrial fibrillation (AF) is frequently associated in patients with mitral valve disease who require operation. Most of these patients remained AF after the mitral valve surgery, and suffered from the risk of thromboembolism and symptoms. The maze procedure for AF was developed by Cox [1] [2], and its modification has been carried out widely for the last 5 years [3] [4] [5] [6] [7]. Although the results of the maze procedure for lone AF was satisfactory, the success rate in sinus rhythm conversion in patients with mitral valve lesion remained low in our institute. The causes of AF with mitral valve disease are thought to be inhomogeneous depolarization potentials, refractory periods, and conduction properties in the enlarged right and left atria [8] [9] [10]. As the maze procedure elongates the cardiac arrest time, cardiopulmonary bypass time, and operation time, the mortality and morbidity might be increased. Therefore, it is very important to select the patients preoperatively according to the hemodynamic and demographic data if these data are highly predictive of the results. In the present study we examined the criteria for patients’ selection retrospectively for the first half period, and the improvement of the success rate prospectively in the second half period.

	Patients and methods

Top Abstract Introduction Patients and methods Results Discussion References

 
Patients
Between May 1992 and June 1997, we carried out the maze procedure in 220 patients as a combined operation with the mitral valve surgery. The patients were composed of 101 men and 119 women, and their age at operation ranged from 29 to 83 years with an average of 58.3±9.0 years (±S.D.). Concomitant valve diseases were aortic valve disease in 77 patients, and tricuspid regurgitation in 107. Of the patients, 5 had coronary artery disease, 1 had anomalous origin of the left coronary artery from the pulmonary artery, 212 patients had chronic sustained AF, and 8 patients had paroxysmal AF or atrial flutter.

Preoperative electrocardiography (ECG) was recorded, and the maximum amplitude of the f-wave not on T-wave in lead V1 was defined as the voltage of f-wave [5]. The cardiothoracic ratio (CTR) was also measured before the operation. Left atrial (LA) dimension was determined by trans-thoracic echocardiography.

Simultaneous procedures with the maze operation are listed in Table 1. As for the maze procedure, we carried out Kosakai’s modified maze procedure [5] in 169 patients, the modified Cox maze II procedure in 13, and maze III procedure in 38.

Changes of indication and procedure
From January 1992 to December 1994 (period 1), 120 patients underwent the maze procedure basically in a consecutive fashion. We analyzed the data to determine the patients’ selection criteria for successful maze procedure retrospectively. From January 1995 to June 1997 (period 2), we prospectively carried out the maze procedure in 100 patients who had the high possibility of sinus rhythm conversion. The patients were composed of 64 patients who satisfied arbitrarily decided new criteria (voltage of f-wave >0.1 mV, CTR <70%, and LA dimension <70 mm) from our previous studies [5] [11] [12], and 36 patients out of the criteria. In addition, we had the tendency to avoid the maze procedure in patients who had a longer than 10-year duration of AF and/or reoperation. The older age >75 years was a relative contraindication. We resected the right and left atrium and made the width of divided compartments smaller than 4 cm in width in advanced valvular heart disease more frequently (P=0.0007) in period 2 (17%) than in period 1 (34%). The incidence of reoperation, rheumatic heart disease, presence of tricuspid lesion, duration of AF, and CTR were significantly (P=0.043, P=0.0013, P=0.0045, P=0.0025, and P=0.01) higher in period 1 than period 2 (Table 2).

	Results

Top Abstract Introduction Patients and methods Results Discussion References

 
Of all the patients, 4 (1.8%) died of causes unrelated to the maze procedure in hospital. There were 4 late deaths (1.8%) later than 8 months after the procedure. Successful sinus conversion rate was 73% as a total (Table 3). Success rate was significantly (P=0.012) higher in period 2 (82%) than in period 1 (65%). Success rate was significantly higher in patients within criteria than out of criteria both in period 1, period 2, and total (77 versus 48%, P=0.018; 90 versus 66%, P=0.004; and 83 versus 55%, P=0.0001).

View larger version (23K): [in this window] [in a new window]   Fig. 1. Duration of AF was significantly (P=0.0001) shorter in patients with sinus restoration (6.9±5.3 years) than without sinus restoration (12.8±7.1 years) in period 1 (6.9±5.3 years). There was no significant difference between the two groups in period 2 (6.4±6.4 years vs. 9.1±11.0 years).

View larger version (19K): [in this window] [in a new window]   Fig. 2. Voltage of f-wave was significantly (P=0.029) higher in patients with sinus restoration (0.16±0.10 mV) than without sinus restoration (0.11±0.07 mV) in period 1. There was no significant difference between the two groups in period 2 (0.15±0.08 vs. 0.10±0.08 mV).

View larger version (24K): [in this window] [in a new window]   Fig. 3. Preoperative CTR was significantly smaller in patients with sinus restoration than without sinus restoration in period 1 (61±8 vs. 67 ±11%, P=0.003), and period 2 (60±6 vs. 63±5%, P=0.031).

View larger version (24K): [in this window] [in a new window]   Fig. 4. Preoperative LAD was significantly smaller in patients with sinus restoration than without sinus restoration in period 1 (57±10 vs. 65 ±15 mm, P=0.0013), and period 2 (57±9 vs. 67±11 mm, P=0.0005).

	Discussion

Top Abstract Introduction Patients and methods Results Discussion References

There are two kinds of failure in sinus rhythm recovery. One is sustained AF, atrial flutter, or atrial tachycardia. The other is sick sinus syndrome in spite of successful defibrillation. The causes of failure might be attributed not to inappropriate surgical procedure but more likely to overindication. The substitution of a cryoablation for a surgical incision, and the damage to the sinus node artery could be causes of the failure. Those are able to be avoided by meticulous surgical procedure. A previous pathological study reported that the markedly attenuated contiguity of the sinoatrial junction cells, severe fibrosis, and lipomatous changes in the right atrium were noted in spite of the patency of the sinoatrial nodal artery in patients with AF [18]. Some patients in the present study already had sick sinus syndrome before the operation. On the contrary, some patients may have high possibility of recurrent AF because of degenerated atrial muscle due to rheumatic heart disease and excessively enlarged right and left atria due to long-standing hemodynamic abnormalities. If the conduction velocity of the atrium is slow (0.1 m/s), and the refractory period is short (200 ms), the wave length of the reentry circuit is theoretically only 2 cm by the concept of Thomas Lewis [19]. Therefore, AF could occur even if all the macroreentry circuits were cut by Cox’s theory [20].

The risk factors for failure to regain sinus rhythm were duration of AF, voltage of f-wave, CTR, and LA dimension. Duration of AF was not a risk factor in period 2, but a risk factor in period 1. Even in patients with duration of AF >10 years, success rate was 72% in period 2. As AF sometimes occurs without a patient’s notice, it is very difficult to evaluate the accurate onset of chronic AF in many patients. Duration of AF was also not related to the degeneration of the sinus node and atrial muscles. It is not appropriate to select the patients for the maze procedure according to the duration of AF. Postoperative CTR, and LA dimension were explanatory variables for successful sinus conversion. The f-wave is a sum of the total electric activity of the atrial muscles, and the amplitude is a reflection of the degree of degeneration of the atrium. Increased CTR means atrial and ventricular enlargement. Although CTR is not a specific index of some issue, it is a simple index to measure universally. LA dimension was also a very important risk factor to predict the outcome of the maze procedure in mitral valve disease. The causes of AF with mitral valve disease are thought to be inhomogeneous depolarization potentials, refractory periods, and conduction properties in the enlarged LA. LA wall is usually very thin, and LA degeneration is probably present if the LA is very enlarged. Sueda and associates reported that the shortest fibrillation cycle length was located at the posterior LA in mitral valve disease, and this site is the electrical activation of AF [21]. Therefore, if the LA was enlarged postoperatively, AF or atrial tachycardia could recur easily due to micro- and relatively smaller macroreentry circuits because of elevated automaticity and shorter refractory period of LA muscles.

In the present study, the success rate in patients within criteria in period 2 was 90%. This value is mostly attributed to the patients’ selection. However, success rates were both improved in patients within criteria and out of criteria from periods 1 to period 2. This improvement was probably due to the resection of right and left atrium. Because the estimated minimum wavelength of reentry circuit for AF is 12 cm in humans according to Allessie’s concept [19], we tried to make the width of the divided atrial wall smaller than 4 cm (12 cm/) in width. As the atrium was enlarged and degenerated in mitral valve disease, especially in rheumatic heart disease, macroreentry could easily occur. Therefore, the effect of atrial resection was very important in these patients. With regards to the low mortality and the improved success rate in selected patients in period 2, the maze procedure in these patients is recommended as a concomitant operation with mitral valve surgery. In patients with relatively high operative risks and excessively enlarged atria, the indication of the maze procedure should be meticulous.

	Footnotes

 
Presented at the 11th Annual Meeting of the European Association for Cardio-thoracic Surgery, Copenhagen, Denmark, 28 September–1 October, 1997.

	References

Top Abstract Introduction Patients and methods Results Discussion References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Yoshio Kosakai Kiyoharu Nakano Yoshikado Sasako Fumio Yamamoto Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kobayashi, J. Articles by Yamamoto, F. Search for Related Content PubMed PubMed Citation Articles by Kobayashi, J. Articles by Yamamoto, F.