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Eur J Cardiothorac Surg 2006;30:728-736
© 2006 Elsevier Science NL
a Department of Thoracic and Cardiovascular Surgery, College of Medicine, Korea University, Seoul, Republic of Korea
b Division of Cardiovascular Surgery, Sejong Heart Institute, Sejong General Hospital, Bucheon, Republic of Korea
c Division of Cardiology and Electrophysiology, Sejong Heart Institute, Sejong General Hospital, Bucheon, Republic of Korea
d Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
Received 19 April 2006; received in revised form 24 August 2006; accepted 25 August 2006.
* Corresponding author. Address: Department of Thoracic and Cardiovascular Surgery, Guro Hospital, College of Medicine, Korea University, 80 Guro-Dong, Guro-Gu, Seoul 152-703, Republic of Korea. Tel.: +82 2 818 6073; fax: +82 2 818 6377. (Email: mdmjbaek{at}korea.ac.kr).
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Abstract |
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 Top Abstract 1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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Key Words: Atrial fibrillation • Arrhythmia surgery • Rheumatic • Mitral valve • Cryoablation
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1. Introduction |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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The maze procedure was first performed using the cut-and-sew technique alone at our institution in July 1997, and it had been performed in a limited number of AF cases because of the complexity and complications. Meanwhile, cryoablation was introduced at our center in March 2000 and Dr Kosakai [11] reported several modifications of the maze procedure using cryoablation, showing excellent results despite its simplicity. Thereafter, our group modified the conventional Cox-maze and Kosakai-maze procedures, extending the indications of those to various cardiac conditions. Nowadays, we are performing the modified Cox-maze and Kosakai-maze procedures using cryoablation in all patients with AF associated with organic cardiac disease. However, until recently, there have been no comparative studies between the patients undergoing the modified Cox-maze and those undergoing the Kosakai-maze procedures. Moreover, many studies have suffered from conflicting results of the diverse outcomes in treating chronic AF associated with rheumatic mitral disease [6–9,12].
Accordingly, in this study we evaluated the mid-term outcomes of our maze procedures using cryoablation to treat chronic AF associated with rheumatic mitral valve disease, by comparing the surgical results of the modified Cox-maze procedure with those of the modified Kosakai-maze procedure, and assessed the risk factors for late recurrence of AF.
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2. Patients and methods |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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In this study, the patients undergoing a prior mitral valve replacement were excluded because of the uncertainties of the etiologies of the previous mitral valve disease, but patients undergoing a prior repair for rheumatic mitral disease were included. Seven patients (4.1%) had previous cardiac operations, including mitral valve repairs in three, aortic and mitral valve repairs in one, and an aortic valve replacement in one. Written, informed consent, specifying the uncertainties regarding the end-results of the maze procedure for AF, was obtained from all patients before the operation.
2.1 Surgical method
All procedures were performed using routine cardiopulmonary bypass with bicaval and aortic cannulation under moderate hypothermia. After complete cardiac arrest was accomplished, the maze procedure was performed using cryoablation in all patients (Fig. 1
). The details of the operative technique of our modified maze procedure were described previously [13]. Cryoablation using a dual-probe cardiac cryosurgical system (Frigitronics, Cooper Surgical, Shelton, CN) was applied for 90 s to 2 min at –60 °C according to the thickness of the atrial wall. Our modifications included the substitution of cryoablation for the multiple atrial incisions, preservation of the right atrial appendage in all patients and of the left atrial appendage in selected patients, and reduction of the both atrial dimensions by partial resection of the atrial wall.
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Then a right-sided maze procedure was performed while preserving the right appendage in all patients. In the CM group, a small right lateral incision was made, and through that, we applied the cryoablation toward the anterior annulus of the tricuspid valve. A posterior longitudinal right atriotomy was made, and from that a T incision was extended toward the posterior annulus of the tricuspid valve which was later cryoablated. A septal incision was made obliquely toward the coronary sinus. In the KM group, a right-sided maze was performed within only a curvilinear atrial incision. Cryoablation was applied at the interatrial septum transversely, superior edge of the lateral incision toward the anterior annulus of the tricuspid valve, and isthmic portion between the posterior annulus of the tricuspid valve and inferior vena cava.
After the maze procedure other cardiac procedures were performed. The data related to the operative procedures are given in Table 2 . The rheumatic mitral valve was replaced in 153 patients (90%) and repaired in 17 (10%). Tricuspid and aortic valve procedures were performed in 136 (80%) and 48 (28%) patients, respectively. Other concomitant procedures included left atrial thrombectomies in 30 patients, atrial septal defect closures in 7, decalcification and endocardiectomies of the left atrial wall in 5, coronary artery bypass grafting in 2, aortic root enlargements in 2, reduction aortoplasties with wrappings in 2, an ascending aortic graft replacement in 1, ventricular septal defect closure in 1, and pulmonary valve repair in 1.
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After discharge, the patients were followed up with a clinical examination, chest X-ray, ECG, echocardiogram, Holter monitoring and coronary angiography, when indicated. A standard 12-lead ECG was checked during the hospitalization, 3 and 6 months after discharge when followed up, and annually thereafter. The closing date for enrolling patient data in this study was December 31, 2004. Thus, all patients, except for one who died 3 months after the discharge, had a minimum of 6 months’ of follow-up, which was achieved in 96% (89/93) of the patients in the CM group and 97% (75/77) in the KM group by outpatient clinic visits or telephone interviews. The mean duration of the follow-up was 26.6 ± 15.2 months for all patients (range, 3–57.7 months).
2.3 Statistical analysis
Continuous data were presented as the mean ± standard deviation and categorical variables were expressed as the number of cases and percentage. The significance of the differences between the groups was assessed by the Mann–Whitney test for continuous variables and chi-square test or Fisher's exact test for categorical variables. The actuarial survivals and freedom from stroke and cardiac-related events were estimated using the Kaplan–Meier method, expressed as the mean ± standard error of the estimate and compared with the log-rank test. To assess the risk for late recurrence of AF, both univariate and multivariate analyses with the logistic regression model were used. The results were considered significant at a 95% confidence interval, p
0.05. The data were analyzed with the SPSS for Windows version 10.0 (SPSS Inc., Chicago, IL, USA).
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3. Results |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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3.2 Mortality and morbidity
There were three in-hospital deaths (1.8%). Two patients died in the CM group (2.2%). One patient, a 63-year-old female with an old cerebral infarction, died from repeated cerebral hemorrhages on postoperative day 18, and the other, a 53-year-old female with severe pulmonary hypertension, died 5 months postoperatively from respiratory failure and sepsis that developed after tracheal and esophageal reconstructions for tracheal stenosis with a tracheoesophageal fistula. Another patient in the KM group (1.3%), a 37-year-old female, died 16 days postoperatively from a diffuse brain injury related to a subclavian arterial injury that developed during the central catheterization.
Reexploration for bleeding was required in five patients (2.9%), including four (4.3%) in the CM group (an aorta-graft anastomosis site in one, resection site of the left atrial appendage in one, and diffuse oozing due to coagulopathy in two) and one (1.3%) in the KM group due to a left ventricular rupture after a mitral valve replacement with a bioprosthetic valve. The other postoperative complications included a low cardiac output syndrome requiring a temporary assist from cardiopulmonary bypass or a high-dose infusion of inotropic agents in seven patients (4.1%), pericardial or pleural effusions requiring intervention in six (3.5%), respiratory failure requiring prolonged mechanical ventilation in five (2.9%), transient ischemic attacks in three (1.8%), wound dehiscence in three (1.8%), early cardiac reoperation related to the structural failure of a valvular prosthesis or dysfunction of a repaired valve in two (1.2%), and acute renal failure requiring dialysis and ulcer bleeding in one each (0.6%).
During the follow-up, there was only one death (0.6%) in the CM group. That patient, a 43-year-old female maintaining sinus rhythm after aortic and mitral valve replacements with mechanical valves and tricuspid annuloplasty with a prosthetic ring, died suddenly 3 months postoperatively from an unknown etiology. The 4-year actuarial survival was 98.9 ± 1.1% in the CM group and 100% in the KM group (p = 0.36).
Cardiac reoperation was required in two patients (1.2%) in the CM group. One patient undergoing aortic and mitral valve replacements required an urgent coronary artery bypass grafting 3 months postoperatively for unstable angina with a non-Q myocardial infarction. The other patient undergoing aortic and mitral valve repairs required aortic and mitral valve replacements and a redo-maze procedure 39 months postoperatively for progression of aortic and mitral valve diseases and recurrent AF. There were no differences in the incidence of the mortality and complications during the postoperative and follow-up periods between the groups.
3.3 Stroke rate
Postoperatively, strokes occurred in four patients (2.4%), including two (2.2%) in the CM group and two (2.6%) in the KM group. In the CM group, one patient, that maintained sinus rhythm after a mitral valve replacement with a mechanical valve, tricuspid valve annuloplasty and left atrial thrombectomy, had a cerebral infarction 3 days after the operation with complete recovery, and the other that had an old cerebral infarction died due to repeated cerebral hemorrhages. In the KM group, one patient with a sequelae involving a left-sided hemiparesis from multiple old cerebral infarcts had a recurrent cerebral infarction with left-sided hemipleiga, and the other also died due to a diffuse brain injury.
During the follow-up, cerebrovascular accidents occurred in three patients (3.3%) in the CM group and one (1.3%) in the KM group. One patient in the CM group, who had right hemiparesis due to an old cerebral infarction and hemorrhage, experienced a recurrent cerebral infarction with right hemiplegia 40 months postoperatively on anticoagulant therapy for a mechanical mitral valve and AF, and another two in the CM group taking an oral anticoagulant therapy for mechanical mitral valves in sinus rhythm experienced cerebral hemorrhages 8 days after their discharge and 43 months postoperatively, but recovered without any sequelae. One patient in the KM group, who maintained sinus rhythm after mitral and tricuspid valve repairs, had a cerebral infarction 18 months postoperatively and underwent thrombolytic therapy but had right hemiplegia. There were no significant differences in the stroke rate during the postoperative and follow-up periods between the groups.
The 1- and 4-year actuarial survival free from stroke rates were 98.9 ± 1.1% and 90.3 ± 5.9% in the CM group, and 100% and 96.4 ± 3.5% in the KM group, respectively (p = 0.68) (Fig. 2 ). The 1- and 4-year event-free survival rates as assessed by the freedom from late death, cardiac-related reoperation, pacemaker implantation and stroke were 96.7 ± 1.9% and 81.2 ± 7.4% in the CM group, and 100% and 96.4 ± 3.5% in the KM group, respectively (p = 0.078).
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3.5 Predictors of a late recurrence of atrial fibrillation
According to the restoration of sinus rhythm at the last follow-up, the 167 survivors were divided into the two groups: sinus rhythm was not restored in 26 patients (16%; group AF) and restored in 141 (84%; group SR). The variables assessed for the predictors of late recurrence of atrial fibrillation after the maze procedure are described in Table A.1.
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10 years, and left atrial diameter >65 mm was as low as 30, 30, and 26%, respectively. Also using the univariate analysis for the categorical variables, the repair for rheumatic mitral valve disease was a significant predictor for the late recurrence of AF. Finally, using the multivariate analysis, a left atrial diameter of >65 mm (p
= 0.011) and repair for rheumatic mitral valve disease (p
= 0.038) were independent predictors for a late recurrence of AF (Table 4
).
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A mitral valve repair was performed in 17 patients (10%), including 8 (8.6%) in the CM group and 9 (11.7%) in the KM group. The predominant pathophysiology was pure regurgitation in 14 patients and mixed lesions in 3. During the follow-up, one patient, who had prior mitral and aortic repairs, underwent aortic and mitral valve replacements and tricuspid annuloplasty due to progressive valvular disease and tricuspid regurgitation. There was no residual stenosis or regurgitation in 11 patients, trivial regurgitation in 3, mild stenosis and grade I and II regurgitation in 1 each.
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4. Discussion |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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The conventional cut-and-sew maze procedure prolongs the cardiac ischemic time because of multiple and extensive incisions, and has the potential risk of postoperative complications, such as bleeding, sick sinus syndrome, and myocardial dysfunction [3,4]. However, the maze procedure using cryoablation is advantageous in reducing the postoperative complications by minimizing the incisions and shortening the operative time. These effects of cryoablation in the maze procedure were proven in a case-matched study by Nakajima and colleagues [10]. In our series, despite the higher incidence of other concomitant cardiac procedures, the mean cardiopulmonary bypass and aortic cross-clamp times were significantly shorter, being 190 and 145 min, respectively, compared to 242 and 170 min in our unpublished data for the conventional maze procedure using the cut-and-sew technique alone, and were also comparable to those of other studies on the conventional Cox-maze procedure [3,12,15].
Bleeding related to the maze procedure, although recently not a main problem, is still morbid, with an incidence of 6–8% for reoperations in the conventional maze procedure [3,4,7]. In our early experience, the cut-and-sew technique for pulmonary vein isolation was time-consuming and somewhat technically demanding, and bleeding especially was mostly attributed to this suture line and sometimes required cardiac arrest to control it. Since the report by Kosakai [11], we have modified the maze procedure by using cryoablation. In this series, the left-sided maze procedure could be easily performed with only a standard left atriotomy, which could be easily accessed for bleeding. Although bleeding which required reexploration developed in five patients (2.9%) in our study, it was related to the maze procedure itself in only one patient who had bleeding from the suture line of the excised left atrial appendage.
The incidence of sick sinus syndrome has been reported as being 6–23% in patients after the conventional maze procedure, requiring a pacemaker placement [3,4,14,16]. Although this higher incidence included patients who required a pacemaker for a preoperative diagnosis of sick sinus syndrome, it is still a major problem. In this study, sick sinus syndrome occurred in only two patients (1.2%) postoperatively, of which only one required a pacemaker but spontaneously regained sinus rhythm during the follow-up, and the other is doing well without a pacemaker implantation. In our series a low output syndrome occurred in seven patients (4.1%), of which six preoperatively required intensive care for severe ventricular dysfunction, and they all recovered completely. Also, our series had three in-hospital deaths, but no patients died from complications related to the prolongation of the operative time.
On the other hand, this study compared the outcomes of the modified Cox-maze procedure with those of the modified Kosakai-maze procedure using cryoablation. The patient groups were similar in both groups, but the operative times were significantly longer in the CM group than in the KM group. This was mostly attributed to the difference in the right-sided maze between both groups. However, the sinus rhythm rate at the last follow-up was the same for both the CM and KM groups and was 84 and 86%, respectively, and there were no differences in the morbidity and mortality rate during the postoperative or follow-up periods in either group. These effects have helped us to determine to continue with the modified Kosakai-maze procedure.
The impact of the maze procedure on strokes in patients with AF was proven by other reports [3,4,10,12,19]. Particularly, in a long-term follow-up study, Cox and his colleagues [3,19] reported an excellent effect of the maze procedure in reducing strokes. Jatene and colleagues [12] also reported a zero stroke rate in patients undergoing the maze procedure. In our series, the maze procedure exhibited positive effects in reducing the stroke rate. Preoperatively, 23 patients (14%) had one or more previous embolic events, which were cerebrovascular in 21 patients. At a follow-up of about 4 years, four patients (2.4%) in our study had cerebrovascular accidents, which were strokes in only two patients in which one had an old cerebral infarction and the other a new onset cerebral infarction. These results suggest that the restoration of sinus rhythm after the maze procedure could play an important role in reducing the strokes in patients with AF.
An advanced age, the duration of AF, increased cardiothoracic ratio, low f-wave voltage, and severely enlarged left atrium are well known risk factors for late recurrence of AF [7,16–18]. In this study the significant predictors of late recurrences of AF by using a univariate analysis were the duration of AF, f-wave voltage, left atrial dimension, and a repair of mitral valve disease. In particular, the patients with an f-wave <0.1 mV, AF duration 10 years, and left atrial diameter >65 mm had a significantly lower sinus rhythm restoration rate of 30, 30, and 26%, respectively. Finally the multivariate analysis assessed that the left atrial dimension and repair of mitral valve disease were the predictors for recurrence of AF. Considering the results from other reports [12,20], there was an interesting finding in our study in that a valvular repair for rheumatic mitral disease was an independent predictor for late recurrence of AF in both the univariate and multivariate analyses. This was related to one of the patient characteristics in which there was a larger percentage of patients with a lower f-wave voltage and longer AF duration in the repair group when compared with that of the replacement group.
The drawback of this study was that it was retrospective, with a lack of randomization in selecting the maze procedure and patients. However, there were no significant differences in the baseline characteristics of the patients between the CM and KM groups, except for the higher grade of mitral regurgitation and a trend toward a lower incidence of aortic valve replacements in the KM group. The restoration of the atrial transport function is an important goal of the maze procedure. However, unfortunately we did not investigate that issue in this study. Also, we had no data on what is the extent of the damaged atrial muscle around a lesion caused by cryothermia and what is the decreased atrial contractile function caused by the damaged muscle; this issue has been documented in many other studies. Lastly, although the mid-term results of our study are encouraging, further follow-up and study on the atrial transport function will be required to draw valid conclusions.
In summary, the maze procedure by using cryoablation is safe and effective in treating chronic AF in patients with rheumatic mitral valve disease, with an acceptable sinus conversion rate, mortality and morbidity. For the selection of the maze procedure, both the modified Cox-maze and Kosakai-maze procedures using cryoablation had similar outcomes despite the shorter operative times in the KM group. A left atrial dimension of >65 mm and repair for rheumatic mitral valve disease were significant predictors for a late recurrence of AF. For these reasons we recommend an earlier surgical correction of rheumatic mitral valve disease before the development of AF. Also if AF or dilatation of the left atrium develops, more aggressive intervention should be considered.
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Appendix A |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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Acknowledgments |
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References |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AReferences |
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