Outcome of the modified maze procedure for atrial fibrillation combined with rheumatic mitral valve disease using cryoablation
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《血管的通路杂志》
Department of Cardiovascular Surgery, Sejong General Hospital, Sejong Heart Institute, Sosa Bon 2-dong, Sosa-ku, Bucheon, Kyungki-do, South Korea
Abstract
This study evaluated the mid-term results of the modified maze procedure using cryoablation for treating atrial fibrillation associated with rheumatic mitral valve disease. Between March 2000 and February 2004, 177 consecutive patients underwent the modified maze procedure using cryoablation concomitant with mitral valve surgery, were divided into the modified Cox-Maze III (group CM, n=88), modified Kosakai-Maze (group KM, n=63) and left atrial maze (group LA, n=26) procedures. Postoperative and follow-up results were analyzed and compared between the groups, with a mean follow-up time of 22.4±15.1 months. There were three hospital deaths (1.7%). The operative time was significantly longer in the group CM than the KM or LA groups, respectively. One late death developed in the CM group. At last follow-up, 139 patients had sinus rhythm (79.9%), which was regained in 67 CM (77.9%), 50 KM (80.7%) and 22 (84.6%) LA group (P=0.743) patients. Freedom from stroke at 4 years was 84.6% in the CM, 95.0% in the KM, and 92.9% in the LA (P=0.916) groups. There were no significant differences in the sinus conversion or stroke rate between patients with the left atrial appendage preserved and those with it excised or obliterated. The modified maze procedure using cryoablation is safe and effective, with an acceptable sinus conversion rate and clinical improvement.
Key Words: Atrial fibrillation; Arrhythmia surgery; Cryoablation; Mitral valve surgery
1. Introduction
Atrial fibrillation (AF) is the most prevalent arrhythmia frequently associated with mitral valve disease, resulting in significant morbidity and mortality [1,2]. The Cox-maze procedure is currently accepted as the surgical treatment of choice for medically refractory AF [3]. However, it is complex and has the potential risk of postoperative morbidities. Therefore, modified maze procedures using alternative ablation methods have been proposed to produce transmural conduction block [4–8], and there have been several electrophysiologic studies showing the left-sided maze procedure alone could cure AF in many patients [9,10].
On the other hand, the outcomes of the maze procedure for rheumatic AF have been known to be, although excellent in certain reports [6,11], less satisfactory than for lone or non-rheumatic AF [12,13]. Accordingly, in this study we investigated the mid-term outcomes of our modified maze procedure, including both biatrial and left-sided maze procedures using cryoablation, for AF associated with rheumatic mitral valve disease.
2. Materials and methods
Between March, 2000 and February 2004, 177 consecutive patients, who underwent the modified maze procedure using cryoablation concomitant with mitral valve surgery for AF associated with rheumatic mitral valve disease, were enrolled in this study and divided into the modified Cox-Maze III (CM group, n=88), modified Kosakai-Maze (KM group, n=63) and left atrial maze (LA group, n=26) procedures.
We retrospectively reviewed data from medical records. The clinical characteristics of the three groups are shown in Table 1. There were 64 men and 113 women, with a mean age of 51.4 years (20–75 years). Sixty-seven patients (37.9%) had a left atrial dimension 65 mm. The pathophysiology of rheumatic mitral valve disease was mixed lesion in 96 patients (54.2%), stenosis in 52 (29.4%) and regurgitation in 29 (16.4%). Thrombi in the left atrium (LA) were observed in 31 patients (17.5%). Previous thromboembolic events were present in 18 patients (10.2%), and among them, 16 had cerebrovascular complications.
2.1. Surgical technique
Routine cardiopulmonary bypass (CPB) with double venous cannulation and moderate hypothermia was used. Cardiac arrest was induced with antegrade or retrograde infusion of cold crystalloid or blood cardioplegia. A standard LA incision was made and extended superiorly and inferiorly. Cryoablation using a dual-probe cardiac cryosurgical system (Frigitronics, Cooper Surgical, Shelton, CN) was applied for 90 s to 2 min at –60 °C.
In this study, we performed three modified maze procedures using cryoablation (Fig. 1). Firstly, the CM group patients underwent a modified Cox-Maze III procedure. Briefly, two probes were applied simultaneously, beginning at the superior and inferior edge of the left atriotomy, respectively, and extended to the left atrial appendage (LAA) isolating the superior and inferior pulmonary veins. The LAA was excised, or, if not, ablated in a linear or circular fashion and then internally obliterated, externally ligated, or fully preserved. The left isthmus was cryoablated. Then a right-sided maze procedure was performed without isolation of the right atrial appendage. A small right lateral incision was made, and through that, we applied cryoablation toward the anterior annulus of the tricuspid valve (TV). A posterior longitudinal right atriotomy was made, and from that a T incision was extended toward the posterior annulus of the TV which was later cryoablated. A septal incision was made obliquely toward the coronary sinus. The KM group underwent a modified Kosakai-maze procedure [14]. The left-sided maze was the same as that for the CM group. The right-sided maze procedure was only performed within a curvilinear incision with several modifications that included cryoablation at the interatrial septum, anterior annulus of the TV and cavotricuspid isthmus. The procedure used in the LA group was a modification of the technique, reported by Sueda et al. [9], and was the same as that used in the CM and KM groups.
After the maze procedure, combined cardiac procedures were performed and the intraoperative data are given in Table 2. Written, informed consent was obtained from all patients.
2.2. Postoperative management and follow-up
Postoperatively amiodarone was loaded and orally maintained for 3 months according to the heart rhythm. In all patients, oral anticoagulation was maintained and discontinued in patients undergoing valve repair or replacement with bioprostheses who were in sinus rhythm (SR) postoperatively for 3 to 6 months, and then switched to aspirin. A standard 12-lead electrocardiogram was checked during the hospitalization, after discharge when followed-up at 3 and 6 months, and annually thereafter. The follow-up was completed in 94.3% of survivors with a mean time of 22.4±15.1 months.
2.3. Statistical analysis
Continuous data were expressed as mean±S.D. The significance of differences between the groups was assessed by the one-way ANOVA followed by Duncan's post hoc test for continuous variables, and chi-square test or Fisher's exact test for categorical variables. Actuarial survival and freedom from stroke and cardiac events were estimated using the Kaplan–Meier method, expressed as mean±standard error and compared with the log-rank test. Results were considered significant at a 95% confidence interval, P0.05.
3. Results
The mean operative time, such as CPB and aortic cross-clamp (ACC) time, were significantly longer in the CM group than the KM and LA groups, respectively, but there were no significant differences between the KM and LA groups. The incidence of TV procedures was significantly lower in the LA group (20%) than the CM and KM groups (80% and 79%, respectively). The LAA was resected in a significantly higher population of patients in the CM group and internally obliterated in a higher population of patients in the KM and LA groups. However, there were no significant differences in the overall incidence of procedures for isolating the LAA between the three groups.
There were three in-hospital deaths (1.7%), including two in the CM group (2.3%) (recurrent cerebral hemorrhage in one; respiratory failure and sepsis in one) and one in the KM group (1.6%) (brain death). Postoperative complications included pericardial or pleural effusions (n=7), low output syndrome (n=6), stroke (n=4), transient ischemic attack (n=3), respiratory failure (n=3), and early reoperation (n=2). Postoperative bleeding requiring reexploration developed in 6 patients (3.4%) including 5 in the CM group and 1 in the KM group, and related to the maze procedure itself in one patient due to resection of the LAA. There were no significant differences in the incidence of early mortality and morbidity between the three groups.
During follow-up, there was one late death (0.6%) in the CM group due to an unknown etiology. The 4-year actuarial survival was 98.8±1.2% in the CM group and 100% in the KM and LA groups, respectively (P=0.596). Stroke developed in 5 of all the patients (2.9%). The 4-year freedom from stroke was 84.6±9.4% in the CM group, 95.0±4.9% in the KM group, and 92.9±6.9% in the LA group (P=0.916) (Fig. 2). Cardiac-related reoperations were required in two CM group patients (1.2%). One patient required an urgent CABG 3 months postoperatively for unstable angina with a non-Q myocardial infarction related to newly developed coronary artery disease, and the other underwent an aortic and mitral valve replacement, tricuspid annuloplasty and redo-maze procedure 39 months postoperatively. The 4-year event-free survival was 73.8±10.4% in the CM group, 95.0±4.9% in the KM group, and 92.9±6.9% in the LA group (P=0.164).
Immediately after operation, SR was regained in 170 of all the patients (96.1%), and 86 CM group (97.7%), 61 (96.8%) KM group and 23 (88.5%) LA group patients (P=0.096). Perioperatively AF and flutter recurred in 41 (23.2%) and 15 (8.5%) of the total patients, respectively. At discharge, SR was maintained in 125 (70.6%) of the total patients, and 59 CM group (67.1%), 44 (69.8%) KM group and 22 (84.6%) LA group patients (P=0.262). Sick sinus syndrome developed in two patients (1.1%), of which one (1.6%) in the KM group, who required a pacemaker implantation, spontaneously regained stable SR, and the other (1.1%) in the CM group has been in AF without symptoms during the follow-up.
At last follow-up, 139 patients showed stable SR (79.9%), which was maintained in 67 CM group (77.9%), 50 (80.7%) KM group, and 22 (84.6%) LA group patients (P=0.743). A permanent pacemaker was implanted in two CM group patients (1.2%) (including one with sick sinus syndrome and the other with complete AV block). AF and flutter persisted in 25 (14.4%) and 9 (5.2%) of the total patients, respectively. There were no significant differences in the incidence of sinus conversion, atrial tachyarrhythmias, sick sinus syndrome and pacemaker implantation between the three groups during the hospitalization and follow-up.
According to the technique used for isolating the LAA, at last follow-up the rate of SR was 78.3% and 79.7% in patients it was excised or obliterated, respectively, and 85.7% in patients it was preserved (P=0.170). Stroke developed in 5 of the total patients (2.9%), including 2 (3.3%) and 2 (2.9%) patients the LAA was excised and obliterated, respectively, and 1 (2.4%) it was preserved (P=0.982).
Preoperatively, the NYHA functional class was 2.6±0.6 and 100 patients (56.5%) were class III or IV, and at last follow-up, it decreased to 1.2±0.4 (P<0.0001) and 137 patients (78.7%) were class I, and the remaining were class II.
4. Discussion
Since the introduction of cryoablation in March, 2003, we have extended the indications of the maze procedure to all AF with cardiac disease. Although this was not a comparative study between the maze procedure using cryoablation and conventional maze, the application of cryoablation in the maze procedure seems to be advantageous in the aspect of reducing the operative time, postoperative complications, such as bleeding and sick sinus syndrome, and preventing stroke. In our series, the mean operative time, such as CPB and ACC times, in all groups were comparable to that of other reports [4,7,11–13]. Especially the KM and LA groups had the CPB time significantly shortened by 37 and 58 min, respectively, and ACC time by 21 and 46 min, respectively, as compared to the CM group requiring multiple incisions for the right-sided maze. Also, postoperative bleeding and sick sinus syndrome requiring pacemaker implantation have been known as important complications related to the Cox-maze procedure, with incidences of 6–8% and 3.2–25%, respectively [3,4,12,13]. However, in this series the maze procedure using cryoablation could definitely decrease the incidence of postoperative bleeding and sick sinus syndrome by simplifying the procedure. Postoperative bleeding requiring reexploration developed in 6 patients (3.4%), and that related to the maze procedure itself, developed only in one patient due to resection of the LAA. Sick sinus syndrome occurred only in two (1.1%) and one patient (1.2%) during the postoperative and follow-up, respectively. The impact of the maze procedure on stroke has been proven by other reports [7,11–13,15]. In our series, the maze procedure showed positive effects in reducing the stroke rate. Preoperatively, 16 patients (9%) had strokes, which developed in 5 (2.9%) during the follow-up.
On the other hand, Cox et al. [15] emphasized the importance of excision or obliteration of the LAA and restoration of SR for preventing stroke. However, to the contrary, Isobe et al. [16] reported a high SR and low stroke rate despite preserving the bilateral appendages. In our series, the right atrial appendage was preserved in all cases, while the LAA was preserved in 43 (24.3%) patients. As a result, there were no significant differences in the SR and stroke rate between the patients in which the LAA was preserved and those it was excised or obliterated, with an acceptable SR and low stroke rate. This result was similar to that of Isobe et al. [16].
The surgical results of the maze procedure for AF associated with rheumatic mitral valve disease have been known to be less effective than for lone or non-rheumatic AF [12,13]. Lee et al. [6] and Jatene et al. [11] reported a SR rate of about 95%, but in our series it was 79.9% for all patients, and 77.9% in the CM group, 80.7% in the KM group and 84.6% in the LA group at last follow-up. This result was, although not entirely satisfactory, acceptable and comparable to that of other reports [4,5,8]. This diversity of the SR rate for rheumatic AF has no precise reasons as of yet. Kosakai et al. [4] and Fukada et al. [5] stated that the lower SR rate was attributed to the fibrotic and calcific degeneration of the atrial tissue, resulting from severe dilatation by chronic pressure and volume overloading or rheumatic myocaditis, rather than modification of atriotomies or the use of cryoablation. Our unpublished data showed that the SR rate was affected by the presence of rheumatic mitral valve. Contrary to these opinions, Lee et al. [6] insisted that the early outcomes of the maze procedure had nothing to do with the rheumatic inflammation, and Cox et al. [3,13,15] emphasized the importance of the surgical completeness of the maze procedure.
The effects of the left-sided maze procedure for AF are controversial. The left-sided maze procedure alone can cure the majority of chronic AF complicated mitral valve disease [9,10] but it has a risk of atrial flutter usually of right atrial origin. In our series the incidence of atrial flutter was 11.5% in the LA group postoperatively and decreased to 3.9% at last follow-up, but could not be completely avoided. For those reasons, recently we usually perform the biatrial maze procedure instead of the left-sided one.
Our study has several limitations. This was a retrospective study, with the lack of randomization for selecting the maze procedure, overall small number and disparity of the patient group in each group, resulting in some bias. Unfortunately, we did not investigate the recovery of the atrial contractile function after the maze procedure in the current study; however, this issue has been reported in the majority of studies.
In conclusion, the results of this study show that the modified maze procedure, by using cryoablation, is safe and effective in treating AF in patients with rheumatic mitral valve disease, by not only simplifying the operative procedure, but also by supporting an acceptable sinus conversion rate and clinical improvement.
References
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Abstract
This study evaluated the mid-term results of the modified maze procedure using cryoablation for treating atrial fibrillation associated with rheumatic mitral valve disease. Between March 2000 and February 2004, 177 consecutive patients underwent the modified maze procedure using cryoablation concomitant with mitral valve surgery, were divided into the modified Cox-Maze III (group CM, n=88), modified Kosakai-Maze (group KM, n=63) and left atrial maze (group LA, n=26) procedures. Postoperative and follow-up results were analyzed and compared between the groups, with a mean follow-up time of 22.4±15.1 months. There were three hospital deaths (1.7%). The operative time was significantly longer in the group CM than the KM or LA groups, respectively. One late death developed in the CM group. At last follow-up, 139 patients had sinus rhythm (79.9%), which was regained in 67 CM (77.9%), 50 KM (80.7%) and 22 (84.6%) LA group (P=0.743) patients. Freedom from stroke at 4 years was 84.6% in the CM, 95.0% in the KM, and 92.9% in the LA (P=0.916) groups. There were no significant differences in the sinus conversion or stroke rate between patients with the left atrial appendage preserved and those with it excised or obliterated. The modified maze procedure using cryoablation is safe and effective, with an acceptable sinus conversion rate and clinical improvement.
Key Words: Atrial fibrillation; Arrhythmia surgery; Cryoablation; Mitral valve surgery
1. Introduction
Atrial fibrillation (AF) is the most prevalent arrhythmia frequently associated with mitral valve disease, resulting in significant morbidity and mortality [1,2]. The Cox-maze procedure is currently accepted as the surgical treatment of choice for medically refractory AF [3]. However, it is complex and has the potential risk of postoperative morbidities. Therefore, modified maze procedures using alternative ablation methods have been proposed to produce transmural conduction block [4–8], and there have been several electrophysiologic studies showing the left-sided maze procedure alone could cure AF in many patients [9,10].
On the other hand, the outcomes of the maze procedure for rheumatic AF have been known to be, although excellent in certain reports [6,11], less satisfactory than for lone or non-rheumatic AF [12,13]. Accordingly, in this study we investigated the mid-term outcomes of our modified maze procedure, including both biatrial and left-sided maze procedures using cryoablation, for AF associated with rheumatic mitral valve disease.
2. Materials and methods
Between March, 2000 and February 2004, 177 consecutive patients, who underwent the modified maze procedure using cryoablation concomitant with mitral valve surgery for AF associated with rheumatic mitral valve disease, were enrolled in this study and divided into the modified Cox-Maze III (CM group, n=88), modified Kosakai-Maze (KM group, n=63) and left atrial maze (LA group, n=26) procedures.
We retrospectively reviewed data from medical records. The clinical characteristics of the three groups are shown in Table 1. There were 64 men and 113 women, with a mean age of 51.4 years (20–75 years). Sixty-seven patients (37.9%) had a left atrial dimension 65 mm. The pathophysiology of rheumatic mitral valve disease was mixed lesion in 96 patients (54.2%), stenosis in 52 (29.4%) and regurgitation in 29 (16.4%). Thrombi in the left atrium (LA) were observed in 31 patients (17.5%). Previous thromboembolic events were present in 18 patients (10.2%), and among them, 16 had cerebrovascular complications.
2.1. Surgical technique
Routine cardiopulmonary bypass (CPB) with double venous cannulation and moderate hypothermia was used. Cardiac arrest was induced with antegrade or retrograde infusion of cold crystalloid or blood cardioplegia. A standard LA incision was made and extended superiorly and inferiorly. Cryoablation using a dual-probe cardiac cryosurgical system (Frigitronics, Cooper Surgical, Shelton, CN) was applied for 90 s to 2 min at –60 °C.
In this study, we performed three modified maze procedures using cryoablation (Fig. 1). Firstly, the CM group patients underwent a modified Cox-Maze III procedure. Briefly, two probes were applied simultaneously, beginning at the superior and inferior edge of the left atriotomy, respectively, and extended to the left atrial appendage (LAA) isolating the superior and inferior pulmonary veins. The LAA was excised, or, if not, ablated in a linear or circular fashion and then internally obliterated, externally ligated, or fully preserved. The left isthmus was cryoablated. Then a right-sided maze procedure was performed without isolation of the right atrial appendage. A small right lateral incision was made, and through that, we applied cryoablation toward the anterior annulus of the tricuspid valve (TV). A posterior longitudinal right atriotomy was made, and from that a T incision was extended toward the posterior annulus of the TV which was later cryoablated. A septal incision was made obliquely toward the coronary sinus. The KM group underwent a modified Kosakai-maze procedure [14]. The left-sided maze was the same as that for the CM group. The right-sided maze procedure was only performed within a curvilinear incision with several modifications that included cryoablation at the interatrial septum, anterior annulus of the TV and cavotricuspid isthmus. The procedure used in the LA group was a modification of the technique, reported by Sueda et al. [9], and was the same as that used in the CM and KM groups.
After the maze procedure, combined cardiac procedures were performed and the intraoperative data are given in Table 2. Written, informed consent was obtained from all patients.
2.2. Postoperative management and follow-up
Postoperatively amiodarone was loaded and orally maintained for 3 months according to the heart rhythm. In all patients, oral anticoagulation was maintained and discontinued in patients undergoing valve repair or replacement with bioprostheses who were in sinus rhythm (SR) postoperatively for 3 to 6 months, and then switched to aspirin. A standard 12-lead electrocardiogram was checked during the hospitalization, after discharge when followed-up at 3 and 6 months, and annually thereafter. The follow-up was completed in 94.3% of survivors with a mean time of 22.4±15.1 months.
2.3. Statistical analysis
Continuous data were expressed as mean±S.D. The significance of differences between the groups was assessed by the one-way ANOVA followed by Duncan's post hoc test for continuous variables, and chi-square test or Fisher's exact test for categorical variables. Actuarial survival and freedom from stroke and cardiac events were estimated using the Kaplan–Meier method, expressed as mean±standard error and compared with the log-rank test. Results were considered significant at a 95% confidence interval, P0.05.
3. Results
The mean operative time, such as CPB and aortic cross-clamp (ACC) time, were significantly longer in the CM group than the KM and LA groups, respectively, but there were no significant differences between the KM and LA groups. The incidence of TV procedures was significantly lower in the LA group (20%) than the CM and KM groups (80% and 79%, respectively). The LAA was resected in a significantly higher population of patients in the CM group and internally obliterated in a higher population of patients in the KM and LA groups. However, there were no significant differences in the overall incidence of procedures for isolating the LAA between the three groups.
There were three in-hospital deaths (1.7%), including two in the CM group (2.3%) (recurrent cerebral hemorrhage in one; respiratory failure and sepsis in one) and one in the KM group (1.6%) (brain death). Postoperative complications included pericardial or pleural effusions (n=7), low output syndrome (n=6), stroke (n=4), transient ischemic attack (n=3), respiratory failure (n=3), and early reoperation (n=2). Postoperative bleeding requiring reexploration developed in 6 patients (3.4%) including 5 in the CM group and 1 in the KM group, and related to the maze procedure itself in one patient due to resection of the LAA. There were no significant differences in the incidence of early mortality and morbidity between the three groups.
During follow-up, there was one late death (0.6%) in the CM group due to an unknown etiology. The 4-year actuarial survival was 98.8±1.2% in the CM group and 100% in the KM and LA groups, respectively (P=0.596). Stroke developed in 5 of all the patients (2.9%). The 4-year freedom from stroke was 84.6±9.4% in the CM group, 95.0±4.9% in the KM group, and 92.9±6.9% in the LA group (P=0.916) (Fig. 2). Cardiac-related reoperations were required in two CM group patients (1.2%). One patient required an urgent CABG 3 months postoperatively for unstable angina with a non-Q myocardial infarction related to newly developed coronary artery disease, and the other underwent an aortic and mitral valve replacement, tricuspid annuloplasty and redo-maze procedure 39 months postoperatively. The 4-year event-free survival was 73.8±10.4% in the CM group, 95.0±4.9% in the KM group, and 92.9±6.9% in the LA group (P=0.164).
Immediately after operation, SR was regained in 170 of all the patients (96.1%), and 86 CM group (97.7%), 61 (96.8%) KM group and 23 (88.5%) LA group patients (P=0.096). Perioperatively AF and flutter recurred in 41 (23.2%) and 15 (8.5%) of the total patients, respectively. At discharge, SR was maintained in 125 (70.6%) of the total patients, and 59 CM group (67.1%), 44 (69.8%) KM group and 22 (84.6%) LA group patients (P=0.262). Sick sinus syndrome developed in two patients (1.1%), of which one (1.6%) in the KM group, who required a pacemaker implantation, spontaneously regained stable SR, and the other (1.1%) in the CM group has been in AF without symptoms during the follow-up.
At last follow-up, 139 patients showed stable SR (79.9%), which was maintained in 67 CM group (77.9%), 50 (80.7%) KM group, and 22 (84.6%) LA group patients (P=0.743). A permanent pacemaker was implanted in two CM group patients (1.2%) (including one with sick sinus syndrome and the other with complete AV block). AF and flutter persisted in 25 (14.4%) and 9 (5.2%) of the total patients, respectively. There were no significant differences in the incidence of sinus conversion, atrial tachyarrhythmias, sick sinus syndrome and pacemaker implantation between the three groups during the hospitalization and follow-up.
According to the technique used for isolating the LAA, at last follow-up the rate of SR was 78.3% and 79.7% in patients it was excised or obliterated, respectively, and 85.7% in patients it was preserved (P=0.170). Stroke developed in 5 of the total patients (2.9%), including 2 (3.3%) and 2 (2.9%) patients the LAA was excised and obliterated, respectively, and 1 (2.4%) it was preserved (P=0.982).
Preoperatively, the NYHA functional class was 2.6±0.6 and 100 patients (56.5%) were class III or IV, and at last follow-up, it decreased to 1.2±0.4 (P<0.0001) and 137 patients (78.7%) were class I, and the remaining were class II.
4. Discussion
Since the introduction of cryoablation in March, 2003, we have extended the indications of the maze procedure to all AF with cardiac disease. Although this was not a comparative study between the maze procedure using cryoablation and conventional maze, the application of cryoablation in the maze procedure seems to be advantageous in the aspect of reducing the operative time, postoperative complications, such as bleeding and sick sinus syndrome, and preventing stroke. In our series, the mean operative time, such as CPB and ACC times, in all groups were comparable to that of other reports [4,7,11–13]. Especially the KM and LA groups had the CPB time significantly shortened by 37 and 58 min, respectively, and ACC time by 21 and 46 min, respectively, as compared to the CM group requiring multiple incisions for the right-sided maze. Also, postoperative bleeding and sick sinus syndrome requiring pacemaker implantation have been known as important complications related to the Cox-maze procedure, with incidences of 6–8% and 3.2–25%, respectively [3,4,12,13]. However, in this series the maze procedure using cryoablation could definitely decrease the incidence of postoperative bleeding and sick sinus syndrome by simplifying the procedure. Postoperative bleeding requiring reexploration developed in 6 patients (3.4%), and that related to the maze procedure itself, developed only in one patient due to resection of the LAA. Sick sinus syndrome occurred only in two (1.1%) and one patient (1.2%) during the postoperative and follow-up, respectively. The impact of the maze procedure on stroke has been proven by other reports [7,11–13,15]. In our series, the maze procedure showed positive effects in reducing the stroke rate. Preoperatively, 16 patients (9%) had strokes, which developed in 5 (2.9%) during the follow-up.
On the other hand, Cox et al. [15] emphasized the importance of excision or obliteration of the LAA and restoration of SR for preventing stroke. However, to the contrary, Isobe et al. [16] reported a high SR and low stroke rate despite preserving the bilateral appendages. In our series, the right atrial appendage was preserved in all cases, while the LAA was preserved in 43 (24.3%) patients. As a result, there were no significant differences in the SR and stroke rate between the patients in which the LAA was preserved and those it was excised or obliterated, with an acceptable SR and low stroke rate. This result was similar to that of Isobe et al. [16].
The surgical results of the maze procedure for AF associated with rheumatic mitral valve disease have been known to be less effective than for lone or non-rheumatic AF [12,13]. Lee et al. [6] and Jatene et al. [11] reported a SR rate of about 95%, but in our series it was 79.9% for all patients, and 77.9% in the CM group, 80.7% in the KM group and 84.6% in the LA group at last follow-up. This result was, although not entirely satisfactory, acceptable and comparable to that of other reports [4,5,8]. This diversity of the SR rate for rheumatic AF has no precise reasons as of yet. Kosakai et al. [4] and Fukada et al. [5] stated that the lower SR rate was attributed to the fibrotic and calcific degeneration of the atrial tissue, resulting from severe dilatation by chronic pressure and volume overloading or rheumatic myocaditis, rather than modification of atriotomies or the use of cryoablation. Our unpublished data showed that the SR rate was affected by the presence of rheumatic mitral valve. Contrary to these opinions, Lee et al. [6] insisted that the early outcomes of the maze procedure had nothing to do with the rheumatic inflammation, and Cox et al. [3,13,15] emphasized the importance of the surgical completeness of the maze procedure.
The effects of the left-sided maze procedure for AF are controversial. The left-sided maze procedure alone can cure the majority of chronic AF complicated mitral valve disease [9,10] but it has a risk of atrial flutter usually of right atrial origin. In our series the incidence of atrial flutter was 11.5% in the LA group postoperatively and decreased to 3.9% at last follow-up, but could not be completely avoided. For those reasons, recently we usually perform the biatrial maze procedure instead of the left-sided one.
Our study has several limitations. This was a retrospective study, with the lack of randomization for selecting the maze procedure, overall small number and disparity of the patient group in each group, resulting in some bias. Unfortunately, we did not investigate the recovery of the atrial contractile function after the maze procedure in the current study; however, this issue has been reported in the majority of studies.
In conclusion, the results of this study show that the modified maze procedure, by using cryoablation, is safe and effective in treating AF in patients with rheumatic mitral valve disease, by not only simplifying the operative procedure, but also by supporting an acceptable sinus conversion rate and clinical improvement.
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