The present study showed that preoperative history of stroke would increase the risk of postoperative stroke after Cox-Maze procedure with mitral valve repair. Buber et al. suggested left atrial mechanical contraction and left atrial size as the postoperative risks of stroke after Cox-Maze procedure [
8]. However, there were few studies that analyze the risk factors for postoperative stoke. Many studies focused on the factors influencing the outcome of Cox-Maze procedure itself [
13‐
17], but few studies focused on postoperative stroke [
8]. Owing to the fact that AF increases stroke incidence by five folds [
1], previous studies have focused on either restoring sinus rhythm or analysis of the risk factors that lead to failure of Cox-Maze procedure. Furthermore, the incidence of postoperative stroke is a mere 1-3% [
13,
18,
19], making it difficult to analyze the risk factors of postoperative stroke. On the other hand, having the incidence rate of postoperative stroke of 6.7% in this study is considerably higher than that of other previous studies. However, heterogeneous population, witnessed in this investigation, involving a large numbers of rheumatic mitral valve and double valve diseases, may affect the incidence rate of stroke. It was remarkable that twelve of sixteen patients (75%) with postoperative stroke demonstrated sinus rhythm while eight of the twelve (67%) patients had left atrial mechanical contraction in echocardiography at the onset of stroke. This result did not concur with that of Buber et al. study [
8]. Buber et al. reported fifteen cases of stroke (10% in patients with normal sinus rhythm or 6.4% of the entire Cohort) in patients with sinus rhythm following successful Cox-Maze procedure, and also demonstrated that restoration of sinus rhythm would not enough to avoid the stroke [
8]. Furthermore, they concluded that the absence of left atrial mechanical contraction would be a strong independent risk factor for the postoperative stroke. The consideration is that a history of preoperative stroke is closely related with postoperative stroke regardless of left atrial mechanical contraction, albeit only univariate analysis which had been carried out. Meanwhile, the CHA
2DS
2-VASc score for stroke prediction [
20] was analyzed as a risk factor. Univariate analysis showed that high CHA
2DS
2-VASc score (score ≥2) appeared not to be related with postoperative stroke (p = 0.08). This was consistent with the result of Buber and colleague [
8]. This outcome was unexpected due to the fact that stroke risk score took account of history of stroke, transient ischemic attack and thromboembolism, which would be considered high risk in these cases. Such finding might have resulted from the aspect that the CHA
2DS
2-VASc score consisted of the combination of several risk factors.
In this study, all patients underwent left atrial ablation with cryoablation system. Left atrial ablation has the benefits of less procedure time, less procedure extent and less incidence of bradyarrhythmias. The left atrial ablation would be a more appropriated procedure than biatrial ablation with respect to a minimally invasive technique [
21,
22]. Based on the fact that it is the procedure for patients with a mitral valve disease in which AF developed in the posterior wall of the left atrium and the periphery of pulmonary veins, it was judged that sufficient efficacy could be attained with the left-sided Cox Maze IV procedure. Only the left-sided procedure was carried out on the notion that, since the procedure could be performed in merely about 10 minutes, there would be no effect on morbidity or mortality by the surgery, and that there were reports of safe, simple and excellent results coming out of this procedure [
10,
21]. This study revealed that overall success rate of Cox-Maze procedure was about 70% (Table
3). This was comparable to that of previous report in which patient underwent left-sided maze procedure with mitral valve surgery [
21]. However this rate was lower than the biatrial maze with its rate showing 90% [
5‐
7]. Compared with biatrial ablation, more frequent recurrence of atrial fibrillation in patients with mitral valve surgery [
18] were evident in left atrial ablation. In this study, 139 patients (58%) had rheumatic mitral valve disease and 80 patients (33%) underwent concomitant aortic valve surgery. Previous studies demonstrated that patients with a rheumatic mitral valve disease and a multiple valvular disease have worse outcomes [
16,
21,
23]. These reports supported the low success rate of the maze procedure among these patients with a valvular ailment.
Table 3
Postoperative rhythm status
3 months | 71.1% | 25.1% | 2.1% | 1.7% |
6 months | 70.9% | 25.6% | 1.7% | 1.7% |
1 year | 73.4% | 22.7% | 2.1% | 1.7% |
2 years | 72.2% | 23.9% | 1.7% | 2.2% |
This study had a number of limitations. Having conducted a retrospective study with observational data, albeit all subjects were followed up for observations, these subjects were not homogenous and follow-up duration was relatively short. Only 142 of 240 patients underwent isolated mitral valve surgery including mitral valve repair, repair of function tricuspid regurgitation as well as Cox-Maze procedure, and others had surgery of double valve diseases or of the concomitant coronary artery surgery. This might have affected the success rate of the Cox-Maze procedure and the incidence rate of the stroke. A long-term study is necessary to confirm the results of this investigation. The results of this study were reported with rhythm statuses at intervals, and this might have overestimated the success rate of the Cox-Maze procedure [
17]. A large scaled multi-center study is needed to overcome several limitations of which limited sample size and a single-center study.