Long-term outcomes of concomitant Cox-Maze III procedure in patients with aortic valve diseases and preoperative atrial fibrillation

Introduction

Atrial fibrillation is an atrial arrhythmia with the highest prevalence in the general population and patients with acquired heart diseases (1). Treatment of atrial fibrillation is classified into medical therapy, including rate control and rhythm control; interventional therapy, such as radiofrequency catheter ablation (RFCA); and surgical therapy, represented by the Cox-Maze procedure. Preoperative atrial fibrillation is a well-known risk factor for increased perioperative mortality and morbidity after open heart surgery, raising the need for concurrent surgical treatment for atrial fibrillation along with treatment for underlying heart disease (2-5). Since the Cox-Maze procedure effectively induces sinus conversion in patients with atrial fibrillation and only slightly increases the risk of cardiac surgery, it is recommended to be performed simultaneously with underlying heart diseases in patients with preoperative atrial fibrillation (6-9).

The concomitant Cox-Maze procedure along with mitral valve surgery have been reported to improve the patients’ functional capacity and left ventricular function and reduce the incidence of stroke in patients with mitral valve disease (10). However, there is relatively little evidence for the clinical significance of the concomitant Cox-Maze procedure in patients with aortic valve disease, and there is hesitation to make an additional incision on the left atrium (LA) for the concomitant Cox-Maze procedure (8,11,12). According to the Society of Thoracic Surgeons (STS) database, only 31% of patients diagnosed with atrial fibrillation preoperatively who underwent aortic valve replacement (AVR) for aortic valve disease received the concomitant arrhythmia surgery, in contrast to 56% of patients who underwent mitral valve surgery (7). Considering the prevalence of atrial fibrillation (8.2–13.6%) in patients with aortic valve disease, it is necessary to establish evidence for the concomitant Cox-Maze procedure with aortic valve surgery (5,9).

Therefore, this study aimed to evaluate the early and long-term outcomes of the concomitant Cox-Maze procedure for atrial fibrillation in patients undergoing AVR. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1223/rc).

Methods

Patient selection

A total of 2,316 patients who underwent AVR for aortic valve stenosis or regurgitation at our institution between January 1994 and December 2020 were assessed for eligibility. A total of 703 patients diagnosed with atrial fibrillation before AVR were selected. Exclusion criteria included patients with a history of previous cardiac surgery, patients who underwent concomitant tricuspid valve/mitral valve replacement or coronary artery bypass grafting (CABG) along with AVR, patients diagnosed with infective endocarditis, patients diagnosed with other valvular heart diseases of more than a moderate degree, and patients who underwent arrhythmia surgery other than the Cox-Maze III procedure. A total of 101 patients were enrolled in this study, after excluding 602 patients who met the exclusion criteria. The concomitant Cox-Maze III procedure was performed in 47 patients (46.5%, CM group), and not in 54 patients (53.5%, non-CM group). The baseline characteristics are summarized in Table 1.

Operative techniques

All operations were performed via median sternotomy. AVR was performed using a non-everting mattress suture buttress reinforced with polytetrafluoroethylene as a tubule or pledget. In the CM group, the Cox-Maze III procedure was performed concomitantly with AVR. The basic lesion set performed at our center is almost the same as the Cox Maze III procedure originally proposed by Dr. James L. Cox, with a slight modification according to the surgeon: (I) right side lesion sets: superior/inferior vena cava, septal line, tricuspid valve annulus, and right atrial appendage line; (II) left size lesion sets: pulmonary vein isolation, mitral valve annulus, left atrial appendage line, and coronary sinus (13). Surgical ablation was performed using only cryoablation until 2004, and bipolar radiofrequency ablation was added from 2005 according to the surgeon’s discretion. Since 2015, all surgical ablations have been performed using cryoablation alone. In the CM group, left atrial appendage was excised or obliterated (internally or externally) in 44 (93.6%) patients.

Clinical outcomes

The clinical endpoints of this study were early and long-term outcomes after AVR, with or without a concomitant Cox-Maze procedure. As one of the early outcomes, operative mortality was defined as death from any cause during index hospitalization or within 30 days after surgery. Acute kidney injury (AKI) was defined as an increase in serum creatinine levels of more than 2-fold compared with baseline. Low cardiac output syndrome was defined as the need for mechanical circulatory support (intra-aortic balloon pump, left ventricular assist device, or extracorporeal membrane oxygenation) after surgery, or hemodynamic instability requiring continued pharmacological support with more than two inotropic medications on postoperative day 1. After discharge, postoperative follow-ups were regularly performed in the outpatient clinic at 3–6-month intervals. In addition, data on death from any cause and cardiac events were obtained from the death certificates available from Statistics Korea. Cardiac death was defined as death related to cardiac events, including sudden death during the follow-up. Sinus conversion or occurrence of atrial fibrillation was judged 3 months after the index operation. The occurrence of atrial fibrillation was defined as maintaining atrial fibrillation, atrial flutter, or pacing rhythm with underlying atrial fibrillation, including recurred atrial fibrillation after the Cox-Maze procedure. Sinus rhythm was defined as normal sinus rhythm or junctional rhythm. Warfarin and new oral anticoagulant drugs (NOACs) were used as anticoagulants for atrial fibrillation, and administration or discontinuation of the anticoagulants was analyzed by period. The median duration of follow-up was 70.7 months [interquartile range (IQR), 36.2–118.8 months].

Statistical analysis

Statistical analyses were performed using the IBM SPSS statistical software version 28.0 (IBM Inc., Armonk, NY, USA) and SAS version 9.4 (SAS Institute, Cary, NC, USA). Continuous variables were described as the mean ± standard deviation for normally distributed data or as the median with IQR for non-normally distributed data. Categorical variables are presented as the number and percentage of participants. Differences in the baseline and operative characteristics of patients in the CM and non-CM groups were compared using the t-test or Mann-Whitney U test for continuous variables and the chi-square test or Fisher’s exact test for categorical variables, as appropriate. To correct for the effect of selection bias or potential confounding factors in a retrospective observational study, inverse probability of treatment weighting (IPTW) was performed between the two groups for demographic factors, underlying diseases, and cardiac factors. These factors are listed in Table 1. The differences between the two groups were summarized as standardized mean difference (SMD), and the two groups were evaluated as being appropriately balanced if SMD was within ±0.1. The survival rate during the follow-up period was estimated using the Kaplan-Meier method. The cumulative incidences of cardiac death, thromboembolic events, bleeding events, occurrence of atrial fibrillation, and discontinuation of anticoagulation therapy were estimated with death as a competing risk using Gray’s test. Risk factors associated with occurrence of atrial fibrillation were analyzed using the Fine-Gray’s proportional subdistribution hazards model. For multivariable analysis, preoperative variables and operative factors with a P value less than 0.10 in univariable analyses were included.

Ethical statement

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Institutional Review Board of Seoul National University Hospital (No. 2206-057-1331) and individual consent for this retrospective analysis was waived.

Results

Basic and operative characteristics

Mean age at operation was 70.1±10.1 and 70.8±8.5 years in the CM and non-CM group, respectively. Before IPTW adjustment, persistent atrial fibrillation was more common in the CM group (n=45, 95.7% in the CM group vs. n=40, 74.1% in the non-CM group, SMD =−0.64), and aortic stenosis was more common in the non-CM group (n=33, 70.2% in the CM group vs. n=43, 79.6% in the non-CM group, SMD =0.22). After IPTW adjustment, the differences between the two groups were corrected, except for the type of atrial fibrillation and EuroSCORE II. Even after the IPTW adjustment, persistent atrial fibrillation was more common in the CM group (94.0% in the CM group vs. 85.0% in the non-CM group, SMD =−0.26) (Table 1).

The choice of valve prosthesis (tissue or mechanical) showed no statistically significant difference between the two groups (mechanical, n=13, 27.7% in the CM group vs. n=17, 31.5% in the non-CM group, SMD =0.08). The most frequently performed concomitant surgery in the study cohort was aortic surgery (n=15, 31.9% in the CM group vs. n=19, 35.2% in the non-CM group), followed by mitral valve repair (n=8, 17.0% in the CM group vs. n=10, 18.5% in the non-CM group) (Table 1). The CM group showed significantly longer mean cardiopulmonary bypass (CPB) time (210.7±52.3 minutes in the CM group vs. 154.2±49.1 minutes in the non-CM group, P<0.001) and aortic cross-clamp (ACC) time (145.4±33.6 minutes in the CM group vs. 94.9±34.1 minutes in the non-CM group, P<0.001).

Early outcomes

There was one case of early mortality in each group (n=1, 2.1% in the CM group vs. n=1, 1.9% in the non-CM group, P=0.92), which also had no statistical significance after IPTW adjustment (2.1% in the CM group vs. 4.3% in the non-CM group, P=0.44). There were no differences between the two groups in terms of postoperative complications such as low cardiac output syndrome, stroke, and permanent pacemaker insertion, except for AKI. Postoperative AKI was more common in the CM group before and after the IPTW adjustment (n=11, 23.4% in the CM group vs. n=2, 3.7% in the non-CM group, P=0.009, before IPTW; 19.4% vs. 3.1%, P<0.001, after IPTW). The CM group showed a longer stay in the intensive care unit (ICU) (88.5±52.8 hours in the CM group vs. 64.3±42.8 hours in the non-CM group, P=0.01, before IPTW; 91.6±52.0 vs. 64.7±45.8 hours, P=0.009, after IPTW), but there was no significant difference in the total hospital stay between the two groups (24.7±53.1 days in the CM group vs. 21.8±5.5 days in the non-CM group, P=0.79, before IPTW; 23.6±50.2 vs. 18.8±43.7 days, P=0.61, after IPTW). The CM group had a significantly higher rate of sinus rhythm restoration at discharge compared to the non-CM group (n=35, 76.1% in the CM group vs. n=15, 28.3% in the non-CM group, P<0.001, before IPTW; 75.0% vs. 20.9%, P<0.001, after IPTW) (Table 2).

Long-term outcomes

The 1-, 3-, and 5-year overall survival rates before IPTW adjustment were 91%, 80%, and 74% in the CM group and 93%, 89%, and 77% in the non-CM group, and there were no significant differences in overall survival between the two groups before and after IPTW adjustment (P=0.56 and P=0.77, respectively; Figure 1). There were no significant differences between the two groups in the cumulative incidence of cardiac death, thromboembolic events, bleeding events, and the composite of thromboembolism and bleeding (Figures S1-S3).

Figure 1 Overall survival curves of patients undergoing aortic valve replacement with or without the concomitant Cox-Maze procedure with 1-, 3-, and 5-year overall survival rate. (A) Before IPTW, (B) after IPTW. CM, Cox-Maze procedure; IPTW, inverse probability of treatment weighting.

Occurrence of atrial fibrillation and anticoagulation

The analysis for occurrence of atrial fibrillation was performed without IPTW adjustment due to missing electrocardiogram data during the outpatient clinic follow-up. The cumulative incidence of atrial fibrillation occurrence was significantly lower in the CM group (1-, 3-, and 5-year incidence of 19%/34%/37% in the CM group vs. 63%/73%/78% in the non-CM group, respectively; P<0.001) (Figure 2). The cumulative incidence of anticoagulation discontinuation was significantly higher in the CM group both before and after IPTW adjustment (1-, 3-, and 5-year incidences 43%/45%/45% in the CM group vs. 17%/23%/23% in the non-CM group, P=0.01, before IPTW; 48%/49%/49% vs. 15%/19%/19%, P=0.001, after IPTW) (Figure 3). In the subgroup analysis of patients with tissue valves, the cumulative incidence of anticoagulation discontinuation was significantly higher in the CM group (1-, 3-, and 5-year incidences 60%/63%/63% in the CM group vs. 25%/34%/34% in the non-CM group, P=0.007) (Figure 4). Multivariable risk factor analysis identified the concomitant Cox-Maze procedure as a significant prognostic factor [subdistribution hazard ratio (sHR) 0.33, 95% confidence interval (CI): 0.20–0.53, P<0.001] for occurrence of atrial fibrillation (Table S1).

Figure 2 Cumulative incidence curves for occurrence of atrial fibrillation in patients undergoing aortic valve replacement with or without the concomitant Cox-Maze procedure with 1-, 3-, and 5-year cumulative incidence. CM, Cox-Maze procedure.

Figure 3 Cumulative incidence curves for anticoagulation discontinuation in patients undergoing aortic valve replacement with or without the concomitant Cox-Maze procedure with 1-, 3-, and 5-year cumulative incidence. (A) Before IPTW, (B) after IPTW. CM, Cox-Maze procedure; IPTW, inverse probability of treatment weighting.

Figure 4 Cumulative incidence curves for anticoagulation discontinuation in patients undergoing aortic valve replacement with tissue valves, with or without the concomitant Cox-Maze procedure with 1-, 3-, and 5-year cumulative incidence. CM, Cox-Maze procedure.

During the follow-up period, three patients (1 in the CM group and 2 in the non-CM group) underwent cardioversion, and one patient (CM group) received RFCA. In the non-CM group, 2 patients underwent cardioversion for rhythm control at 2 and 6 years after AVR, respectively. In the CM group, one patient, who was in sinus rhythm at discharge after AVR and the Cox-Maze procedure, experienced atrial fibrillation recurrence at 6 months after operation. This patient underwent cardioversion twice, at 1 and 3 years after operation, and RFCA at 4 years after operation.

Discussion

This study has two main findings. First, the concomitant Cox-Maze procedure in patients with atrial fibrillation undergoing AVR did not increase early mortality and morbidity, except for AKI. Second, the concomitant Cox-Maze procedure in patients with atrial fibrillation undergoing AVR showed favorable long-term results in terms of rhythm outcomes and discontinuation of anticoagulants.

Although the concomitant Cox-Maze procedure showed favorable long-term outcomes, concerns remain regarding the early results. It is known that when the Cox-Maze procedure is performed with mitral valve surgeries, CPB and ACC time increases by 30–60 and 20–30 minutes, respectively (14,15), and increases the risk of postoperative AKI (14,16). The concomitant Cox-Maze procedure with AVR requires more time because left atrial incision is needed additionally for surgical ablation. Owing to concerns about technical complexity and procedure-related risks, operators performing AVR have been hesitant to perform the concomitant Cox-Maze procedure. Indeed, according to studies using the STS database and national claims data of South Korea, while 56% of patients with preoperative atrial fibrillation undergoing mitral valve replacement underwent arrhythmia surgery, only 25–31% of patients undergoing AVR had concurrent arrhythmia surgery (7,12).

Several studies have reported that the concomitant Cox-Maze procedure does not increase perioperative mortality and morbidity, and based on these studies, current guidelines recommend performing the Cox-Maze procedure along with other cardiac surgeries when atrial fibrillation is diagnosed (6-9,15). Similarly, the results of this study showed no significant differences in mortality and morbidity, except for postoperative AKI, when comparing AVR with the concomitant Cox-Maze procedure to isolated AVR. Several studies have reported that the risk of AKI increases when the Cox-Maze procedure is performed concurrently, with postoperative AKI occurring in approximately 30% of operations and acute renal failure (ARF) in approximately 6% (14,16). The causes of AKI after the Cox-Maze procedure are attributed to the extended CPB time, changes in the neurohormonal system, and increase in inflammatory substances after the Cox-Maze procedure, although the exact mechanisms are not yet fully understood (14,16-19). In this study, postoperative AKI was found in 23.4% of the patients who underwent AVR with the Cox-Maze procedure, which was similar to the statistics reported in the literature.

The AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management) study demonstrated that maintaining sinus rhythm in patients with atrial fibrillation has significant benefits for long-term survival (20). In this study, we hypothesized that performing the Cox-Maze procedure along with AVR could offer long-term benefits in terms of overall survival, anticoagulation-related bleeding, and ischemic complications compared to the isolated AVR group; however, no significant differences were found. This is thought to be due to the relatively small sample size and number of events. However, although the proportion of patients with persistent atrial fibrillation was significantly higher in the CM group, even after IPTW adjustment, the proportions of patients maintaining sinus rhythm and those who discontinued anticoagulation therapy were significantly higher in the CM group. These results suggest that the concomitant Cox-Maze procedure in AVR can offer advantages in terms of long-term survival and improve the quality of life by decreasing the complications related to anticoagulation. The incidence of atrial fibrillation recurrence after the Cox-Maze procedure was somewhat high in this study. However, the majority of patients in the CM group (95.7%) had persistent atrial fibrillation. Given that the sinus rhythm restoration rate after the Cox-Maze procedure in patients with persistent or long-standing persistent atrial fibrillation has been reported to be around 70–90% at 5 years (21-23), our findings are consistent with those of previous studies.

The findings of this study are consistent with previous reports on AVR with the concomitant Cox-Maze procedures. Ad et al. [2012] demonstrated that the Cox-Maze procedure, when performed alongside AVR or CABG, did not significantly increase perioperative morbidity (8). Similarly, Yoo et al. [2014] showed that concomitant surgical ablation in patients undergoing AVR increased sinus rhythm restoration and reduced the need for anticoagulation, without increasing morbidity or mortality (11). Additionally, Kim et al. [2024] reported comparable early and long-term outcomes, with the ablation group showing a lower incidence of late ischemic stroke (12).

The present study has strengths in that it analyzed patients over a period of >20 years and had a long-term follow-up duration. In addition, this study analyzed not only major hard endpoints, including survival, cardiac death, and thromboembolic complications, but also patients’ long-term rhythm outcomes and anticoagulant administration. This study had some limitations. First, this was a retrospective observational study performed at a single institution. Second, the number of patients enrolled in this study was relatively small, which could have weakened the statistical power of the comparative analysis between the two groups. Third, during the follow-up period of over 20 years, there were changes in the energy devices used in surgical ablation and the introduction of NOAC as anticoagulants, which may serve as confounding factors. Lastly, although the IPTW analysis was performed to correct bias in this retrospective observational study, the type of atrial fibrillation (paroxysmal or persistent) was not balanced, which could potentially affect the outcome of the Cox-Maze procedure.

Conclusions

The concomitant Cox-Maze procedure in patients with atrial fibrillation undergoing AVR does not increase early mortality and morbidity, except for AKI. Moreover, the concomitant Cox-Maze procedure showed favorable long-term results in terms of rhythm outcomes and discontinuation of anticoagulation in patients with atrial fibrillation indicated for AVR.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1223/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1223/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1223/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1223/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by Institutional Review Board of Seoul National University Hospital (No. 2206-057-1331) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Andrade J, Khairy P, Dobrev D, et al. The clinical profile and pathophysiology of atrial fibrillation: relationships among clinical features, epidemiology, and mechanisms. Circ Res 2014;114:1453-68. [Crossref] [PubMed]
2. Ngaage DL, Schaff HV, Barnes SA, et al. Prognostic implications of preoperative atrial fibrillation in patients undergoing aortic valve replacement: is there an argument for concomitant arrhythmia surgery? Ann Thorac Surg 2006;82:1392-9. [Crossref] [PubMed]
3. Quader MA, McCarthy PM, Gillinov AM, et al. Does preoperative atrial fibrillation reduce survival after coronary artery bypass grafting? Ann Thorac Surg 2004;77:1514-22; discussion 1522-4. [Crossref] [PubMed]
4. Banach M, Mariscalco G, Ugurlucan M, et al. The significance of preoperative atrial fibrillation in patients undergoing cardiac surgery: preoperative atrial fibrillation--still underestimated opponent. Europace 2008;10:1266-70. [Crossref] [PubMed]
5. Schulenberg R, Antonitsis P, Stroebel A, et al. Chronic atrial fibrillation is associated with reduced survival after aortic and double valve replacement. Ann Thorac Surg 2010;89:738-44. [Crossref] [PubMed]
6. Calkins H, Hindricks G, Cappato R, et al. 2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation. Heart Rhythm 2017;14:e275-444. [Crossref] [PubMed]
7. Wyler von Ballmoos MC, Hui DS, Mehaffey JH, et al. The Society of Thoracic Surgeons 2023 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation. Ann Thorac Surg 2024;118:291-310. [Crossref] [PubMed]
8. Ad N, Henry L, Hunt S, et al. Do we increase the operative risk by adding the Cox Maze III procedure to aortic valve replacement and coronary artery bypass surgery? J Thorac Cardiovasc Surg 2012;143:936-44. [Crossref] [PubMed]
9. Saxena A, Dinh DT, Reid CM, et al. Does preoperative atrial fibrillation portend a poorer prognosis in patients undergoing isolated aortic valve replacement? A multicentre Australian study. Can J Cardiol 2013;29:697-703. [Crossref] [PubMed]
10. Bando K, Kasegawa H, Okada Y, et al. Impact of preoperative and postoperative atrial fibrillation on outcome after mitral valvuloplasty for nonischemic mitral regurgitation. J Thorac Cardiovasc Surg 2005;129:1032-40. [Crossref] [PubMed]
11. Yoo JS, Kim JB, Ro SK, et al. Impact of concomitant surgical atrial fibrillation ablation in patients undergoing aortic valve replacement. Circ J 2014;78:1364-71. [Crossref] [PubMed]
12. Kim JS, Kim J, Kang Y, et al. Clinical benefits of surgical ablation during isolated aortic valve replacement: a nationwide study. Eur J Cardiothorac Surg 2024;65:ezae085. [Crossref] [PubMed]
13. Cox JL. The standard Maze-III procedure. Oper Tech Thorac Cardiovasc Surg 2004;9:3-23. [Crossref]
14. Bakir NH, Khiabani AJ, MacGregor RM, et al. Concomitant surgical ablation for atrial fibrillation is associated with increased risk of acute kidney injury but improved late survival. J Thorac Cardiovasc Surg 2022;164:1847-1857.e3. [Crossref] [PubMed]
15. Prasad SM, Maniar HS, Camillo CJ, et al. The Cox maze III procedure for atrial fibrillation: long-term efficacy in patients undergoing lone versus concomitant procedures. J Thorac Cardiovasc Surg 2003;126:1822-8. [Crossref] [PubMed]
16. Hong HJ, Lee Y, Kim SH, et al. Incidence and risk factors of acute kidney injury after maze operation in patients with rheumatic mitral valve disease. J Thorac Dis 2022;14:3408-14. [Crossref] [PubMed]
17. Karkouti K, Wijeysundera DN, Yau TM, et al. Acute kidney injury after cardiac surgery: focus on modifiable risk factors. Circulation 2009;119:495-502. [Crossref] [PubMed]
18. Yoshihara F, Nishikimi T, Kosakai Y, et al. Atrial natriuretic peptide secretion and body fluid balance after bilateral atrial appendectomy by the maze procedure. J Thorac Cardiovasc Surg 1998;116:213-9. [Crossref] [PubMed]
19. Richter B, Gwechenberger M, Socas A, et al. Markers of oxidative stress after ablation of atrial fibrillation are associated with inflammation, delivered radiofrequency energy and early recurrence of atrial fibrillation. Clin Res Cardiol 2012;101:217-25. [Crossref] [PubMed]
20. Corley SD, Epstein AE, DiMarco JP, et al. Relationships between sinus rhythm, treatment, and survival in the Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) Study. Circulation 2004;109:1509-13. [Crossref] [PubMed]
21. Lapenna E, De Bonis M, Giambuzzi I, et al. Long-term Outcomes of Stand-Alone Maze IV for Persistent or Long-standing Persistent Atrial Fibrillation. Ann Thorac Surg 2020;109:124-31. [Crossref] [PubMed]
22. Ad N, Holmes SD, Friehling T. Minimally Invasive Stand-Alone Cox Maze Procedure for Persistent and Long-Standing Persistent Atrial Fibrillation: Perioperative Safety and 5-Year Outcomes. Circ Arrhythm Electrophysiol 2017;10:e005352. [Crossref] [PubMed]
23. McGilvray MMO, Bakir NH, Kelly MO, et al. Efficacy of the stand-alone Cox-Maze IV procedure in patients with longstanding persistent atrial fibrillation. J Cardiovasc Electrophysiol 2021;32:2884-94. [Crossref] [PubMed]