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Incremental risk of the Cox-maze IV procedure for patients with atrial fibrillation undergoing mitral valve surgery

Published:September 03, 2013DOI:https://doi.org/10.1016/j.jtcvs.2013.06.048

      Objective

      More than 50% of atrial fibrillation surgery occurs in the setting of mitral valve surgery. Despite this, no risk models have been validated for concomitant arrhythmia surgery. The purpose of the present study was to quantify the additional risk of performing the Cox-maze IV procedure for patients undergoing mitral valve surgery.

      Methods

      From January 2002 to June 2011, 213 patients with mitral valve disease and preoperative atrial fibrillation underwent mitral valve surgery only (n = 109) or in conjunction with a Cox-maze IV procedure (n = 104). The operative mortality for the mitral valve procedure alone was predicted for each group using the Society of Thoracic Surgeons perioperative risk calculator. The risk attributed to the added Cox-maze IV procedure was calculated by comparing the predicted mortality rate of an isolated mitral valve procedure and the actual mortality rate of mitral valve surgery with a concomitant Cox-maze IV procedure.

      Results

      For patients not undergoing a Cox-maze IV procedure, the predicted and actual postoperative mortality rate was 5.5% and 4.6% (5 of 109), respectively. For patients receiving mitral valve surgery and a concomitant Cox-maze IV, the predicted and actual postoperative mortality of the mitral valve procedure was 2.5% and 2.9% (3 of 104), respectively, and not significantly different. Patients not offered a Cox-maze IV procedure had significantly more serious comorbidities.

      Conclusions

      For patients with atrial fibrillation and mitral valve disease undergoing mitral valve surgery, the decision to offer a concomitant Cox-maze IV procedure will be influenced by the underlying comorbid conditions. Nonetheless, in selected lower risk patients, the addition of a Cox-maze IV procedure did not significantly affect the procedural mortality.

      CTSNet classification

      Abbreviations and Acronyms:

      AF (atrial fibrillation), CMIV (Cox-maze IV), MV (mitral valve), STS (Society of Thoracic Surgeons)
      The Cox-maze procedure was originally designed as a concomitant procedure by Dr James Cox for the treatment of atrial fibrillation (AF) in patients undergoing mitral valve (MV) surgery. However, both the complexity of the operation and the time required to complete the procedure limited its clinical application to patients with lone AF for many years. After several iterations, the Cox-maze IV (CMIV) procedure was introduced in 2002. The CMIV simplified the procedure by replacing most of the atrial incisions of the Cox-maze lesion set with linear lines of ablation, making the operation technically easier and faster to perform.
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      • et al.
      A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation.
      With the introduction of ablation devices, the number of surgeries performed in the United States for the correction of AF more than doubled.
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      • Haddad M.
      • Milford-Beland S.
      • Welke K.F.
      • Ferguson Jr, T.B.
      • O’Brien S.M.
      • et al.
      Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database.
      Currently, more than 80% of these procedures are completed with the assistance of ablation technology, and more than 95% are performed as concomitant operations to other cardiac surgical procedures.
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      • Haddad M.
      • Milford-Beland S.
      • Welke K.F.
      • Ferguson Jr, T.B.
      • O’Brien S.M.
      • et al.
      Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database.
      For patients undergoing cardiac surgery, the prevalence of AF is greatest among patients with MV disease. Concordantly, more than one half of all AF corrective surgeries performed each year occur in patients undergoing MV operations.
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      • Milford-Beland S.
      • Welke K.F.
      • Ferguson Jr, T.B.
      • O’Brien S.M.
      • et al.
      Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database.
      Despite the proven efficacy of AF corrective surgery for patients with AF undergoing MV surgery, a subgroup of patients with AF and concomitant MV disease exists that is less likely to be offered surgical AF correction.
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      • Albage A.
      • David T.E.
      • Yau T.M.
      • Armstrong S.
      The efficacy of the Cox maze procedure combined with mitral valve surgery: a matched control study.
      • Saint L.L.
      • Bailey M.S.
      • Prasad S.
      • Guthrie T.J.
      • Bell J.
      • Moon M.R.
      • et al.
      Cox-Maze IV results for patients with lone atrial fibrillation versus concomitant mitral disease.
      • von Oppell U.O.
      • Masani N.
      • O'Callaghan P.
      • Wheeler R.
      • Dimitrakakis G.
      • Schiffelers S.
      Mitral valve surgery plus concomitant atrial fibrillation ablation is superior to mitral valve surgery alone with an intensive rhythm control strategy.
      Many possible reasons exist for this omission, but 1 possibility is that the operating surgeon believes that an additional operative risk is conferred by the AF correction procedure itself. Currently, no risk models are available for concomitant arrhythmia surgery; thus, the extent of the additional associated risk has been poorly defined.
      Given these data, the importance of characterizing the additional risk of concomitant AF surgery in this group of patients is critical. The purpose of the present study was to quantify the additional risk of performing the CMIV procedure in selected patients undergoing MV surgery.

      Methods

       Participants and Procedure

      The CMIV procedure has been previously described and the technique was similar for all patients during the study period, with the exception of a “superior connecting lesion” that was added in 2005.
      • Voeller R.K.
      • Bailey M.S.
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      • et al.
      Isolating the entire posterior left atrium improves surgical outcomes after the Cox maze procedure.
      This additional lesion connected the right and left superior pulmonary veins, isolating the entire posterior left atrium as part of the “box-lesion set.”
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      • Aubuchon K.
      • et al.
      Isolating the entire posterior left atrium improves surgical outcomes after the Cox maze procedure.
      Of the patients who underwent MV surgery with a concomitant CMIV, 89% (n = 92) had a “box lesion set.” Pulmonary vein isolation was confirmed when possible in all patients undergoing a CMIV procedure by demonstration of an exit block from each of the pulmonary veins. Confirmation of an exit block from the pulmonary veins was not performed in those patients with a left atrial appendage thrombus precluding cardioversion or in patients who were unable to be successfully cardioverted at surgery.
      To determine the additional risk conferred by the CMIV procedure for patients undergoing MV surgery, the operative mortality for the MV procedure alone was predicted for each group using the Society of Thoracic Surgeons (STS) perioperative risk calculator. The risk attributed to the added CMIV procedure was calculated by comparing the predicted mortality rate of an isolated MV procedure and the actual mortality rate of MV surgery with a concomitant CMIV procedure. Late death was defined as all-cause mortality occurring at a median follow-up of 2.3 and 3.3 years (interquartile range, 1.2-5.2 and 1.8-6.2) for the patients undergoing isolated MV surgery and MV surgery with concomitant CMIV, respectively, as determined by individual patient follow-up according to the Social Security Death Index.
      The Washington University School of Medicine institutional review board approved the present study. Each participant provided informed -consent and permission for release of information.

       Statistical Analysis

      Continuous variables are expressed as the mean ± standard deviation or as the median and interquartile range (25%-75%) if the data were not normally distributed. Categorical variables are expressed as frequencies and percentages. Categorical outcomes were compared using either the chi-square or Fisher exact test. Continuous outcomes were compared using the t test for mean values of normally distributed continuous variables and the Wilcoxon rank sum nonparametric test for skewed distributions.
      Significant covariates identified by univariate analysis (P ≤ .10) or covariates deemed clinically relevant were entered into a multivariate binary logistic regression analysis. Twelve preoperative and perioperative variables were evaluated using multivariate analysis to identify the predictors of 30-day mortality and late death. These included age, preoperative renal failure, diabetes mellitus, chronic obstructive pulmonary disease, previous myocardial infarction, hypertension, hyperlipidemia, cerebrovascular disease, previous cerebrovascular accident, previous coronary artery bypass grafting, previous valve surgery, and concomitant CMIV procedure. All data analyses were done using the Statistical Package for Social Sciences, version 20.0, for Windows (SPSS Inc, Chicago, Ill).

      Results

      From January 2002 through June 2011, 213 patients with preoperative AF and concomitant MV disease underwent MV surgery only (n = 109) or combined with a CMIV procedure (n = 104).
      Although the patients in the 2 groups were similar with regard to age, gender, New York Heart Association classification, and preoperative ejection fraction, the groups differed with respect to several comorbidities (Table 1). Patients in whom a concomitant CMIV was not performed were more likely to have renal failure (P < .01), diabetes mellitus (P = .02), chronic obstructive pulmonary disease (P < .01), hyperlipidemia (P = .01), previous myocardial infarction (P < .01), previous cerebrovascular accident (P < .01), and previous coronary artery bypass grafting or valve surgery (P < .01). The increased comorbidities in this group were reflected in a predicted STS 30-day mortality score of 5.5%, which was significantly greater than the predicted mortality score of 2.5% for the patients who underwent MV surgery and concomitant CMIV (P < .01).
      Table 1Demographics
      VariableLone MV (n = 109)MV plus CMIV (n = 104)P value
      Age (y)65.6 ± 13.263.5 ± 11.8.21
      Women53 (49)57 (55).41
      NYHA class III or IV84 (77.1)74 (71).35
      Ejection fraction (%)50 ± 1451 ± 11.17
      Renal failure12 (11)1 (1%)<.01
      Diabetes29 (27)14 (14).02
      COPD41 (38)20 (19)<.01
      Hyperlipidemia63 (58)42 (40).01
      Previous MI30 (28)4 (4)<.01
      Previous CVA20 (18)5 (5)<.01
      Previous CABG22 (20)3 (3)<.01
      Previous valve operation44 (40)12 (12)<.01
      Predicted STS operative mortality (%)5.5 ± 5.22.5 ± 1.9<.01
      Data presented as mean ± standard deviation or n (%). MV, Mitral valve; CMIV, Cox-maze IV; NYHA, New York Heart Association; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; CVA, cerebrovascular accident; CABG, coronary artery bypass grafting; STS, Society of Thoracic Surgeons.
      The types of MV pathologic features also differed significantly between the 2 groups (Table 2). The distribution of the etiology of MV disease was skewed for patients undergoing MV surgery with concomitant CMIV, favoring etiologies such as rheumatic heart disease, mitral stenosis, annular dilatation, and degenerative disease. In contrast, the distribution of the etiology of MV disease for patients in the isolated MV surgery group was skewed to reflect a history of endocarditis and ischemic disease (P < .01). Despite the difference in etiology of MV disease, the 2 groups were similar with regard to the coexistence of pulmonary hypertension and their MV dysfunction (69% vs 63%, P = .39).
      Table 2Valve pathologic features
      VariableLone MV (n = 109)MV plus CMIV (n = 104)P value
      MV disease etiology<.01
       Calcific2 (2)5 (5)
       Endocarditis15 (14)1 (1)
       Myxomatous32 (30)42 (41)
       Rheumatic20 (18)34 (33)
       Prosthetic valve failure18 (17)5 (5)
       Annular dilatation7 (6)17 (16)
       Ischemic15 (14)0
      Mitral stenosis24 (22)37 (36).03
      Pulmonary hypertension75 (69)65 (63).39
      Data presented as n (%). MV, Mitral valve; CMIV, Cox-maze IV.
      Of the patients who underwent MV surgery with concomitant CMIV, 41% had paroxysmal AF, 16% had persistent AF, and 43% had long-standing persistent AF. Eleven percent of patients in this group had a previous failed catheter ablation. The mean duration of AF in this group was 60.2 ± 89.4 months. However, the AF history of patients not offered CMIV was not well characterized with respect to the AF type and duration.
      The MV procedures performed were similar between the groups (P = .17), as was the use of bioprosthetic valves in the case of MV replacement surgery (P = .55, Table 3). The aortic crossclamp and cardiopulmonary bypass times were significantly longer in patients undergoing MV surgery with a concomitant CMIV procedure (93 ± 23 and 187 ± 40 minutes) than in patients who underwent isolated MV surgery (80 ± 35 and 126 ± 60 minutes, respectively, P < .01). Importantly, the amount of additional crossclamp time required to perform the CMIV was minimal, averaging only 13 minutes between the 2 groups. Isolated MV patients were more likely to require an intraoperative or postoperative balloon pump (P = .02), and other perioperative features, such as surgical status and the presence of thrombus in the left atrial appendage were no different between the 2 groups.
      Table 3Perioperative details
      VariableLone MV (n = 109)MV plus CMIV (n = 104)P value
      Urgent or emergent procedure3 (3)1 (1).62
      Required IABP intra- or postoperatively15 (14)4 (4).02
      MV replacement60 (55)47 (45).17
       Bioprosthetic replacement valve40 (67)28 (60).55
      Aortic crossclamp time (min)80 ± 3593 ± 23<.01
      CPB time (min)126 ± 60187 ± 40<.01
      LAA thrombus0 (0)4 (4).06
      Lesion setNA
       Box82 (89)
       Nonbox12 (12)
      Data presented as n (%) or mean ± standard deviation. IABP, Intra-aortic balloon pump; CPB, cardiopulmonary bypass; LAA, left atrial appendage; MV, mitral valve; CMIV, Cox-maze IV; NA, not applicable.
      Postoperatively, the MV surgery and concomitant CMIV group required fewer blood products (P < .01). However, no differences were found in the postoperative outcomes with regard to the rates of stroke, reoperation for bleeding, postoperative renal failure, and length of stay in the intensive care unit (Table 4). The patients who underwent MV surgery with a concomitant CMIV procedure experienced a greater incidence of early atrial tachyarrhythmia (P < .01) than did patients who underwent isolated MV surgery.
      Table 4Postoperative morbidity
      VariableLone MV (n = 109)MV plus CMIV (n = 104)P value
      Operative mortality5 (5)3 (3).72
      Stroke2 (2)1 (1).99
      Pneumonia19 (17)10 (10).11
      Ventilation time (h)20 (IQR, 11-49)17 (IQR, 6-42).09
      Required reintubation9 (8)6 (6).60
      Reoperation for bleeding9 (8)4 (4).25
      Postoperative infusion of blood products85 (78)58 (56)<.01
      Deep sternal wound infection1 (1)0 (0).99
      Renal failure8 (7)8 (8).99
      Heart block2 (2)6 (6).16
      Early atrial tachyarrhythmias10 (9)62 (60)<.01
      Postoperative pacemaker placement5/80 (6)11/96 (11).30
      Length of stay in ICU (h)79 (IQR, 45-143)73 (IQR, 44-129).40
      Data presented as n (%) or median (IQR). ICU, Intensive care unit; IQR, interquartile range; MV, mitral valve; CMIV, Cox-maze IV.
      The observed 30-day mortality for patients not offered a CMIV procedure at their MV surgery was 4.6% (expected 5.5%), yielding an observed/expected 30-day mortality ratio of 0.84 (95% confidence interval, 0.13-1.54) in this group. The observed 30-day mortality for patients undergoing MV surgery with a concomitant CMIV procedure was 2.9%. The STS predicted score for isolated MV surgery in this group was 2.5%. The resultant observed/expected 30-day mortality ratio was 1.16 (95% confidence interval, 0.13-2.44), and the difference was not statistically significant.
      On multivariate analysis, the only significant predictor of 30-day mortality for either group was age. However, at a median follow-up of 2.3 and 3.3 years (interquartile range, 1.2-5.2 and 1.8-6.2 years for patients undergoing isolated MV surgery and MV surgery with a concomitant CMIV, respectively), age, chronic obstructive pulmonary disease, cerebrovascular disease, previous myocardial infarction, and renal failure were significant predictors of late death. The addition of a concomitant CMIV procedure was identified as protective from late death, and this trend nearly reached statistical significance (P = .06).
      In patients with AF who underwent a concomitant CMIV procedure at MV surgery, freedom from AF and atrial tachyarrhythmia was 85%, 91%, and 84% at 3, 6, and 12 months, respectively. Freedom from AF and atrial tachyarrhythmia without antiarrhythmic medications in this population was 54%, 77%, and 77% at 3, 6, and 12 months, respectively.

      Discussion

      A substantial increase in arrhythmia surgery has occurred in recent years owing to both the increase in AF frequency in our aging population and the introduction of ablative technologies that have made AF correction procedures easier to perform. Because AF correction procedures are most commonly performed as concomitant operations with other cardiac procedures, the ability to determine the incremental risk incurred by a concomitant AF correction procedure is an important component of surgical decision-making and counseling of the surgical patient.
      In our series, patients who were not offered a concomitant CMIV with their MV surgery were generally more ill, with more comorbidities than those in whom a CMIV was performed. A paucity of data was available characterizing the AF type these patients experienced preoperatively, a recognized weakness of the present study. Not surprisingly, both the observed and expected risks of 30-day mortality were greater for these higher risk patients than the observed and expected mortality rates for the lower risk patients who had undergone a concomitant CMIV procedure.
      The STS perioperative risk calculator, the use of which is becoming more commonplace in clinical trials and other arenas, was accurate in predicting the risk for this population of patients.
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      Transcatheter aortic-valve replacement for inoperable severe aortic stenosis.
      This risk calculator has previously been validated in patients undergoing isolated mitral valve procedures and in patients undergoing other cardiac surgical procedures, most notably aortic valve surgery.
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      The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 2—isolated valve surgery.
      Despite the multiple comorbidities present in these patients, the only predictor in the higher risk isolated MV surgery group for 30-day mortality on multivariate analysis was age, consistent with reported series of MV procedures.
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      Outcomes for mitral valve surgery among Medicare fee-for-service beneficiaries, 1999 to 2008.
      The principle finding of our investigation was that, for properly selected patients at an experienced center, the addition of a CMIV procedure to MV surgery did not add any incremental risk to the patients. In the present study, the observed 30-day mortality for patients undergoing a concomitant CMIV procedure was not different from that predicted for isolated MV surgery for these patients. Although the CMIV procedure did require an increase in cardiopulmonary bypass time and a small increase in ischemic time, no additional quantifiable risk with respect to death, stroke, or major postoperative morbidity could be identified. The only increased postoperative morbidity associated with this group was the presence of early atrial tachyarrhythmia, which is common in patients undergoing a CMIV procedure and has been shown to have no demonstrable effect on the late recurrence of AF.
      • Ishii Y.
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      • Boineau J.P.
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      • et al.
      Atrial tachyarrhythmias after the maze procedure: incidence and prognosis.
      The findings of the present investigation were consistent with other published reports regarding the additional risk of concomitant arrhythmia surgery performed at MV surgery.
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      • Milford-Beland S.
      • Welke K.F.
      • Ferguson Jr, T.B.
      • O’Brien S.M.
      • et al.
      Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database.
      • Raanani E.
      • Albage A.
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      • Yau T.M.
      • Armstrong S.
      The efficacy of the Cox maze procedure combined with mitral valve surgery: a matched control study.
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      • Chin D.T.
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      Left atrial radiofrequency ablation during mitral valve surgery for continuous atrial fibrillation: a randomized controlled trial.
      However, unlike previous reports, the present study was the first to examine the effect of a single arrhythmia procedure, the CMIV procedure, on the perioperative morbidity and mortality when performed with MV surgery. Other reports have been hampered because “arrhythmia surgery” is often an amalgamation of a wide variety of procedures ranging from pulmonary vein isolation to a traditional cut and sew Cox-maze III, each with a very distinct risk and benefit profile. Additionally, our series is unique in that the cohorts were homogeneous with respect to valvular heart disease and described only patients undergoing isolated mitral valve surgery. The only surgical variable in the present study was the presence or absence of a concomitant CMIV procedure.
      A recognized weakness of the present study was that the group of patients with AF who received concomitant CMIV was a selected lower risk population. The lesser extent to which the these patients experienced preoperative comorbid conditions was reflected in the treatment assignment bias evident in the present study, such that the operating surgeon made a decision that these patients should be able to tolerate the additional surgical time and manipulation incurred by a concomitant CMIV procedure. The judgment and skill of an experienced MV and arrhythmia surgeon cannot be underestimated and is perhaps the most responsible for the low morbidity and mortality demonstrated in the present series.
      It is likely that the incorporation of ablation technology is also largely responsible for the lack of increased risk demonstrated in the present series of concomitant CMIV patients. Ablation technology simplifies the technical aspects of performing the Cox-maze lesion set and reduces the procedural crossclamp and cardiopulmonary bypass times compared with the traditional Cox-maze III procedure.
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      Fewer incisions are required, minimizing bleeding complications, and newer technologies have allowed for minimal collateral tissue damage, if correctly applied.
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      Finally, MV surgery is particularly well suited to the addition of a CMIV procedure, compared with coronary artery bypass grafting or aortic valve procedures. Performing a concomitant CMIV procedure with of MV surgery is relatively straightforward and does not require changes in surgical strategy, because the atrial incisions and cannulation sites for cardiopulmonary bypass are not necessarily different from those required for an isolated MV procedure.
      The number of patients with AF and concomitant MV disease has continued to increase as the population ages and represents a group of patients that could derive substantial benefit from surgical AF correction. The benefits of AF corrective surgery include fewer bleeding complications from chronic anticoagulation and a decreased risk of thromboembolism and subsequent stroke.
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      Moreover, it has been shown in several studies that patients with AF and concomitant MV disease are unlikely to experience a return to normal sinus rhythm after MV surgery alone.
      • Raanani E.
      • Albage A.
      • David T.E.
      • Yau T.M.
      • Armstrong S.
      The efficacy of the Cox maze procedure combined with mitral valve surgery: a matched control study.
      • von Oppell U.O.
      • Masani N.
      • O'Callaghan P.
      • Wheeler R.
      • Dimitrakakis G.
      • Schiffelers S.
      Mitral valve surgery plus concomitant atrial fibrillation ablation is superior to mitral valve surgery alone with an intensive rhythm control strategy.
      In contrast, the efficacy of the CMIV procedure in these patients has been excellent, with a rate of freedom from AF and atrial tachyarrhythmia of 85%, 91%, and 84% at 3, 6, and 12 months in the present series, respectively. The rate of freedom from AF and atrial tachyarrhythmia without antiarrhythmic medications in this population was 54%, 77%, and 77% at 3, 6, and 12 months, respectively.
      Although not demonstrated in the present series, the CMIV procedure does have its own attendant risks, including the greater rate of permanent pacemaker implantation in patients undergoing concomitant CMIV at MV surgery.
      • Gammie J.S.
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      • Welke K.F.
      • Ferguson Jr, T.B.
      • O’Brien S.M.
      • et al.
      Atrial fibrillation correction surgery: lessons from the Society of Thoracic Surgeons National Cardiac Database.
      However, the benefits of restoration of sinus rhythm, and the consequential diminutive risk of chronic anticoagulation or stroke likely outweigh these risks.
      • Doukas G.
      • Samani N.J.
      • Alexiou C.
      • Oc M.
      • Chin D.T.
      • Stafford P.G.
      • et al.
      Left atrial radiofrequency ablation during mitral valve surgery for continuous atrial fibrillation: a randomized controlled trial.
      • Pet M.
      • Robertson J.O.
      • Bailey M.
      • Guthrie T.J.
      • Moon M.R.
      • Lawton J.S.
      • et al.
      The impact of CHADS2 score on late stroke after the Cox Maze procedure.
      • Fukunaga S.
      • Hori H.
      • Ueda T.
      • Takagi K.
      • Tayama E.
      • Aoyagi S.
      Effect of surgery for atrial fibrillation associated with mitral valve disease.
      • Handa N.
      • Schaff H.V.
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      • Anderson B.J.
      • Kopecky S.L.
      • Enriquez-Sarano M.
      Outcome of valve repair and the Cox maze procedure for mitral regurgitation and associated atrial fibrillation.
      Additionally, although it did not reach significance in the present study, the addition of a CMIV procedure to MV surgery in select patients was associated with a protective effect against late death.
      In conclusion, for select low-risk patients, the addition of a concomitant CMIV procedure does not appear to increase the operative risk greater than that expected for MV surgery alone and produces a high degree of freedom from AF and antiarrhythmic medications in these patients. Although the decision to offer a concomitant CMIV procedure at MV surgery appears to be primarily influenced by underlying comorbid conditions, the remaining question is whether a concomitant CMIV procedure should be offered to a wider population of higher risk patients with AF and MV disease. In the present series, the only predictor of 30-day mortality in the isolated MV group was age, which might represent the highest risk group. These data suggest that an advantage could exist with the addition of a concomitant CMIV procedure in younger patients, despite the presence of other comorbidities.
      The present study had several recognized limitations. As reported, the type and duration of AF in our patients who were not offered a concomitant CMIV procedure with their MV surgery were not well characterized; thus, it is unknown whether the preoperative AF burden was comparable between the 2 groups. Additionally, this was a single-center retrospective review incorporating cases performed by 2 principle surgeons, both with substantial experience in MV and arrhythmia surgery. Furthermore, the focus of our investigation was the 30-day morbidity and mortality. Longer follow-up of a larger group of patients with AF and MV disease is needed to fully characterize the additional risks and benefits of performing the CMIV procedure in this group of patients in conjunction with MV surgery.

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