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. 2013 Sep 30;18(1):73–79. doi: 10.1093/icvts/ivt402

Mitral valve repair versus replacement for moderate-to-severe mitral regurgitation in patients undergoing concomitant aortic valve replacement

Gwan Sic Kim a, Joon Bum Kim a, Seungbong Han b, Suk Jung Choo a, Cheol Hyun Chung a, Jae Won Lee a, Sung-Ho Jung a,*
PMCID: PMC3867030  PMID: 24087829

Abstract

OBJECTIVES

Whether to repair or replace the mitral valve for patients with significant mitral regurgitation undergoing aortic valve replacement is still controversial.

METHODS

From January 1990 to December 2011, a total of 663 patients underwent aortic valve replacement combined with mitral valve surgery. Among these, 253 patients (mean age 55.9 ± 14.5 years, 91 females) with moderate-to-severe mitral regurgitation were enrolled to compare the outcomes between double valve replacement (DVR group, n = 158) and aortic valve replacement plus mitral valve repair (AVR plus MVr group, n = 95). Survival and valve-related events were compared by the inverse-probability-treatment-weighted method using propensity scores to reduce treatment selection bias.

RESULTS

Early mortality was similar between the groups (1.9% in the DVR group when compared with 3.2% in the AVR plus MVr group, P = 0.55). During the mean follow-up period of 72.1 ± 56.7 months, 45 patients died (28 in DVR and 17 in AVR plus MVr) and 31 experienced valve-related events including valve reoperation in 11, anticoagulation-related bleeding in 14, thromboembolism complications in 9 and infective endocarditis in 3. After adjustment for baseline risk profiles, the DVR group showed no difference with regard to risks of death (hazard ratio [HR], 1.79; 95% confidence interval [CI], 0.79–4.01; P = 0.16) and valve-related events (HR, 1.15; 95% CI, 0.40–3.30; P = 0.80) compared with the AVR plus MVr group.

CONCLUSIONS

Although the outcomes of either mitral valve repair or replacement for moderate-to-severe mitral regurgitation in patients undergoing concomitant aortic valve replacement show no statistical significance in terms of long-term survival and valve-related event rates, DVR seems more hazardous than AVR plus MVr based on the estimated HR in terms of survival.

Keywords: Mitral valve, Aortic valve, Repair, Replacement

INTRODUCTION

For patients with aortic and mitral valve disease, although several studies have been conducted to compare the clinical outcomes of double valve replacement (DVR) and aortic valve replacement plus mitral valve repair (AVR plus Mitral valve [MV]r) [17], there still remains controversy as to which strategy is superior [8].

There were several reasons why the comparison between the two strategies in this population was difficult. One of the most important reasons was that most previous studies were retrospective and analysed limited data with considerable heterogeneity in patients’ baseline characteristics. Although a previous study conducted an analysis using a propensity score to minimize the effect of these limitations, further study is needed to elucidate the precise comparison of the two strategies [2, 8].

In this regard, for the appropriate comparison of the strategies, it will be important to balance the significant differences between the baseline characteristics of patients in the DVR group and the AVR plus MVr group. Furthermore, among the mitral valve lesions including mitral stenosis and regurgitation, a comparative study in patients only with moderate-to-severe mitral regurgitation may present a more reliable conclusion, because it minimizes the heterogeneity of the patient population.

Therefore, by the inverse-probability-treatment-weighted method using propensity scores, the present study sought to determine whether DVR or AVR plus MVr in patients undergoing AVR with moderate-to-severe mitral regurgitation is superior in terms of survival and clinical outcomes.

MATERIALS AND METHODS

Patients

From January 1990 to December 2011, 725 patients underwent concomitant AVR and mitral valve surgery at Asan Medical Center, Seoul, South Korea. Of these, patients with associated valve lesions (n = 10; 1 pulmonary valve replacement and 9 tricuspid valve replacement) and redo surgery (n = 52) were excluded. However, patients who had undergone concomitant coronary artery bypass grafting or concomitant tricuspid repair were not excluded. Thus, 663 patients undergoing AVR combined with either mitral valve replacement (n = 524) or repair (n = 139) were identified. Among these, patients with predominant mitral stenosis were excluded because there is a strong tendency to perform replacement rather than repair on them in our centre, and it is inappropriate to compare the outcomes between repair and replacement in these settings. Finally, a total of 253 patients with predominant mitral regurgitation (≥3 grade) were enrolled to compare the outcomes between DVR group (n = 158) and AVR plus MVr group (n = 95). Survival and valve-related events were compared by the inverse-probability-treatment-weighted method using propensity scores. This study was approved by our institutional review board, which waived the requirement for informed patients consent, based on the retrospective nature of the study.

Surgical procedures

A median sternotomy approach and conventional ascending aorta and bicaval cannulations were used for all patients. Moderately hypothermic cardiopulmonary bypasses were used, and myocardial protection was achieved with cold or tepid blood cardioplegia. After aortic cross-clamping, the aorta was opened either with a transverse or oblique aortotomy. Morphology of the aortic valve was then inspected and excision of the valve was performed. After the native aortic valve excision, a longitudinal right-sided left atriotomy was the conventional approach for exposure to the mitral valve. The decision to perform either MVr or replacement was dependent on the operating surgeon, and thus, indications naturally varied according to surgical experience and judgement. If MVr was selected, they were performed according to the pathology of each level of the annulus, leaflet and subvalvular apparatus, as described previously [9]. Details of the MVr techniques are summarized in Table 1. After completing MVr, the aortic valve was replaced with a mechanical valve or a tissue valve. The Maze procedure (n = 38) was performed using a modified Cox-Maze III procedure (cryoablation in 34 and microwave in 4). Since February 2006, all Maze procedures were performed by cryoablation using a flexible probe, SurgiFrost (Medtronic, Minneapolis, MN, USA). The lesion sets for the modified Cox-Maze III procedure have been described previously [10, 11].

Table 1:

Surgical techniques of mitral valve repair (N = 95)

No. of cases (%)
Mitral valve repair
 Annuloplasty
  Rigid, complete ring 33 (34.7)
  Semi-rigid, complete ring 21 (22.1)
  Flexible, complete ring 15 (15.8)
  Flexible, partial ring 21 (22.1)
  Sliding annuloplasty 2 (2.1)
 Leaflet repair
  Commissurotomy or leaflet mobilization 14 (14.7)
  Leaflet extension or augmentation 5 (5.3)
  Triangular or quadrangular resection 4 (4.2)
Subvalvular apparatus repair
 Chordae
  Shortening 1 (1.1)
  New chordate formation 15 (15.8)
  Cutting 3 (3.2)
 Papillary muscle splitting 8 (8.4)

Postoperative anticoagulation

Patients who underwent valve repair or bioprosthetic valve implantation were routinely administered warfarin for 3–6 months postoperatively, with a target international normalized ratio (INR) of 1.5–2.5. The maintenance of anticoagulation therapy thereafter was determined according to the presence of thromboembolic risks and cardiac rhythm status in each patient. For patients with mechanical valve implantation, a target INR of 2.5–3.0 was the aim in the DVR group and 2.0–2.5 in the AVR plus MVr group.

Follow-up

Follow-up data of patients were obtained from hospital records, clinical visits and telephone interviews up to 31st May 2012. Data on vital statuses and dates of death were obtained from the Korean national registry of vital statistics. Follow-up transthoracic echocardiographic evaluations were generally performed at 6-month intervals in the first year and every 2 years thereafter. Early mortality was defined as death within 30 days of surgery. Deaths were classified as cardiac or non-cardiac on the basis of medical records. The definition of valve-related events was based on the Guidelines for Reporting Mortality and Morbidity after Cardiac Valve Interventions [12].

Echocardiography

Two-dimensional and Doppler echocardiographic examinations were performed in all patients using either a Hewlett-Packard Sonos 2500 or 5500 imaging system equipped with a 2.5-MHz transducer (Hewlett-Packard; Andover, MA, USA). Preoperative echocardiography was performed in all patients <2 months prior to surgery. Mitral regurgitation (MR) was graded as either moderate (0.2 cm2 ≤ effective regurgitant orifice area (ERO) <0.4 cm2) or severe (ERO ≥ 0.4 cm2). Significant pulmonary hypertension was defined as a tricuspid regurgitation peak velocity of >3.4 ms−1, equal to a pulmonary artery pressure of >50 mmHg. Postoperative significant mitral valve dysfunctions were defined as follows: (i) mitral regurgitation > mild or (ii) mitral stenosis defined by a mitral valve area of ≤1.5 cm2.

Statistical analysis

Categorical variables are presented as frequencies and percentages, and continuous variables are expressed as means ± SD, or as medians and ranges. Kaplan–Meier curves were employed to delineate overall survival and freedom from valve-related events. Stratified survival curves were plotted to determine unadjusted differences between the DVR and AVR plus MVr (log-rank test). To reduce the impact of treatment selection bias and potential confounding factors in an observational study, a propensity score to estimate the probability, on the basis of patient and baseline characteristics (Tables 2 and 3) that patients would be selected for DVR was developed with the use of logistic regression to adjust for between-group differences. Inverse probability weighting that was based on the propensity score was then used as the primary tool to adjust for differences between the two treatment groups. This approach, which was implemented to create balance, involved weighting each patient who underwent DVR by the inverse of the probability that he or she would be selected for DVR, and weighting each patient who underwent AVR plus MVr by the inverse of the probability that he or she would be selected for AVR plus MVr. We verified the performance of the propensity model by comparing the distribution of covariates and propensity scores between treatment groups both before and after inverse probability weighting [13]. Results were expressed as hazard ratios (HRs) with 95% confidence intervals (CIs). P-values of <0.05 were significantly considered. SPSS version 18.0 (SPSS, Inc., Chicago, IL, USA) and a statistical R software version 2.13 (R Foundation for Statistical Computing, Vienna, Austria; www.r-project.org) were used for all statistical analyses. To obtain propensity scores for inverse probability weighting, we adopted an automated procedure using twang package and generalized boosted regression in the R software [14].

Table 2:

Baseline characteristics of patients

DVR (N = 158) AVR plus MVr (N = 95) P-value
Age (years) 53.2 ± 14.1 60.5 ± 13.9 <0.001
Female gender (n, %) 61 (38.6) 30 (31.6) 0.259
Body mass index 22.2 ± 3.1 24.5 ± 21.8 0.183
NYHA Class
 I 31 (19.6) 18 (18.9) 0.346
 II 77 (48.7) 45 (47.4)
 III 45 (28.5) 24 (25.3)
 IV 5 (3.2) 8 (8.4)
Underlying condition (n, %)
 Hypertension 32 (20.3) 32 (33.7) 0.017
 Diabetes mellitus 7 (4.4) 7 (7.4) 0.322
 COPD 2 (1.3) 0 0.529
 History of thromboembolic events 9 (5.7) 6 (6.3) 0.840
 Creatinine (mg/dl) 1.3 ± 1.3 1.3 ± 1.2 0.841
 Dialysis 4 (2.5) 5 (5.3) 0.302
 Preoperative atrial fibrillation 70 (44.3) 29 (30.5) 0.030
 LV ejection fraction (%) 55.0 ± 10.3 46.0 ± 13.0 <0.001
 Significant pulmonary hypertension 47 (29.7) 39 (41.1) 0.071
Aetiology of mitral and aortic valve
 Rheumatic 88 (55.7) 27 (28.4) <0.001
 Degenerative 30 (19.0) 56 (58.9)
 Endocarditis 40 (25.3) 12 (12.6)
Mitral regurgitation grade (n, %)
 III 62 (39.2) 46 (48.4) 0.153
 IV 96 (60.8) 49 (51.6)
Aortic valve lesion (n, %)
 Predominant aortic stenosis 20 (12.7) 17 (17.9) 0.167
 Predominant aortic regurgitation 119 (75.3) 61 (64.2)
 Mixed steno-regurgitation 19 (12.0) 17 (17.9)

DVR: double valve replacement; AVR: aortic valve replacement; MVr: mitral valve repair; NYHA: New York Heart Association; EF: ejection fraction; COPD: chronic obstructive pulmonary disease; LV: left ventricle.

Table 3:

Operative data of patients

DVR (N = 158) AVR plus MVr (N = 95) P-value
Cardiopulmonary bypass time (min) 171.9 ± 69.9 182.2 ± 72.6 0.263
Aortic cross-cramping time (min) 118.9 ± 46.1 127.6 ± 49.8 0.158
Maze procedure (n, %) 23 (14.6) 15 (15.8) 0.856
Aortic valve type (n, %)
 Tissue 21 (13.3) 46 (48.4) <0.001
 Mechanical 137 (86.7) 49 (51.6)
Mitral valve type, if replacement (n, %)
 Tissue 21 (13.3)
 Mechanical 137 (86.7)
Concomitant surgery (n, %)
 CABG 3 (1.9) 17 (17.9) <0.001
 Aorta graft replacement 3 (1.9) 11 (11.6) 0.002
Tricuspid valve repair
 Ring annuloplasty 13 (8.2) 13 (13.7) 0.290
 Suture annuloplasty 23 (14.6) 10 (10.5)

DVR: double valve replacement; AVR: aortic valve replacement; MVr: mitral valve repair; MVR: mitral valve replacement; CABG: coronary artery bypass grafting.

RESULTS

Baseline characteristics

Table 2 summarizes baseline characteristics of the study patients. Before adjustment with the use of inverse probability weighting, the patients undergoing DVR, when compared with those undergoing AVR plus MVr, were younger, and more patients had preoperative atrial fibrillation. More patients in the AVR plus MVr group than in the DVR group had hypertension and a lower left ventricle ejection fraction. The aetiologies of mitral and aortic valves were significantly different between the two groups. Aortic valve types were also different between the groups, with patients in the DVR group more often using mechanical valves and those in the AVR plus MVr group more often using tissue valve. More patients in the AVR plus MVr group than in the DVR had concomitant surgery of coronary artery bypass grafting and aorta graft replacement. After adjustment with the use of inverse probability weighting, all the clinical covariates were well balanced (Table 4).

Table 4:

Adjusted data with the use of inverse probability weighting

DVR (N = 158) AVR plus MVr (N = 95) P-value
Age (years) 55.0 ± 14.2 57.7 ± 14.3 0.195
Female gender (%) 37.6 29.6 0.243
Body mass index 22.2 ± 3.0 23.5 ± 17.1 0.347
NYHA Class (%)
 I 18.9 22.1 0.280
 II 46.9 52.8
 III 29.8 18.1
 IV 4.4 7.1
Underlying condition (%)
 Hypertension 23.4 31.9 0.204
 Diabetes mellitus 5.9 6.6 0.841
 COPD 2.4 0 0.232
 History of thromboembolic events 5.2 5.2 0.988
 Creatinine (mg/dl) 1.3 ± 1.3 1.2 ± 1.0 0.676
 Dialysis 3.4 4.1 0.808
 Preoperative atrial fibrillation 43.7 30.8 0.064
 LV ejection fraction (%) 53.2 ± 11.7 49.8 ± 13.3 0.076
 Significant pulmonary hypertension 32.8 39.4 0.355
Aetiology of mitral and aortic valve (%)
 Rheumatic 50.8 37.5 0.104
 Degenerative 26.1 41.4
 Endocarditis 23.1 21.1
Aortic valve lesion (%)
 Predominant aortic stenosis 14.8 14.6 0.104
 Predominant aortic regurgitation 72.3 66.6
 Mixed steno-regurgitation 12.9 18.8
Cardiopulmonary bypass time (min) 176.6 ± 71.1 173.5 ± 69.7 0.752
Aortic cross-cramping time (min) 121.6 ± 46.4 123.4 ± 49.0 0.786
Maze procedure (%) 13.4 16.1 0.597
Aortic valve type (%)
 Tissue 21.2 34.6 0.046
 Mechanical 78.8 65.4
Concomitant surgery (%)
 CABG 4.4 11.3 0.137
 Aorta graft replacement 2.2 8.2 0.032
 Tricuspid valve repair 22.7 27.1 0.496

DVR: double valve replacement; AVR: aortic valve replacement; MVr: mitral valve repair; NYHA: New York Heart Association; EF: ejection fraction; COPD: chronic obstructive pulmonary disease; LV: left ventricle.

Early outcomes

There were 7 (2.8%) early deaths; 3 (1.9%) patients in the DVR group and 4 (3.2%) in the AVR plus MVr group. In the DVR group, 2 patients died of postoperative low cardiac output syndrome and 1 died of postoperative cerebral haemorrhage 1 day after surgery. In the AVR plus MVr group, 1 patient died of postoperative low cardiac output syndrome and 3 died of septic shock. There were 29 cases of early postoperative complications. These included postoperative bleeding in 12 (4.7%, 7 in the DVR group and 5 in the AVR plus MVr) patients, postoperative acute renal failure in 3 (1.2%, only in the DVR group), sick sinus syndrome or complete atrioventricular block in 4 (1.6%, only in the DVR group), wound problems in 3 (1.2%, only in the DVR group), paravalvular leakage in 3 (1.2%, only in the DVR group) , postoperative low cardiac syndrome in 2 (0.8%, only in the DVR group) , cerebral infarction in 1 (0.4%, only in the DVR group) and ascending aorta rupture of cannulation site in 1 patient undergoing AVR plus MVr.

Late outcomes

Clinical follow-up was 100% (n = 253), with a mean follow-up duration of 72.1 ± 56.7 months. There were 38 late deaths; 25 (15.8%) patients in the DVR and 13 (13.7%) in the AVR plus MVr. There were cardiovascular-related deaths in 32 patients; 21 (13.3%) in DVR and 11 (11.2%) in AVR plus MVr. There were non-cardiovascular deaths in 6 patients; 4 (2.5%) in DVR and 2 (2.0%) in AVR plus MVr. The causes of cardiovascular-related deaths included unknown origin in 19 patients, congestive heart failure in 9, myocardial infarction in 3 and intractable gastrointestinal bleeding due to warfarin intoxication in 1. Non-cardiovascular causes of death were malignancy in 4 patients, uncontrolled c-line-related sepsis in 1 and industrial accident in 1 patient. Unadjusted survival curves are shown in Fig. 1A. Overall survival at 10 years was 77.2 ± 4.4% in the DVR group and 73.0 ± 6.4% in the AVR plus MVr group, respectively (P = 0.840).

Figure 1:

Figure 1:

Kaplan–Meier curves of long-term outcomes for patients who underwent double valve surgery. (A) Overall survival and (B) freedom from valve-related events. DVR: double valve replacement; AVR: aortic valve replacement; MVr: mitral valve repair.

During the follow-up period, 31 patients experienced valve-related events including valve reoperation in 11, anticoagulation-related bleeding in 14, thromboembolisms in 9 and infective endocarditis in 3. The causes of reoperation included paravalvular leakage of previous prosthetic mitral valve in 5 patients, infective endocarditis in 3, dysfunction of previous aortic bioprothetic valve in 1, paravalvular leakage of previous aortic valve in 1 and severe tricuspid regurgitation in 1. Unadjusted freedom from valve-related event curves are shown in Fig. 1B. Freedom from valve-related events at 10 years was 84.5 ± 3.7% in the DVR group and 80.5 ± 7.1% in the AVR plus MVr group, respectively (P = 0.648). Unadjusted Kaplan–Meier curves of freedom from reoperation, bleeding, thromboembolic event and infective endocarditis are shown in Fig. 2. For those four components, no component showed a significant difference between the two groups.

Figure 2:

Figure 2:

Kaplan–Meier curves of long-term outcomes for patients that were subjected to double valve surgery. (A) Freedom from reoperation, (B) freedom from bleeding, (C) freedom from thromboembolic event and (D) freedom from infective endocarditis. DVR: double valve replacement; AVR: aortic valve replacement; MVr: mitral valve repair.

Mitral valve dysfunction in the aortic valve replacement plus mitral valve repair group

Among the AVR plus MVr group (n = 95), seventy-four (77.9%) patients were evaluated with echocardiography for >6 months postoperatively. During a mean echocardiography follow-up duration of 50.2 ± 53.0 months, 16 (16.8%) patients showed either significant mitral regurgitation (>mild; n = 14) or significant mitral stenosis (mitral valve area of ≤1.5 cm2; n = 2). No patient showed a significant mixed mitral steno-regurgitation pattern. Freedoms from moderate-to-severe mitral valve dysfunctions at 5 and 10 years were 76.4 ± 5.9 and 66.8 ± 8.2%, respectively (Fig. 3). The aetiology of mitral valve disease (rheumatic vs non-rheumatic) was evaluated in the Cox model; however, rheumatic origin did not emerge as a significant risk factor of mitral valve dysfunction even in univariate analysis (P = 0.555) in the current study.

Figure 3:

Figure 3:

Kaplan–Meier curve for freedom from mitral dysfunctions in the AVR plus MVr group. AVR plus MVr: aortic valve replacement plus mitral valve repair.

Adjusted outcomes using an inverse-probability-treatment-weighted method

Table 5 presents adjusted HRs for clinical outcomes after DVR when compared with AVR plus MVr. After adjustment for baseline risk profiles, the DVR group showed no difference with regard to risks of death (HR, 1.79; 95% CI, 0.79–4.01; P = 0.16) and valve-related events (HR, 1.15; 95% CI, 0.40–3.30; P = 0.80) compared with the AVR plus MVr group.

Table 5:

Adjusted hazard ratios for clinical outcomes after DVR when compared with after AVR plus MVr

Outcomes HR 95% CI P-value
Death
 Crude 0.94 0.51–1.72 0.84
 IPTW 1.79 0.79–4.01 0.16
Valve-related events
 Crude 0.85 0.41–1.74 0.65
 IPTW 1.15 0.40–3.30 0.80
Reoperation
 Crude 1.52 0.40–5.73 0.54
 IPTW 4.03 1.29–12.61 0.02
Thromboembolism
 Crude 1.04 0.26–4.18 0.95
 IPTW 0.81 0.31–2.17 0.68
Bleeding
 Crude 0.41 0.14–1.18 0.10
 IPTW 0.52 0.25–1.11 0.09

DVR: double valve replacement; AVR plus MVr: aortic valve replacement plus mitral valve repair; HR: hazard ratio; CI: confidence interval; IPTW: inverse-probability-treatment-weighting.

Among the four components of valve-related events, the risks of thromboembolism and bleeding were not statistically different between the two groups. Because there were small events of infective endocarditis, the fitting for comparison between the DVR and AVR plus MVr groups could not be applicable, and we could not estimate the HRs, CIs and P-valve of the component. The rate of reoperation was higher in the DVR group than in the AVR plus MVr group (HR, 4.03; 95% CI, 1.29–12.61; P = 0.02).

DISCUSSION

For the surgical strategy of mitral valve for moderate-to-severe mitral regurgitation in patients undergoing concomitant AVR, this study demonstrated that both DVR and AVR plus MVr provided excellent long-term survival and valve-related event rates. This was favourably compared with other studies [15, 16]. After adjustment for baseline risk profiles, the DVR group showed similar risks of death (HR, 1.79; 95% CI, 0.79–4.01; P = 0.16) and valve-related events (HR, 1.15; 95% CI, 0.40–3.30; P = 0.80) compared with the AVR plus MVr group.

Among each four components of valve-related events including reoperation, bleeding, thromboembolism and infective endocarditis, freedom from thromboembolic complication (94.8% in the DVR group vs 96.4% in the AVR plus MVr group at 10 years) or freedom from bleeding (93.6% in the DVR group vs 92.9% in the AVR plus MVr group at 10 years) was similar between the DVR and AVR plus MVr groups. Even after adjustment of baseline profiles, the risks of thromboembolism and bleeding were similar between the two groups. Results of the present study corresponded with a previous study [2]. This finding reflected that the natural advantage of AVR plus MVr over DVR, in terms of thromboembolism and bleeding, was not significant enough to recommend AVR plus MVr. This is presumably due to a larger number of patients with a mechanical aortic valve in the AVR plus MVr group and the difficulty of strict control of the INR level with a target INR of 2.5–3.0 in the DVR group and 2.0–2.5 in the AVR plus MVr group for patients with mechanical valve implantation. Freedom from infective endocarditis was also similar between the DVR and AVR plus MVr groups up to 10 years. However, the event number of infective endocarditis (only 3 cases in the DVR group) was too small, so that we could not estimate the HR of DVR compared with AVR plus MVr after adjustment.

Regarding reoperation, freedom from reoperation was similar between the groups before adjustment. However, after adjustment, a significantly higher incidence of reoperation was observed in the DVR group. This result of the study contrasted with the previous study [2]. The previous study revealed that structural valvular deterioration of the bioprosthetic valve was the significant risk factor of reoperation in the AVR plus MVr group compared with the DVR group. However, in the present study, the major cause of reoperation was paravalvular leakage after DVR, whereas there was 1 case of structural valvular dysfunction-related reoperation after AVR plus MVr.

In this study, another interesting finding was that a significant number of patients subjected to AVR plus MVr experienced postoperative mitral valve dysfunction despite the acceptable reoperation rate. The freedom from reoperation and moderate-to-severe mitral dysfunction rates at 10 years were 89.3 and 66.8%, respectively. A previous study suggested that there was a significant gap between the reoperation and the MV dysfunction rates after rheumatic MVr [17]. Although patients who experience significant MV dysfunctions do not necessarily undergo valve reoperation, this result provides an important understanding about the durability to be considered to obtain the better choice of surgical strategies, DVR vs AVR plus MVr.

Limitations

This study was subjected to the limitations inherent to a retrospective study using an observational data of a single centre. Another major limitation of our study was that it was not randomized, and there were significant differences between the baseline characteristics of patients in the DVR and AVR plus MVr groups. The inverse-probability-treatment-weighted method was therefore employed to correct the selection bias. Although adjustment with the use of inverse-probability-treatment-weighted method resulted in good balance between the DVR and AVR plus MVr populations, concomitant surgical histories of aortic graft replacement and implanted aortic valve type were different between the two groups, and also the potential remains for unmeasured confounders to have influenced the clinical outcomes. The sample size was small to draw a firm conclusion; and therefore, studies on larger populations are needed to verify the results of the current study. Functional MR was present in 38 (40.0%) and 11 (7.2%) patients in the AVR plus MVr and DVR groups, respectively. This factor also might have affected the decision to repair or replace the MV. Furthermore, because several surgeons performed the surgery, inter-surgeon variability in determining the reparability of the MV might have existed. This variability can have a significant impact on the study results. Finally, late (>6 months) postoperative echocardiography data were not available in 22.1% of the patients.

CONCLUSIONS

In conclusion, although the outcomes of either MVr or replacement for moderate-to-severe mitral regurgitation in patients undergoing concomitant AVR show no statistical significance in terms of long-term survival and valve-related events rate, DVR seems more hazardous than AVR plus MVr based on the estimated HR in terms of survival. Moreover, it should be noted that DVR is associated with a higher risk of reoperation, while AVR plus MVr may lead to progressive native mitral valve dysfunction.

Conflict of interest: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.

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