Impact of valve type on outcomes after redo mitral valve replacement in patients aged 50 to 69 years

Impact of valve type on outcomes after redo mitral valve replacement in patients aged 50 to 69 years Abstract OBJECTIVES Little data are available with regard to valve selections in redo valvular surgery. We investigated the impact of valve types on late outcomes after redo mitral valve replacement (MVR). METHODS We retrospectively reviewed 66 patients aged 50–69 (mean age 62.2 ± 5.1)  years who underwent redo MVR over the past 25 years. In redo MVR, 46 (69.7%) redo procedures were the 1st redo valvular surgeries, 16 (24.2%) were 2nd redos, 3 (4.5%) were 3rd redos and 1 was a 4th (1.5%) redo. We classified 66 patients into 2 groups: mechanical MVR group (M-MVR, n = 44) and biological MVR group (B-MVR, n = 22). The mean follow-up period was 8.2 ± 6.3 years. RESULTS Hospital mortality rates were 3.3% in M-MVR and 9.7% in B-MVR (P = 0.3328). Survival rates in M-MVR and B-MVR at 5 and 10 years were 93.0 ± 4.8% vs 76.0 ± 10.5% and 77.6 ± 9.1% vs 51.3 ± 13.7%, respectively (log-rank test, P = 0.0072). Late death occurred in 7 patients in M-MVR and 9 in B-MVR. Freedom rates from valve-related events in M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). No bleeding and thromboembolic events were observed in M-MVR, whereas gastrointestinal bleeding (n = 1), subarachnoid haemorrhage (n = 1) and cerebral infarction (n = 2) were observed in B-MVR. A predictor of late death was a biological valve in redo MVR (P = 0.0206, hazard ratio = 3.402, 95% confidence interval 1.207–9.591). CONCLUSIONS It would seem that redo MVR using a mechanical valve was associated with better early and late outcomes in this age group. Valve types , Late outcomes , Redo mitral valve replacement INTRODUCTION Appropriate prosthetic valve selection for mitral valve replacement (MVR) in patients aged 50–70 years is a matter of discussion. The 2014 ACC/AHA guideline for the management of patients with valvular heart disease suggests that it is reasonable in patients aged 60–70 years to receive mechanical or biological valves in the mitral position [1]. The guideline was based on mainly 2 randomized trials, in which there was no difference in long-term survival in patients receiving a mechanical valve when compared with those who received a biological valve [2, 3]. A randomized trial to assess outcomes between mechanical and biological valves reported no difference in long-term survival among patients receiving mechanical valve versus biological valve [4]. These trials included valves that are currently unavailable and did not focus on the specific age cohort [2, 4]. Up until now, the choice of heart valve type focuses on patients undergoing initial valvular surgeries. Currently, the number of redo valvular surgeries has been increasing dramatically. We have enough information that the early and late outcomes have been improving, especially in younger patients [5, 6]. In the past 6 years (between 2010 and 2015), the total number of redo valvular procedures reached 188 cases, which was about 2-fold when compared with that for the period prior to 2010. In addition to the increasing number of elderly patients, more and more younger patients have received redo surgery [7]. We believe that the same question of valve selection applies to younger patients undergoing redo valvular surgery. No data are available with regard to valve selections in redo valvular surgery. Additionally, there is no guideline on valve selections in such situations. Therefore, we investigated the impact of valve types on survival and valve-related events after redo MVR in patients aged 50–69 years. MATERIALS AND METHODS This study was approved by the institutional review board. We retrospectively reviewed the medical records of 66 patients aged 50–69 (mean age 62.2 ± 5.1) years who underwent redo MVR at our hospital from January 1990 to December 2015 (>25 years). This study was performed in accordance with the Society of Thoracic Surgeon Guidelines [8]. All patients underwent 1 or more MVRs previously at our hospital or another hospital. Previous isolated aortic valve replacement, mitral valve repair and concomitant Bentall procedure, aortic surgery and coronary artery bypass grafting were excluded. In addition, current concomitant aortic valve surgery, aortic surgery or coronary artery bypass were also excluded. Non-elective surgery was excluded in this study. For MVR, the choice of biological or mechanical valves was basically based on the patient’s age. Even in younger patients, if patient’s wishes after detailed discussion, biological valves were selected for implantation. Additionally, if the anticoagulation was contraindicated, biological valves were selected. Patients with a history of bleeding or shorter prognosis secondary to malignancy received biological valves. In 66 patients who received redo MVR, 46 (69.7%) redo procedures were 1st redo valvular surgeries, 16 (24.2%) were 2nd redos, 3 (4.5%) were 3rd redos and 1 was a 4th (1.5%) redo. Overall, 91 redo MVRs were performed over the past 25 years. We classified 66 patients into 2 groups: mechanical MVR group (M-MVR, n = 44) and biological MVR group (B-MVR, n = 22) to assess late survival and valve-related events between groups. We followed up patients who received redo surgery at least every 6 or 12 months in the outpatient clinic, and the decision for performing redo surgery was made by the authors. The mean follow-up period was 8.2 ± 6.3 years, and the rate of follow-up was 87.9%. Statistical analysis All statistical analyses were conducted using the StatView version 5.0 software (SAS Institute, Cary, NC, USA). Categorical variables were analysed using the Fisher’s exact probability and are expressed as percentages. Continuous variables were analysed by the Student’s t-test and are expressed as mean ± standard deviation. The Mann–Whitney U-test was also used for data with non-normal distribution. The Kaplan–Meier method was applied to calculate estimates of late survival, freedom from valve-related events, bleeding and thromboembolic events. Univariable analysis was performed using the Fisher’s exact probability and t-tests. Variables with a univariable probability value of ≤0.2, but failing to meet the level of statistical significance, were submitted for the Cox regression multivariable analysis to determine predictors of late survival. Surgical techniques All patients underwent redo MVR via a median resternotomy. If the right ventricle was positioned close to the sternum, or if the right ventricular pressure was elevated during redo MVR, extracorporeal circulation was established via peripheral cannulation before resternotomy. Extracorporeal circulation was used before resternotomy in most patients undergoing multiple redo surgeries. The techniques of exposure of the mitral prosthesis comprised the standard left atriotomy being the most common and trans-septal approach. For myocardial protection, antegrade, retrograde or both antegrade and retrograde, cold blood cardioplegia was used. After standard cardioplegic arrest, we investigated the mitral prostheses. Mitral prostheses were removed, and the mitral annulus was carefully debrided with the removal of old suture materials. If we could preserve the subvalvular apparatus for MVR, we did. However, especially in multiple redo MVR, we could not preserve it. Annulus suture was placed, and prostheses were implanted. RESULTS Patient characteristics are summarized in Table 1. The mean age of the patients in M-MVR and B-MVR was 60.8 ± 4.7 years and 65.0 ± 4.7 years, respectively (P = 0.0015). More than 50% of patients in both groups had a history of renal dysfunction ≥1.5 mg/dl (P = 0.5932). Atrial fibrillation was observed in almost 70% of patients in both groups, which was not statistically significant (P = 0.5244). EuroSCORE II was 12.0 ± 9.0 in M-MVR and 13.8 ± 10.5 in B-MVR (P = 0.3338). The distribution of the number of redo surgeries was similar between both groups. With regard to causes of redo, more than 70% were structural valve deterioration (SVD). Although this was not statistically significant (P = 0.7346), more patients were diagnosed with non-SVD in M-MVR (P = 0.0856). Thrombus formation was not observed. Table 1: Patient profile (n = 66) Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; BSA: body surface area; CAD: coronary artery disease; COPD: chronic obstructive pulmonary disease; LVEF: left ventricular ejection fraction; M-MVR: mechanical mitral valve replacement; NYHA: New York Heart Association; PAD: peripheral arterial disease; PVL: perivalvular leakage; SD: standard deviation; SVD: structural valve deterioration. Table 1: Patient profile (n = 66) Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; BSA: body surface area; CAD: coronary artery disease; COPD: chronic obstructive pulmonary disease; LVEF: left ventricular ejection fraction; M-MVR: mechanical mitral valve replacement; NYHA: New York Heart Association; PAD: peripheral arterial disease; PVL: perivalvular leakage; SD: standard deviation; SVD: structural valve deterioration. Previous and current valvular surgery Details on previous and current valvular surgery are listed in Table 2. Isolated MVR was performed more in B-MVR (P = 0.1778) than in M-MVR. In both groups, previous MVR was performed using a biological valve in more than 70% of patients (P = 0.3536). Table 2: Previous and current surgery Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Results are represented as mean ± SD or n (%). AVR: aortic valve replacement; AoX: aortic cross clamp; B-MVR: biological MVR; CPB: cardiopulmonary bypass; M-MVR: mechanical MVR; MVR: mitral valve replacement; SD: standard deviation; TAP: tricuspid annuloplasty; TVR: tricuspid valve replacement. Table 2: Previous and current surgery Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Results are represented as mean ± SD or n (%). AVR: aortic valve replacement; AoX: aortic cross clamp; B-MVR: biological MVR; CPB: cardiopulmonary bypass; M-MVR: mechanical MVR; MVR: mitral valve replacement; SD: standard deviation; TAP: tricuspid annuloplasty; TVR: tricuspid valve replacement. Table 3: Early outcomes Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; ICU: intensive care unit; M-MVR: mechanical mitral valve replacement; SD: standard deviation. Table 3: Early outcomes Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; ICU: intensive care unit; M-MVR: mechanical mitral valve replacement; SD: standard deviation. Operative intervals between previous and current surgery in M-MVR/B-MVR were 13.0 ± 5.6 years and 12.4 ± 3.1 years, respectively (P = 0.1376). Isolated MVR was performed in 36% of patients in M-MVR and in 50% in B-MVR (P = 0.3036). The higher frequency of concomitant tricuspid valve surgeries was performed in M-MVR. In M-MVR, the CarboMedics (CarboMedics, Austin, TX, USA) mechanical valve was used in more than 70% of patients. Some mechanical valves are currently unavailable. Three types of biological valves were implanted in B-MVR with relatively similar frequency. Durations of cardiopulmonary bypass and aortic cross clamp were similar between the 2 groups. Postoperatively, we used an international normalized ratio of prothrombin time (PT-INR) 2.0–2.5 after M-MVR. When bleeding events occurred, the value of PT-INR was reduced. In B-MVR, oral aspirin (100 mg/day) was used. Warfarin was also used in B-MVR, but without atrial fibrillation or other indications of oral anticoagulant, and it was discontinued 3 months after surgery. Early outcomes Hospital mortality rates were 3.3% (2 of 60 redo procedures) in M-MVR and 9.7% (3 of 31 redo procedures) in B-MVR (P = 0.3328) (Table 3). The causes of death included hepatic failure (n = 1) and low-output syndrome (n = 1) in M-MVR and multiorgan failure (n = 2) and sudden death (n = 1) in B-MVR. These 5 patients were classified as preoperative New York Heart Association Class III (n = 4) and IV (n = 1). Additionally, these patients had been subjected to undergo M-MVR previously. Two 2nd redos were included in B-MVR. The mean age of the 5 patients was 59.0 ± 1.4 years in M-MVR and 62.0 ± 7.0 years in B-MVR (P = 0.8743). There was no statistically significant difference in postoperative complications between groups. Intensive care unit stay tended to be longer in B-MVR than that in M-MVR without statistical significance (7.8 ± 10.7 days vs 6.4 ± 8.1 days, P = 0.3127). Late outcomes Survival Survival rates in M- and B-MVR at 5 and 10 years were 93.0 ± 4.8% vs 76.0 ± 10.5% and 77.6 ± 9.1% vs 51.3 ± 13.7%, respectively (log-rank test, P = 0.0072) (Fig. 1). Late death occurred in 16 patients (M-MVR, n = 7; B-MVR, n = 9). Late death was defined as all-cause mortality [8]. The causes included heart failure (n = 3), multi-organ failure (n = 2), sudden death (n = 2), pneumonia (n = 2), bleeding (n = 2), ventricular fibrillation (n = 1), prosthetic valve endocarditis (n = 1), cerebral infarction (n = 1), hepatic failure (n = 1) and pancreatic cancer (n = 1). The mean age of patients who died from causes as mentioned was 61.0 ± 5.0 years in M-MVR and 64.5 ± 5.7 years in B-MVR (P = 0.1901). In addition, the mean number of redo surgeries was 2.9 ± 0.7 in M-MVR and 2.2 ± 0.4 in B-MVR, respectively (P = 0.0167). Figure 1: View largeDownload slide There was a significant difference in survival rate between M-MVR and B-MVR (93.0 ± 4.8% vs 76.0 ± 10.5% at 5 years and 77.6 ± 9.1% vs 51.3 ± 13.7% at 10 years, log-rank test, P = 0.0072). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Figure 1: View largeDownload slide There was a significant difference in survival rate between M-MVR and B-MVR (93.0 ± 4.8% vs 76.0 ± 10.5% at 5 years and 77.6 ± 9.1% vs 51.3 ± 13.7% at 10 years, log-rank test, P = 0.0072). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. With regard to freedom from cardiac death at 10 years, a significant difference between groups (93.3 ± 6.4% in M-MVR vs 55.6 ± 14.2% in B-MVR, log-rank test, P = 0.0015) was also observed. Freedom from valve-related events The definition of valve-related event included valve-related mortality, valve-related morbidity and the need for a new permanent pacemaker or defibrillator within 14 days after surgery (Fig. 2) [7]. Figure 2: View largeDownload slide Freedom rates from valve-related events between M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Figure 2: View largeDownload slide Freedom rates from valve-related events between M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Freedom rates from valve-related events in M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). Four events occurred in M-MVR. Heart failure (n = 2) in M-MVR occurred more than 10 years after redo MVR. One of these 2 patients died due to heart failure. The remaining 2 events were sudden deaths. Nine events were observed in B-MVR. Heart failure (n = 3), bleeding (n = 2), cerebral infarction (n = 2), ventricular fibrillation (n = 1) and prosthetic valve endocarditis (n = 1) were observed in B-MVR. Of these, 7 patients (heart failure, n = 2; bleeding, n = 2; cerebral infarction, n = 1; ventricular fibrillation, n = 1; prosthetic valve endocarditis, n = 1) died. Fortunately, reoperation for SVD did not occur during the study follow-up period. Freedom from bleeding events There was no bleeding event in M-MVR. However, gastrointestinal bleeding (n = 1) and subarachnoid haemorrhage (n = 1) were reported approximately 7 years after surgery in B-MVR (Fig. 3A). Freedom rates from bleeding events at 5 and 10 years in B-MVR were 100.0 ± 0.0% and 76.2 ± 14.8%, respectively. These 2 patients died due to bleeding events. One patient took oral warfarin due to chronic atrial fibrillation. Figure 3: View largeDownload slide There was no bleeding event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 100.0 ± 0.0% and 76.2 ± 14.8%, respectively (A). There was no thromboembolic event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 87.8 ± 8.1% and 87.8 ± 8.1%, respectively (B). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Figure 3: View largeDownload slide There was no bleeding event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 100.0 ± 0.0% and 76.2 ± 14.8%, respectively (A). There was no thromboembolic event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 87.8 ± 8.1% and 87.8 ± 8.1%, respectively (B). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Freedom from thromboembolic events There was no thromboembolic event in M-MVR (Fig. 3B). Two cases of cerebral infarction occurred approximately 1 year after surgery in B-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 87.8 ± 8.1% and 87.8 ± 8.1%, respectively. These 2 patients had a history of chronic atrial fibrillation. Additionally, they repeated cerebral infarction before redo surgery despite anticoagulation. Predictors of late survival A predictor of late death was a biological valve in redo MVR (P = 0.0206, hazard ratio = 3.402, 95% confidence interval: 1.207–9.591). Age and the number of redo surgeries did not reach statistical significance based on the Cox regression multivariable analysis (P = 0.6645 and 0.2798, respectively) (Table 4). Table 4: Predictors of late survival   Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096          Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096        AoX: aortic cross clamp; BSA: body surface area; CAD: coronary artery disease; CI: confidence interval; COPD: chronic obstructive pulmonary disease; CPB: cardiopulmonary bypass; HF: heart failure; HR: hazard ratio; LVEF: left ventricular ejection fraction; NYHA: New York Heart Association; PAD: peripheral artery disease; TV: tricuspid valve. Table 4: Predictors of late survival   Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096          Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096        AoX: aortic cross clamp; BSA: body surface area; CAD: coronary artery disease; CI: confidence interval; COPD: chronic obstructive pulmonary disease; CPB: cardiopulmonary bypass; HF: heart failure; HR: hazard ratio; LVEF: left ventricular ejection fraction; NYHA: New York Heart Association; PAD: peripheral artery disease; TV: tricuspid valve. DISCUSSION The decision between the use of M-MVR and B-MVR in patients younger than 70 years is a matter of discussion. One problem is that younger patients who receive biological valves experience earlier calcification due to an increased turnover of calcium, fatigue-induced lesions and collagen degeneration, which causes limited durability of valves and reoperation [9]. Considering the durability of biological valves, mechanical valves are traditionally used for younger patients [10]. Nonetheless, the number of implanted biological valves has been increasing. In Japan, the ratio of biological/mechanical valves has changed dramatically in the past 10 years, and the use of biological valves is 77.5% (36.7% in 2004) in the aortic position and 25.2% (14.8% in 2004) in the mitral position in 2014 [11]. Ruel et al. [12] described a long-term observation after valve replacement with biological valve versus mechanical valve in patients younger than 60 years. In their study, 20- and 25-year survival rates were 51.4 ± 4.4% and 33.8 ± 5.3% in patients who received biological valves and 43.2 ± 5.7% and 40.8 ± 5.9% in those who received mechanical valves. A significant difference in long-term survival was not observed with higher reoperation rates with biological valves. A mechanical valve may not necessarily be warranted in patients younger than 60 years in an initial, single left-heart valve replacement. A study from the same university showed that long-term survival was equivalent between patients aged 50–65 years implanted with a biological valve versus a mechanical valve. The incidence rates of thromboembolic events and bleeding were greater in patients who received M-MVR, whereas reoperation was more common in patients with a biological valve [13]. A retrospective analysis using propensity matching showed that in patients younger than 65 years who underwent MVR with mechanical (n = 125) or biological valves (n = 125), both with lower survival rate (P = 0.001) and higher reoperation rate (P = 0.004), were observed in B-MVR when compared with those in M-MVR. They recommended a mechanical valve for MVR in patients younger than 65 years [14]. Another study revealed no significant survival difference at 15 years in patients aged 50–69 years matched using propensity score who underwent M-MVR and B-MVR (P = 0.62). The incidences of stroke and bleeding were significantly higher in patients who received M-MVR when compared with those who received B-MVR [15]. In this study, the incidence rates of bleeding and thromboembolic events were similar between the groups (Fig. 3). It is because we used strict monitoring for PT-INR 2.0–2.5 in M-MVR. Additionally, patients frequently visit outpatient clinic for the purpose of monitoring for PT-INR after discharge. Physicians or cardiac surgeons regularly check patients and PT-INR in outpatient clinics. This effort should contribute to the lower rate of bleeding or thromboembolic events after M-MVR, leading to our conclusion. The aforementioned discussion focuses only on initial MVR patients. We also observed younger patients who underwent redo MVR. From our experience, we confirmed that there is currently an increasing number of redo valvular surgeries. Nonetheless, the choice of valve type in redo surgery has not been discussed. A possible reason for this is that we cannot expect long-term survival due to high mortality and comorbidity rates after redo surgery. In fact, hospital mortality rate for redo valvular surgery remained high, and it reached up to 7.8% for mitral procedures [11]. However, our previous report revealed that the hospital mortality rate including all the valvular procedures was 6.7% [5]. Furthermore, in the past 6 years (between 2010 and 2015), the mortality rate dramatically decreased to 3.2% [7], which suggests that mortality rate in this type of surgery is apparently improving. In addition, long-term survival rates at 5, 10 and 15 years were 83.6 ± 2.2%, 70.7 ± 3.4% and 61.5 ± 4.5%, respectively. These survival rates after redo valvular surgery are similar to those published in previous studies focusing only on patients who underwent initial MVR [12–15]. With regard to the choice of valve, the same evaluation should be performed for younger patients undergoing redo MVR. This study focused on late outcomes in patients aged 50–69 years who underwent redo MVR. The main findings were lower survival rate and freedom from valve-related events in patients who received biological valves. Survival rates in M-MVR were significantly higher than those in B-MVR (log-rank test, P = 0.0072). The age of patients in redo surgery and the number of redo surgeries were not associated with lower survival. Survival rate in B-MVR dropped dramatically 5 years after redo surgery, although no reoperation due to SVD was observed during the follow-up period. Bleeding (n = 2) and cerebral infarction (n = 1) in B-MVR were associated with late death. As Chikwe et al. [15] described, stroke and major bleeding events were associated with increased 30-day mortality. Similar to this study, these events were responsible for lowering late survival in B-MVR. Two patients who experienced gastrointestinal bleeding and cerebral infarction during the follow-up period in B-MVR took warfarin for chronic atrial fibrillation preoperatively. With indications for anticoagulation, the use of biological valves did not prevent anticoagulant therapy. This is one explanation as to why the biological valve group had a bleeding risk similar to that of the mechanical valve group [16]. In this study, all the patients with atrial fibrillation did not receive a mechanical valve in redo surgery because we could lower the value of PT-INR in B-MVR when compared with M-MVR, even in the setting of atrial fibrillation. The issue of atrial fibrillation did not affect valve selection. We could detect a biological valve in redo MVR (P = 0.0206, hazard ratio = 3.402, 95% confidence interval 1.207–9.591) as a negative predictor of survival. Published data by Kaneko et al. support this finding [14]. Age and the number of redo surgeries were not associated with late survival in this study. With regard to early mortality, explanting mechanical valves in redo surgery was associated with higher mortality rate than biological valves due to different mode of failure and presentation [16]. This result is similar to our finding. Among 5 hospital deaths, all had undergone M-MVR previously. Although explanting mechanical valves might affect early outcomes, it was not found to be associated with late survival. As a result of 1 or more previous MVRs, mitral annulus becomes damaged and may not be strong enough to hold the new prosthetic valves. Surrounding structures also may become damaged during valve implantation. In these cases, reconstruction of the mitral annulus using glutaraldehyde-fixed bovine pericardium makes reoperative MVR safer [17]. Limitations This study has some limitations. The 1st limitation is that this study was a retrospective analysis of redo valvular surgery over the past 25 years. During this period, 2 surgeons used different surgical strategies, and the durability of the biological valves, selection bias of surgical techniques applied, patterns of usage of mechanical over biological valves and pre/postoperative management of patients has changed. The 2nd limitation is that the sample cohort was small with only 66 patients receiving redo MVR. The 3rd is that underestimations of late bleeding or thromboembolic events are possible because we cannot follow-up all the patients carefully, and subsequent events also cannot be followed up. To balance the clinical characteristics of the 2 groups, we used propensity score adjustment with inverse probability weighting approach using the R software, version 3.4.3 (R Foundation for Statistical Computing, Vienna, Austria). We used a logistic regression model based on patient age, history of liver cirrhosis or stroke to estimate the propensity score. Even after propensity score adjustment, patients with mechanical valve had a lower risk of survival (P < 0.001, hazard ratio = 0.227, 95% confidence interval 0.125–0.410). We showed our experience of redo MVR with late outcomes based on valve types implanted. 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Impact of valve type on outcomes after redo mitral valve replacement in patients aged 50 to 69 years

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1569-9293
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1569-9285
D.O.I.
10.1093/icvts/ivy109
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Abstract

Abstract OBJECTIVES Little data are available with regard to valve selections in redo valvular surgery. We investigated the impact of valve types on late outcomes after redo mitral valve replacement (MVR). METHODS We retrospectively reviewed 66 patients aged 50–69 (mean age 62.2 ± 5.1)  years who underwent redo MVR over the past 25 years. In redo MVR, 46 (69.7%) redo procedures were the 1st redo valvular surgeries, 16 (24.2%) were 2nd redos, 3 (4.5%) were 3rd redos and 1 was a 4th (1.5%) redo. We classified 66 patients into 2 groups: mechanical MVR group (M-MVR, n = 44) and biological MVR group (B-MVR, n = 22). The mean follow-up period was 8.2 ± 6.3 years. RESULTS Hospital mortality rates were 3.3% in M-MVR and 9.7% in B-MVR (P = 0.3328). Survival rates in M-MVR and B-MVR at 5 and 10 years were 93.0 ± 4.8% vs 76.0 ± 10.5% and 77.6 ± 9.1% vs 51.3 ± 13.7%, respectively (log-rank test, P = 0.0072). Late death occurred in 7 patients in M-MVR and 9 in B-MVR. Freedom rates from valve-related events in M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). No bleeding and thromboembolic events were observed in M-MVR, whereas gastrointestinal bleeding (n = 1), subarachnoid haemorrhage (n = 1) and cerebral infarction (n = 2) were observed in B-MVR. A predictor of late death was a biological valve in redo MVR (P = 0.0206, hazard ratio = 3.402, 95% confidence interval 1.207–9.591). CONCLUSIONS It would seem that redo MVR using a mechanical valve was associated with better early and late outcomes in this age group. Valve types , Late outcomes , Redo mitral valve replacement INTRODUCTION Appropriate prosthetic valve selection for mitral valve replacement (MVR) in patients aged 50–70 years is a matter of discussion. The 2014 ACC/AHA guideline for the management of patients with valvular heart disease suggests that it is reasonable in patients aged 60–70 years to receive mechanical or biological valves in the mitral position [1]. The guideline was based on mainly 2 randomized trials, in which there was no difference in long-term survival in patients receiving a mechanical valve when compared with those who received a biological valve [2, 3]. A randomized trial to assess outcomes between mechanical and biological valves reported no difference in long-term survival among patients receiving mechanical valve versus biological valve [4]. These trials included valves that are currently unavailable and did not focus on the specific age cohort [2, 4]. Up until now, the choice of heart valve type focuses on patients undergoing initial valvular surgeries. Currently, the number of redo valvular surgeries has been increasing dramatically. We have enough information that the early and late outcomes have been improving, especially in younger patients [5, 6]. In the past 6 years (between 2010 and 2015), the total number of redo valvular procedures reached 188 cases, which was about 2-fold when compared with that for the period prior to 2010. In addition to the increasing number of elderly patients, more and more younger patients have received redo surgery [7]. We believe that the same question of valve selection applies to younger patients undergoing redo valvular surgery. No data are available with regard to valve selections in redo valvular surgery. Additionally, there is no guideline on valve selections in such situations. Therefore, we investigated the impact of valve types on survival and valve-related events after redo MVR in patients aged 50–69 years. MATERIALS AND METHODS This study was approved by the institutional review board. We retrospectively reviewed the medical records of 66 patients aged 50–69 (mean age 62.2 ± 5.1) years who underwent redo MVR at our hospital from January 1990 to December 2015 (>25 years). This study was performed in accordance with the Society of Thoracic Surgeon Guidelines [8]. All patients underwent 1 or more MVRs previously at our hospital or another hospital. Previous isolated aortic valve replacement, mitral valve repair and concomitant Bentall procedure, aortic surgery and coronary artery bypass grafting were excluded. In addition, current concomitant aortic valve surgery, aortic surgery or coronary artery bypass were also excluded. Non-elective surgery was excluded in this study. For MVR, the choice of biological or mechanical valves was basically based on the patient’s age. Even in younger patients, if patient’s wishes after detailed discussion, biological valves were selected for implantation. Additionally, if the anticoagulation was contraindicated, biological valves were selected. Patients with a history of bleeding or shorter prognosis secondary to malignancy received biological valves. In 66 patients who received redo MVR, 46 (69.7%) redo procedures were 1st redo valvular surgeries, 16 (24.2%) were 2nd redos, 3 (4.5%) were 3rd redos and 1 was a 4th (1.5%) redo. Overall, 91 redo MVRs were performed over the past 25 years. We classified 66 patients into 2 groups: mechanical MVR group (M-MVR, n = 44) and biological MVR group (B-MVR, n = 22) to assess late survival and valve-related events between groups. We followed up patients who received redo surgery at least every 6 or 12 months in the outpatient clinic, and the decision for performing redo surgery was made by the authors. The mean follow-up period was 8.2 ± 6.3 years, and the rate of follow-up was 87.9%. Statistical analysis All statistical analyses were conducted using the StatView version 5.0 software (SAS Institute, Cary, NC, USA). Categorical variables were analysed using the Fisher’s exact probability and are expressed as percentages. Continuous variables were analysed by the Student’s t-test and are expressed as mean ± standard deviation. The Mann–Whitney U-test was also used for data with non-normal distribution. The Kaplan–Meier method was applied to calculate estimates of late survival, freedom from valve-related events, bleeding and thromboembolic events. Univariable analysis was performed using the Fisher’s exact probability and t-tests. Variables with a univariable probability value of ≤0.2, but failing to meet the level of statistical significance, were submitted for the Cox regression multivariable analysis to determine predictors of late survival. Surgical techniques All patients underwent redo MVR via a median resternotomy. If the right ventricle was positioned close to the sternum, or if the right ventricular pressure was elevated during redo MVR, extracorporeal circulation was established via peripheral cannulation before resternotomy. Extracorporeal circulation was used before resternotomy in most patients undergoing multiple redo surgeries. The techniques of exposure of the mitral prosthesis comprised the standard left atriotomy being the most common and trans-septal approach. For myocardial protection, antegrade, retrograde or both antegrade and retrograde, cold blood cardioplegia was used. After standard cardioplegic arrest, we investigated the mitral prostheses. Mitral prostheses were removed, and the mitral annulus was carefully debrided with the removal of old suture materials. If we could preserve the subvalvular apparatus for MVR, we did. However, especially in multiple redo MVR, we could not preserve it. Annulus suture was placed, and prostheses were implanted. RESULTS Patient characteristics are summarized in Table 1. The mean age of the patients in M-MVR and B-MVR was 60.8 ± 4.7 years and 65.0 ± 4.7 years, respectively (P = 0.0015). More than 50% of patients in both groups had a history of renal dysfunction ≥1.5 mg/dl (P = 0.5932). Atrial fibrillation was observed in almost 70% of patients in both groups, which was not statistically significant (P = 0.5244). EuroSCORE II was 12.0 ± 9.0 in M-MVR and 13.8 ± 10.5 in B-MVR (P = 0.3338). The distribution of the number of redo surgeries was similar between both groups. With regard to causes of redo, more than 70% were structural valve deterioration (SVD). Although this was not statistically significant (P = 0.7346), more patients were diagnosed with non-SVD in M-MVR (P = 0.0856). Thrombus formation was not observed. Table 1: Patient profile (n = 66) Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; BSA: body surface area; CAD: coronary artery disease; COPD: chronic obstructive pulmonary disease; LVEF: left ventricular ejection fraction; M-MVR: mechanical mitral valve replacement; NYHA: New York Heart Association; PAD: peripheral arterial disease; PVL: perivalvular leakage; SD: standard deviation; SVD: structural valve deterioration. Table 1: Patient profile (n = 66) Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Age (years)  60.8 ± 4.7  65.0 ± 4.7  0.0015  BSA (m2)  1.50 ± 0.15  1.46 ± 0.17  0.4117  Hypertension  2 (6.8)  3 (13.6)  0.3235  Diabetes mellitus  6 (13.6)  1 (4.5)  0.4094  Dyslipidaemia  3 (6.8)  0 (0)  0.5452  Creatinine >1.5 (mg/dl)  26 (59.1)  15 (68.2)  0.5932  COPD  1 (2.3)  2 (9.1)  0.2558  PAD  0 (0)  1 (4.5)  0.3333  Haemodialysis  1 (2.3)  0 (0)  0.9999  Liver cirrhosis  2 (4.5)  3 (13.6)  0.3235  CAD  1 (2.3)  0 (0)  0.9999  Stroke  10 (22.7)  8 (36.4)  0.2569  Atrial fibrillation  36 (81.8)  16 (72.7)  0.5244  NYHA   I/II  26 (59.1)  12 (54.5)  0.1032   III  17 (38.6)  9 (40.9)  0.9999   IV  1 (2.3)  1 (4.5)  0.9999  LVEF ≥60%  14 (31.8)  4 (18.2)  0.3797  EuroSCORE II (%)  12.0 ± 9.0  13.8 ± 10.5  0.3338  Number of redo   1st  32 (72.7)  14 (63.6)  0.5713   2nd  9 (20.5)  7 (31.9)  0.3761   3rd  2 (4.5)  1 (4.5)  0.9999   4th  1 (2.3)  0 (0)  0.9999  Causes of redo surgery   SVD  34 (77.3)  19 (86.4)  0.7346   Non-SVD  7 (15.9)  0 (0)  0.0856   PVL  3 (6.8)  3 (13.6)  0.3919   Thrombus  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; BSA: body surface area; CAD: coronary artery disease; COPD: chronic obstructive pulmonary disease; LVEF: left ventricular ejection fraction; M-MVR: mechanical mitral valve replacement; NYHA: New York Heart Association; PAD: peripheral arterial disease; PVL: perivalvular leakage; SD: standard deviation; SVD: structural valve deterioration. Previous and current valvular surgery Details on previous and current valvular surgery are listed in Table 2. Isolated MVR was performed more in B-MVR (P = 0.1778) than in M-MVR. In both groups, previous MVR was performed using a biological valve in more than 70% of patients (P = 0.3536). Table 2: Previous and current surgery Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Results are represented as mean ± SD or n (%). AVR: aortic valve replacement; AoX: aortic cross clamp; B-MVR: biological MVR; CPB: cardiopulmonary bypass; M-MVR: mechanical MVR; MVR: mitral valve replacement; SD: standard deviation; TAP: tricuspid annuloplasty; TVR: tricuspid valve replacement. Table 2: Previous and current surgery Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value  Previous surgery   Isolated MVR  26 (59.1)  17 (77.3)  0.1778    +AVR  3 (6.8)  0 (0)  0.5452    +TVR/TAP  10 (22.7)  4 (18.2)  0.7588    +AVR+TVR/TAP  5 (11.4)  1 (4.5)  0.6549  Mechanical valve  11 (25.0)  3 (13.6)  0.3536  Biological valve  33 (75.0)  19 (86.4)  0.3536  Interval (years)  13.0 ± 5.6  12.4 ± 3.1  0.1376  Current surgery         Isolated MVR  16 (36.4)  11 (50.0)  0.3036    +TVR/TAP  28 (63.6)  11 (50.0)  0.3036  Implant valves (mm)   Bicarbon (27)  1 (2.3)       Bjork–Shiley (27–31)  5 (11.4)       Carbomedics (27–31)  32 (72.7)       Jyros (28,30)  2 (4.5)       Medtronic-Hall (29)  1 (2.3)       St. Jude Medical (25,27)  3 (6.8)       Carpentier–Edwards (27–31)    8 (36.4)     Hancock (27–31)    9 (40.9)     Mosaic (27,29)    5 (22.7)    CPB duration (min)  191.7 ± 62.6  178.7 ± 61.8  0.7314  AoX duration (min)  117.6 ± 42.1  99.7 ± 34.2  0.5441  Results are represented as mean ± SD or n (%). AVR: aortic valve replacement; AoX: aortic cross clamp; B-MVR: biological MVR; CPB: cardiopulmonary bypass; M-MVR: mechanical MVR; MVR: mitral valve replacement; SD: standard deviation; TAP: tricuspid annuloplasty; TVR: tricuspid valve replacement. Table 3: Early outcomes Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; ICU: intensive care unit; M-MVR: mechanical mitral valve replacement; SD: standard deviation. Table 3: Early outcomes Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Variables  M-MVR (n = 44)  B-MVR (n = 22)  P-value    60 redos  31 redos    Hospital mortality (%)  2 (3.3)  3 (9.7)  0.3328  ICU stay (days)  6.4 ± 8.1  7.8 ± 10.7  0.3127  Re-exploration for bleeding  5 (8.3)  1 (4.5)  0.6598  Cardiac tamponade  0 (0)  0 (0)  0.9999  Cerebral infarction  0 (0)  0 (0)  0.9999  Pneumonia  1 (1.7)  1 (4.5)  0.9999  Intestinal bleeding  1 (1.7)  0 (0)  0.9999  Pacemaker implantation  1 (1.7)  1 (4.5)  0.9999  Newly required haemodialysis  0 (0)  0 (0)  0.9999  Results are given as the mean ± SD or n (%). B-MVR: biological mitral valve replacement; ICU: intensive care unit; M-MVR: mechanical mitral valve replacement; SD: standard deviation. Operative intervals between previous and current surgery in M-MVR/B-MVR were 13.0 ± 5.6 years and 12.4 ± 3.1 years, respectively (P = 0.1376). Isolated MVR was performed in 36% of patients in M-MVR and in 50% in B-MVR (P = 0.3036). The higher frequency of concomitant tricuspid valve surgeries was performed in M-MVR. In M-MVR, the CarboMedics (CarboMedics, Austin, TX, USA) mechanical valve was used in more than 70% of patients. Some mechanical valves are currently unavailable. Three types of biological valves were implanted in B-MVR with relatively similar frequency. Durations of cardiopulmonary bypass and aortic cross clamp were similar between the 2 groups. Postoperatively, we used an international normalized ratio of prothrombin time (PT-INR) 2.0–2.5 after M-MVR. When bleeding events occurred, the value of PT-INR was reduced. In B-MVR, oral aspirin (100 mg/day) was used. Warfarin was also used in B-MVR, but without atrial fibrillation or other indications of oral anticoagulant, and it was discontinued 3 months after surgery. Early outcomes Hospital mortality rates were 3.3% (2 of 60 redo procedures) in M-MVR and 9.7% (3 of 31 redo procedures) in B-MVR (P = 0.3328) (Table 3). The causes of death included hepatic failure (n = 1) and low-output syndrome (n = 1) in M-MVR and multiorgan failure (n = 2) and sudden death (n = 1) in B-MVR. These 5 patients were classified as preoperative New York Heart Association Class III (n = 4) and IV (n = 1). Additionally, these patients had been subjected to undergo M-MVR previously. Two 2nd redos were included in B-MVR. The mean age of the 5 patients was 59.0 ± 1.4 years in M-MVR and 62.0 ± 7.0 years in B-MVR (P = 0.8743). There was no statistically significant difference in postoperative complications between groups. Intensive care unit stay tended to be longer in B-MVR than that in M-MVR without statistical significance (7.8 ± 10.7 days vs 6.4 ± 8.1 days, P = 0.3127). Late outcomes Survival Survival rates in M- and B-MVR at 5 and 10 years were 93.0 ± 4.8% vs 76.0 ± 10.5% and 77.6 ± 9.1% vs 51.3 ± 13.7%, respectively (log-rank test, P = 0.0072) (Fig. 1). Late death occurred in 16 patients (M-MVR, n = 7; B-MVR, n = 9). Late death was defined as all-cause mortality [8]. The causes included heart failure (n = 3), multi-organ failure (n = 2), sudden death (n = 2), pneumonia (n = 2), bleeding (n = 2), ventricular fibrillation (n = 1), prosthetic valve endocarditis (n = 1), cerebral infarction (n = 1), hepatic failure (n = 1) and pancreatic cancer (n = 1). The mean age of patients who died from causes as mentioned was 61.0 ± 5.0 years in M-MVR and 64.5 ± 5.7 years in B-MVR (P = 0.1901). In addition, the mean number of redo surgeries was 2.9 ± 0.7 in M-MVR and 2.2 ± 0.4 in B-MVR, respectively (P = 0.0167). Figure 1: View largeDownload slide There was a significant difference in survival rate between M-MVR and B-MVR (93.0 ± 4.8% vs 76.0 ± 10.5% at 5 years and 77.6 ± 9.1% vs 51.3 ± 13.7% at 10 years, log-rank test, P = 0.0072). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Figure 1: View largeDownload slide There was a significant difference in survival rate between M-MVR and B-MVR (93.0 ± 4.8% vs 76.0 ± 10.5% at 5 years and 77.6 ± 9.1% vs 51.3 ± 13.7% at 10 years, log-rank test, P = 0.0072). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. With regard to freedom from cardiac death at 10 years, a significant difference between groups (93.3 ± 6.4% in M-MVR vs 55.6 ± 14.2% in B-MVR, log-rank test, P = 0.0015) was also observed. Freedom from valve-related events The definition of valve-related event included valve-related mortality, valve-related morbidity and the need for a new permanent pacemaker or defibrillator within 14 days after surgery (Fig. 2) [7]. Figure 2: View largeDownload slide Freedom rates from valve-related events between M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Figure 2: View largeDownload slide Freedom rates from valve-related events between M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Freedom rates from valve-related events in M-MVR and B-MVR at 5 and 10 years were 100.0 ± 0.0% vs 76.5 ± 10.3% and 93.3 ± 6.4% vs 52.4 ± 13.6%, respectively (log-rank test, P < 0.0001). Four events occurred in M-MVR. Heart failure (n = 2) in M-MVR occurred more than 10 years after redo MVR. One of these 2 patients died due to heart failure. The remaining 2 events were sudden deaths. Nine events were observed in B-MVR. Heart failure (n = 3), bleeding (n = 2), cerebral infarction (n = 2), ventricular fibrillation (n = 1) and prosthetic valve endocarditis (n = 1) were observed in B-MVR. Of these, 7 patients (heart failure, n = 2; bleeding, n = 2; cerebral infarction, n = 1; ventricular fibrillation, n = 1; prosthetic valve endocarditis, n = 1) died. Fortunately, reoperation for SVD did not occur during the study follow-up period. Freedom from bleeding events There was no bleeding event in M-MVR. However, gastrointestinal bleeding (n = 1) and subarachnoid haemorrhage (n = 1) were reported approximately 7 years after surgery in B-MVR (Fig. 3A). Freedom rates from bleeding events at 5 and 10 years in B-MVR were 100.0 ± 0.0% and 76.2 ± 14.8%, respectively. These 2 patients died due to bleeding events. One patient took oral warfarin due to chronic atrial fibrillation. Figure 3: View largeDownload slide There was no bleeding event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 100.0 ± 0.0% and 76.2 ± 14.8%, respectively (A). There was no thromboembolic event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 87.8 ± 8.1% and 87.8 ± 8.1%, respectively (B). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Figure 3: View largeDownload slide There was no bleeding event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 100.0 ± 0.0% and 76.2 ± 14.8%, respectively (A). There was no thromboembolic event in M-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 87.8 ± 8.1% and 87.8 ± 8.1%, respectively (B). B-MVR: biological mitral valve replacement; M-MVR: mechanical mitral valve replacement; pts: patients. Freedom from thromboembolic events There was no thromboembolic event in M-MVR (Fig. 3B). Two cases of cerebral infarction occurred approximately 1 year after surgery in B-MVR. The freedom rates from thromboembolic events at 5 and 10 years were 87.8 ± 8.1% and 87.8 ± 8.1%, respectively. These 2 patients had a history of chronic atrial fibrillation. Additionally, they repeated cerebral infarction before redo surgery despite anticoagulation. Predictors of late survival A predictor of late death was a biological valve in redo MVR (P = 0.0206, hazard ratio = 3.402, 95% confidence interval: 1.207–9.591). Age and the number of redo surgeries did not reach statistical significance based on the Cox regression multivariable analysis (P = 0.6645 and 0.2798, respectively) (Table 4). Table 4: Predictors of late survival   Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096          Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096        AoX: aortic cross clamp; BSA: body surface area; CAD: coronary artery disease; CI: confidence interval; COPD: chronic obstructive pulmonary disease; CPB: cardiopulmonary bypass; HF: heart failure; HR: hazard ratio; LVEF: left ventricular ejection fraction; NYHA: New York Heart Association; PAD: peripheral artery disease; TV: tricuspid valve. Table 4: Predictors of late survival   Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096          Univariable   Multivariable   Variables  P-value  HR  95% CI  P-value  Age (years)  0.6645        Sex  0.2704        BSA  0.4614        Hypertension  0.6499        Diabetes mellitus  0.6706        Hyperlipidaemia  0.5457        COPD  0.2356        PAD  0.9999        Stroke  0.9999        Liver cirrhosis  0.0023  0.534  0.141–2.026  0.3562  Creatinine >1.5(mg/dl)  0.4147        CAD  0.9999        Atrial fibrillation  0.7534        Congestive HF  0.1391  0.830  0.222–3.101  0.7822  LVEF ≥60%  0.4756        LVEF <40%  0.2973        NYHA III/IV  0.9999        Year of surgery  0.5261        Redo ≥2nd  0.2798        TV surgery  0.7942        Biological valves  0.0104  3.402  1.207–9.591  0.0206  CPB duration  0.3599        AoX duration  0.8096        AoX: aortic cross clamp; BSA: body surface area; CAD: coronary artery disease; CI: confidence interval; COPD: chronic obstructive pulmonary disease; CPB: cardiopulmonary bypass; HF: heart failure; HR: hazard ratio; LVEF: left ventricular ejection fraction; NYHA: New York Heart Association; PAD: peripheral artery disease; TV: tricuspid valve. DISCUSSION The decision between the use of M-MVR and B-MVR in patients younger than 70 years is a matter of discussion. One problem is that younger patients who receive biological valves experience earlier calcification due to an increased turnover of calcium, fatigue-induced lesions and collagen degeneration, which causes limited durability of valves and reoperation [9]. Considering the durability of biological valves, mechanical valves are traditionally used for younger patients [10]. Nonetheless, the number of implanted biological valves has been increasing. In Japan, the ratio of biological/mechanical valves has changed dramatically in the past 10 years, and the use of biological valves is 77.5% (36.7% in 2004) in the aortic position and 25.2% (14.8% in 2004) in the mitral position in 2014 [11]. Ruel et al. [12] described a long-term observation after valve replacement with biological valve versus mechanical valve in patients younger than 60 years. In their study, 20- and 25-year survival rates were 51.4 ± 4.4% and 33.8 ± 5.3% in patients who received biological valves and 43.2 ± 5.7% and 40.8 ± 5.9% in those who received mechanical valves. A significant difference in long-term survival was not observed with higher reoperation rates with biological valves. A mechanical valve may not necessarily be warranted in patients younger than 60 years in an initial, single left-heart valve replacement. A study from the same university showed that long-term survival was equivalent between patients aged 50–65 years implanted with a biological valve versus a mechanical valve. The incidence rates of thromboembolic events and bleeding were greater in patients who received M-MVR, whereas reoperation was more common in patients with a biological valve [13]. A retrospective analysis using propensity matching showed that in patients younger than 65 years who underwent MVR with mechanical (n = 125) or biological valves (n = 125), both with lower survival rate (P = 0.001) and higher reoperation rate (P = 0.004), were observed in B-MVR when compared with those in M-MVR. They recommended a mechanical valve for MVR in patients younger than 65 years [14]. Another study revealed no significant survival difference at 15 years in patients aged 50–69 years matched using propensity score who underwent M-MVR and B-MVR (P = 0.62). The incidences of stroke and bleeding were significantly higher in patients who received M-MVR when compared with those who received B-MVR [15]. In this study, the incidence rates of bleeding and thromboembolic events were similar between the groups (Fig. 3). It is because we used strict monitoring for PT-INR 2.0–2.5 in M-MVR. Additionally, patients frequently visit outpatient clinic for the purpose of monitoring for PT-INR after discharge. Physicians or cardiac surgeons regularly check patients and PT-INR in outpatient clinics. This effort should contribute to the lower rate of bleeding or thromboembolic events after M-MVR, leading to our conclusion. The aforementioned discussion focuses only on initial MVR patients. We also observed younger patients who underwent redo MVR. From our experience, we confirmed that there is currently an increasing number of redo valvular surgeries. Nonetheless, the choice of valve type in redo surgery has not been discussed. A possible reason for this is that we cannot expect long-term survival due to high mortality and comorbidity rates after redo surgery. In fact, hospital mortality rate for redo valvular surgery remained high, and it reached up to 7.8% for mitral procedures [11]. However, our previous report revealed that the hospital mortality rate including all the valvular procedures was 6.7% [5]. Furthermore, in the past 6 years (between 2010 and 2015), the mortality rate dramatically decreased to 3.2% [7], which suggests that mortality rate in this type of surgery is apparently improving. In addition, long-term survival rates at 5, 10 and 15 years were 83.6 ± 2.2%, 70.7 ± 3.4% and 61.5 ± 4.5%, respectively. These survival rates after redo valvular surgery are similar to those published in previous studies focusing only on patients who underwent initial MVR [12–15]. With regard to the choice of valve, the same evaluation should be performed for younger patients undergoing redo MVR. This study focused on late outcomes in patients aged 50–69 years who underwent redo MVR. The main findings were lower survival rate and freedom from valve-related events in patients who received biological valves. Survival rates in M-MVR were significantly higher than those in B-MVR (log-rank test, P = 0.0072). The age of patients in redo surgery and the number of redo surgeries were not associated with lower survival. Survival rate in B-MVR dropped dramatically 5 years after redo surgery, although no reoperation due to SVD was observed during the follow-up period. Bleeding (n = 2) and cerebral infarction (n = 1) in B-MVR were associated with late death. As Chikwe et al. [15] described, stroke and major bleeding events were associated with increased 30-day mortality. Similar to this study, these events were responsible for lowering late survival in B-MVR. Two patients who experienced gastrointestinal bleeding and cerebral infarction during the follow-up period in B-MVR took warfarin for chronic atrial fibrillation preoperatively. With indications for anticoagulation, the use of biological valves did not prevent anticoagulant therapy. This is one explanation as to why the biological valve group had a bleeding risk similar to that of the mechanical valve group [16]. In this study, all the patients with atrial fibrillation did not receive a mechanical valve in redo surgery because we could lower the value of PT-INR in B-MVR when compared with M-MVR, even in the setting of atrial fibrillation. The issue of atrial fibrillation did not affect valve selection. We could detect a biological valve in redo MVR (P = 0.0206, hazard ratio = 3.402, 95% confidence interval 1.207–9.591) as a negative predictor of survival. Published data by Kaneko et al. support this finding [14]. Age and the number of redo surgeries were not associated with late survival in this study. With regard to early mortality, explanting mechanical valves in redo surgery was associated with higher mortality rate than biological valves due to different mode of failure and presentation [16]. This result is similar to our finding. Among 5 hospital deaths, all had undergone M-MVR previously. Although explanting mechanical valves might affect early outcomes, it was not found to be associated with late survival. As a result of 1 or more previous MVRs, mitral annulus becomes damaged and may not be strong enough to hold the new prosthetic valves. Surrounding structures also may become damaged during valve implantation. In these cases, reconstruction of the mitral annulus using glutaraldehyde-fixed bovine pericardium makes reoperative MVR safer [17]. Limitations This study has some limitations. The 1st limitation is that this study was a retrospective analysis of redo valvular surgery over the past 25 years. During this period, 2 surgeons used different surgical strategies, and the durability of the biological valves, selection bias of surgical techniques applied, patterns of usage of mechanical over biological valves and pre/postoperative management of patients has changed. The 2nd limitation is that the sample cohort was small with only 66 patients receiving redo MVR. The 3rd is that underestimations of late bleeding or thromboembolic events are possible because we cannot follow-up all the patients carefully, and subsequent events also cannot be followed up. To balance the clinical characteristics of the 2 groups, we used propensity score adjustment with inverse probability weighting approach using the R software, version 3.4.3 (R Foundation for Statistical Computing, Vienna, Austria). We used a logistic regression model based on patient age, history of liver cirrhosis or stroke to estimate the propensity score. Even after propensity score adjustment, patients with mechanical valve had a lower risk of survival (P < 0.001, hazard ratio = 0.227, 95% confidence interval 0.125–0.410). We showed our experience of redo MVR with late outcomes based on valve types implanted. It would seem that redo MVR using a mechanical valve was associated with better early and late outcomes in this age group. Conflict of interest: none declared. REFERENCES 1 Nishimura RA, Otto CM, Bonow RO, Carabello BA, Erwin JP, Guyton RA et al.   2014 AHA/ACC guideline for the management of patients with valvular heart disease. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation  2014; 129: e521– 643. Google Scholar CrossRef Search ADS PubMed  2 Oxenham H, Bloomfield P, Wheatley DJ, Lee RJ, Cunningham J, Prescott RJ et al.   Twenty year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses. Heart  2003; 89: 715– 21. Google Scholar CrossRef Search ADS PubMed  3 Stassano P, Tommaso LD, Monaco M, Iorio F, Pepino P, Spampinato N et al.   Aortic valve replacement: a prospective randomized evaluation of mechanical versus biological valves in patients ages 55 to 70 years. 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Interactive CardioVascular and Thoracic SurgeryOxford University Press

Published: Mar 29, 2018

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