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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 32  |  Issue : 2  |  Page : 592-598

Clinical implications of moderate ischemic mitral regurgitation in patients undergoing coronary artery bypass grafting


1 Department of Cardiothoracic Surgery, Faculty of Medicine, Menoufia University, Shibin-El-Kom, Egypt
2 Department of Cardiothoracic Surgery, National Heart Institute, Cairo, Egypt
3 Department of Cardiac Surgery, El-Mahalla Cardiac Center, El-Mahalla El-Kubra, Gharbia Governorate, Egypt

Date of Submission02-Oct-2017
Date of Acceptance19-Nov-2017
Date of Web Publication25-Jun-2019

Correspondence Address:
Yasser F Asswaf
El-Mahalla El-Kubra 31951, Gharbia Governorate
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_690_17

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  Abstract 


Objective
The aim of this study was to explore the fate of moderate ischemic mitral regurgitation (IMR) following isolated coronary artery bypass grafting (CABG).
Background
IMR is a frequently encountered problem seen in patients with coronary artery disease. A much-debated question is whether surgical revascularization alone will correct moderate (2+) IMR in such patients.
Patients and methods
The study group included 20 patients with moderate IMR associated with coronary artery disease undergoing isolated CABG. All patients had an ejection fraction of more than 30%. The patients were clinically and echocardiographically evaluated preoperatively, 1 week postoperatively and at 3- and 6-month intervals.
Results
CABG alone reduced the degree of IMR in 12 (60%) patients, did not improve it in five (25%) patients, and increased its degree to 3–4 + in three (15%) patients at 6-month follow-up echocardiography. Our study showed improved functional capacity of the patients. A significant reduction in the New York Heart Association functional class was observed. The mean preoperative value for New York Heart Association was 2.45 ± 0.51 versus 2.05 ± 0.88 postoperatively (P = 0.042). Some important variables showed a role in the progression of IMR. These were: left ventricular end-systolic dimension, left ventricular end-diastolic dimension, preoperative ejection fraction%, and failure to graft the diseased right coronary system.
Conclusion
The presence of moderate IMR in patients undergoing revascularization alone does not add additional burden to the operative risk nor does it affect the short-term outcome of these patients.

Keywords: coronary artery bypass grafting, echocardiography, mitral valve insufficiency


How to cite this article:
Dokhan AL, Taher AH, El-Hag-Aly MA, Asswaf YF. Clinical implications of moderate ischemic mitral regurgitation in patients undergoing coronary artery bypass grafting. Menoufia Med J 2019;32:592-8

How to cite this URL:
Dokhan AL, Taher AH, El-Hag-Aly MA, Asswaf YF. Clinical implications of moderate ischemic mitral regurgitation in patients undergoing coronary artery bypass grafting. Menoufia Med J [serial online] 2019 [cited 2019 Sep 20];32:592-8. Available from: http://www.mmj.eg.net/text.asp?2019/32/2/592/260912




  Introduction Top


Ischemic mitral regurgitation (IMR) is an observed complication in up to 40% of patients affected by coronary artery disease (CAD) and those undergoing coronary artery bypass grafting (CABG) surgeries. It is associated with a 5-year mortality of 62%[1],[2].

In chronic IMR, the leaflets and subvalvular apparatus appear normal. It is, therefore, a ventricular problem, which depends on the left ventricular (LV) size and geometry. Adverse LV remodeling is the fundamental mechanism producing incomplete leaflet coaptation[3]. This pathological process significantly influences the papillary muscles and the mitral annulus. After myocardial ischemia, LV remodeling may result in papillary muscle displacement away from the mitral annulus. The mitral valve leaflets become tethered and their motion is restricted. In addition, the LV becomes more spherical in shape and the global LV dilatation may cause annular enlargement and distortion[4],[5].

Moderate IMR has been shown to regress after CABG due to a reduction in LV size[6]. Uncorrected IMR following CABG has a potential impact on prognosis. Different descriptions have resulted in heterogeneous patient groups, which in turn complicate comparisons between studies[7],[8].

As a result of the confounding terminology, chronic IMR has been defined as that occurring more than 1 week after myocardial infarction (MI) with: (i) LV segmental wall motion abnormalities; (ii) significant CAD in the territory supplying the wall motion abnormality; and (iii) structurally normal mitral valve leaflets and the chordae tendineae. This definition should ensure homogeneity of patient populations and facilitate comparison between studies[5],[7].

Many studies have proved that IMR is associated with reduced survival. Mortality risk is directly related to the degree of IMR; those with more severe MR have the greatest reduction in survival. This effect is particularly pronounced in patients with an ejection fraction (EF) of less than 40%[9],[10].

Till now the decision to correct moderate IMR is left solely to the surgeon and is institution dependent. The recently published European guidelines did not resolve the controversy regarding the optimal surgical approach of moderate IMR in patients undergoing CABG. This is because of the limited data regarding chronic secondary mitral regurgitation (MR) and the lower level of evidence for treatment recommendations for this condition[11].

We investigated the course of unrepaired moderate IMR, after CABG surgery solely, to predict its fate.


  Patients and Methods Top


In this prospective study, 20 consecutive patients with multivessel CAD associated with moderate IMR comprise the study group. Patients were admitted to Mahalla Cardiac Center, for CABG during the period between April 2013 and October 2015.

This study was approved by the ethics committee of our local organization and each patient signed an informed consent form after a brief explanation of the operation and its consequences.

Inclusion criteria

All patients with moderate IMR undergoing CABG were enrolled into our study. The degree of MR was verified as moderate if on preoperative transthoracic echocardiography (TTE), the regurgitant jet area was estimated to be 4–8 cm2.

The ischemic etiology of MR was verified by: a frank history and coronary angiographic evidence of ischemic heart disease (IHD), absence of any history of valvular disease preceding the onset of IHD, presence of structurally normal mitral valve leaflets and chordae tendineae on resting preoperative TTE and by the absence of TTE stigmata of rheumatic, infective, degenerative, or congenital mitral valve disease.

Preoperative evaluation

All patients were thoroughly evaluated preoperatively and the following echocardiographic data were collected: LV size, left atrial (LA) dimension, MR grade, and EF.

Exclusion criteria

The following patients were excluded from the study; patients with other etiologies for MR, mild or severe degrees of IMR, emergency cases, EF of less than 30%, concomitant mitral stenosis, other valvular pathologies requiring intervention, associated LV aneurysm or ischemic ventricular septal defects, recent infarction in the last month, severe associated comorbidities such as severe hepatic, renal, or respiratory impairment and patients with CABG reoperations.

Intraoperative evaluation

In all the patients, routine anesthetic techniques were used. After median sternotomy, harvesting of the left internal mammary artery (LIMA) was done. Concomitantly, harvesting of the great saphenous vein took place. After cardioplegia, a continuous technique was utilized to perform the distal anastomoses using a no. 7/0 polypropylene suture. A vascular side occlusion clamp was applied to the proximal ascending aorta to perform proximal anastomoses. Polypropylene 6/0 suture using a continuous technique was utilized to perform proximal anastomoses.

The following variables were recorded in the operative technique: the number of grafts done, use of the LIMA to the left anterior descending coronary artery and whether the right coronary system was grafted or not, the total bypass and cross-clamp times. All the patients were transferred to the cardiothoracic ICU and were mechanically ventilated.

Postoperative evaluation

We collected data about postoperative hemodynamics, mechanical ventilation period, inotropic support, need for a postoperative intra-aortic balloon pump, total ICU stay, and complications, if present.

Follow-up

In addition to clinical evaluation, echocardiography was done at 1 week following CABG, at 3- and 6-month intervals.

Statistical analysis

The results were expressed as mean of SD or n (%). Comparison between preoperative and postoperative data was performed using paired Student's t-test. The quantitative data were examined by Kolmogrov–Smirnov test for normality of data. Categorical variables were compared using χ2 analysis for testing the independency. One-way analysis of variance test was used for multivariate continuous normally distributed data. The data were considered significant if P values were equal to or less than 0.05; values of up to 0.01 were considered highly significant. Statistical analysis was performed with the aid of the IBM statistical package for social science, version 24 (IBM Corporation, Armonk, New York, USA).


  Results Top


The mean age of the study group was 65 ± 2.5 years with a predominance of men 65% (13 patients). Diabetes mellitus was present in nine (45%) patients, hypertension in 13 (65%) patients, dyslipidemia in 12 (60%) patients, and smoking in eight (40%) patients. Cardiac examination showed murmur in only nine (45%) patients. The ECG showed that 80% of the patients had MI, of whom nine had posterior MI, five had anterior, and two had extensive MI [Table 1].
Table 1: Preoperative demographics of the studied population

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All the patients were submitted to CABG alone. The mean total bypass time was 85 ± 2 min and the mean cross-clamp time was 55.5 ± 14.8 min [Figure 1]. LIMA was used for all patients. The total ICU stay was 40 ± 7 h. The mean period of mechanical ventilation was 15 ± 5 h and inotropic support was 20.7 ± 13.1 h [Figure 2].
Figure 1: Operative data. The figure represents intraoperative details including total bypass time, cross-clamp time, and operation time (min).

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Figure 2: ICU data. The figure represents ICU details including mean length of ICU stay, mean durations for mechanical ventilation, and inotropic support (h).

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The postoperative morbidity included: two cases of exploration for bleeding, three cases of atrial fibrillation, one case of wound infection and renal insufficiency did not occur in any patient [Figure 3].
Figure 3: Postoperative morbidity and mortality. The figure represents the incidence of postoperative complications in our study cohort.

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Clinical and echocardiographic follow-up was complete in 100% of patients. Collected echocardiographic data were compared. The preoperative echocardiographic data showed a mean left ventricular end-systolic dimension (LVESD) of 4.1 ± 0.4 cm, a mean left ventricular end-diastolic dimension (LVEDD) of 5.7 ± 0.1 cm, a mean LA dimension of 4 ± 0.5 cm and a mean EF of 54 ± 4% [Table 2].
Table 2: Echocardiographic data obtained during the study

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Echocardiography was done for all patients at 1 week. The mean LVESD was 4.1 ± 0.1 cm, mean LVEDD was 5.1 ± 0.95 cm, mean LA dimension was 4 ± 0.1 cm, and the mean EF was 55.3 ± 2.5%. There were very minute differences in postoperative LVEDD, LVESD, and LA dimensions as compared with the preoperative echocardiography. There was, however, an improvement in the EF [Table 2].

Three-month follow-up echocardiographic data showed a mean LVESD of 3.9 ± 0.2 cm, mean LVEDD of 5.5 ± 0.2 cm, mean LA dimension of 3.9 ± 0.1 cm, and a mean EF of 58.5 ± 2.4%. After 6 months, the mean cardiac dimensions were significantly decreased to 5.3 ± 0.2 cm for LVEDD (P = 0.025), 3.8 ± 0.2 cm for LVESD (P = 0.049), and 3.9 ± 0.1 cm for LA diameter (P = 0.039). The mean EF significantly improved to 59 ± 2.2% (P = 0.021) [Table 2].

The degree of MR as measured in the 3-month follow-up echocardiography was: 0–1+ in 13 (65%) patients, 2+ in five (25%) patients, and increased to 3–4+ in two (10%) patients. The mean value for the degree of MR (1.45 ± 0.47) was decreased in a highly statistically significant way (P = 0.00198) [Table 3]. The degree of MR was echocardiographically measured after 6 months. CABG alone corrected IMR to 0–1+ in 12 (60%) patients. It, however, failed to do so in the remaining eight patients (five cases remained in 2+ and three progressed to 3–4+). The mean value for MR (1.55 ± 0.75) showed a statistically significant improvement (P = 0.0157) [Table 3].
Table 3: Degree of mitral regurgitation at postoperative 3- and 6-month follow-up period

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In assessing the patient functional state at 3 months, dyspnea improvement was observed in six (30%) patients, they had dyspnea New York Heart Association (NYHA) class I. Twelve (60%) patients had NYHA class II, one (5%) patient NYHA class III, and one (5%) patient NYHA class IV. The mean NYHA (1.85 ± 0.74) showed a highly statistically significant value of (P = 0.0075). After 6 months, dyspnea was found to be as follows: five (25%) patients having dyspnea NYHA class I, 11 (55%) patients NYHA class II, two (10%) patients NYHA class III, and two (10%) patients NYHA class IV. The mean value of the NYHA class (2.05 ± 0.88) elucidated a statistically significant difference (P = 0.042) [Table 4].
Table 4: New York Heart Association functional state during the study

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Using Spearman's rank correlation coefficient, we detected a relation between preoperative LV profile and the postoperative degree of IMR and its progression. Increased preoperative cardiac dimensions and decreased EF were associated with a tendency to postoperative worsening of IMR degree. A highly statistically significant positive correlation was found between preoperative LVEDD and the grade of IMR after CABG (r = 0.640, P = 0.001). Patients with increased preoperative LVEDD tended to have more liability for the deterioration of their post-CABG IMR degree. In addition, a statistically significant positive correlation was observed between preoperative LVESD and the post-CABG grade of IMR (r = 0.352, P = 0.026). A highly statistically significant negative correlation was found between the preoperative EF% (r = −0.533, P = 0.001), grafting of the right coronary system (r = −0.560, P = 0.001), and the grade of IMR after CABG [Table 5] and [Figure 4].
Table 5: Correlation between ischemic mitral regurgitation grade follow-up and different variables

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Figure 4: Correlation between ischemic mitral regurgitation grade follow-up and different variables. Preoperative EDD (r = 0.640; P < 0.001) (a), ESD (r = 0.352; P < 0.026) (b), preoperative EF (r = -0.533; P < 0.001) (c). EDD, end-diastolic dimension; EF, ejection fraction; ESD, end-systolic dimension; MR, mitral regurgitation.

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  Discussion Top


There is a general consensus that patients with severe IMR should undergo mitral valve surgery in addition to CABG. However, the optimal management of moderate IMR is still debated. Clinical studies have a diverse fate of moderate IMR following CABG alone[1].

Our patients represented a homogeneous sample regarding their preoperative profile. All of the included patients in the study by Lam et al.[12] had a previous MI as opposed to 80% in ours. Fifty-three percent of their patients had moderate to severe LV dysfunction (EF < 40%), and 6% of them had preoperative atrial fibrillation as opposed to none in our series. It was found that 45 and 25% of our patients had previous posteroinferior and anterior infarctions, respectively. Although anterior infarctions are common to occur in IHD patients, the occurrence of IMR is more common after a posteroinferior MI[13].

Although we had no mortality in our study group, some authors demonstrated increased perioperative mortality of patients with moderate IMR undergoing isolated CABG surgery. Our patients had a good preoperative clinical profile with no major comorbidities, preserved EF, and short operative time. Compared with other series, Kim et al.[3] reported a mortality rate of 4.2% (seven of the 168 patient cohort). The causes of death were cardiac in four and noncardiac in three patients. The authors reported a mean pump time of 1.4 ± 0.8 h and a mean cross-clamp time of 1.0 ± 0.6 h; these values were prolonged when compared with ours. They reported a mean number of bypass grafts of 3.0 ± 1.0. Fifty-one percent of their patients had severe MR, 15% had renal insufficiency, and 6% had prior CABG, in contrast to none in our series. Operative mortality was reported by many series to range from 9.5 to 15% when revascularization is combined with mitral valve repair (MVr), in comparison with 3–4% for revascularization alone.

We observed that CABG alone was able to decrease preoperative moderate IMR to mild or absent in 60% of patients. The grade remained moderate in 25% and increased in only 15% of cases. There is a discrepancy in the literature as to agreement with these results.

Lam et al.[12] reported a 22% progression to severe IMR in patients with moderate IMR undergoing CABG alone. By contrast, Tolis et al.[14] reported 49 patients undergoing CABG alone for mild to moderate IMR and showed improvement of MR mean grade from 1.73 to 0.54. The authors agree with our results. In their patients, EF improved from 22.0 to 31.5% after CABG.

This outcome variation is related to the completeness of revascularization and to the LV contractile reserve. CABG will restore viable LV segments in the region of papillary muscle attachment and thus may relieve tethering of the mitral valve[15].

Moderate or severe MR was reported by Smith et al.[16] in 31% of patients, whereas 69% had improvement in the CABG-alone group. On the contrary, studies by Hung et al.[17] and McGee et al.[18] reported up to one-third of patients to have a recurrence of moderate or even progression to severe MR in the combined CABG+MVr group.

We found a positive correlation between LVEDD and LVESD on one side and grade of postoperative IMR on the other side. A negative correlation was found between the preoperative EF%, grafting of the right coronary system and the grade of IMR. This refers to the fact that patients in whom IMR does not improve are those with a sicker ventricle preoperatively. Larger ventricles are less liable to undergo reverse remodeling and thus preoperative LVEDD may be considered as a predictor of outcome, reverse remodeling, and improvement of IMR.

The mean NYHA functional class was significantly improved over a 6-month follow-up. Similarly, Altarabsheh et al.[19], in a meta-analysis of more than 1450 patients, compared the clinical outcome of isolated CABG and concomitant MVr. The authors demonstrated the same functional class in the two groups irrespective of the surgery.

Our results are partially consistent with Smith et al.[16], who reported the results of the Cardiothoracic Surgical Network Trial. A number of 151 patients with moderate IMR were included in the CABG-alone arm versus 150 in the combined procedure arm. Significant reductions in the LV end-systolic volume index were revealed in both arms of the trial, but the addition of MVr did not result in a higher degree of LV reverse remodeling. Overall, 69% of patients in the CABG-alone group had no or mild MR, as compared with 89% in the combined procedure group. Thus, many of the Cardiothoracic Surgical Network investigators support CABG alone for the management of moderate IMR. Similar to our results, clinical outcomes, including functional status, quality of life, and mortality improved in the study population.

In the Randomized Ischemic Mitral Evaluation Trial, Chan et al.[20] studied 73 patients with moderate IMR. Patients undergoing CABG+MVr had a median NYHA functional class of I, compared with a median class of II in the isolated CABG group. Patients undergoing CABG+MVr had a 22% increase in peak oxygen consumption, which was utilized as a measure of functional capacity, in contrast to a 5% increase in the isolated CABG group. Although no distinction in overall survival between groups was discovered, the study supported the addition of MVr to CABG.


  Conclusion Top


The presence of moderate IMR in patients undergoing revascularization alone does not add additional burden to the operative risk or short-term outcome. Myocardial revascularization alone without additional maneuvers directed to the mitral valve may be sufficient to ameliorate the degree of moderate IMR, especially in patients with good preoperative LV profile. This is translated into an improvement in the functional class and the quality of life postoperatively. Moderate IMR progresses to severe grades in a limited number of patients (15%, three out of 20) during the 6-month follow-up period. A larger LV size, lower EF, and failure to graft the right coronary artery territory can lead to the persistence or progression of moderate IMR following isolated CABG.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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2.
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3.
Kim YH, Czer LS, Soukiasian HJ, de Robertis M, Magliato KE, Blanche C, et al. Ischemic mitral regurgitation: revascularization alone versus revascularization and mitral valve repair. Ann Thorac Surg 2005; 79:1895–1901.  Back to cited text no. 3
    
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LaPar DJ, Acker MA, Gelijns AC, Kron IL. Repair or replace for severe ischemic mitral regurgitation: prospective randomized multicenter data. Ann Cardiothorac Surg 2015; 4:411–416.  Back to cited text no. 4
    
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Hernandez-Vaquero D, Díaz R, Álvarez-Cabo R, Vigil-Escalera C, Silva J. Editorial: mitral valve repair for moderate ischemic mitral regurgitation. JThorac Dis2016; 8:1410–1413.  Back to cited text no. 5
    
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Borger MA, Alam A, Murphy PM, Doenst T, David TE. Chronic ischaemic mitral regurgitation: repair, replace or rethink? Ann Thorac Surg 2006; 81:1153–1161.  Back to cited text no. 7
    
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Charles EJ, Kron IL. Data not Dogma for ischemic mitral regurgitation. J Thorac Cardiovasc Surg 2017; 154:137–138.  Back to cited text no. 8
    
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Trichon BH, Felker GM, Shaw LK, Cabell CH, O'Connor CM. Relation of frequency and severity of mitral regurgitation to survival among patients with left ventricular systolic dysfunction and heart failure. Am J Cardiol 2003; 91:538–543.  Back to cited text no. 9
    
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Ellis SG, Whitlow PL, Raymond RE, Schneider JP. Impact of mitral regurgitation on long-term survival after percutaneous coronary intervention. Am J Cardiol 2002; 89:315–318.  Back to cited text no. 10
    
11.
Baumgartner H, Falk V, Bax JJ, de Bonis M, Hamm C, Holm PJ, et al. 2017 ESC/EACTS Guidelines for the management of valvular heart disease. The Task Force for the Management of Valvular Heart Disease of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS). Eur Heart J 2017; 00:1–53.  Back to cited text no. 11
    
12.
Lam BK, Gillinov AM, Blackstone EH, Rajeswaran J, Yuh B, Bhudia SK, et al. Importance of moderate ischaemic mitral regurgitation. Ann Thorac Surg 2005; 79:462–470.  Back to cited text no. 12
    
13.
Calafiore AM, di Mauro M, Gallina S, di Giammarco G, Iacò AL, Teodori G, et al. Mitral valve surgery for chronic ischaemic mitral regurgitation. Ann Thorac Surg 2004; 77:1989–1997.  Back to cited text no. 13
    
14.
Tolis GA, Korkolis DP, Kopf GS, Elefteriades JA. Revascularization alone (without mitral valve repair) suffices in patients with advanced ischemic cardiomyopathy and mild moderate mitral regurgitation. Ann Thorac Surg 2002; 74:1476–1481.  Back to cited text no. 14
    
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Campwala SZ, Bansal RC, Wang N, Razzouk A, Pai RG. Mitral regurgitation progression following isolated coronary artery bypass surgery: frequency, risk factors, and potential prevention strategies. Eur J Cardiothorac Surg 2006; 29:348–354.  Back to cited text no. 15
    
16.
Smith PK, Puskas JD, Ascheim DP, Voisine P, Gelijns AC, Moskowitz AJ, et al. Surgical treatment of moderate ischemic mitral regurgitation. N Engl J Med 2014; 371:2178–2188.  Back to cited text no. 16
    
17.
Hung J, Papakostas L, Tahta SA, Hardy BG, Bollen BA, Duran CM, et al. Mechanism of recurrent ischemic mitral regurgitation after annuloplasty: continued LV remodeling as a moving target. Circulation 2004; 110:85–90.  Back to cited text no. 17
    
18.
McGee EC, Gillinov AM, Blackstone EH, Rajeswaran J, Cohen G, Najam F, et al. Recurrent mitral regurgitation after annuloplasty for functional ischaemic mitral regurgitation. J Thorac Cardiovasc Surg 2004; 128:916–924.  Back to cited text no. 18
    
19.
Altarabsheh SE, Deo SV, Dunlay SM, Erwin PJ, Obeidat YM, Navale S, et al. Meta-analysis of usefulness of concomitant mitral valve repair or replacement for moderate ischemic mitral regurgitation with coronary artery bypass grafting. Am J Cardiol 2017; 119:734–741.  Back to cited text no. 19
    
20.
Chan KM, Punjabi PP, Flather M, Wage R, Symmonds K, Roussin I, et al. Coronary artery bypass surgery with or without mitral valve annuloplasty in moderate functional ischemic mitral regurgitation final results of the Randomized Ischemic Mitral Evaluation (RIME) trial. Circulation 2012; 126:2502–2510.  Back to cited text no. 20
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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