Discussion On Common Problems In Surgical Treatment Of Severe Ischemic Mitral Regurgitation

Ischemic mitral regurgitation(IMR),which results from functional valve incompetence due to myocardial injury and adverse left ventricular remodeling,develops in approximately 50%of patients after an infarction.The leaflets themselves are normal,and the disease occurs in the myocardium rather than in the valve itself.IMR is a consequence of adverse left ventricular remodeling after myocardial injury with reduced closing forces,enlargement of the left ventricular chamber and mitral annulus,apical and lateral migration of the papillary muscles,and leaflet tethering.These processes lead to malcoaptation of the leaflets and variable degrees of mitral regurgitation that can fluctuate dynamically as a function of volume status.Practice guidelines recommend consideration of chordal-sparing replacement or mitral-valve repair for patients with severe IMR that is causing symptoms despite the best available medical therapy and,possibly cardiac resynchronization.Because of lacking conclusive evidence to indicate which of these interventions is superior,these guidelines do not specify whether to repair or replace the mitral valve.2016 update to the american association for thoracic surgery consensus guidelines on IMR indicated that:MV surgery is reasonable at time of other cardiac surgery(e.g.,CABG,AVR)(COR Ⅱa,LOE C),MV surgery may be considered as an isolated procedure for treatment of patients with severe symptoms(NYHA III/IV)despite GDMT(COR Ⅱb,LOE C).① Mitral valve replacement(MVR)is reasonable in patients with severe IMR who remain symptomatic despite Guidelinedirected medial and cardiac device therapy,and who have a basal aneurysm/dyskinesis,significant leaflet tethering,and/or severe left ventricle dilation(LVEDD>6.5 cm)(COR Ⅱa,LOE B).②Mitral valve repair with an undersized complete rigid annuloplasty ring may be considered in patients with severe IMR who remain symptomatic despite Guideline-directed medical and cardiac device therapy and who do not have a basal aneurysm/dyskinesis,significant leaflet tethering,or severe left ventricle enlargement(COR Ⅱb,LOE B).However,there are various defects in the research projects on which the above guidelines are based.The most prominent problem is that the follow-up time is short,and the conclusions of the study do not fully address the specific characteristics of the patients to propose individualized treatment.Since there is currently no optimal treatment for severe IMR,we need to conduct studies to further investigate the treatment of severe IMR.Therefore,we retrospectively reviewed patients with severe chronic IMR admitted to our hospital who were undergoing surgical treatment between January 2002 and December 2014.We aimed to evaluate the long-term outcomes in patients with severe chronic IMR undergoing mitral valve annuloplasty(MVA)versus MVR,and then we assessed the long-term outcomes in patients with severe chronic IMR undergoing MVA,subvalvular sparing MVR,or non-subvalvular sparing MVR.Further more,we tried to predict and prevent functional mitral stenosis after MVA.In IMR,ring annuloplasty is associated with a significant rate of recurrent mitral regurgitation,and the selection of ring size is only based on intertrigonal distance which is defective.Based on those facts,we advance the notion that it is beneficial to adjust the size of ring in the perioperative period according to mitral valve function.As the size of current rings can not be adjusted perioperatively,we have successfully developed a novel adjustable annuloplasty ring which has been patented.In the present study,we aim to assess the impact of changes in the size of ring on IMR treatment to verify the effectiveness of the novel adjustable ring,as well as detect the mechanism.Furthermore,we will determine whether the current downsizing annuloplasty should not be applied to the treatment of IMR to provide suggestions for the selection of ring size.Finally,the study is expected to provides new ideas for the individualized treatment of IMR.This study is divided into three chapters to discuss:The first chapter Mitral valve annuloplasty versus replacement for severe ischemic mitral regurgitationBACKGROUND:Although practice guidelines recommend surgery for patients with severe IMR,they do not specify whether to repair or replace the mitral valve.METHODS:436 consecutive patients with severe CIMR were eligible for inclusion in the study,of which 316(72.5%)underwent MVA whereas 120(27.5%)received MVR.After adjustment for baseline differences with Cox proportional hazard model and propensity score matching,the long-term outcomes were compared.RESULTS:At 59 months(interquartile range,37-85 months)follow-up,though the left ventricle end-diastolic diameter was markedly larger(P=0.019),and the incidence of mitral regurgitation recurrence was significantly higher in the MVA group than in the MVR group(P<0.001),no significant difference was observed between the two propensity score-matched groups in overall survival,freedom from cardiac death,or avoidance of major adverse cardiac or cerebrovascular events(MACCE).MVA provides better results than MVR in freedom from cardiac death in subgroups of age≥65years and left ventricular ejection fraction(EF)≥50%(P=0.014 and P=0.016,respectively),whereas MVR was associated with a lower risk of MACCE than MVA in subgroups of age<65 years,EF<50%and left ventricular inferior basal wall motion abnormality(BWMA)(for age:P=0.010;for EF:P=0.007,and for BWMA:P=0.016).CONCLUSIONS:MVR is a suitable management of patients with severe CIMR,and it is more favorable to ventricular remodeling.The choice of MVA or MVR should depend on major high-risk clinical factors.The secend chapter Long-Term outcomes of whether preserving subvalvular structure in MVR and thecomparison with MVABACKGROUND:Although practice guidelines recommend surgery for patients with severe IMR,they do not specify whether to repair or replace the mitral valve.The purpose of this study was to evaluate the long-term outcomes in patients with severe IMR undergoing MVA、subvalvular sparing MVR、non-subvalvular sparing MVR.METHODS:436 consecutive patients with severe CIMR were eligible for inclusion in the study,of which 316(72.5%)underwent MVA whereas 120(27.5%)received MVR.Mitral leaflets were preservedwhenever possible(94/120,78.3%),with posteriorleaflet preservation in 58(48.3%)patients,posterior and partial anterior leaflet preservation in 8(6.7%)patients,and both leaflets preservation in 28(23.3%)patients.After adjustment for baseline differences with propensity score matching,the long-term outcomes were compared.RESULTS:After adjustment for baseline differences with propensity score matching,at 53 months(interquartile range,34-81 months)follow-up,there was no significant difference between MVA、subvalvular sparing MVR、non-subvalvular sparing MVR in risks of MACCE,cardiac death,or all-cause death(P>0.05).CONCLUSIONS:MVA,subvalvular sparing MVR and non-subvalvular sparing MVR are suitable management of patients with severe IMR.Considering that this study is retrospective and with a small sample size,an appropriately powered,randomized,controlled trial evaluating the optimal management ofseverelMR would be useful to confirm our results.The third chapter Predicting functional mitral stenosis after restrictive annuloplasty for ischemic mitral regurgitationBACKGROUND:Although we have realized that Restrictive mitral valve annuloplasty(MVA)may result in clinically significant functional mitral stenosis(MS),it still can’t be predicted.The purpose of this study was to identify the risk factors for clinically significant functional MS following restrictive MVA surgery for chronic ischemic mitral regurgitation(IMR).METHODS:We retrospectively reviewed 114 patients who underwent restrictive MVA with coronary artery bypass grafting(CABG)for treatment of chronic IMR.Clinically significant functional MS was defined as resting transmitral peak pressure gradient(PPG)≥13 mmHg.RESULTS:During the follow-up period(range 6-12 months),28 patients(24.56%)developed clinically significant functional MS.The PPG at follow-up was significantly higher than that measured in the early postoperative stage(3-5 days after surgery).Moreover,there was linear correlation between the two measurements(r = 0.398;P<0.001).Annuloplasty size<27 mm and early postoperative PPG>7.4 mm Hg could predict clinically significant functional MS at 6-12 months postoperatively.CONCLUSIONS:Chronic IMR patients treated with restrictive MVA and CABG have significant increase in PPG postoperatively.Annuloplasty size<27 mm and early postoperative PPG≥7.4 mm Hg can predict clinically significant functional MS at 6-12 months after surgery.The forth chapter The study on a novel adjustable mitral annuloplasty ringAt present,mitral annuloplasty has become an important way to treat IMR.Among the numerous techniques for mitral valve plasty,the use of annuloplasty ring has become more and more important,while ring annuloplasty is associated with a significant rate of recurrent mitral regurgitation,and the selection of ring size is only based on intertrigonal distance which is defective.Based on those facts,we advance the notion that it is beneficial to adjust the size of ring in the perioperative period according to mitral valve function.As the size of current rings can not be adjusted perioperatively,we have successfully developed a novel adjustable annuloplasty ring which has been patented.In the future,we will assess the impact of changes in the size of ring on IMR treatment to verify the effectiveness of the novel adjustable ring,as well as detect the mechanism.Furthermore,we will determine whether the current downsizing annuloplasty should not be applied to the treatment of IMR to provide suggestions for the selection of ring size.Finally,the study is expected to provides new ideas for the individualized treatment of IMR.