Surgical Strategies in Moderate Ischemic Mitral Insufficiency in Patients Undergoing Coronary Artery Bypass Graft

Ischemic mitral regurgitation (IMR) is a common complication of myocardial infarction, with a reported prevalence of 13-59%. Approximately one-third of these patients have at least moderate MR .

The mechanism of IMR is complex and multifactorial.IMR results from the distortion and remodeling of the left ventricle after myocardial infarction ,where the papillary muscles are displaced away from the annular plane. Coupled with annular flattening, enlargement, and decreased contraction, this spatial deformation exerts traction on the chordae tendineae, leading to mal-coaptation of the structurally normal mitral valve and subsequently to secondary MR. Furthermore, the MR-related left ventricular(LV) volume overload promotes LV remodeling, resulting in exacerbation of the MR (MR begets more MR) . Two patterns of leaflet tethering have been reported in secondary MR: asymmetric tethering and symmetric tethering. Asymmetric tethering occurs with regional LV remodeling, resulting in displacement of the posterior papillary muscle in a lateral direction. Symmetric tethering generally results from global LV remodeling, resulting in apical tethering of both the anterior and posterior papillary muscles.

Most studies show that severe IMR is not usually improved by revascularization alone and that residual MR is associated with an increased mortality risk. It is generally accepted that severe IMR should be corrected at the time of Coronary artery bypass grafting(CABG).

Surgical correction of moderate IMR at the time of coronary revascularization is still an unresolved controversy.CABG alone did reduce MR at follow-up; nevertheless, CABG alone cannot be sufficient to eliminate MR in all cases , Adding mitral valve annuloplasty to CABG may eliminate MR immediately after surgery; however, recurrent MR did occur after CABG plus mitral valve annuloplasty, and no benefit for long-term survival was observed. There was also a tendency toward higher morbidity and mortality in CABG plus mitral valve procedure as compared with CABG alone in high-risk patients with moderate IMR. The latest American Association for Thoracic Surgery (AATS)guidelines suggested that for moderate IMR, mitral valve repair with an undersized complete rigid ring annuloplasty "may be considered" during CABG surgery, but not necessarily "preferred" over revascularization alone.Therefore ,the benefits of adding mitral valve procedure to CABG for treating moderate IMR have not been clearly established.

This study is aiming to determine the short term morbidity in patients undergoing CABG alone and comparing them with patients undergoing concomitant MV repair by assessment of morbidity and mortality in both groups postoperatively .