The RIME trial: Are we closer to the answer of when to repair ischemic mitral regurgitation?

Abstract

BACKGROUND The development of mitral valve regurgitation as a result of left ventricular remodelling following myocardial infarction carries adverse implications on survival and quality of life (QOL). There is uncertainty whether mitral valve repair at the time of surgical revascularization improves survival and quality of life and enhances left ventricular reverse remodelling in patients with moderate ischemic mitral regurgitation (IMR). The Randomized Ischemic Mitral Evaluation (RIME) trial investigators tried to address this issue by studying whether repairing moderate IMR at the time of surgical revascularization can lead to more favourable outcomes compared with surgical revascularization only. Results of this multicentre, randomized, controlled trial were recently published in Circulation. 1 RIME was conducted in 6 centres in the UK and one in Poland. Out of 172 patients referred for CABG with moderate IMR, the RIME investigators randomized 73 eligible patients to receive either CABG alone (CABG group; n ¼ 39 patients) or CABG with mitral valve repair (Repair group; n ¼ 34 patients) The primary end-point was oxygen consumption at maximal exercise (VO2Max) measured by cardiopulmonary exercise testing, as an objective measure of functional capacity, at one year. The secondary end-points were left ventricular end-systolic volume indexed to body surface area (LVESVI) and mitral regurgitation volume as well as plasma B-type natriuretic peptide (BNP). All measurement were performed before enrollment and at one year postoperatively. Moderate IMR was defined by echocardiographically derived quantitative measures – namely regurgitant orifice area, regurgitant volume and vena contracta width – as per the ACC/AHA/ASE Valvular Heart Disease Guidelines. Patients were considered eligible if they met any of the above criteria whether at rest or during exercise. 2 Patients were excluded if they had ejection fraction ,30%, structural mitral valve disease (including papillary muscle rupture), significant aortic valve disease, previous or active endocarditis, previous cardiac surgery, unstable angina, symptoms of advanced heart failure or cardiogenic shock or significant comorbidities like liver or renal impairment and chronic obstructive airway disease. All CABG procedures utilized the left internal mammary artery to graft the left anterior descending coronary artery All technically graftable, significantly narrowed coronary arteries were addressed. Mitral repair was performed using a complete annuloplasty ring with the aim of achieving a leaflet coaptation length of at least 8mm and no or trace mitral regurgitation at the end of the operation. Both groups received similar number of grafts but the repair group expectedly had longer bypass and cross clamp times compared to the CABG group. The trial met all its end points with high statistical significance at the proposed follow up period of one year. The primary end point of change in peak oxygen consumption (Peak VO2) showed significant improvement at 1 year. The Peak VO2 in the repair group increased by 22% (from 14.8 ^ 3.2 to 18.1 ^ 2.9mL/kg/min) while the CABG group only increased by 5% (from 15.1 ^ 3.3 to