Functinal mitral regurgitation (FMR) in patients with ischemic cardiomyopathy is associated with increased morbidity and mortality. Clinical guidelines recommend restrictive mitral annuloplasty (RMA) or mitral valve replacement (MVR) in patients with severe FMR undergoing CABG. However, in cases of moderate FMR, the decision to address the mitral valve concomitantly with coronary intervention remains controversial. Some authors propose that revascularization alone promotes left ventricular (LV) remodeling and improves mitral regurgitation (MR), while others advocate for annuloplasty or valve replacement with a prosthesis. Numerous studies supporting these theories continue to fuel the open debate. 

This article evaluates the reduction in LV end-systolic volume (LVESV) in patients diagnosed with FMR and undergoing CABG with RMA. The outcomes were assessed via transthoracic echocardiography (TTE) one year after the procedure. This retrospective study includes a total of 157 patients with ischemic LV dilation, treated over a 10-year period (1995-2015). Of the total study group, 84 patients (54%) had FMR (8% mild, 58% moderate, and 33% severe) and underwent concurrent RMA with CABG (regardless of regurgitation severity), while 73 patients were treated with CABG alone. In all cases, the decision to proceed with revascularization was made by the surgeon (with or without cardiopulmonary bypass, graft type and number, etc.). 

At one year post-surgery, TTE was performed to evaluate the reduction in LV end-systolic volume. A significant reduction was observed in the group of patients who underwent CABG+RMA compared to those who underwent only CABG (from 32 to 15 mL/m² and from 37 to 21 mL/m², respectively). Improvement in ejection fraction (EF) was more pronounced in the CABG+RMA group compared to the “CABG only” group, although the results were not statistically significant (44% vs. 39% in the CABG+RMA group and “CABG only” group, respectively). No differences in survival were observed between the two groups. 

The authors conclude that patients undergoing CABG+RMA experience a significant reduction in LV end-systolic volume compared to those treated with CABG alone, recommending this surgical approach while acknowledging the need for further studies to determine the impact of RMA on patient survival. 

COMMENTARY: 

The controversy surrounding the optimal surgical approach for patients with coronary artery disease and moderate FMR has existed since I began my residency in cardiac surgery. Despite many years, the debate remains unresolved, with decision-making varying by institution and often based on studies from experienced centers or older trends referenced in classical surgical texts. In my view, the study by Misumi et al. fails to categorically clarify any uncertainties on the matter. 

In the present article, the authors conclude that for patients with FMR and ischemic heart disease indicated for coronary surgery, restrictive annuloplasty should be performed, as one year post-intervention shows significant LV reverse remodeling. However, the study design has notable gaps and raises many questions. First, this is a non-randomized study, and the groups seem non-comparable, as patients with preoperative FMR have higher morbidity and a higher EuroSCORE II compared to the “CABG only” group. Nonetheless, this did not correlate with poorer mortality outcomes. 

The criteria for performing annuloplasty remain unclear. Notably, seven patients (8%) in the CABG+RMA group with mild preoperative MR underwent reductive annuloplasty. The author justifies this as these patients had a “history of prior hospitalizations and exacerbations of their MR,” a somewhat unconvincing rationale. Was a mitral valve procedure really necessary, or could they have improved with CABG alone? Indeed, it is notable that CABG alone led to a reduction in LV end-systolic volume. This effect warrants consideration of the isolated impact of revascularization or optimized medical therapy (diuretics, neurohormonal agents) post-surgery. 

Regarding the mitral valve (MV) technique employed, the author notes that “undersizing of the valve was left to the surgeon’s discretion,” acknowledging that “the most commonly used technique was a two-size ring reduction.” Additionally, “up to 8% underwent papillary muscle approximation also based on the surgeon’s criteria.” While the outcomes are commendable (only 10% residual MR at any degree one year post-procedure is reported in the results section), the study conveys a sense of case heterogeneity and high surgical variability. It is also noteworthy that many patients underwent additional concurrent procedures, such as tricuspid annuloplasty (52%) and atrial fibrillation surgery (14.2%), which could impact overall results. Furthermore, there is a lack of information on surgical times. It would be of interest to evaluate whether the aortic cross-clamp time added by addressing the mitral valve is offset by improved functional class and/or patient survival, particularly in those with moderate FMR. 

While the authors demonstrate the effectiveness of RMA in reducing LV volumes one year post-surgery, the improvement in LVEF was not significant in the annuloplasty group, nor did it appear to impact survival. Does this justify a mitral procedure if the MR is moderate? As noted in the discussion section, previous randomized studies have shown mixed results in this regard. So, what should we do? 

Misumi et al. define a significant LV end-systolic volume index (LVESVI) reduction as equal to or greater than 27%. Among the groups, reverse remodeling was achieved in 68% of the CABG+RMA group and 38% of the “CABG only” group. For the subgroup of patients with moderate FMR (49 patients), 63.2% achieved significant reverse remodeling, a noteworthy finding despite its limited impact on clinical variables. Why was significant reverse remodeling not achieved in the remaining cases? Was the surgical effort worthwhile? For those with severe MR, might some of these patients be better suited for mitral valve replacement? Will these results hold over time? 

The authors openly acknowledge the limitations of their study, an honesty we appreciate. They consider the sample size small and note the need for a prospective, randomized study. It is unfortunate that LV volumes were not evaluated with additional imaging modalities, such 08as cardiac MRI, one year post-procedure. Misumi et al. leave many questions unanswered, and I fear the debate remains open. 

REFERENCE: 

Misumi Y, Kainuma S, Toda K, Miyagawa S, Yoshioka D, Hirayama A, et al; with the Osaka Cardiovascular Surgery Research study group. Restrictive annuloplasty on remodeling and survival in patients with end-stage ischemic cardiomyopathy. J Thorac Cardiovasc Surg. 2024 Mar;167(3):1008-1019.e2. doi: 10.1016/j.jtcvs.2022.04.049.