Benefits of Mitral Valve Repair in STICH Patients: Time to Re-Evaluate a Much Maligned Therapy Option?

Abstract

Mitral regurgitation (MR) is an important complication of ischemic heart disease and is associated with increasedmortality, even when mild in extent. Understanding the pathophysiology of ischemic MR may lead to the logical conclusion that the correction of MR should improve the hemodynamic parameters of the left ventricle (LV) and consequently the clinical outcomes of such patients. Nevertheless, evidence is generally lacking that surgical correction of ischemic MR leads to demonstrable clinical benefit in patients with decreased LV function. Therefore there has been justifiable reluctance within the cardiology community to refer patients with ischemic MR for mitral valve (MV) surgery. The exact prevalence of functional MR has been difficult to estimate as a result of the heterogeneity of MR patients included in many clinical studies. However, it is known that there is a growing population with an unmet clinical need as only 5% of patients with MR and LV ejection fraction (EF) <50% receive surgical treatment. The surprisingly large positive effect of MV clipping on freedom from rehospitalization and survival in patients with functional MR, as demonstrated by the recently published Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation (COAPT) trial, has led to increased interest in MV intervention in patients with ischemic MR. The Surgical Treatment for Ischemic Heart Failure (STICH) trial was the first prospective, randomized, multicenter study evaluating the effect of cardiac surgery in patients with reduced LVEF(≤ 35%) and coronary artery disease. The study enrolled 2,112 patients with the simultaneous investigation of two separate hypotheses. In hypothesis 1, a total of 1,212 patients were randomized to evaluate whether coronary artery bypass grafting (CABG) improves outcomes when added to medical therapy in ischemic heart failure (HF) patients. An important secondary finding of the study was that in the medical therapy arm, increasing severity of MR was associated with decreased long-term survival at 5 years. Within the CABG subgroup, concomitant moderate to severe MR was present in 91 patients (14.9%), of which 49 underwent concomitant MV surgery (98.0% repair) and 42 did not. On propensity-matched analysis, patients that underwent concomitant MV surgery had a significant reduction in longterm mortality when compared with those who did not. The STICHES (STICH-Extended Study) examined the 10year results of the hypothesis 1 population. Patients who were randomized to the CABG arm experienced significantly lower rates of death from any cause, death from cardiovascular causes, and death from any cause or cardiovascular hospitalization over 10 years than those who were randomized to receive medical therapy alone. The hypothesis 2 arm of the STICH trial enrolled 1,000 patients with LVEF ≤ 35% and dominant anterior wall hypo-/ dyskinesia in order to determine whether the addition of surgical ventricular reconstruction (SVR) to CABG improves outcomes in ischemic cardiomyopathy. Concomitant SVR was associated with significantly reduced LV volumes, but no difference in regard to the primary endpoint of death and cardiac hospitalization. In addition, SVR did not result in any statistically significant improvements in patient symptoms or exercise tolerance. In this issue of Structural Heart: Journal of the Heart Team, Tsang and colleagues examine the effects of MV repair among hypothesis 2 STICH patients with moderate-to-severe MR and ischemic cardiomyopathy. ConcomitantMVrepairwas associated with improved 4-year survival compared to isolated CABG in patients who did not undergo SVR surgery (84% vs. 45%, p = 0.006). Although this difference was statistically significant, it should be stressed that this was a secondary finding that was not a part of the original STICH hypothesis. In addition, the decision of whether or not to perform MV surgery in patients with concomitant MR was left to the discretion of the surgeon. Although other studies ofMV surgery for ischemicMRhavemostly failed to demonstrate survival benefits, several have shown significant reverse LV remodeling and improvements in New York Heart Association (NYHA) class and quality of life post-MV repair. The significantly improved survival in patients undergoing concomitant MV repair in the study by Tsang et al., similar to the previously published findings in the STICH hypothesis 1 patients, is a very interesting observation that deserves further attention. The recently published COAPT trial demonstrated a surprisingly large mortality benefit for MitraClip (Abbott Vascular, Menlo Park, CA) therapy compared to optimal medical treatment in patients with functional MR. In contrast, the