Percutaneous Treatment of IMR
MitraClip system (Abbott Inc. Irvine, CA, USA) has been approved since 2013 for the treatment of degenerative MR patients with prohibitive or high risk surgery for mitral valve repair or replacement [50]. Over 75% of patients randomized to EVEREST II trial had degenerative MR and the rest of the cohort had FMR. However, it has never been meticulously studied as to what percentage of patients randomized had IMR.
Subsequently, COAPT trial (the Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation) randomized 614 patients with FMR to medical therapy versus MitraClip therapy [51]. The etiology of FMR was ischemic in nearly 61% of the cohort. The subgroup analysis of the patients demonstrated that MitraClip treatment arm significantly decreased the primary endpoint of the trial (heart failure hospitalization in 2 years) as well as cardiovascular mortality and all-cause mortality. Although these results are tremendously encouraging in treating the patients with FMR due to ischemic cardiomyopathy, however, it still does not explain whether the etiology of MR in the ischemic group of MitraClip patients was IMR. In other words, the association of MR in the setting of ischemic cardiomyopathy is not consistent with the pathophsiology of IMR, as noted above. Considering all of these limitations, in our view, MitraClip therapy seems to be an excellent option for patients with IMR for the time being. Vast majority of patients with IMR already have high risk or prohibitive risk for conventional open heart surgery. Furthermore, the risk to the MitraClip procedure is extremely low, as has been proven in the COAPT trial. Therefore, a therapeutic intervention for IMR patients seems quite plausible. Whether treating IMR patients with MitraClip is going to change their outcomes with respect to mortality or heart failure remains to be seen. It is quite possible that we will never have another trial specifically looking into this patient population due to the heterogeneity of the disease and lack of enthusiasm from the cardiovascular community to enroll these patients into a randomized controlled trial. Furthermore, the comparator arm, either by medical therapy or surgery continues to have poor outcomes. Therefore, MitraClip therapy at the moment remains the only available percutaneous option for these patients.