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.