Page 112 - Advanced echocardiography in characterization and management of patients with secondary mitral regurgitation

Chapter five. MV geometry: The COAPT Trial
MR are also likely to benefit from MR reduction. In contrast, patients with very advanced LV remodeling and marked dilatation may not respond to MR reduction with the MitraClip, even if the baseline EROA is abnormal. In COAPT, enrollment was strictly controlled to require 3+ or 4+ secondary MR (confirmed by a echocardiographic core laboratory prior to randomization), and LV dimensions were restricted by requiring a LV end-systolic diameter of <7 cm. This requirement likely limited the degree of mitral annular dilatation present in the patients enrolled. Whether the MitraClip would be effective if used in patients with greater LV remodeling and anteroposterior mitral annular diameters than studied with COAPT cannot be addressed by this study. Moreover, whether therapies such as mitral valve annuloplasty may be of greater benefit than the MitraClip or further improve outcomes if used in combination with the MitraClip when the mitral annulus is dilated deserves further study. Similarly, identifying when LV dilatation and mitral annular diameters are too abnormal to benefit from the MitraClip (or other therapies aimed at reducing secondary MR) is essential for optimal patient triage to transcatheter mitral valve repair or replacement versus an LV assist device or heart transplantation.
Predictors of mitral regurgitation reduction after MitraClip
Procedural success rates with the MitraClip have steadily improved with increasing operator experience and advanced imaging guidance. In the present trial 92.3% of MitraClip-treated patients achieved a reduction in baseline MR grade of 3+ or 4+ to <2+ at 30 days. Residual secondary MR 33+ has not surprisingly been shown in COAPT and other studies to be strongly associated with subsequent adverse events (27-30). In a study of 300 patients with secondary MR undergoing MitraClip treatment, the EROA, mitral valve orifice area (MVOA), and transmitral pressure gradient were associated with inadequate MR reduction (28). The early EVEREST II trial also excluded patients with LV end-systolic dimension >55 mm, MVOA <4.0 cm2, and those with secondary MR and advanced tethering with either coaptation depth >11 mm or vertical coaptation length <2 mm (31). In contrast, COAPT excluded patients with degenerative mitral valve disease, LV end-systolic dimension >70 mm, MVOA <4.0 cm2 and those who in the opinion of the site operator had leaflet anatomy that may preclude MitraClip implantation, proper positioning or sufficient reduction in MR; specific anatomic exclusion criteria were not otherwise provided (11). Among patients meeting the enrollment criteria, we identified MR severity 4+ rather than 3+ (but not EROA), tethering location (especially P3), greater mitral posterior leaflet angle, stroke volume, LV end-diastolic volume index and RVSP as predictors of greater residual MR after MitraClip implantation. Further analyses are underway to characterize the mechanisms and implications of these observations.
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