Page 111 - Advanced echocardiography in characterization and management of patients with secondary mitral regurgitation

Mitral valve geometry, MR severity and clinical outcomes
LV remodeling in patients with ischemic and non-ischemic cardiomyopathy causes tethering of the mitral valve leaflets and reduced mitral valve closing forces (23). Specifically, global and regional LV remodeling results in increased LV sphericity, papillary muscle displacement, mitral annular dilation and planar flattening. Mitral valve closing forces are reduced due to impaired LV contractility, LV dyssynchrony and reduced mitral annular contraction. The deleterious effects of mitral leaflet tethering and impaired mitral valve closing force leads to lack of leaflet coaptation. The deformation of the mitral valve apparatus may vary greatly depending on the extent of LV remodeling and dysfunction (24). How the various alterations of the mitral valve geometry influence the outcomes of HF patients treated with MitraClip compared with GDMT alone has not been extensively investigated. Mantegazza et al showed that a severely enlarged anteroposterior mitral annular diameter (≥4.44 cm) was associated with significant residual MR after MitraClip implantation, but the authors did not report its effect on outcomes (25). The present substudy from the COAPT trial provides novel evidence by demonstrating an independent association between increasing anteroposterior mitral annular dilation and the composite 2-year outcome of all-cause mortality and HFH, and with the endpoint of HFH alone. Moreover, these associations were similar in both treatment arms suggesting that MitraClip plus GDMT will improve the relative prognosis across the range of anteroposterior mitral annular diameters enrolled within the COAPT trial, with the absolute benefits being greater with larger anteroposterior diameters.
Quantitative measures of MR severity (such as the EROA) have been associated with impaired outcomes. In secondary MR, an EROA >0.2 cm2 has been associated with poor survival (19). However, randomized controlled trials have shown that surgical or TMVr techniques in patients with secondary MR have a prognostic benefit when the EROA (as a measure of MR severity) is at least 0.3 cm2 (13,14,26).
In the COAPT trial, in which the vast majority of patients had a baseline EROA 30.3 cm2,(15) an increasing EROA was independently associated with increased risk of all- cause mortality alone but not with HFH. MitraClip reduced mortality to a similar relative degree regardless of baseline EROA; as such, the absolute reduction of mortality was greater in patients with greater severity baseline MR treated with the MitraClip.
Grayburn, Packer and colleagues have ventured that the MitraClip is especially likely to improve event-free survival in patients with secondary MR with an EROA that is disproportionate to the extent of LV remodeling (8). Many patients with proportionate
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