Valvular Heart Disease
Mechanisms of Functional Mitral Regurgitation in Ischemic Cardiomyopathy Determined by Transesophageal Echocardiography (from the Surgical Treatment for Ischemic Heart Failure Trial)

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The mechanisms underlying functional mitral regurgitation (MR) and the relation between mechanism and severity of MR have not been evaluated in a large, multicenter, randomized controlled trial. Transesophageal echocardiography (TEE) was performed in 215 patients at 17 centers in the Surgical Treatment for Ischemic Heart Failure (STICH) trial. Both 2-dimensional (n = 215) and 3-dimensional (n = 81) TEEs were used to assess multiple quantitative measurements of the mechanism and severity of MR. By 2-dimensional TEE, leaflet tenting area, anterior and posterior leaflet angles, mitral annulus diameter, left ventricular (LV) end-systolic volume index, LV ejection fraction (LVEF), and sphericity index (p <0.05 for all) were significantly different across MR grades. By 3-dimensional TEE, mitral annulus area, leaflet tenting area, LV end-systolic volume index, LVEF, and sphericity index (p <0.05 for all) were significantly different across MR grades. A multivariate analysis showed a trend for annulus area (p = 0.069) and LV end-systolic volume index (p = 0.071) to predict effective regurgitant orifice area and for annulus area (p = 0.018) and LV end-systolic volume index (p = 0.073) to predict vena contracta area. In the STICH trial, multiple quantitative parameters of the mechanism of functional MR are related to MR severity. The mechanism of functional MR in ischemic cardiomyopathy is heterogenous, but no single variable stands out as a strong predictor of quantitative severity of MR.

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Methods

All participating STICH study sites were invited to participate in the STICH MR TEE substudy; 17 accepted. All 17 sites were provided with a detailed study protocol for obtaining TEE images to define the mechanism and severity of functional MR.17, 18, 19 An Institutional Review Board approval was obtained from each site, and written informed consent was obtained from all patients. At the time the STICH trial was initiated, real-time 3D imaging was not available. Sites equipped with a Philips

Results

TEE studies were obtained in 214 subjects; of whom, 81 had both 2D and 3D TEEs performed and 134 had only 2D TEE. Of these, 210 studies (97.7%) were of sufficient quality to assess MR severity. There were 57 patients with no MR, 120 with mild, 29 with moderate, and 4 with severe MR. Of the subset of patients with 3D TEE, 26 had no MR, 44 had mild MR, and 11 had moderate or severe MR. Given the small sample of severe MR and the fact that even moderate MR portends a poor prognosis in heart

Discussion

It has been well accepted that in ischemic cardiomyopathy, functional MR is primarily caused by LV dilation and/or dysfunction, such that coaptation of normal or nearly normal mitral leaflets is prevented by a combination of reduced systolic closing force, leaflet tethering, and mitral annular dilation. This ancillary study of the STICH trial offered the opportunity to systematically assess many of these variables using high-resolution measurements of the mitral leaflets and annulus by TEE. The

Disclosures

E.J.V. and P.A.G. report research grants with Abbott Vascular; no other conflicts of interest to report regarding this manuscript.

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    This work was supported by grants RO1HL72430, UO1HL69015, and UO1HL60913 from the National Institutes of Health, Bethesda, Maryland.

    See page 1817 for disclosure information.

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