Three-Chamber Images Are More Useful than Four-Chamber Images for the Volumetric Method of Degenerative Mitral Regurgitation

<b>Background/Objectives:</b> Effective regurgitant orifice area (EROA) is a critical parameter in assessing mitral regurgitation (MR) severity. The Japanese Circulation Society recommends a volumetric method which uses mitral annular diameters from apical four-chamber (A4C) and two-chamber (A2C) views. However, given the elliptical shape of the mitral annulus, use of apical long-axis (A3C) and A2C views, which reflect the anatomical long and short axes, may improve measurement accuracy. This study aimed to determine the optimal echocardiographic view combination for precise EROA quantification in degenerative MR (DMR). <b>Methods:</b> We retrospectively analyzed 98 patients with DMR who underwent both transthoracic echocardiography (TTE) and three-dimensional transesophageal echocardiography (3D TEE) within three months between April 2018 and December 2023. EROA was calculated using volumetric methods based on two TTE view combinations, A4C-A2C (EROA 4/2) and A3C-A2C (EROA 3/2). These were compared with 3D TEE-derived vena contracta area (VCA), which served as reference standard. <b>Results:</b> Mean values of EROA were 0.57 ± 0.23 cm² for EROA 4/2, 0.50 ± 0.21 cm² for EROA 3/2, and 0.49 ± 0.18 cm² for 3D TEE VCA. EROA 4/2 was significantly larger than VCA (<i>p</i> < 0.01), whereas EROA 3/2 did not significantly differ from VCA (<i>p</i> = 0.41) and showed a stronger correlation with VCA than EROA 4/2 (r = 0.829 vs. r = 0.638, <i>p</i> < 0.01). <b>Conclusions:</b> Volumetric EROA assessment using A3C and A2C views provides more accurate quantification in DMR than the conventional A4C and A2C approach. Anatomically appropriate imaging planes should be prioritized to enhance the accuracy of MR severity evaluation.