True mitral annulus diameter is underestimated by two-dimensional echocardiography as evidenced by real-time three-dimensional echocardiography and magnetic resonance imaging

Background: Mitral annulus assessment is of great importance for the diagnosis and treatment of mitral valve disease. The present study sought to assess the value of real-time three-dimensional echocardiography for the assessment of true mitral annulus diameter (MAD). Methods: One hundred and fifty patients (mean age 38 ± 18 years) with adequate two-dimensional (2D) echocardiographic image quality underwent assessment of MAD_2D and MAD_3D (with real-time three-dimensional echocardiography). In a subgroup of 30 patients true MAD was validated with magnetic resonance imaging (MRI). Results: There was a good interobserver agreement for MAD_2D (mean difference = -0.25 ± 2.90 mm, agreement: -3.16, 2.66) and MAD _3D (mean difference = 0.29 ± 2.03, agreement = -1.74, 2.32). Measurements of MAD_2D and MAD_3D were well correlated (R = 0.81, P < 0.0001). However, MAD_3D was significantly larger than MAD_2D (3.7 ± 0.9 vs. 3.3 ± 0.8 cm, P < 0.0001). In the subgroup of 30 patients with MRI validation, MAD_3D and MAD _MRI were significantly larger than MAD_2D (3.3 ± 0.5 and 3.4 ± 0.5 cm vs. 2.9 ± 0.4 cm, both P < 0.001). There was no significant difference between MAD_MRI and MAD_3D. Conclusion: MAD_3D can be reliably measured and is superior to MAD_2D in the assessment of true mitral annular size.