Accurate measurement of mitral annular area by using single and biplane linear measurements: comparison of conventional methods with the three-dimensional planimetric method

The planimetry method using three-dimensional (3D) echocardiography is useful for providing an accurate mitral annulus area (MAA) value. However, this method is relatively unavailable. Therefore, we evaluated the accuracy of conventional methods for MAA measurement compared with that of 3D planimetry.

Two-dimensional (2D) and 3D transoesophageal echocardiography (TEE) were performed in 70 patients. The mitral annulus diameter (MAD) was measured using four standard TEE imaging planes: four-chamber (4Ch), two-chamber (2Ch), anterior–posterior (LAX), and commissure–commissure (CC). MAA was calculated using a single diameter based on that of a circle and using two diameters based on that of an ellipse. MAA measurements using the single 4Ch MAD method (r = 0.84, P < 0.001), and two anatomically orthogonal MAD method in 4Ch/2Ch (r = 0.93, P < 0.001) and LAX/CC (r = 0.97, P < 0.001) planes correlated with 3D planimetric MAA measurements. Further analysis with Bland–Altman plots revealed that the LAX/CC MAD measurement exhibited the closest limits of agreement with the 3D planimetric MAA measurement. Notably, in patients showing an elliptical annulus shape, only LAX/CC MAD, but not 4Ch or 4Ch/2Ch MAD, provided results comparable with those of 3D planimetric MAA measurements. However, in patients with a circular annulus shape, reliable MAA measurements can be achieved using either single 4Ch MAD or any biplane MAD.

Conventional LAX/CC MAD can be recommended for MAA measurements in a diverse patient population. This method is applicable as an alternative to the 3D planimetric method, regardless of the mitral annulus shape.