IntroductionMitral regurgitation severity assessment is usually carried out using qualitative, semiquantitative, and quantitative parameters. The mitral valve navigation (MVN) tool allows to measure the mitral effective regurgitant orifice (MERO) from 3D echo datasets. Our aim was to validate the MVN as a new tool to quantify MERO. A secondary aim was to assess the intra‐ and interobserver variability.MethodsThis is a retrospective study in which consecutive subjects undergoing a transoesophageal echocardiogram for more than mild mitral regurgitation evaluation were included. MERO measurement obtained by means of 3D color Doppler was used as the gold standard method for comparison. In every patient, MERO was also obtained using the MVN tool.ResultsFifty‐nine consecutive patients were analyzed (47.5% female; mean age 50.8 years). Mitral regurgitation was moderate in 23 (39%) and severe in 36 (61%) patients. Forty patients (67.8%) had a primary and 19 (32.2%) a secondary mitral regurgitation. The intraclass correlation coefficient (ICC) between 3D color Doppler and MVN was excellent (ICC: 0.95; 95% CI: 0.82 to 0.98; P < 0.001) in the total group and for patients with primary and secondary mitral regurgitation. Intra‐ and interobserver agreements were also good.ConclusionsMitral valve navigator shows an excellent accuracy for measuring MERO when the transoesophageal 3D color Doppler is used as the reference method, either primary or secondary mitral regurgitation. Intraobserver reproducibility and interobserver reproducibility are also excellent. These findings make this software a good alternative method to measure mitral regurgitation severity.