Objectives .– Planimetry measured by two-dimensional transthoracic echocardiography (TTE, MVA2D) is the reference method for the evaluation of the severity of mitral stenosis (MS) but is significantly less reliable when performed by non-experienced operators. Real-time three-dimensional transoesophageal echocardiography (RT3DTEE, MVA3D) may overcome this limitation but its accuracy has never been evaluated.

Materials and methods .– We prospectively enrolled 43 patients (59 ± 15 years, 86% female) referred for MS evaluation who underwent the same day a TTE and a RT3DTEE. MVA2D was assessed by experienced operators, MVA3D was measured by one experienced (Level III) and one non-experienced operator (Level I) blinded of any clinical and TTE information. RT3DE images were digitally stored and analysed offline on a workstation using dedicated software (QLab, Philips) in a random order. MVA3D was measured at the best cross-section of the mitral valve defined as the most perpendicular and smallest orifice

Results .– MVA3D measured by the experienced operator (1.07 ± 0.31 cm ² [range 0.45–1.85]) did not differ from and correlated well with MVA2D (1.08 ± 0.32 cm ² [range 0.54–2.00], P = 0.84, r = 0.71, P < 0.001), and mean difference was small (−0.01 ± 0.24 cm ² ). Similarly, the MVA3D measured by the non-experienced operator (1.03 ± 0.31 cm ² [range 0.45–1.69]) did not differ from and correlated well with MVA2D ( P = 0.27, r = 0.66, P < 0.001; mean difference −0.05 ± 0.26 cm ² ). RT3DTEE intra- and interobserver (between experienced and non-experienced operators) variability were respectively 0.13 ± 0.10 cm ² and 0.19 ± 0.14 cm ² .

Conclusion .– RT3DTEE provides accurate and reproducible MVA measurements similar to 2D planimetry performed by experienced operators. Thus, RT3DTEE should be considered as an alternative tool for the evaluation of MS severity, especially in patients with poor echocardiographic windows or for team less accustomed to evaluate patients with MS.