Reproducibility of transthoracic 3D echocardiography in the assessment of mitral valve area in patients with rheumatic mitral stenosis: real time versus ECG-gated 3D echocardiography

Purpose: To assess reproducibility of Real time 3D echocardiography (RT3D) and ECG-gated 3D echocardiography (EG3D) when measuring the mitral valve area (MVA) in rheumatic mitral stenosis (MS). Methods: MVA was assessed by three operators in 68 MS patients using RT3D and EG3D. Reproducibility of each technique was determined by calculating the standard error of measurements (SEM). Results: SEM was similar between RT3D and EG3D. MVA variability was of 0.4 cm(2) or 30% of any RT3D or EG3D measured MVA. The minimal change in MVA above which two measurements should be considered to differ significantly for the same operator was of 0.4 cm(2) for RT3D and 0.5 cm(2) for EG3D. For two different operators making successive measurements, the minimum significant change was of 0.5 cm(2) for RT3D and 0.6 cm(2) for EG3D. The minimum significant difference when switching from RT3D to EG3D or vice versa is of 0.6 cm(2). Low temporal resolution of 6 Hz has the least variability when using RT3D (0.19 cm(2) vs. 0.26 cm(2), p = 0.009) but significantly underestimated MVA (1.3 +/- 0.4 cm(2) vs. 1.4 +/- 0.4 cm(2), p < 10- 3) when compared to EG3D. MVA variability was significantly higher in mild MS when compared to severe MS whether it is RT3D (0.23 cm(2) vs. 0.18 cm(2), p = 0.02) or EG3D (0.27 cm(2) vs. 0.16 cm(2), p < 0.001). Conclusion: RT3D and EG3D are equally reproducible in the assessment of MVA in patients with MS. Further measurements standardization is required to have a clinically acceptable estimations of the true 3D MVA and minimal detectable differences.