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 cm² 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 cm² for RT3D and 0.5 cm² for EG3D. For two different operators making successive measurements, the minimum significant change was of 0.5 cm² for RT3D and 0.6 cm² for EG3D. The minimum significant difference when switching from RT3D to EG3D or vice versa is of 0.6 cm². Low temporal resolution of 6 Hz has the least variability when using RT3D (0.19 cm² vs. 0.26 cm², p = 0.009) but significantly underestimated MVA (1.3 ± 0.4 cm² vs. 1.4 ± 0.4 cm², 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 cm² vs. 0.18 cm², p = 0.02) or EG3D (0.27 cm² vs. 0.16 cm², 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.