Standardized Delineation of Endocardial Boundaries in Three-Dimensional Left Ventricular Echocardiograms

Three-dimensional (3D) echocardiography is fundamental for left ventricular (LV) assessment. The aim of this study was to determine discrepancies in 3D LV endocardial tracings and suggest tracing guidance.

Forty-five 3D LV echocardiographic data sets were traced by three experienced operators, from different centers, according to predefined guidelines. The 3D meshes were compared with one another, and the endocardial areas of discrepancies were identified. A discussion and retracing protocol was used to reduce discrepancies. For each data set, an average 3D mesh was produced (reference mesh). Subsequently, four novice operators, divided into two groups, traced 20 of the data sets. Two operators followed the tracing protocol and two did not.

The intraclass correlation coefficients among the three experienced operators for end-diastolic volume, end-systolic volume, and ejection fraction were 0.952, 0.955, and 0.932. The absolute distances between tracings were 1.11 ± 0.45 mm. The highest tracing discrepancies were at the apical cap and anterior and anterolateral walls in end-diastole and end-systole and also at the basal anteroseptum in end-systole. Agreement with the reference meshes was better for the novice operators who followed the guidance (10.9 ± 17.3 mL, 10.2 ± 14.7 mL, and -2.2 ± 4.1% for end-diastolic volume, end-systolic volume, and ejection fraction) compared with those who did not (16.3 ± 16.4 mL, 17.0 ± 16.0 mL, and -4.2 ± 4.1%, respectively).

Comparing 3D LV tracings, the endocardial areas that are the most difficult to delineate were identified. The suggested protocol for LV tracing resulted in very good agreement among operators. The reference 3D meshes are available for online testing and ranking of LV tracing algorithms.