Reference values for the volumes of foetal heart atrial wall by three-dimensional ultrasound using STIC and VOCAL methods between 20w0d and 33w6d weeks of gestation

Objective: To establish reference values for the volumes of foetal heart atrial wall by three-imensional (3D) ultrasound using spatio-temporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL) methods. Methods: We performed a retrospective cross-sectional study with 170 normal singleton pregnancies between 20 weeks + 0 days (20w0d) and 33 weeks + 6 days (33w6d) of gestation. Foetal heart atrial wall volume was obtained by VOCAL method with 30-degree rotation (six planes) subtracting the internal volume from the atrium volume. Polynomial regression with adjustments by determination coefficient (R-2) was performed. To calculate the interobserver reproducibility, concordance correlation coefficient (CCC) was applied. Results: The mean +/- standard deviation (SD) for the left atrium wall volume (cm(3)) ranged from 0.54 +/- 0.21 at 20w0d-20w6d to 2.17 +/- 0.30 at 33w0d-33w6d. The mean +/- SD for the right atrium wall volume (cm(3)) ranged from 0.45 +/- 0.16 at 20w0d-20w6d to 2.17 +/- 0.62 at 33w0d-33w6d. We observed a satisfactory interobserver reproducibility with CCC = 0.69 and 0.58 for the left and right volumes of foetal heart atrial wall, respectively. The best-fit models were first-degree: volume for the left atrium wall = -2.194 + 0.139*GA (R-2 = 0.41) and volume for the right atrium wall = -2.757 + 0.155*GA (R-2 = 0.37). Conclusion: Reference values for the volumes of foetal heart atrial wall by 3D ultrasound using STIC and VOCAL methods between 20w0d and 33w6d weeks of gestation were established.