Viewing rate and reference ranges for papillary muscle areas of the fetal heart using four-dimensional ultrasound in the rendering mode.

Objectives: The aims of this study were to assess the viewing rate and determine reference ranges ​​for the papillary muscle areas in the fetal atrio-ventricular valves using four-dimensional (4D) ultrasound and spatio-temporal image correlation (STIC) in the rendering mode.

Methods: This cross-sectional prospective study included 310 4D STIC volume data sets of normal fetuses between 18 weeks 0 day and 34 weeks 0 day of gestation. The papillary muscles were antero-lateral (MPAL) and postero-medial (MPPM) to the mitral valve and antero-superior (MPAS), inferior (MPI) and septal (MPS) to the tricuspid valve. Polynomial regressions were built to determine the reference ranges, and adjustments were made using the determination coefficient (R(2) ). To assess inter-observer reproducibility, the intra-class correlation coefficient (ICC) was used.

Results: Identification of the papillary muscles was possible in 89.3% patients. The best-fit regression equations between papillary muscle areas and gestational age were second degree. The inter-observer reproducibility was good (ICC: 0.98 to MPAS, 0.97 to MPI, 0.98 to MPS, 0.98 to MPAL and 0.97 to MPPM).

Conclusions: Identification of the papillary muscles of the fetal valves was possible in most of the 4D STIC volume data sets, enabling the determination of reference ranges using the rendering mode. The reference ranges ​​for the papillary muscle areas were determined.