Fetal cardiac ventricle volumetry in the second half of gestation assessed by 4D ultrasound using STIC combined with inversion mode.

OBJECTIVE

Quantification of fetal heart ventricle volume can aid in the evaluation of functional and anatomical aspects of congenital heart disease. The aim of this study was to establish nomograms for ventricular volume using three-dimensional (3D) inversion mode ultrasonography with the spatio-temporal image correlation (STIC) modality and to calculate ejection fraction and stroke volume.

METHODS

The fetal heart was scanned using the STIC modality, during fetal quiescence with abdomen uppermost, at an angle of 30-50 degrees , without color Doppler flow mapping. In post-processing, starting with the classic four-chamber view plane in the A-frame, the reference point was moved to the center of the ventricle. The operator used the edit volume followed by Virtual Organ Computer-aided AnaLysis (VOCAL) mode options; in manual trace the VOCAL settings were set to 15 degrees . The trace was drawn and included the myocardium; inversion mode thresholding provided the volume of the intraventricular (anechoic) voxels within the region of interest. The total volume and the intraventricular volume were displayed. The process was repeated for right (R) and left (L) ventricles at end diastole (EDV) and end systole (ESV). The stroke volume (SV = EDV - ESV) and ejection fraction (EF = SV/EDV) were calculated from these measurements. Intraclass correlation was used to evaluate intra- and interobserver agreement.

RESULTS

One hundred fetuses ranging from 20 + 5 to 40 + 0 gestational weeks were included in the study. In addition, six fetuses diagnosed during the study period with a cardiac anomaly were examined and their ventricular volumes compared with those of the main study group. LEDV ranged from a mean of 0.53 cm(3) at midgestation to a mean of 3.96 cm(3) at term. LESV ranged from a mean of 0.17 cm(3) at midgestation to 1.56 cm(3) at term. REDV ranged from a mean of 0.68 cm(3) at midgestation to a mean of 5.44 cm(3) at term. RESV ranged from a mean of 0.26 cm(3) at midgestation to 2.29 cm(3) at term. Total stroke volume ranged from a mean of 0.78 cm(3) at midgestation to a mean of 5.5 cm(3) at term. The mean right : left ventricle ratio was 1.4, and left ejection fraction ranged from 42.5 to 86% in these fetuses. Nomograms were created for RESV, LESV, REDV, LEDV and total stroke volumes vs. estimated fetal weight and gestational age. Intra- and interobserver agreement reached 96%.

CONCLUSIONS

3D inversion mode sonography combined with STIC represents a simple and reproducible method for estimating fetal cardiac ventricle volume. This innovative methodology may add to overall evaluation of cardiac volume and function, and improve our understanding of normal and abnormal cardiac structure, as well as the severity and prognosis of cardiac lesions.