Examination of the Fetal Heart by Four-Dimensional Ultrasound with Spatiotemporal Image Correlation during Routine Second-Trimester Examination: The ‘Three-Steps Technique’

OBJECTIVE: To prospectively analyze the accuracy and rapidity of four-dimensional (4D) ultrasonography with spatiotemporal image correlation (STIC) in the assessment of four-chamber view and outflow tracts in unselected fetuses and in fetuses with congenital heart defects (CHD) at 19-23 weeks of gestation. MATERIALS AND METHODS: 112 consecutive pregnancies undergoing routine second-trimester ultrasonographic scan and 10 pregnancies with fetuses with CHD affecting the great arteries formed the study group. From the four-chamber view, volumes of the fetal heart were acquired by the STIC technique and stored for a later offline analysis that was performed by two examiners blinded to the characteristics of the fetuses. Offline analysis was performed using a simplified multiplanar approach based on 3 different steps and one rotation finalized to visualize the four-chamber view and the left and right outflow tracts. RESULTS: Adequate recognition of four-chamber view and outflow tracts was obtained in more than 80% of the volumes. There were no false-positives and only one observer had a false-negative (interrupted aortic arch classified as normal). The mean time required to interpret 4D volumes was 3.7 min. CONCLUSIONS: The standard fetal cardiac anatomy survey can be performed in the second-trimester fetus by 4D STIC in both normal and abnormal hearts. This approach may reduce the operator's dependency in diagnosis of CHD.