Fetal Cardiac Axis in Fetuses with Conotruncal Anomalies.

The purpose of this study was to assess the cardiac axis in fetuses with conotruncal anomalies during four-chamber view scanning.  We retrospectively evaluated the cardiac axis of 150 fetuses with conotruncal anomalies within the second and third trimester between October 2008 and August 2014. The cardiac axis was obtained by the angle of two lines in a transverse view of the fetal thorax at the level of the four-chamber view. The first line divided the thorax into two equal halves starting from the spine posteriorly ending at the sternum. The second line was placed through the interventricular septum of the fetal heart. The angle was calculated using OsiriX software.  23 had double outlet right ventricle (DORV), 17 had truncus arteriosus communis (TAC), 36 had tetralogy of Fallot (TOF), and 74 had complete transposition of the great arteries (d-TGA). In fetuses with DORV ≤ 24 + 6 weeks of gestation (wks), the mean cardiac axis was 52.5° (p = 0.005), at ≥ 25 + 0 wks it was 51.1° (p = 0.0003). In fetuses with TAC ≤ 24 + 6 wks, the mean cardiac axis was 56.8° (p = 0.01), at ≥ 25 + 0 wks it was 50.0° (p = 0.05). In fetuses with TOF ≤ 24 + 6 wks, the mean cardiac axis was 67.5° (p < 0.0001), at ≥ 25 + 0 wks it was 63.8° (p < 0.0001). In fetuses with d-TGA ≤ 24 + 6 wks, the mean cardiac axis was 45.6°, at ≥ 25 + 0 wks it was 45.4° (not significant). Throughout gestation, the cardiac axis did not show a difference in the two separate examinations.  In fetuses with DORV, TAC and TOF, the cardiac axis is significantly different from the normal axis, but in fetuses with TGA there is no significant difference compared to the normal axis. Therefore, analysis of the heart axis could be useful for screening for conotruncal anomalies.