Objective: To investigate the association between cardiac axis and fetal congenital heart defects to demonstrate the potential clinical applicability of cardiac axis measurement for detection of congenital heart defect in early gestation.
Methods: This case-control study was undertaken in three tertiary centers with expertise in fetal imaging in early gestation. Fetal cardiac axis was evaluated between 11 0/7 and 14 6/7 weeks of gestation in 197 fetuses with confirmed congenital heart defects. A control group was selected by matching each fetus with a congenital heart defect with two fetuses in the control group with similar crown-rump length (± 5 mm) and date of study (± 2 months). Cardiac axis was measured on the four-chamber view as the angle between the line that traces the long axis of the heart and the line that bisects the thorax in an anteroposterior direction.
Results: In the control group, mean cardiac axis was 44.5 ± 7.4°. The cardiac axis did not significantly change in early pregnancy. In the congenital heart defect group, 25.9% of fetuses had cardiac axis measurements within normal limits. In 74.1%, the cardiac axis was abnormal including 110 fetuses in the case group with left deviation (cardiac axis > 97.5th percentile), 19 fetuses in the case group with right deviation (cardiac axis < 2.5th percentile), and 17 fetuses in the case group with nonidentifiable cardiac axis. The performance of cardiac axis measurement in detection of major congenital heart defect was significantly better than enlarged nuchal translucency, tricuspid regurgitation, or reversed A-wave in ductus venosus used alone or in combination.
Conclusion: Abnormal cardiac axis is present in two-thirds of fetuses with congenital heart defect in early gestation. Adding cardiac axis assessment to the nuchal translucency measurement is helpful in defining a population at risk for fetal congenital heart defect.