Background: Fetal echocardiography is an important method in prenatal diagnosis of Congenital Heart Disease (CHD). Fetal cardiac axis can be used as a reliable parameter in the diagnosis of CHD. The objective of this study was to discuss the abnormal fetal cardiac axis in the diagnostic value of fetal congenital heart disease.
Methods: In a 3-year period, 296 women with 20 and 40 weeks' singleton gestations referred for perinatal ultrasound consultation underwent evaluation of the fetal cardiac axis. For measurement of fetal cardiac axis, the chest axial image was obtained at the level of the four-chamber view. Of the 296 pregnancies, 260 healthy pregnancies were categorized as Group A while 36 pregnancies with severe heart disease were Group B. Cardiac anomaly was confirmed either by neonatal echocardiography or autopsy.
Results: Cardiac anomaly has been found in 36 women, 24 had abnormal axis (three with axis smaller than normal; 21 with axis larger than normal). The mean of cardiac axis for Group A (38.1±7.6°) was significantly smaller than that of Group B (52.6±19.8°) (P<0.001). The cardiac axis was independent from gestational age. With two standard deviations above and below the mean of Group A as normal cardiac axis (22.9°-53.5°), abnormal fetuses were defined as having axis < 23° or > 54°. There were 6 cases (2.3%) of cardiac axis larger than normal and no case (0%) smaller in group A, and 21 cases (58.3%) larger and 3 cases (8.3%) smaller in group B. The difference in two groups of patients with abnormal cardiac axis was statistically significant (P<0.01). The incidence of abnormal cardiac axis of group A was less than group B.
Conclusions: The measurement of fetal cardiac axis is simple and effective. Any larger or smaller fetal cardiac axis than normal is suggestive of a cardiac anomaly and requires further investigation. Four-chamber view is an important plane of fetal echocardiography.