LEVOROTATION OF THE FETAL CARDIAC AXIS - A CLUE FOR THE PRESENCE OF CONGENITAL HEART-DISEASE

Objective: To evaluate the use of the cardiac axis within the chest fo r the prenatal detection of congenital heart defects. Methods: We revi ewed retrospectively the sonographic findings of all fetuses scanned b etween 17 and 40 weeks' gestation and diagnosed prenatally as having h eart defects. The cardiac diagnoses were confirmed postnatally. The co ntrol group consisted of 75 consecutive fetuses with normal fetal surv eys and newborn follow-up examinations. The cardiac axes were measured retrospectively using an image of the four-chamber view of the heart and measuring the angle between the interventricular septum and a line bisecting the chest. Mean and standard deviations (SDs) of the axis m easurements in normal and abnormal fetuses were compared by Student t test. Results: The 75 fetuses with heart defects diagnosed by prenatal sonogram had a mean cardiac axis of 56 +/- 13 degrees, compared with 43 +/- 7 degrees in normal fetuses (P < .001). Using 57 degrees (two S Ds above the mean for normal fetuses) as the upper limit of normal, 33 of 75 (44%) abnormal fetuses versus none of 75 normal fetuses were id entified. The frequency of cardiac rotation was greater in fetuses wit h truncus arteriosus, Ebstein's anomaly, pulmonic stenosis, coarctatio n of the aorta, and tetralogy of Fallot. Conclusion: The presence of a cardiac axis exceeding 57 degrees in the fetal chest is associated wi th a substantial risk of congenital heart defects. The finding of an a bnormal axis should prompt further evaluation of the fetal heart.