Cardiac Axis Deviation in Anomaly Scan: A Marker for Underlying Cardiac Anomalies

Congenital heart defects (CHD) is a leading cause of perinatal morbidity and mortality. Cardiac axis assessment on the four-chamber view has been proposed as a simple adjunct marker for detecting underlying cardiac anomalies during second-trimester anomaly scans.

The aim of the study was to evaluate the association between cardiac axis deviation and congenital cardiac defects and assess its diagnostic performance as a screening parameter.

This prospective observational study included 810 pregnant women undergoing routine anomaly scans at 18-24-week gestation at a tertiary care center. Cardiac axis was measured on the four-chamber view and classified as normal (25°-65°), left deviation (>65°), or right deviation (<25°). Fetuses with suspected abnormalities underwent detailed fetal echocardiography and postnatal follow-up where feasible. Associations between axis category and anomalies were analyzed using the Chi-square test. Diagnostic performance indices were calculated.

Cardiac axis was normal in 746 (92.1%) fetuses, large in 46 (5.7%), and small in 18 (2.2%). Cardiac anomalies were detected in 51 (6.3%) cases. Anomalies were present in 31/46 (67.4%) with large axis and 15/18 (83.3%) with small axis, compared with 5/746 (0.7%) with normal axis (P < 0.001). Septal defects (atrial septal defect + ventricular septal defect VSD) were most frequent. Cardiac axis deviation showed sensitivity 90.2%, specificity 97.6%. Significant associations were also observed with selected extracardiac anomalies. Adverse pregnancy outcomes were more common when cardiac anomalies were present (P < 0.001).

Cardiac axis deviation is a strong marker of congenital cardiac anomalies and provides a high rule-out value when normal. Routine cardiac axis assessment during anomaly scans can aid early risk stratification and targeted referral.