The ECGs of 473 infants under the age of 3 months who were referred to a paediatric cardiological unit were analysed; 47 (10%) of the ECGs showed a superior axis (dominantly negative deflection S wave, in lead aVF). Of these, the majority of noncyanosed patients with plethora on chest x-ray proved to have either an atrioventricular canal defect or a large ventricular septal defect. When cyanosis and pulmonary plethora on x-ray were present, tricuspid atresia with increased pulmonary flow (types Ic or IIc) or d-transposition with ventricular septal defect accounted for most cases. With cyanosis and pulmonary oligaemia on x-ray, tricuspid atresia (types Ia and b) or pulmonary atresia with ventricular septal defect accounted for all cases. Finally, 2 patients with superior axis presenting in a shocked condition were found to exhibit the hypoplastic left heart syndrome.
Recognition of superior axis in the ECG provides a useful diagnostic aid in congenital heart disease in early infancy.