Tetralogy of Fallot (in a 7-month-old boy): right axis deviation with a mean frontal QRS axis of +120 degrees, large R waves in leads V1 and V2 and upright T wave in lead V1 suggest right ventricular hypertrophy.

Pulmonary atresia with ventricular septal defect (in an 11-year-old girl): right axis deviation with a mean frontal QRS axis of +90 degrees, large R waves in leads V1 and V2 and right ventricular strain pattern (inversion of T wave in lead aVF) is related to right ventricular hypertrophy.

Transposition of the great arteries (in a newborn baby): sinus rhythm with a mean frontal QRS axis +90 degrees, the ECG findings are typically normal for age early after birth.

Ebstein's anomaly of the tricuspid valve (in a 7-year-old girl): mild right axis deviation with a mean frontal QRS axis of +100 degrees, prolonged PR interval (180 ms), tall P waves due to right atrial dilation, small QRS voltages over the right praecordial leads due to diminished right ventricular forces (atrialization of the right ventricle), and widening of QRS complex due to intraventricular conduction delay.