Four cardiac anomalies make up tetralogy of Fallot: a ventricular septal defect, pulmonary stenosis, an overriding aorta, and right ventricular hypertrophy. There are other associated defects in certain cases. Pulmonary stenosis results in reduction of pulmonary blood flow; the ventricular septal defect allows mixing of oxygenated and unoxygenated blood. (From Ashwill, JW & James, SR: Nursing Care of Children: Principles and Practice. WB Saunders, Philadelphia, 2007.)