A congenital cardiac anomaly that consists of four defects: pulmonic stenosis, ventricular septal defect, malposition of the aorta so that it arises from the septal defect or the right ventricle, and right ventricular hypertrophy.

Tetralogy of Fallot is actually four defects in combination.

First, the septum that divides the two ventricles is incomplete (so there is a ventricular septal defect), and oxygen-poor blood is thus allowed to mix with oxygen-rich blood.

Second, the passageway from the...