OME Cardiac Modules Practice Test

Tetralogy of Fallot is defined by four defects that interact to produce cyanotic blood flow: a ventricular septal defect, an overriding aorta, pulmonic (pulmonic) stenosis, and right ventricular hypertrophy. The VSD creates a pathway for mixing oxygen-poor and oxygen-rich blood between the ventricles. Because the aorta sits over the VSD, it receives this mixed blood. The narrowed outflow to the lungs (pulmonic stenosis) raises right ventricular pressures and reduces pulmonary blood flow, which promotes more shunting of blood from right to left through the VSD. The ongoing pressure load on the right ventricle leads to hypertrophy. This combination explains the characteristic cyanosis and the typical boot-shaped heart on imaging. Other options include defects like PDA, ASD, or truncus arteriosus, which are not part of Tetralogy of Fallot and don’t define this condition.