Tetralogy of Fallot

Tetralogy of Fallot is a congenital heart defect defined by a ventricular septal defect, pulmonary stenosis, an overriding aorta, and right ventricular hypertrophy. These abnormalities reduce blood flow to the lungs and can cause cyanosis.

Ventricular septal defect: An opening between the heart’s right and left ventricles that permits blood to pass between them. This opening allows blood to cross between ventricles when pulmonary outflow is obstructed.
Echocardiography: Ultrasound imaging that shows the heart’s structure, movement, and blood flow. It identifies the four defects and assesses their severity before treatment.
Cardiac neural crest: A population of embryonic cells that contributes to structures involved in heart and great-vessel development. Abnormal development of these cells is implicated in some conotruncal defects.
Hypercyanotic spell: A sudden episode of worsening cyanosis and oxygen deprivation in a person with tetralogy of Fallot. Acute increases in right-to-left shunting can produce this characteristic emergency.
Transposition of the great arteries: A congenital heart defect in which the aorta and pulmonary artery arise from the opposite ventricles. It causes cyanosis through parallel circulations rather than tetralogy’s obstructed outflow and septal shunt.
Pulmonary stenosis: Narrowing that obstructs blood flow from the right ventricle toward the pulmonary arteries. This obstruction drives the pressure and shunting pattern characteristic of the condition.
Pulse oximetry: A noninvasive method for estimating blood oxygen saturation using light transmitted through tissue. It helps detect and monitor low oxygen levels associated with cyanotic spells.
Conotruncal septation: Embryonic partitioning of the outflow tract into the aorta and pulmonary artery. Abnormal outflow-tract development contributes to the malalignment underlying the defect pattern.
Pulmonary regurgitation: Backward flow from the pulmonary artery into the right ventricle through an incompetent pulmonary valve. It is a common late consequence after surgical relief of outflow obstruction.
Truncus arteriosus: A congenital defect in which one arterial trunk leaves the heart instead of separate aorta and pulmonary artery. It shares an outflow-tract developmental origin but has a single common arterial vessel.

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Congenital heart defectBroader topic: Its combination of defects can cause cyanosis and typically requires surgical repair.