From the Guidelines
Tetralogy of Fallot (TOF) is characterized by four key components: a ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta, as described in the most recent and highest quality study 1. The components of TOF are:
- A ventricular septal defect (VSD), which is a hole between the right and left ventricles
- Pulmonary stenosis, which involves narrowing of the pulmonary valve and outflow tract
- Right ventricular hypertrophy, where the right ventricle muscle becomes abnormally thickened
- An overriding aorta, where the aorta is positioned directly over the ventricular septal defect rather than connecting solely to the left ventricle These defects develop during fetal heart formation and result in oxygen-poor blood being pumped to the body, causing cyanosis (bluish discoloration of the skin) 1. The fundamental problem stems from anterior displacement of the infundibular septum during embryonic development, which leads to unequal division of the ventricular outflow tract, resulting in these four characteristic abnormalities, as supported by the guidelines for the management of adults with congenital heart disease 1. It is essential to note that the severity of TOF can vary, and a morphological spectrum exists, with the most extreme form being pulmonary atresia with VSD, as mentioned in the guidelines 1. Treatment typically involves surgical correction in infancy to close the VSD and relieve the pulmonary stenosis, allowing proper blood flow to the lungs and body, with a high success rate and survival rates of > 98% in multiple series 1.
From the Research
Components of Tetralogy of Fallot (TOF)
The components of Tetralogy of Fallot (TOF) include:
- A malaligned ventricular septal defect 2, 3, 4, 5, 6
- Right ventricular outflow and/or pulmonary valve/artery stenosis or atresia 2, 3, 4, 5, 6
- A dextraposed overriding aorta 2, 3, 4, 5, 6
- Right ventricular hypertrophy 2, 3, 4, 5, 6
Additional Characteristics
Other characteristics of TOF may include:
- Pulmonary outflow tract obstruction 3
- Overriding aortic root 3
- Abnormal development of the pulmonary vasculature, such as peripheral pulmonic stenosis, discontinuous pulmonary arteries, anomalous pulmonary venous return, and the development of aortopulmonary collateral vessels 6
- Membranous ventricular septal defect 4
- Anterior malaligned ventricular septal defect 5
- Subpulmonic stenosis 6