What characterizes blue tetralogy of Fallot?

Blue tetralogy of Fallot, commonly known as "tetralogy of Fallot" (ToF), is characterized by a combination of four specific cardiac anomalies: ventricular septal defect (VSD), pulmonary stenosis, overriding aorta, and right ventricular hypertrophy. In the context of blue tetralogy of Fallot, severe pulmonary stenosis plays a pivotal role because it significantly restricts blood flow from the right ventricle to the pulmonary artery, leading to a right-to-left shunt through the VSD. This shunting causes deoxygenated blood to enter systemic circulation, which results in cyanosis, hence the term "blue" in blue tetralogy of Fallot.

Severe pulmonary stenosis is a critical component of the presentation, as it directly contributes to the degree of cyanosis a patient experiences. When the resistance to blood flow at the level of the pulmonary outflow tract is markedly elevated, oxygen saturation becomes low, leading to the characteristic cyanotic episodes seen in this condition.

Moreover, high blood oxygen levels would not be characteristic of this condition due to the mixing of deoxygenated and oxygenated blood. Similarly, while complete repair is a treatment goal, for many patients with blue tetralogy, they