What is a common acute symptom known as a "tet spell" in Tetralogy of Fallot?

In Tetralogy of Fallot, a "tet spell" refers specifically to episodes of sudden cyanosis and syncope. These spells typically occur due to an obstruction to the right ventricular outflow, leading to decreased blood flow to the lungs and subsequent right-to-left shunting of blood. When this occurs, deoxygenated blood enters systemic circulation, resulting in cyanosis, which is the bluish discoloration of the skin due to low oxygen levels in the blood. Syncope, or fainting, can also occur during these episodes due to decreased blood flow to the brain.

Understanding the mechanism of these spells is critical for recognizing and managing them in clinical practice. In contrast, symptoms such as sudden fever, rapid heart rate, and increased respiratory effort may be associated with other cardiovascular or respiratory conditions but are not characteristic of tet spells in the context of Tetralogy of Fallot.