What is the treatment for sudden worsening of TOF?
**Core Concept**
Tetralogy of Fallot (TOF) is a congenital heart defect characterized by four main components: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. The sudden worsening of TOF, also known as a "tet spell," is a life-threatening condition that requires immediate medical attention.
**Why the Correct Answer is Right**
During a tet spell, there is a sudden increase in pulmonary vascular resistance, leading to a decrease in pulmonary blood flow and an increase in systemic blood flow, causing cyanosis, tachypnea, and even syncope. The treatment of choice for tet spells is the administration of 100% oxygen, which helps to reduce pulmonary vascular resistance and increase pulmonary blood flow.
**Why Each Wrong Option is Incorrect**
* **Option A:** Propranolol is a beta-blocker that can actually worsen the condition by reducing the heart rate and contractility, further decreasing pulmonary blood flow.
* **Option B:** Sodium nitroprusside is a vasodilator that can also worsen the condition by decreasing systemic vascular resistance, leading to an increase in pulmonary blood flow and further reducing systemic blood flow.
* **Option D:** Digoxin is a cardiac glycoside that can increase the contractility of the heart, but it is not the treatment of choice for tet spells and can actually worsen the condition.
**Clinical Pearl / High-Yield Fact**
The treatment of tet spells in TOF involves the "tet protocol": immediate administration of 100% oxygen, followed by the administration of a sedative or anxiolytic to calm the child, and finally, the administration of a vasodilator such as nitric oxide if the child remains cyanotic.
**Correct Answer:** A. 100% oxygen administration.