A 5-month-old pale and lethargic male infant is brought to emergency. On examination, HR is 240 bpm and it does not change with crying. Lungs are clear and no hepatomegaly present. His ECG is given below. Which of the following is the first step in management of this patient?
**Core Concept**
The infant in question is likely suffering from supraventricular tachycardia (SVT), a common arrhythmia in neonates and infants characterized by a rapid heart rate originating from the atria. The heart rate of 240 bpm, which remains constant despite crying, is a hallmark of SVT.
**Why the Correct Answer is Right**
Carotid massage is a first-line treatment for SVT in infants. The vagus nerve, which runs through the carotid sheath, stimulates the sinoatrial node, leading to a decrease in heart rate. When performed correctly, carotid massage can temporarily stop the SVT, allowing the heart to return to a normal rhythm. This is because the vagus nerve stimulates the release of acetylcholine, which inhibits the sinoatrial node and slows the heart rate.
**Why Each Wrong Option is Incorrect**
**Option A:** Rapid verapamil infusion is not the first-line treatment for SVT in infants. Verapamil is a calcium channel blocker that can be used to treat SVT in adults, but its use in infants is not recommended due to the risk of severe hypotension and cardiac arrest.
**Option B:** Transthoracic pacing of the heart is not a first-line treatment for SVT in infants. Pacemakers are typically used in cases of bradycardia or heart block, not tachycardia.
**Option D:** DC cardioversion is not the first-line treatment for SVT in infants. Cardioversion involves the use of electrical shocks to convert an abnormal heart rhythm to a normal one. While it can be effective in treating SVT, it is generally reserved for cases where carotid massage is unsuccessful or not feasible.
**Clinical Pearl / High-Yield Fact**
In infants with SVT, carotid massage is often effective because the vagus nerve is still developing and is more easily stimulated. This is why carotid massage is a first-line treatment for SVT in this age group.
**✓ Correct Answer: C. Carotid massage**