3-4 months baby with heart rate 250/min, QRS complex less than 0.07 sec and no P wave, Diagnosis will be :
💡 Explanation
## **Core Concept**
The question presents a clinical scenario suggestive of a tachyarrhythmia in an infant. The key details provided are a heart rate of 250/min, a QRS complex duration of less than 0.07 seconds, and the absence of a P wave. These findings are critical for distinguishing between types of supraventricular tachycardias (SVTs) and other arrhythmias.
## **Why the Correct Answer is Right**
The correct answer, **. Supraventricular Tachycardia (SVT)**, is supported by the provided clinical details. SVT is characterized by a rapid heart rate, often above 200/min in infants, and can present with a heart rate of 250/min. The QRS complex being less than 0.07 seconds (or 70 milliseconds) suggests that the rhythm disturbance is likely supraventricular in origin because in SVTs, the QRS complex is typically narrow (0.08 seconds) because it originates from a focus within the ventricles, leading to abnormal ventricular depolarization. The narrow QRS complex in this scenario makes VT less likely.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that infants with SVT may present with signs of heart failure or distress due to the high heart rate. Treatment often involves vagal maneuvers initially, followed by adenosine if necessary. Recognizing the narrow QRS complex and the absence of P waves is crucial for the diagnosis of SVT.