A febrile 2-year-old has a heart rate of 185 bpm. The rhythm is slightly irregular, the rate varies between 170 and 200 bpm with activity, and a P wave precedes every QRS complex. There is no structural heart disease. What is the correct interpretation?

• A Atrioventricular nodal reentrant tachycardia requiring adenosine
• B Junctional ectopic tachycardia needing amiodarone infusion
• C Atrial flutter needing synchronized cardioversion
• D Sinus tachycardia secondary to fever, requiring treatment of the underlying cause ✓

Explanation

Sinus tachycardia in infants can reach rates near 200 bpm, but it retains visible P waves before every QRS, varies beat to beat with activity, and starts and stops gradually. Supraventricular tachycardia is characteristically perfectly regular at a fixed rate, has absent or retrograde hidden P waves, and begins abruptly. Treating the fever and hydration status resolves the rate. Recognizing these distinctions prevents unnecessary adenosine use, which is the practical examination point.

Reference: Park's Pediatric Cardiology for Practitioners, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.