A 52-year-old woman without structural heart disease presents with episodic palpitations. A 12-lead ECG during an episode shows a narrow QRS tachycardia at 185 bpm, with a short RP interval (RP < PR) and a pseudo-r' notch in lead V1. What is the MOST likely diagnosis?
- A Atrioventricular nodal re-entrant tachycardia (AVNRT) ✓
- B Atrioventricular re-entrant tachycardia (AVRT) via an accessory pathway
- C Atrial tachycardia with short RP interval
- D Junctional ectopic tachycardia
Correct answer: A. Atrioventricular nodal re-entrant tachycardia (AVNRT)
Explanation
Typical (slow-fast) AVNRT is the most common paroxysmal SVT in adults, characterised by a narrow complex tachycardia with very short RP interval (retrograde P wave buried in or just after the QRS), typically producing a pseudo-r' in V1 or pseudo-S in inferior leads. This is the ECG hallmark. AVRT has a longer RP interval and retrograde P clearly after QRS; atrial tachycardia has clearly visible P waves with variable morphology; junctional ectopic tachycardia is rare in adults.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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