A 28-year-old woman with no structural heart disease presents with recurrent episodes of sudden-onset regular palpitations at 180 bpm, with abrupt termination. ECG during palpitations shows narrow complex tachycardia at 180/min with no visible P waves. The tachycardia terminates with vagal maneuvers. What is the most likely mechanism?
- A AV nodal re-entrant tachycardia (AVNRT) ✓
- B Atrial fibrillation with rapid ventricular response
- C Wolff-Parkinson-White with antidromic conduction
- D Ventricular tachycardia
Correct answer: A. AV nodal re-entrant tachycardia (AVNRT)
Explanation
AVNRT is the most common cause of paroxysmal supraventricular tachycardia (PSVT) in young women without structural heart disease. The re-entry circuit is confined to the AV node (slow and fast pathways), causing retrograde P waves buried in or just after the QRS, giving the appearance of absent P waves. It is regular, narrow-complex, responds to vagal maneuvers (carotid sinus massage, Valsalva) or adenosine, and terminates abruptly. Atrial fibrillation is irregularly irregular; WPW antidromic produces wide QRS tachycardia.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.