A 45-year-old woman develops regular narrow-complex tachycardia at 170 bpm with a retrograde P wave visible shortly after the QRS in lead V1 (short RP tachycardia with RP < PR). Vagal manoeuvres fail. What is the treatment of choice?
- A IV amiodarone
- B IV adenosine 6 mg rapid bolus ✓
- C Synchronised DC cardioversion
- D IV digoxin
Explanation
Short RP tachycardia with retrograde P wave immediately after the QRS (RP < PR) is characteristic of AVNRT (atrioventricular nodal re-entrant tachycardia), the most common paroxysmal supraventricular tachycardia. Adenosine (6 mg IV rapid bolus, can repeat at 12 mg) terminates AVNRT in > 90% of cases by blocking AV nodal conduction transiently. Verapamil or beta-blockers are alternatives if adenosine fails or is unavailable. Amiodarone and DC cardioversion are reserved for haemodynamically unstable patients. Digoxin has a slow onset and is not first-line for acute termination.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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