A 45-year-old man has recurrent palpitations and ECG shows a short PR interval (0.10 s), delta wave, and a wide QRS complex during sinus rhythm. During an episode, he develops a rapid irregular tachycardia at 240 bpm. The CONTRAINDICATED drug in this scenario is:

• A Procainamide IV
• B IV verapamil or digoxin ✓
• C Adenosine IV
• D Electrical cardioversion if haemodynamically unstable

Explanation

This is Wolff-Parkinson-White (WPW) syndrome with pre-excited atrial fibrillation (rapid irregular wide-complex tachycardia at 240 bpm via the accessory pathway). Verapamil and digoxin are absolutely contraindicated because they slow AV nodal conduction without affecting the accessory pathway, potentially increasing conduction through the accessory pathway, accelerating the ventricular rate to >300 bpm, and precipitating ventricular fibrillation. Adenosine is also hazardous in pre-excited AF (may cause haemodynamic deterioration). Procainamide IV is the preferred pharmacological agent; cardioversion is first-line for haemodynamic instability.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.