A 68-year-old man presents with recurrent dizziness. ECG shows a constant PR interval of 0.20 sec with intermittent non-conducted P waves and dropped QRS complexes. The PR interval before the dropped beat is identical to the conducted beats. The QRS is wide (130 ms). What is the most appropriate management?
- A Permanent pacemaker implantation ✓
- B Atropine infusion and observation
- C Increase dose of his beta blocker
- D Temporary transvenous pacing followed by discharge
Correct answer: A. Permanent pacemaker implantation
Explanation
B constant PR interval with dropped beats defines Mobitz II second-degree AV block, which localizes below the AV node in the His-Purkinje system, supported here by the wide QRS. It carries a high risk of progression to complete heart block and sudden death, so a permanent pacemaker is indicated even without frank syncope. Atropine is ineffective and potentially harmful because it accelerates the sinus rate while infranodal conduction worsens.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.