A 72-year-old man has an ECG showing a constant PR interval of 0.22 sec with intermittent non-conducted P waves and no PR prolongation before the dropped beats. The QRS is wide (140 ms). What is the most likely diagnosis?
- A Second-degree AV block Type 1 (Wenckebach)
- B First-degree AV block
- C Second-degree AV block Type 2 (Mobitz II) ✓
- D Third-degree AV block
Correct answer: C. Second-degree AV block Type 2 (Mobitz II)
Explanation
Mobitz II shows constant PR interval with sudden non-conducted P waves and no progressive PR prolongation before the dropped beat. The wide QRS suggests infra-nodal disease. Wenckebach shows progressive PR prolongation before the dropped beat. Third-degree block shows complete AV dissociation with no relationship between P waves and QRS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.