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MBBS QUESTION #10240
Question 1
An ECG shows progressive lengthening of the PR interval over several beats until a QRS complex is dropped entirely, after which the cycle repeats. This pattern describes:
  • Mobitz type I (Wenckebach) second-degree AV block✔️
  • Mobitz type II second-degree AV block
  • Third-degree (complete) AV block
  • First-degree AV block
Correct Answer Explanation
Wenckebach (Mobitz I) block is characterized by progressive PR prolongation culminating in a dropped beat, reflecting progressive AV nodal fatigue; it is usually benign and often reversible, in contrast to Mobitz II, which shows sudden dropped beats without preceding PR prolongation and carries a higher risk of progression to complete heart block.