A patient has an ECG with a PR interval of 320 ms that is constant, and random non-conducted P waves. This describes:

• A Mobitz type II second degree AV block ✓
• B First degree AV block
• C Mobitz type I (Wenckebach) second degree AV block
• D Third degree (complete) AV block

Explanation

Mobitz type II second-degree AV block is characterised by a constant PR interval followed by sudden non-conducted P waves (dropped QRS) without progressive PR prolongation. This indicates an infranodal conduction defect (usually in the bundle of His or bundle branches). In Wenckebach (Mobitz I), the PR interval progressively lengthens before a dropped beat. Mobitz II is clinically more serious, carrying a risk of progression to complete heart block, and usually requires pacemaker insertion.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.