The following ECG (ECG 3) was recorded from a 62-year-old woman presenting with syncopal episodes
What are the abnormalities?
(20% marks)
(the college has not released their ECGs; the image above was appropriated from LITFL without any explicit permission but in the spirit of FOAM)
College Answer
Type 2 (Wenckebach) second degree heart block
Slow transition across the chest leads (? Old anteroseptal infarct)
Discussion
Little discussion is possible in this routine pattern recognition exercise. The syncopal woman has a PR interval which gradually gets longer and longer over several beats, until a P wave is not followed by a QRS complex, indicating a failure of conduction through the AV node. This is a second degree heart block, or Mobitz heart block; specifically it is a Mobitz type I (Whereas a Mobitz type II is an intermittent failure of AV conduction without PR prolongation).
The Wenckebach phenomenon referred to by the college is a Mobitz Type 1 second degree heart block, which makes their answer weird. A Type 2 second degree heart block is also an eponymous phenomenon (Hay block), and is nothing like a Wenckebach block.
Heart blocks of all sorts are discussed in greater detail elsewhere.
References
From "the ECG made easy", by Hampton (2003), and ECGs shamelessly stolen from Life in The Fastlane without any sort of permission, but in the non-commercial spirit of free education
2012 ACCF/AHA/HRS Focused Update of the 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines