Heart Blocks ECG Quiz 4 Answer

1. Normal sinus rhythm
2. Third degree AV block (a.k.a. complete heart block)
3. Inferior ST elevation myocardial infarction (Inferior STEMI)
4. Incomplete right bundle branch block

Ischemia of the AV node and enhanced vagal tone (partially though the Bezold-Jarisch reflex) can occur in the setting of an inferior myocardial infarction resulting in differing degrees of AV block. This ECG demonstrates third degree heart block which may be only transient in this setting, although can persist as well. 

Related Topic Reviews: 3rd Degree AV Block, Inferior MI ECG Review, Right Bundle Branch Block