Mobitz II AV block is characterized by sudden unexpected blocked P waves without variation or prolongation of the PR interval.

Electrophysiological studies have proved that Mobitz II block is due to an infranodal His-Purkinje system conduction delay. It generally is associated with a wide QRS complex, except in some patients whose delays are localized within the bundle of His.

Mobitz II block most commonly is caused by acute MI (anterior or inferior).