Second Degree AV Block Mobitz Type 2

Type 2 Second-degree AV block, also known as "Mobitz II," is almost always a disease of the distal conduction system (His-Purkinje System).

Mobitz II heart block is characterized on a surface ECG by intermittently nonconducted P waves not preceded by PR prolongation and not followed by PR shortening. There is usually a fixed number of non-conducted P waves for every successfully conducted QRS complex, and this ratio is often specified in describing Mobitz II blocks. For example, Mobitz II block in which there are two P waves for every one QRS complex may be referred to as "2:1 Mobitz II block".

The medical significance of this type of AV block is that it may progress rapidly to complete heart block, in which no escape rhythm may emerge. In this case, the person may experience a Stokes-Adams attack, cardiac arrest, or sudden cardiac death. The definitive treatment for this form of AV Block is an implanted pacemaker.

The impairment is usually below the AV node. Although the terms infranodal block or infrahisian block are often applied to this disorder, they refer to the anatomic location of the block, whereas Mobitz II refers to an electrocardiographic pattern.