Atrioventricular block

In atrioventricular (AV) block, or heart block, there is impaired electrical conduction between the atria and ventricles. There are three types:

First degree heart block

• PR interval > 0.2 seconds

Second degree heart block

• type 1 (Mobitz I, Wenckebach): progressive prolongation of the PR interval until a dropped beat occurs
• type 2 (Mobitz II): PR interval is constant but the P wave is often not followed by a QRS complex

Third degree (complete) heart block

• there is no association between the P waves and QRS complexes