Also known as complete heart block
No conduction through the AV node, causing the atria and ventricles beat completely independently from each other
The ventricular beat is an escape rhythm anywhere from the AV node to the bundle-branches (normally slow, varying from 35 to 45 beats per minute)
Congenital
Acquired
Ischemia
Increased vagal tone
Hypothyroidism
Hyperkalemia
Drugs
Structural heart disease
Ischemia
Increased vagal tone
Hypothyroidism
Hyperkalemia
Drugs
Structural heart disease
Third degree AV block
First degree AV block
Second degree AV block type I 
Wide-complex tachycardia
Second degree AV block type II
Left bundle branch block
Narrow-complex tachycardia
AV dissociation without complete heart block