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Etiology of atrioventricular block

William H Sauer, MD
Section Editor
Leonard I Ganz, MD, FHRS, FACC
Deputy Editor
Brian C Downey, MD, FACC


Atrioventricular (AV) block is defined as a delay or interruption in the transmission of an impulse from the atria to the ventricles due to an anatomical or functional impairment in the conduction system. The conduction disturbance can be transient or permanent, and it can have many causes (table 1).

The conduction can be delayed, intermittent, or absent. The commonly used terminology includes first degree (slowed conduction without loss of atrioventricular synchrony), second degree (intermittent loss of atrioventricular conduction, often in a regular pattern, eg, 2:1, 3:2, or higher degrees of block), and third degree or complete AV block. (See "ECG tutorial: Atrioventricular block".)

The etiology of AV block will be reviewed here. The management of the specific types of AV block is discussed separately. (See "First degree atrioventricular block" and "Second degree atrioventricular block: Mobitz type I (Wenckebach block)" and "Second degree atrioventricular block: Mobitz type II" and "Third degree (complete) atrioventricular block".)


Increased vagal tone — Enhanced vagal tone due to sleep, athletic training, pain, carotid sinus massage, or hypersensitive carotid sinus syndrome can result in slowing of the sinus rate and/or the development of AV block. (See "Arrhythmia in athletes" and "Sick sinus syndrome: Epidemiology, etiology, and natural history" and "Carotid sinus hypersensitivity".)

Idiopathic progressive cardiac conduction disease — Fibrosis and sclerosis of the conduction system accounts for about one-half of cases of AV block and may be induced by several different conditions which often cannot be distinguished clinically [1]. Progressive cardiac conduction defects, referred to as Lenegre's or Lev's disease, are characterized by progressive impairment of the conduction system:


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Literature review current through: Sep 2016. | This topic last updated: Oct 30, 2014.
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