Etiology

AV blocks result from the interruption of the electrical impulse anywhere within the atrioventricular conduction system, including the:

• AV node

• Bundle of His

• Left and right bundle branches

Blocks at the level of the AV node: impulse passes through AV node → normal propagation through conduction system → narrow QRS complex

Infranodal block

• Can be at the level of OR below the bundle of His

• Ventricular depolarization is impeded → wide QRS complex

More distal AV blocks: typically result from more extensive damage to the conducting system → ↑ risk of progression to complete heart block.