Heart Block: An Overview

Overview

Heart block describes impaired electrical conduction in the heart. The sinoatrial node (SAN) sends impulses to the atrioventricular node (AVN) which then sends impulses down the Bundle of his and via the bundle branches towards the apex of the heart which split into fascicles which supply the myocardium.

Types

Heart blocks are classified according to the site of the block:

• Sinoatrial node blocks – blocks within the SAN
• Atrioventricular (AV) blocks – blocks within the AVN, divided into:
  • 1^st-degree AV blocks
  • 2^nd-degree AV blocks, which are further divided into:
    • Mobitz I (Wenckebach) block
    • Mobitz II block
  • 3^rd-degree (complete) heart block
• Hisian blocks – blocks at the bundle of His
• Bundle branch blocks – within the left and right bundle branches
• Fascicular/hemiblocks – within the fascicles of the left bundle branch