Open Access Articles- Top Results for Atrioventricular block

Atrioventricular block

Atrioventricular block
Classification and external resources
ICD-10 I44.0-I44.3
ICD-9 426.0-426.1
eMedicine med/189
NCI Atrioventricular block
Patient UK Atrioventricular block
MeSH D054537

An atrioventricular block (or AV block) involves the impairment of the conduction between the atria and ventricles of the heart. Under normal conditions, the SA node in the atria sets the pace for the heart, and these impulses travel down to the ventricles. In an AV block, this message does not reach the ventricles or is impaired along the way. The ventricles of the heart have their own pacing mechanisms, which can maintain a lowered heart rate in the absence of SA stimulation.

The causes of pathological AV block are varied and include ischaemia, infarction, fibrosis or drugs, and the blocks may be complete or may only impair the signaling between the SA and AV nodes. Certain AV blocks can also be found as normal variants, such as in athletes or children, and are benign.[1] Strong vagal stimulation may also produce AV block. The cholinergic receptor types affected are the muscarinic receptors.

There are three types:

  • First degree AV block - PR interval greater than 0.20sec.
  • Second degree AV block - Type 1 (aka Mobitz 1, Wenckebach): Progressive prolongation of PR interval with dropped beats (the PR interval gets longer and longer; finally one beat drops) . Type 2 (aka Mobitz 2, Hay): PR interval remains unchanged prior to the P wave which suddenly fails to conduct to the ventricles.
  • Third degree AV block - No association between P waves and QRS complexes.
File:Type I A-V block 5-to-4 Wenckebach periods.png
Sinus rhythm with acute inferior infarction complicated by Type I A-V block manifest in the form of 5:4 Wenckebach periods; R-P/P-R reciprocity.
File:Complete A-V block with resulting junctional escape.png
Sinus tachycardia with complete A-V block and resulting junctional escape


  1. ^ Lilly, Leonard (2006). Pathophysiology of Heart Disease. Lippincott Williams and Wilkins. ISBN 978-0-7817-6321-9. 

External links

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