Third degree AV block


  • 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
    • Drugs
    • Structural heart disease

Clinical Features

Differential Diagnosis

AV Blocks


Rhythm 3rdAVblock.jpg
  • No atrial impulses are conducted
    • P waves normal and regular P-P intervals unrelated to slower regular R-R intervals
    • QRS narrow if block above bundle of His
    • QRS wide if block below bundle of His
    • PR variable
  • Differentiate from AV dissociation without complete heart block
AVD without CHB, courtesy of public access Amal Mattu EKG videos



See Also


  1. Sovari AA et al. Second-Degree Atrioventricular Block Treatment & Management. eMedicine. Apr 28, 2014.