MedSchool: Ace Your OSCEsThe Medical Company
GET - On the App Store

Sinoatrial Exit Block



Sinoatrial exit block is a delay in conduction between the sinoatrial node and atrial myocardium.


  • Causes of Sinoatrial Exit Block

  • Idiopathic degeneration
  • Myocardial infarction
  • Infiltrative disease - sarcoidosis, amyloidosis, haemochromatosis
  • Connective tissue disease - SLE, scleroderma, RA
  • Cardiac surgery - valvular surgery, correction of congenital heart disease
  • Infections - Lyme disease, endocarditis


  • ECG Findings

  • First degree - not detectable on ECG
  • 2nd Degree: type I (Wenckebach) - progressively shortened PP intervals, followed by a pause
  • 2nd degree: type II - constant PP interval, with a pause that is a multiple of the PP interval.
  • 3rd degree - complete failure of transmission to the atria; indistinguishable from sinus arrest on ECG
  • Examples

  • 2nd degree SA exit block: type I
  • 2nd degree SA exit block type I
  • 2nd degree SA exit block: type II
  • 2nd degree SA exit block type II
  • 3rd degree SA exit block
  • 3rd degree SA exit block
Next Page
Want more info like this?
  • Your electronic clinical medicine handbook
  • Guides to help pass your exams
  • Tools every medical student needs
  • Quick diagrams to have the answers, fast
  • Quizzes to test your knowledge
Sign Up Now

Snapshot: Initialising...