Heart Block

 September 21

by Jonathan Downham

First-Degree Heart Block:

  • Description: The electrical signals are delayed as they pass through the atrioventricular (AV) node, but all signals eventually reach the ventricles.
  • ECG Findings: Prolonged PR interval (>200 ms)
  • Symptoms: Usually asymptomatic
  • Treatment: Generally, no treatment is required.


Second-Degree Heart Block (Type I or Mobitz I/Wenckebach):

  • Description: Progressive lengthening of the PR interval until a QRS complex is dropped.
  • ECG Findings: Increasing PR interval with dropped QRS complex
  • Symptoms: May be asymptomatic or may experience dizziness
  • Treatment: Close monitoring, may require a pacemaker

Second-Degree Heart Block (Type II or Mobitz II):

  • Description: Some electrical signals are blocked, leading to dropped QRS complexes without PR interval prolongation.
  • ECG Findings: Dropped QRS complexes with constant PR interval
  • Symptoms: Dizziness, fainting
  • Treatment: Usually requires a pacemaker

Third-Degree Heart Block (Complete Heart Block):

  • Description: No electrical signals from the atria reach the ventricles.
  • ECG Findings: Atria and ventricles beat independently
  • Symptoms: Fatigue, dizziness, fainting
  • Treatment: Requires immediate pacemaker implantation

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