Cardiovascular Medicine Book

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Atrial Fibrillation

Bradycardia

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Symptoms

Tachycardia

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Atrioventricular BlockAka: Atrioventricular Node Block, Wenckebach AV Block, Mobitz I AV Block, Mobitz II AV Block, Heart Block, AV Block, AV Node Block, First Degree Atrioventricular Block, Second Degree Atrioventricular Block, Third Degree Atrioventricular Block, Sinoatrial Exit Block

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  1. Pathophysiology
    1. Impaired conduction in Atria, AV node or His-Purkinje
  2. Types: First Degree Atrioventricular Node Block
    1. Causes
      1. Normal finding in >1% of healthy adults
      2. Increased vagal tone
      3. Digitalis affect
    2. Findings
      1. Regular narrow-complex rhythm at 40-60 beats/minute
      2. Prolonged PR interval >0.20 seconds
    3. Treatment: None needed
  3. Types: Second Degree Atrioventricular Node Block
    1. Also known as Sinoatrial Exit Block
    2. Type I Second Degree Atrioventricular Node Block
      1. Known as Mobitz I or Wenckeback Block
      2. Acute condition affecting AV Node
      3. Causes
        1. Inferior Myocardial Infarction
        2. Rheumatic Fever
        3. Digitalis Toxicity
        4. Increased vagal tone
        5. Beta Blocker
      4. Response to Maneuvers
        1. Improves in response to Atropine and Exercise
        2. Worsens with carotid massage
      5. EKG Findings
        1. Progressive increase PR interval until beat dropped
        2. Cycle repeats after beat dropped
    3. Type II Second Degree Atrioventricular Node Block
      1. Known as Mobitz II Block
      2. Chronic condition affects infranodal conduction path
      3. Causes
        1. Anteroseptal Myocardial Infarction
        2. Lenegre Disease
        3. Lev Disease
        4. Cardiomyopathy
      4. Response to Maneuvers
        1. Worsens in response to Atropine and Exercise
        2. Improves with carotid massage
      5. EKG Findings
        1. No change in PR interval
        2. Regularly dropped Q waves at consistent interval
        3. Patterns: 2 to 1, 3 to 1 or 4 to 1
      6. Prognosis
        1. Worse than Mobitz I Block
        2. May progress to complete heart block
      7. Management
        1. Pacemaker indicated
  4. Types: Third Degree Atrioventricular Node Block
    1. Complete electrical and mechanical AV dissociation
    2. P and QRS waves are present but unrelated
    3. Subtypes
      1. Congenital Third Degree AV Node Block
        1. Narrow complex escape rhythm at 45 to 60 bpm
        2. Associated with limited Exercise tolerance
      2. Acquired Third Degree AV Node Block
        1. Wide complex escape beat at 30 to 45 bpm
        2. Hemodynamic instability requires stabilization
          1. Transcutaneous pacing

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