Cardiology: Atrioventricular (AV) Block
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Questions and Answers

What is the most common cause of atrioventricular (AV) block?

  • Genetic disorders
  • Increased vagal tone
  • Idiopathic fibrosis and sclerosis of the conduction system (correct)
  • Ischemic heart disease

    • Which of the following statements best describes First Degree AV Block?

  • All P waves are followed by QRS complexes with a PR interval greater than 0.20 seconds. (correct)
  • Some P waves are not followed by QRS complexes.
  • There is complete dissociation between P waves and QRS complexes.
  • PR interval is consistently normal.

    • Which characteristic differentiates Mobitz type I from Mobitz type II Second Degree AV Block?

  • Molitz type II has progressively lengthening PR intervals.
  • Mobitz type I has a progressively lengthening PR interval until a QRS complex is dropped. (correct)
  • Mobitz type I features dropped QRS complexes at regular intervals.
  • PR interval is constant in Mobitz type I.

    • What does third-degree AV block signify?

    <p>Complete interruption with no AV communication.</p> Signup and view all the answers

    In Mobitz type II Second Degree AV Block, how does the PR interval behave?

    <p>It remains constant across beats.</p> Signup and view all the answers

    What is a characteristic finding in Mobitz type I AV Block regarding QRS complexes?

    <p>They are dropped in a pattern following progressively longer PR intervals.</p> Signup and view all the answers

    What is the typical heart rate observed in First Degree AV Block?

    <p>60 bpm</p> Signup and view all the answers

    Which of the following medications is NOT commonly associated with AV block?

    <p>Antibiotics</p> Signup and view all the answers

    Study Notes

    Atrioventricular (AV) Block

    • AV block is an interruption of electrical impulses traveling from atria to ventricles

    Causes of AV Block

    • Idiopathic fibrosis & sclerosis of conduction system (50% of patients)
    • Ischemic heart disease (40%)
    • Medications (beta-blockers, calcium channel blockers, digoxin, amiodarone)
    • Increased vagal tone
    • Valvulopathy
    • Congenital heart disease, genetic, or other disorders

    First Degree AV Block

    • All normal "P" waves are followed by "QRS" complexes
    • PR interval is longer than normal, greater than 0.20 seconds
    • Rate: 60 bpm
    • Rhythm: Regular
    • P wave: Normal
    • PR interval: 0.32 sec
    • QRS: 0.08 sec

    Second Degree AV Block

    • Some "P" waves are followed by "QRS" complexes, while others are not
    • Divided into Mobitz Type I and Mobitz Type II

    Mobitz Type I

    • PR interval progressively lengthens with each beat until atrial impulse is not conducted and "QRS" complex is dropped
    • Also called Wenckebach phenomenon
    • AV nodal conduction resumes with the next beat, and the sequence repeats
    • Rate: 60 bpm
    • Rhythm: Regularly irregular
    • P wave: Present, 1-2 before "QRS"
    • PR interval: 0.2-0.36 sec (progressively lengthens)
    • QRS: 0.08 sec, skipped every after 3 beats

    Mobitz Type II

    • PR interval is constant
    • Beats are intermittently nonconducted and "QRS" complexes dropped, usually in a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block) "P" wave
    • Rate: 60 bpm
    • Rhythm: Regularly irregular
    • P wave: Normal, present
    • PR interval: 0.12 sec
    • QRS: 0.08 sec, skipped every after 3 beats

    Third-Degree AV Block

    • Complete heart block with no electrical communication between atria and ventricles
    • No relationship between "P" waves and "QRS" complexes (AV dissociation)

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    Description

    This quiz covers the concept of Atrioventricular (AV) block, including its causes, types, and characteristics. You will explore First Degree and Second Degree AV blocks, along with their specific features such as PR intervals and rhythms. Test your knowledge on this essential topic in cardiology!

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