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Site and Etiology of Atrioventricular Block

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Insights into Electrocardiograms with MCQs

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Abstract

Electrocardiographic findings can differentiate block at the level of atrioventricular node from block at the level of bundle branches. These differences are discussed with representative electrocardiograms. Holter monitoring can be helpful in detecting transient changes in atrioventricular conduction. Representative tracings are shown and clinical significance of various findings are discussed. In some cases electrocardiographic changes during exercise stress testing, use of intravenous atropine, and carotid massage can give diagnostic clue. Representative electrocardiographic tracings are shown with their interpretation. In doubtful cases electrophysiologic study may be needed to find the exact site of delay in the atrioventricular conduction. Common causes of atrioventricular block and site of block in these conditions are discussed with representative electrocardiograms. Summary and MCQs at the end of the chapter help in quick revision and self-assessment.

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References

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Author information

Authors and Affiliations

  1. Ex Senior professor and head of the department of cardiology, Jawaharlal Nehru Medical College, Ajmer, India

    Sitaram Mittal

Authors
  1. Sitaram Mittal
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Appendices

Summary

  • Very long PR interval, variation in PR intervals, narrow QRS complex, group beating, and transient atrioventricular block suggest block at the level of the atrioventricular node.

  • Increased sympathetic drive (treadmill stress test or I/V atropine) decreases block at the level of atrioventricular node but increases infra-His block. Vagal stimulation (e.g., carotid sinus compression) has opposite effect.

  • During electrophysiologic study, prolongation of the AH interval suggests block of the level of the atrioventricular node. Prolongation of the HV interval suggests infra-His block.

  • In the setting of inferior myocardial infarction, site of atrioventricular block is usually at the level of the atrioventricular node. Usually, the block gradually advances and gradually recovers.

  • In the setting of anterior myocardial infarction, atrioventricular block is usually at the level of the bundle branches. Atrioventricular block usually appears suddenly and is usually permanent.

  • Congenital atrioventricular block is usually at the level of the atrioventricular node.

  • Beta-blockers, diltiazem, and verapamil delay conduction at the level of the atrioventricular node. Amiodarone, propafenone, and flecainide delay conduction at the level of the His bundle-Purkinje system.

  • Vagotonia delays conduction at the level of the atrioventricular node and is usually accompanied by sinus bradycardia.

  • Chronic atrioventricular block in elderly is usually due to sclerodegeneration of the conduction tissue.

MCQs

Q1. Type I second-degree atrioventricular block with a normal QRS usually occurs at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The Bundle branches

  4. (d)

    The Purkinje system

Q2. Prolonged PR interval with QRS showing bundle branch pattern suggests delay in conduction at:

  1. (a)

    The atrioventricular node

  2. (b)

    The His-Purkinje system

  3. (c)

    Either atrioventricular node or the His-Purkinje system

  4. (d)

    Atrioventricular node with preexisting bundle branch block

Q3. Type II second-degree atrioventricular block occurs more commonly in the setting of:

  1. (a)

    Inferior myocardial infarction

  2. (b)

    Right ventricular infarction

  3. (c)

    Posterior infarction

  4. (d)

    Anterior infarction

Q4. Type II second-degree atrioventricular block with bundle branch block pattern usually occurs at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The Bundle branches

  4. (d)

    The Purkinje system

Q5. In 2:1 atrioventricular block with normal QRS, block is usually at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The bundle branches

  4. (d)

    Any of the above

Q6. In 2:1 atrioventricular block with broad QRS, block is usually at the level of:

  1. (a)

    Junction of intra-atrial conduction tissue with the atrioventricular node

  2. (b)

    The atrioventricular node

  3. (c)

    The His bundle

  4. (d)

    The bundle branches

Q7. Complete atrioventricular block with QRS duration of more than 0.12 s suggests:

  1. (a)

    Block at the level of the atrioventricular node with preexisting bundle branch block

  2. (b)

    Block at the level of the atrioventricular node with bradycardia dependent aberrant ventricular conduction

  3. (c)

    Block at the level of bundle branches

  4. (d)

    All

Q8. Chronic complete atrioventricular block is usually at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The bundle branches

  4. (d)

    The Purkinje system

Q9. Complete atrioventricular block in the setting of acute anterior myocardial infarction in usually at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The bundle branches

  4. (d)

    The Purkinje system

Q10. Complete atrioventricular block in the setting of acute inferior infarction is usually at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The bundle branches

  4. (d)

    The Purkinje system

Q11. In congenital complete atrioventricular block:

  1. (a)

    Ventricular rate is usually above 50/min

  2. (b)

    QRS duration is usually normal

  3. (c)

    QRS configuration is usually normal

  4. (d)

    All

Q12. In the setting of complete atrioventricular block, ventricular rate around 50/min with narrow QRS suggests that the site of atrioventricular block is at the level of:

  1. (a)

    The atrioventricular node

  2. (b)

    The His bundle

  3. (c)

    The bundle branches

  4. (d)

    The Purkinje system

Answers

(1) a; (2) c, d; (3) d; (4) c, d; (5) a; (6) d; (7) d; (8) c; (9) c; (10) a; (11) d; (12) a

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© 2023 The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

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Mittal, S. (2023). Site and Etiology of Atrioventricular Block. In: Insights into Electrocardiograms with MCQs. Springer, Singapore. https://doi.org/10.1007/978-981-99-0127-2_12

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  • DOI: https://doi.org/10.1007/978-981-99-0127-2_12

  • Published:

  • Publisher Name: Springer, Singapore

  • Print ISBN: 978-981-99-0126-5

  • Online ISBN: 978-981-99-0127-2

  • eBook Packages: MedicineMedicine (R0)

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