Trifascicular Block Overview
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Questions and Answers

What is the primary location for conduction delays that result in PR interval prolongation?

  • Right bundle branch
  • Left anterior fascicle
  • Third fascicle
  • AV node (correct)

    • What is the recommended course of action for patients with bifascicular block experiencing syncope?

  • Outpatient follow-up only
  • Immediate pacemaker insertion
  • Admit for monitoring and likely pacemaker insertion (correct)
  • No intervention needed

    • Which of the following conditions is commonly associated with bifascicular block?

  • Aortic stenosis (correct)
  • Sarcoidosis
  • Pulmonary embolism
  • Hyperkalemia

    • What is the classification recommendation for asymptomatic bifascicular block with first-degree AV block?

    <p>Class III indication against pacing</p> Signup and view all the answers

    What term is discouraged by the AHA/ACCF/HRS due to its inaccuracy?

    <p>Trifascicular block</p> Signup and view all the answers

    What is the progression risk to complete heart block for patients with bifascicular block?

    <p>1% risk per year</p> Signup and view all the answers

    Which ECG finding is characteristic of true trifascicular block?

    <p>Right bundle branch block with left axis deviation and third degree heart block</p> Signup and view all the answers

    Which condition does NOT typically contribute to the development of bifascicular block?

    <p>Pulmonary hypertension</p> Signup and view all the answers

    What is the typical yearly risk of progression to complete heart block for patients with asymptomatic bifascicular block?

    <p>1% per year</p> Signup and view all the answers

    Which of the following describes previously termed 'incomplete trifascicular block'?

    <p>Bifascicular block with first degree AV block</p> Signup and view all the answers

    What does Braunwald’s textbook state about bidivisional block with a prolonged PR interval?

    <p>It is associated with a greater risk of complete heart block.</p> Signup and view all the answers

    What is the annual risk of progression to complete heart block in patients with bifascicular block?

    <p>1%</p> Signup and view all the answers

    What is suggested if prolonged PR interval is present in a bifascicular block?

    <p>It may indicate disease of the third subdivision.</p> Signup and view all the answers

    What conclusion did Robert Buttner make about the conduction delay in PR interval prolongation?

    <p>It cannot be determined whether it occurs in the AV node or fascicle.</p> Signup and view all the answers

    Which professionals contributed to the content on ECG in Emergency Medicine?

    <p>Professionals from both emergency medicine and cardiology.</p> Signup and view all the answers

    What is one of Robert Buttner's special interests?

    <p>Diagnostic and procedural ultrasound.</p> Signup and view all the answers

    According to Robert Buttner, how do patients with bifascicular block and first degree AV block compare in risk to those without it?

    <p>Their risks are equivalent.</p> Signup and view all the answers

    What is one of the primary roles of Robert Buttner in relation to the ECG Library?

    <p>Editor-in-chief.</p> Signup and view all the answers

    What social platform does Robert Buttner use to share his work?

    <p>Twitter.</p> Signup and view all the answers

    What type of medicine does John Larkin specialize in?

    <p>Emergency medicine.</p> Signup and view all the answers

    Which components are involved in true trifascicular block?

    <p>Right bundle branch block (RBBB), left anterior fascicular block (LAFB), and left posterior fascicular block (LPFB)</p> Signup and view all the answers

    What is one of the ECG patterns indicative of 3rd degree AV block?

    <p>3rd degree AV block + RBBB + LAFB</p> Signup and view all the answers

    Which condition typically arises from the left anterior or left posterior fascicle in trifascicular block?

    <p>Ventricular escape rhythm</p> Signup and view all the answers

    What clinical misunderstanding is commonly associated with the term 'trifascicular block'?

    <p>It is mistakenly used to describe bifascicular block with normal AV conduction</p> Signup and view all the answers

    Which of the following is a rare indicator of impending trifascicular block?

    <p>RBBB with alternating fascicular blocks on a beat-to-beat basis</p> Signup and view all the answers

    What is a common characteristic of QRS complexes in arrhythmias related to trifascicular block?

    <p>QRS complexes with the appearance of RBBB plus either LPFB or LAFB</p> Signup and view all the answers

    What does bifascicular block refer to in the context of trifascicular block?

    <p>Conduction delay in two of the three fascicles</p> Signup and view all the answers

    Which form of AV block is most commonly associated with trifascicular block?

    <p>1st degree AV block</p> Signup and view all the answers

    What is the main characteristic of true trifascicular block compared to other blocks?

    <p>Involves all three fascicles below the AV node</p> Signup and view all the answers

    Which of these statements is false regarding the signs of trifascicular block?

    <p>QRS morphology remains unchanged in trifascicular block.</p> Signup and view all the answers

    Study Notes

    Trifascicular Block Overview

    • True trifascicular block indicates conduction delay in all three fascicles (Right Bundle Branch Block (RBBB), Left Anterior Fascicular Block (LAFB), Left Posterior Fascicular Block (LPFB)).
    • Clinically manifests as bifascicular block and third-degree AV block.

    Diagnostic Criteria

    • ECG Patterns:
      • Third-degree AV block + RBBB + LAFB.
      • Third-degree AV block + RBBB + LPFB.
    • Ventricular escape rhythm often originates from the left anterior or left posterior fascicle, producing characteristic QRS complexes.

    Impending Trifascicular Block Indicators

    • Alternating normal sinus rhythm with LBBB/RBBB.
    • RBBB with alternating fascicular blocks on a beat-to-beat basis.

    Common Misunderstandings

    • "Trifascicular block" often misused to describe bifascicular block with either first-degree or second-degree AV block.
    • Actual conduction delay typically occurs at the AV node, not in a third fascicle.

    Clinical Implications

    • True trifascicular block (with associated third-degree AV block) necessitates pacemaker insertion.
    • Bifascicular block with syncope/presyncope should be monitored and may require pacing.
    • Asymptomatic bifascicular block with first-degree AV block does not warrant pacing.

    Causes

    • Similar to those causing bifascicular block, primarily related to degeneration in fascicles below the AV node.
    • Significant causes include:
      • Ischaemic heart disease (40-60%).
      • Structural heart disease (50-80% association).
      • Aortic stenosis, anterior myocardial infarction, Lenègre-Lev disease, congenital heart disease.
      • Hyperkalaemia (resolves with treatment), digoxin toxicity.

    ECG Examples

    • True Trifascicular Block: Shows RBBB, LAFB, and third-degree heart block.
    • Incomplete Trifascicular Block: Bifascicular block coupled with first-degree AV block represents functional conduction disease without distinguishing based solely on ECG.
    • Understanding other blocks: Left Bundle Branch Block (LBBB), Right Bundle Branch Block (RBBB), LAFB, LPFB, Interventricular Conduction Delay (IVCD), Bifascicular block, AV blocks, Complete Heart Block (CHB).

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    Quiz Team

    Description

    This quiz explores the diagnostic criteria and implications of true trifascicular block, characterized by conduction delays in all three fascicles below the AV node. Participants will learn about the associated ECG patterns and the significance of various blocks such as RBBB, LAFB, and LPFB in conjunction with third-degree AV block.

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