Junctional Rhythms
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Questions and Answers

What is the primary cause of Premature Junctional Complex (PJC)?

  • Medications causing bradycardia
  • Severe sinus bradycardia
  • High levels of potassium
  • Premature impulse originating within the AV junction (correct)

    • A high frequency of Premature Junctional Complex (PJC) is a concerning sign indicating enhanced automaticity.

    True

    What is a clinical significance of Junctional Escape Rhythm?

    It causes a slower heart rate, leading to poor cerebral and coronary perfusion.

    The AV junction consists of the AV node and the __________.

    <p>Bundle of His</p> Signup and view all the answers

    Match the causes with their respective conditions:

    <p>Adrenaline = Premature Junctional Complex (PJC) Hyperkalaemia = Junctional Escape Rhythm Antiarrhythmics = Premature Junctional Complex (PJC) Beta blockers = Junctional Escape Rhythm</p> Signup and view all the answers

    Which of the following can lead to Junctional Escape Rhythm?

    <p>Sinus arrest</p> Signup and view all the answers

    The P wave in Premature Junctional Complex can never be inverted.

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

    What is the heart rate during the underlying rhythm with a PJC?

    <p>70</p> Signup and view all the answers

    Which condition is associated with dropped beats and intermittent complete blocks below the AV node?

    <p>Mobitz Type 2 (Second Degree AV Block)</p> Signup and view all the answers

    The PR interval remains constant in Mobitz Type 2 AV Block.

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

    What is the primary characteristic of Third Degree AV Block?

    <p>Complete block of electrical activity through the heart.</p> Signup and view all the answers

    In Second Degree AV Block (Mobitz 2), the ratio of P waves to QRS complexes is generally ______.

    <p>4:3</p> Signup and view all the answers

    Match the type of AV block with its characteristic feature:

    <p>First Degree AV Block = Progressively longer PR interval Mobitz Type 1 = Dropped QRS after a series of conducted beats Mobitz Type 2 = Dropping QRS complexes periodically Third Degree AV Block = Complete dissociation of P waves and QRS complexes</p> Signup and view all the answers

    What characteristic of the PR interval may be observed in Mobitz Type 2?

    <p>Relatively normal or excessively delayed</p> Signup and view all the answers

    In Third Degree AV Block, the ventricular rate can be very low, around 20-40 BPM.

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

    What is the typical QRS morphology observed in a complete AV block?

    <p>Narrow and sharp if the SA node is pacing; wide if a ventricular pacemaker is functioning.</p> Signup and view all the answers

    Damage to the _______ walls of the heart can cause a Mobitz Type 2 AV Block.

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

    What is the expected regularity of the RR intervals in Mobitz Type 2?

    <p>Irregularly irregular</p> Signup and view all the answers

    What is the normal PR interval in nonparoxysmal junctional tachycardia?

    <p>Less than 0.12 seconds</p> Signup and view all the answers

    In paroxysmal supraventricular tachycardia, P waves are typically normal.

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

    What is the heart rate range for junctional tachycardia?

    <p>Over 100 beats per minute</p> Signup and view all the answers

    The condition where the AV node delays conduction is referred to as _____________.

    <p>Atrioventricular Block - First Degree</p> Signup and view all the answers

    Match the following conditions with their characteristics:

    <p>Acute Coronary Syndrome = Very significant First Degree AV Block = Consistently prolonged conduction Junctional Tachycardia = Rate over 100 Second Degree AV Block Type 1 = Progressively prolonged conduction</p> Signup and view all the answers

    Which of the following is NOT a known aetiology for junctional tachycardia?

    <p>Increased physical activity</p> Signup and view all the answers

    The PP and RR intervals are typically irregular in paroxysmal supraventricular tachycardia.

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

    What is the typical rate range for atrioventricular block - first degree?

    <p>That of the underlying rhythm</p> Signup and view all the answers

    Sinus arrest leads to a __________ wave in an ECG.

    <p>no P</p> Signup and view all the answers

    Match the following ECG characteristics with their associated conditions:

    <p>Absence of P wave = Dysfunctional SA node Prolonged PR interval = First Degree AV Block Regular rhythm = Nonparoxysmal Junctional Tachycardia Narrow QRS complexes = Supraventricular Tachycardia</p> Signup and view all the answers

    What is the primary origin of junctional tachycardia?

    <p>AV junction</p> Signup and view all the answers

    Patients with First Degree AV Block are typically symptomatic.

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

    What is a common treatment maneuver for paroxysmal supraventricular tachycardia?

    <p>Valsalva manoeuvre</p> Signup and view all the answers

    The heart rate during junctional tachycardia is typically ___________ or higher.

    <p>over 100</p> Signup and view all the answers

    Study Notes

    Premature Junctional Complex (PJC)

    • An impulse originating from the AV junction, causing a compensatory pause.
    • Aetiology:
      • Medications (antiarrhythmics)
      • Adrenaline
      • Hypoxia
      • Junction toxicity
      • Congestive heart failure
      • Coronary artery disease
      • Post heart attack
      • Enhanced automaticity
      • Re-entry of AV junction
    • Clinical significance:
      • Isolated PJCs: Not immediately significant
      • Multiple PJCs: Can cause other dysrhythmias, impact cardiac output, and cause patient anxiety.
      • High frequency: May indicate enhanced automaticity or re-entry, potentially leading to more serious dysrhythmias.
    • ECG analysis:
      • Rate: Typically 70 bpm (underlying rhythm)
      • Regularity: Underlying rhythm is normal, irregular during PJC.
        • Couplets: 2 PJCs in a row
        • Juncture tachycardia: 3+ PJCs in a row
      • P wave: Can be absent, buried in QRS, inverted, or before/after QRS, depending on the location of PJC in the AV junction.
        • Proximal: Atrial depolarization before ventricles, inverted P wave.
        • Mid: At the same time as ventricles, P wave buried in QRS.
        • Distal: Ventricular depolarization first or retrograde, inverted P wave or after QRS.
      • PR interval: Can be RP, under 0.5 seconds.
      • QRS and conduction ratio: Should be normal with normal ratio.
        • Bigeminy: One PJC after every QRS
        • Trigeminy: One PJC after every two QRS
        • Quadrigeminy: One PJC after every three QRS.
      • Origin: AV junction

    Junctional Escape Rhythm

    • Occurs when the AV junction takes over pacing due to absent or infrequent descending impulses from the SA node.
    • Aetiology:
      • Severe sinus bradycardia
      • Sinus arrest
      • Sinoatrial exit block
      • AV block
      • Hyperkalaemia
      • Medications e.g. beta blockers, calcium channel blockers
      • Return of spontaneous circulation (ROSC) - AV junction activates first.
    • Clinical significance:
      • Slower than SA node, leading to slow heart rate and cardiac output, causing poor cerebral, coronary, and organ perfusion.
      • Isolated: Not significant
      • Combined with pre-existing conditions: Highly significant.
    • ECG analysis:
      • Rate: Very slow, generally 40-60 bpm, but can be less.
      • Regularity: Regular.
      • P wave: Depends on the cause of SA node dysfunction.
        • Sinus arrest: No P wave.
        • AV block: No P wave.
        • Random P waves: May be present.
      • PR interval: Under 0.12 seconds.
      • QRS and conduction ratio: Narrow, sharply pointed, abnormal QRS complex due to conduction differences in the left bundle branch. No P wave association with QRS complexes.
      • Origin: AV junction.

    Nonparoxysmal Junctional Tachycardia (Accelerated Junctional Rhythm/Junctional Tachycardia)

    • Continuous, not sudden onset and cessation
    • Occurs when the AV junction rate exceeds the SA node rate.
    • Aetiology:
      • Medications
      • Damage to the AV junction (e.g., coronary artery blockage, heart attack)
      • Hyperkalaemia
      • Hypoxia
    • Clinical significance: Highly significant after a heart attack, in hypoxia, or with sympathetic drug overdose.
    • ECG analysis:
      • Rate:
        • Accelerated Junctional Rhythm: 60-100 bpm
        • Junctional Tachycardia: Over 100 bpm.
      • Regularity: Regular, but fast.
      • P wave: Can be seen before, during, or after QRS.
        • Abnormal: Generally inverted.
        • Normal: Generally unassociated with QRS.
      • PR interval: Under 0.12 seconds in nonparoxysmal tachycardia.
      • QRS and conduction ratio: Sharp, narrow.
      • Origin: AV junction.

    Paroxysmal Supraventricular Tachycardia (PSVT)

    • Definition:
      • Fast heart rate originating above the ventricles.
      • AVNRT (AV nodal re-entry tachycardia): Irregular refractory periods between fast and slow pathways in the AV node cause constant ventricular contraction.
      • AVRT (AV re-entry tachycardia): Two pathways create a circuit causing contraction.
      • Involves re-entry circuits.
    • Aetiology:
      • Premature atrial complex initiating supraventricular tachycardia.
      • Increased sympathetic nervous tone (e.g., amphetamines, cocaine, tobacco, alcohol, coffee).
      • Electrolyte imbalances.
      • Hyperventilation.
    • Clinical significance:
      • Treatment: Valsalva maneuver.
    • ECG analysis:
      • Rate: 150-250 bpm, abrupt onset and termination.
      • Regularity: Irregular at the start and end, but generally not profoundly irregular.
      • P wave: Typically absent, buried in QRS.
        • If present: Not normal, generally inverted.
      • PR interval: Under 0.12 seconds.
      • QRS and conduction ratio: Narrow QRS complexes, relatively normal ventricular conduction, normal duration, 1:1 ratio if P wave is seen.
      • Origin: AV node or accessory pathway outside the AV node causing a re-entry circuit.

    Atrioventricular Block - First Degree

    • Conduction delay through the AV node, potentially blocking transmission.
    • Aetiology:
      • Damage to the AV node (e.g. Myocardial infarction, ischemic heart disease)
      • Excessive vagal tone
      • Medications (beta blockers, calcium channel blockers)
      • Acute rheumatic fever
      • Electrolyte imbalances.
    • Clinical significance:
      • Asymptomatic in isolation, but requires evaluation of the underlying cause.
      • Potential to progress to higher-grade blocks.
    • ECG analysis:
      • Rate: Same as underlying rhythm.
      • Regularity: Same as underlying rhythm.
      • P wave: Consistently normal.
      • PR interval: Longer than 0.20 seconds, indicating delayed conduction through the AV node.
      • QRS and conduction ratio: Normal P waves precede each QRS complex.
      • Origin: Sinus.

    Atrioventricular Block - Second Degree Type 1 (Mobitz 1/Wenckebach)

    • Progressive prolongation of conduction through the AV node leading to absent QRS complexes.
    • Aetiology:
      • Damage to the AV node (e.g., Myocardial infarction, ischemic heart disease)
      • Excessive vagal tone
      • Medications (beta blockers, calcium channel blockers)
      • Acute Rheumatic fever
      • Electrolyte imbalances
    • Pathophysiology: AV conduction progressively slows until the SA node impulse fails to conduct.
    • Clinical significance: Transient and reversible.
    • ECG analysis:
      • Rate: Same as underlying rhythm.
      • Regularity: Irregular RR intervals but regular PP intervals.
      • P wave: Normal.
      • PR interval: Progressively long, and absent in the non-conducted beat.
      • QRS and conduction ratio: Narrow, sharp QRS complex, ratio depends on the frequency of non-conducted P waves.
      • PP and RR: Irregular RR intervals.
      • Origin: Sinus.

    Atrioventricular Block - Second Degree Type 2 (Mobitz 2/Infranodal)

    • Intermittent dropped beats, indicating intermittent complete blocks below the AV node.
    • Aetiology: Damage to the anterior wall of the heart affecting bundle branches.
    • Clinical significance: Slow ventricular rate leading to low cerebral, coronary, and organ perfusion.
    • ECG analysis:
      • Rate: Variable, depending on the frequency of the block.
        • Sinus rate: P wave rate
        • Ventricular rate: QRS complex rate.
      • Regularity: Irregularly irregular.
        • PP: Regular.
        • RR: Irregular
      • P wave: Should be normal.
      • PR interval: Can be normal or excessively delayed (prolonged) depending on the block location.
      • QRS and conduction ratio: Dropped QRS complex, normal QRS complex, wide QRS complex (bundle branch issue). Ratio varies based on the dropped beat frequency (generally 4:3, one more P wave than QRS complex).
      • Origin: Sinus.

    Atrioventricular Block - Third Degree - Complete AV Block

    • Complete block of descending electrical activity through the heart (AV node, Bundle of His, bundle branches).
    • Aetiology: Can be transient and reversible or permanent.
      • Transient: Similar to 1st degree block.
      • Permanent: Severe damage to the AV junction (e.g., myocardial infarction) or chronic degenerative changes in bundle branches.
    • ECG analysis:
      • Rate: Varies based on functional pacemaker location.
        • 40-60 bpm: AV junctional escape rhythm.
        • 20-40 bpm: Ventricular escape rhythm.
      • Regularity: Regular.
        • PP: Regular if SA node fires regularly.
        • RR: Regular.
      • P wave: Normal (if SA node firing), flutter, or fibrillation.
      • PR interval: Difficult to determine, variable, no association with QRS.
      • QRS and conduction ratio: No association with P waves.
        • Narrow and sharp: SA node rhythm.
        • Wide: Ventricular pacemaker.
      • Origin:
        • Sinus: If SA node is pacing.
        • Ventricular: If ventricular pacemaker dominates.

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