Junctional Rhythm Analysis Flashcards

Which feature best differentiates a junctional rhythm from a sinus rhythm with first-degree AV block?

Answer: P wave morphology and axis — junctional P waves are inverted in inferior leads while sinus P waves are upright

The key differentiator is P wave direction: sinus rhythm produces upright P waves in II, III, aVF regardless of PR length, while junctional rhythms produce inverted or absent P waves in inferior leads.

In a junctional escape rhythm, the QRS complex is typically narrow because of which reason?

Answer: The impulse reaches the ventricles via the normal His-Purkinje conduction system

Since junctional impulses travel through the normal bundle of His, bundle branches, and Purkinje fibers to activate the ventricles, the QRS duration is narrow — less than 120 ms — identical to sinus conducted beats.

A patient post-cardiac surgery develops a regular narrow-complex tachycardia at 110 bpm with inverted P waves in lead II occurring just after each QRS. Which rhythm is most likely?

Answer: Junctional tachycardia

Regular narrow-complex tachycardia at 110 bpm with retrograde P waves (inverted in II) immediately after QRS in a post-cardiac surgery patient is consistent with junctional tachycardia due to enhanced automaticity.

What is the significance of a junctional escape rhythm appearing at a rate slower than 40 bpm?

Answer: It may indicate junctional suppression, possibly due to enhanced vagal tone, medication effect, or junctional disease

A junctional rhythm below 40 bpm suggests the junctional pacemaker itself is suppressed, raising concern for medications (beta-blockers, digoxin), hyperkalemia, or intrinsic junctional disease.

Digitalis toxicity is classically associated with which junctional arrhythmia pattern?

Answer: Accelerated junctional rhythm with AV dissociation

Digitalis toxicity enhances junctional automaticity (causing accelerated junctional rhythm at 60-100 bpm) while simultaneously blocking AV conduction, producing AV dissociation.

A rhythm shows no visible P waves, a narrow QRS complex, and a rate of 52 bpm. Which rhythm is this most consistent with?

Answer: Junctional escape rhythm

Absent P waves, narrow QRS, and rate of 40-60 bpm are the hallmarks of a junctional escape rhythm where P waves are buried in the QRS due to simultaneous atrial and ventricular activation.