How does one distinguish ventricular escape rhythm from junctional escape rhythm on an Electrocardiogram (EKG)?

From the Guidelines

To distinguish ventricular escape rhythm from junctional escape rhythm on an EKG, focus on the QRS complex morphology and rate, as ventricular escape rhythms typically have wide QRS complexes (>120 ms) with bizarre morphology and a slower rate, whereas junctional escape rhythms have narrow QRS complexes with a faster rate 1. When evaluating these rhythms, consider the following key characteristics:

• QRS complex morphology: Ventricular escape rhythms have wide QRS complexes (>120 ms) with bizarre morphology, indicating an origin below the bundle of His in the Purkinje fibers or ventricular myocardium 1.
• Rate: Ventricular escape rhythms typically have a slower rate of 20-40 beats per minute, whereas junctional escape rhythms have a faster rate of 40-60 beats per minute 1.
• Origin: Junctional escape rhythms originate from the AV node or bundle of His, resulting in narrow QRS complexes (unless there's aberrant conduction) that look similar to sinus beats 1.
• Clinical significance: Ventricular escape rhythms indicate more severe conduction system disease and may require more urgent intervention with temporary pacing, whereas junctional escape rhythms may be more responsive to autonomic manipulation such as atropine, isoproterenol, and epinephrine administration 1. It is essential to carefully evaluate the ECG, considering the relationship between P waves and QRS complexes, as well as the presence of retrograde P waves, to accurately diagnose and distinguish between ventricular and junctional escape rhythms 1.

From the Research

Distinguishing Ventricular Escape Rhythm from Junctional Escape Rhythm on an EKG

To distinguish ventricular escape rhythm from junctional escape rhythm on an Electrocardiogram (EKG), several key factors must be considered:

• QRS Complex Width:
  • A narrow QRS complex (< 120 ms) is typically associated with a junctional escape rhythm, which originates from the atrioventricular (AV) node or the proximal His-Purkinje system 2.
  • A wide QRS complex (> 120 ms) is usually indicative of a ventricular escape rhythm, originating from the ventricles 2.
• Ventricular Rate:
  • Junctional escape rhythms tend to have a faster ventricular rate, typically in the range of 40-60 beats per minute (bpm) 2.
  • Ventricular escape rhythms usually have a slower ventricular rate, often between 20-40 bpm 2.
• Response to Pharmacological Modulation:
  • The response of the escape rhythm to various medications, such as isoproterenol, atropine, adenosine, lidocaine, and verapamil, can provide clues about its origin. For instance, a rhythm that responds to sympathetic stimulation and vagal blockade may suggest an origin in the distal compact AV node or proximal His bundle 3.
• Clinical Context:
  • The clinical presentation and underlying heart condition can also influence the interpretation of the EKG. For example, patients with complete heart block may exhibit either junctional or ventricular escape rhythms, depending on the level of the block 2, 4.

Key Considerations

• The emergence or disappearance of escape rhythms over time can occur, as observed in long-term follow-up studies after radiofrequency ablation of the atrioventricular junction 5.
• The evaluation of escape rhythms is crucial for determining the risk associated with pacemaker failure and for guiding the management of patients with cardiac conduction disorders 5.
• Alternative pacing sites should be considered to avoid detrimental ventricular dyssynchrony in patients with previous nearly physiological ventricular activation 6.