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 present with wide QRS complexes and a slow rate, while junctional escape rhythms show narrow QRS complexes and a slightly faster rate. When evaluating an EKG for escape rhythms, consider the following key characteristics:
- QRS complex morphology: Ventricular escape rhythms often have wide QRS complexes (>120 ms) with bizarre morphology, resembling bundle branch blocks, whereas junctional escape rhythms typically have narrow QRS complexes (<120 ms) with normal morphology 1.
- Rate: Ventricular escape rhythms usually have a slow rate of 20-40 beats per minute, while junctional escape rhythms have a slightly faster rate of 40-60 beats per minute.
- P wave association: In ventricular escape rhythms, P waves are usually dissociated from QRS complexes or absent, whereas in junctional rhythms, P waves may be absent, inverted (appearing before, during, or after the QRS), or retrograde (inverted in leads II, III, aVF) 1. These differences in EKG characteristics reflect the anatomical origins of the rhythms, with ventricular escapes originating from the ventricles and junctional escapes arising from the AV node or bundle of His 1. It is essential to carefully evaluate the EKG to diagnose atrioventricular block and distinguish between ventricular and junctional escape rhythms, as the management and prognosis of these conditions differ significantly 1. In clinical practice, the distinction between ventricular and junctional escape rhythms has important implications for patient management, as ventricular escapes may indicate more extensive conduction system failure and require prompt attention 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, as the origin of the rhythm is usually above the bifurcation of the His bundle 2. + A wide QRS complex (> 120 ms) is more commonly seen in ventricular escape rhythms, indicating the origin is within the ventricles or the bundle branch-Purkinje system 2, 3.
- Heart Rate: + Junctional escape rhythms tend to have a faster heart rate, typically in the range of 40-60 bpm, due to their more proximal origin in the cardiac conduction system 2. + Ventricular escape rhythms usually have a slower heart rate, often between 20-40 bpm, reflecting their distal origin in the ventricles 2.
- Response to Pharmacological Agents: + The response to certain medications can also help differentiate between the two. For instance, junctional escape rhythms may respond to sympathetic stimulation and vagal blockade, as evidenced by changes in heart rate with administration of drugs like isoproterenol and atropine 4. + Ventricular escape rhythms may show different responses to these agents, and their cycle length can be affected by drugs such as lidocaine, which can prolong the cycle length 4.
- Clinical Context: + The underlying condition leading to the escape rhythm, such as complete heart block or myocardial infarction, should also be considered in the differentiation process 5, 3. + The patient's symptoms, such as bradycardia, hypotension, or signs of heart failure, can provide additional clues about the nature of the escape rhythm 2, 3.