Junctional Ectopic Rhythms

This section will go over junctional ectopic rhythms, which are rhythms originating from automatic foci located in the atrioventricular junctional. This includes junctional escape rhythms, but will focus on junctional tachycardia and accelerated junctional rhythms.

We will go over:

• Clinical features of junctional ectopic rhythms, such as risk factors for this rare rhythm (i.e. ischemia, cardiac surgery, sympathomimetics, digitalis toxicity) and its relative difficulty to treat, especially given the risk of atrioventricular block with ablation.

• Junctional escape rhythm and its differential diagnosis. We will present it in the context of an underlying sinus rhythm, atrial flutter, and atrial fibrillation.

• Accelerated junctional rhythm, and its characteristic presentation with isorhythmic atrioventricular dissociation.

• Junctional ectopic tachycardia and its various manifestations, such as:

  • Junctional tachycardia with retrograde conduction and varying RP intervals. Although classically defined as "high nodal", "mid nodal", or "low nodal" origin based on the timing of the p wave, we will discuss how atrioventricular conduction delays can impair the accurate determination of where the junctional ectopic originates from. We also discuss the differential diagnosis for each phenotype of junctional tachycardia.

  • Junctional tachycardia with varying degrees of ventriculoatrial block (causing impaired retrograde conduction of the junctional impulse to the atria) or atrioventricular block (causing impaired anterograde conduction of the junctional impulse to the atria). 

  • Double junctional rhythm, a scenario wherein two junctional ectopic foci coexist with a block between them, with the higher focus driving the atria and the lower focus driving the ventricles, leading to atrioventricular dissociation.

  • Double tachycardia, an interesting phenomenon whereby an atrial tachyarrhythmia (such as atrial tachycardia) coexists with junctional tachycardia due to atrioventricular dissociation related to concealed conduction.

  • Junctional tachycardia with aberrant conduction and atrioventricular dissociation closely mimicking ventricular tachycardia, to the point that many widely-used diagnostic algorithms would misclassify it.