• When there is a transient sinus pause (and the atrial automaticity focus above fails to produce electrical impulses), a junctional escape beat arises from the junctional automaticity focus and is conducted down the His bundle-Purkinje system.
• Because the junctional automaticity focus is located in the lower part of the AV junction (away from atrial cells), its impulse might not reach the atria and this often times result in absent P waves.
• When impulse from junctional focus reaches the atria in a retrograde fashion, it causes atrial depolarization and retrograde P waves (negatively deflected in inferior leads I, III, aVF and positively deflected in lead V1).
• Since conduction down the His-Purkinje pathway remains intact, QRS complex is normal and narrow.
• As soon as the sinus node resumes its pacemaking activity, the original sinus rhythm also returns to baseline.
• A junctional escape rhythm (commonly referred to as "junctional rhythm") occurs when all electrical activities are generated from the junctional automaticity focus. This happens when there is no electrical activity from above the AV junction such as in the case of complete AV block.
• The junctional automaticity focus sends electrical impulses down the His-Purkinje pathway thus creating normal, narrow QRS complexes.
• Because the junctional automaticity focus is located in the lower part of the AV junction (away from atrial cells), its impulse might not reach the atria and this often times result in absent P waves.
• When impulse from junctional focus reaches the atria in a retrograde fashion, it causes atrial depolarization and retrograde P waves (negatively deflected in inferior leads I, III, aVF and positively deflected in lead V1).
• Junctional rhythm is a type of bradyarrhythmia due to the slow inherent junctional rate (40-60 bpm).
• When the resulting rate is < 40 bpm, it's called junctional bradycardia. On the other hand, when it's 60-100 bpm, it's called accelerated junctional rhythm.
