Junctional Rhythms Overview

Note the different names of junctional rhythms, all determined by heart rate.

 Let’s talk about Junctional Rhythms and beats!

The treatment of Junctional rhythms focus more on isolating the underlying issue, and not on the rhythm itself.

Accelerated Junctional Rhythm (AJR)

Retrograde P waves may be present and can appear before, during or after the QRS complex. They are usually inverted in inferior leads (II, III, aVF), upright in aVR + V1.

Can you explain if/when junctional rhythm is a serious issue?

A Junctional rhythm can happen either due to the sinus node slowing down or the AV node speeding up. It is generally a benign arrhythmia and in the absence of structural heart disease and symptoms, generally no treatment is required.

Junctional Escape Rhythm

Junctional rhythm with a rate of 40-60 bpm. QRS complexes are typically narrow (< 120 ms). No relationship between the QRS complexes and any preceding atrial activity (e.g. P-waves, flutter waves, fibrillatory waves). Under normal conditions, subsidiary pacemakers are suppressed by the more rapid impulses from above (i.e. sinus rhythm). Junctional and ventricular escape rhythms arise when the rate of supraventricular impulses arriving at the AV node or ventricle is less than the intrinsic rate of the ectopic pacemaker.

ECG Basics: Accelerated Junctional Rhythm Overriding Normal Sinus Rhythm

When accelerated junctional rhythm is encountered, you should suspect DIGITALIS TOXICITY - the classic dysrhythmia associated with digitalis toxicity is accelerated junctional rhythm. Other causes in adults could be beta-agonist drugs such as adrenalin, cardiac infection, ischemia, or surgery.

Glucagon treatment for bradycardia and a junctional rhythm caused by excessive beta-blockade

The bradycardia resulted from junctional pacemakers with a slower rate taking over. Glucagon reverses this by activating adenyl cyclase and increasing cAMP independently of β-adrenergic receptors. In some patients glucagon will not convert patients back to a sinus rhythm, but can still improve their heart rate and clinical status as glucagon increases the rate of the junctional pacemaker cells.

Junctional Arrhythmias and AV Blocks

When the AV junction is functioning as the pacemaker of the heart, the electrical impulse produces a wave of depolarization that spreads backward (retrograde) into the atria as well as forward (antegrade) into the ventricles. The location of the P wave relative to the QRS complex depends on the speed of antegrade and retrograde conduction.

Junctional Rhythm

The rate is slower than the SA node. This is because the phase 4 of the action potential is more shallow compared to the SA node and therefore, the time to reach the action potential threshold takes longer. Therefore, the frequency of firing is less and the heart rate is less. There are 3 typical appearances of a junctional rhythm.

Rhythm Nation: Junctional Rhythm due to Hyperkalemia

As mentioned, the hyperkalemic effects on Phase 0 causes myocyte depression, leading to various conduction delays. Eventually, the AV node then SA nodes would stop conducting, resulting in the junctional escape rhythm seen in our patient. The AV node has a focus of automaticity at the AV junction with an inherent rate between 40 to 60 beats per minute. This junctional focus becomes the dominant pacemaker when no longer suppressed by the SA and AV nodes.

Tasty Morsels of EM 031 – Retrograde p waves

an impulse also goes up from the av node and depending on whether the atrium is refractory or not will result in a retrograde (usually inverted p wave). Example here from LITFL of an accelerated junctional rhythm with retrograde p waves(inverted p waves in II, III and aVF).

What Junctional Rhythm Looks Like on Your Watch ECG

To recognize Junctional Rhythm on your watch ECG, look for QRS Complexes without P Waves before them. Sometimes, P Waves may come after your QRS Complexes, or be completely dissociated from them. For clarity, we show visual examples of Junctional Rhythm on watch ECGs in this article.