Junctional Rhythms

The AV junction is the AV node and the proximal His bundle. In a healthy heart, the sinus node runs the show. The junction is the backup. It fires only when the sinus rate drops or sinus impulses fail to get through. When the junction takes over, the atria are activated backward (retrograde) through the AV node. The ventricles still follow the normal His–Purkinje system, so the QRS is usually narrow, and the P wave is absent, inverted or out of step with it.

Three mechanisms make junctional rhythms. The first is an escape: the junction's own automaticity takes over at 40–60 bpm when the sinus node slows or fails. Enhanced automaticity in the junction gives you accelerated junctional rhythm (60–100 bpm) and junctional tachycardia (above 100 bpm). Digoxin toxicity adds triggered activity. Ischemia, surgical injury and electrolyte shifts can also raise junctional automaticity.

The P wave pattern is a consequence of retrograde activation. In II, III and aVF, the sinus P is normally upright, and the retrograde P is inverted there. Where does it land? That depends on the AV delay. It can fall just before the QRS, hide inside it, or follow it.

Rate decides who is in charge. The sinus node runs at 60–100 bpm, the junction at 40–60 bpm and the ventricle at 20–40 bpm. So a junctional escape means the sinus node has slowed, blocked or been suppressed. A junctional tachycardia means the junction has become the faster pacemaker.

Start with the rate. It names the rhythm. Then check the P waves and the QRS. The table below has one row per junctional rhythm.

1. Rate: Measure the R–R interval over several beats and place the rate at 40–60, 60–100 or above 100 bpm.
2. Regularity: Junctional rhythms tick along evenly. An irregular narrow rhythm puts atrial fibrillation or multifocal atrial tachycardia on the list.
3. P waves: Inspect II, III and aVF for absent, inverted or post-QRS P waves. Check V1 if the baseline is noisy.
4. PR or RP: A P before the QRS means the PR is under 120 ms. A P after the QRS means a short RP interval.
5. QRS width: Confirm a narrow QRS. Until proven otherwise, a wide escape is usually infranodal or ventricular.
6. Patient stability: Check perfusion, blood pressure, mental status and chest pain before deciding on treatment.

A junctional escape is a regular rhythm at 40–60 bpm. It takes over when the sinus node is slow, blocked or suppressed. It is a protective rhythm. Many patients with it have no symptoms.

ECG Criteria

• Rate: 40–60 bpm and regular
• P waves: Absent, inverted in II, III and aVF, or buried in the QRS
• PR: Under 120 ms when a P precedes the QRS; a P after the QRS has a short RP interval
• QRS: Narrow (under 120 ms) unless a bundle branch block is present

Causes

• Sinus node dysfunction: sinus bradycardia, sinus pause or sick sinus syndrome; see ECG Rate
• Drugs: beta-blockers, calcium channel blockers, digoxin and other sinus-slowing or AV-nodal drugs
• Ischemia: An inferior MI can slow the sinus node, and the junction then gets its chance to escape
• Hyperkalemia: Severe hyperkalemia can slow the sinus node and AV conduction, and a junctional escape can follow. It usually comes with other hyperkalemic changes, such as peaked T waves and a wide QRS. See T Wave

Clinical Significance

Sometimes the escape is the first sign of sinus node failure. Sometimes it is the first sign of drug or potassium toxicity. Check the medication list, the potassium and the 12-lead ECG. A stable escape that keeps the patient perfusing is a rhythm to watch, not one to suppress.

This one is a regular narrow-complex rhythm at 60–100 bpm. It runs faster than an escape, so the junction now competes with the sinus node. It is often transient. When the patient is stable, it is frequently benign.

ECG Criteria

• Rate: 60–100 bpm, regular
• P waves: Retrograde, absent or buried; sinus P waves may appear as fusion beats when the two rhythms compete
• QRS: Narrow unless a bundle branch block is present

Causes

• Digoxin: One of the classic toxic rhythms. Check the level and potassium.
• Inferior MI: AV-nodal ischemia or reperfusion can speed up the junction. Check the ST segments in II, III, aVF and V4R.
• Post-cardiac surgery: This shows up most after valve and congenital repairs. See the junctional tachycardia section.
• Electrolytes: Abnormal potassium or magnesium can change junctional automaticity. Confirm with a lab value.

Clinical Significance

Patient stable, and the rate holding in this band? Your first job is to find the cause: a digoxin level, potassium, magnesium, a 12-lead ECG, and a review of recent surgery or ischemia. Antiarrhythmic drugs are not needed for a stable rhythm.

On digoxin, a stable accelerated junctional rhythm with mild toxicity gets supportive care and observation. Stop the digoxin. Correct potassium and magnesium, and give potassium cautiously. Call the poison center or toxicology. Digoxin immune Fab is for life-threatening toxicity, so a stable rhythm alone does not earn it.

Premature Junctional Complexes

A premature junctional complex (PJC) is an early narrow QRS from the junction. It lands before the next expected sinus beat. Its P wave is absent, inverted in II, III and aVF, or follows the QRS with a short RP interval. Isolated PJCs are common and usually benign in a patient with a normal heart. Frequent PJCs, or a run of junctional beats, get the same check as an accelerated junctional rhythm: digoxin, potassium, magnesium and a 12-lead ECG.

Junctional tachycardia is a regular narrow-complex rhythm above 100 bpm. Its P waves are absent or retrograde. Junctional ectopic tachycardia (JET) is the postoperative form. It follows cardiac surgery, most often in children with congenital heart disease.

ECG Criteria

• Rate: above 100 bpm, regular; can exceed 200 bpm in infants
• P waves: Absent, retrograde or dissociated from the QRS; AV dissociation is common in JET
• QRS: Narrow unless a bundle branch block is present

Causes

Clinical Significance

Junctional tachycardia from digoxin toxicity or an electrolyte disturbance gets one fix: correct the cause. Congenital JET in neonates and infants is rare and life-threatening, and it is often refractory to conventional antiarrhythmics. A 2025 systematic review found the ivabradine evidence limited to case reports, case series and one cohort. Drug choice and dosing for postoperative JET are center-specific. Decide them with the cardiac team.

Three rhythms get confused at the bedside. Junctional escape, sinus bradycardia and third-degree AV block with a narrow escape all look alike at a glance.

Tachycardia Mimics

Separate junctional tachycardia from the other regular narrow-complex rhythms:

• AVNRT: The most common cause of regular narrow-complex SVT. Onset and offset are typically abrupt, often at 150–250 bpm, with buried P waves or a pseudo-R′ in V1. Adenosine often terminates it (2015 ACC/AHA/HRS SVT guideline, reference 8; 2025 AHA Guidelines for CPR and ECC, Part 9, recommends adenosine for acute treatment of regular narrow-complex tachycardia, COR 1, LOE B-R)
• Sinus or atrial tachycardia: Onset and offset are gradual. Every QRS has a P wave in front of it.
• Junctional tachycardia: It warms up gradually. Look for AV dissociation or retrograde P waves, in a digoxin or postoperative setting. Adenosine can briefly block the AV node so the underlying rhythm shows itself. Not in suspected digoxin toxicity (2025 AHA Guidelines for CPR and ECC, Part 9, wide-complex synopsis)

Artifact & Lead Misplacement

• Limb lead reversal: An inverted P and QRS in lead I suggests reversed limb leads. Repeat the lead placement before you call a junctional rhythm from inverted P waves.
• Tremor or movement: Baseline noise can hide P waves. Check a longer strip in lead II or V1.
• Pacing spikes: A pacemaker spike can pass for a P wave. Check whether every spike captures.
• Transport vibration: repeat the strip when the vehicle is stopped

Start with stability. A stable junctional escape gets observed, and its cause gets treated. A symptomatic escape gets atropine, then pacing or an infusion. Doses vary by protocol; follow local protocols and medical direction.

Stability Approach

Therapy Table

Follow local protocols and online medical direction.

Pediatrics

• Not a normal variant to dismiss: In a child or infant, think congenital heart disease, recent cardiac surgery or digoxin exposure first. Healthy children and young adults with high vagal tone can also show a transient junctional rhythm, during sleep for example. Judge it by symptoms and context
• Age-based rates: Compare the heart rate with the age-specific ranges on Vital Signs
• Congenital JET: In neonates and infants it is rare, life-threatening and often refractory. Refer early to pediatric cardiology
• Digoxin exposure: In a healthy child, an ingestion of 4 mg or more, or more than 0.1 mg/kg, meets the DigiFab label criterion for Fab. That is a potentially fatal ingestion. See digoxin immune Fab
• Bradycardia with poor perfusion (PALS): Treat hypoxia and ventilation first. If the heart rate stays under 60/min with cardiopulmonary compromise despite effective ventilation with oxygen, start CPR (2025 AHA Guidelines for CPR and ECC, Part 8, COR 1, LOE C-EO). Give epinephrine 0.01 mg/kg IV/IO (0.1 mL/kg of 1:10,000; maximum 1 mg) once bradycardia persists after other factors such as hypoxia are corrected (COR 1, LOE C-EO), repeated every 3–5 min. Epinephrine is the default drug. Atropine is reserved for bradycardia from increased vagal tone or atrioventricular block that hypoxia does not cause (COR 1, LOE C-LD)
• Pacing: Emergency transcutaneous pacing may be considered for infants and children with bradycardia and cardiopulmonary compromise from complete heart block or sinus node dysfunction that does not respond to CPR (2025 AHA Guidelines for CPR and ECC, Part 8, COR 2b, LOE C-EO). The data on pacing for refractory bradycardia in children are limited, as AHA notes. Decide with medical direction.
• Dosing: Use Weight-Based Dosing for atropine and infusions; the pediatric doses are in the therapy table

Other Populations

• Older adults on digoxin: Reduced renal clearance raises the risk of toxicity. Check the level, potassium and creatinine together
• Heart transplant (denervated heart): The heart may not respond to atropine (NASEMSO v3.0, reference 7). Move to an adrenergic agonist or transcutaneous pacing. See the atropine page
• Pacemaker or ICD patients: Pacing spikes and paced beats can pass for a junctional rhythm. Check capture and the device settings
• Postoperative patients with epicardial wires: Wire pacing and a junctional rhythm can show up together. Check the wire mode before you change therapy

• Monitoring lead: Use lead II to see P waves; check II, III and aVF when the P-wave origin is unclear
• 12-lead ECG: Obtain one when the rhythm changes, and serially in an inferior MI; add V4R for right ventricular involvement
• Digoxin: Record the time of the last dose and draw the level 6 hours or more after it; keep potassium and magnesium on the transport record
• Pacing readiness: Place anterior–posterior pads before moving an unstable slow patient; check capture by the pulse and the SpO₂ waveform
• Artifact: Vibration and movement can fake P waves or bury them. Repeat the strip when the vehicle is stopped
• Handoff: Report any digoxin ingestion, the time of the last dose, the rate and the response to atropine

1. Measure the rate over several R–R intervals and place it at 40–60, 60–100 or above 100 bpm.
2. Check regularity; a regular narrow rhythm at these rates is a junctional candidate.
3. Inspect II, III and aVF for absent, inverted or post-QRS P waves.
4. Measure the PR or RP to separate junctional from sinus origin.
5. Confirm a narrow QRS; a wide one needs a ventricular or aberrancy analysis.
6. Decide on stability from perfusion, blood pressure, mental status and chest pain.
7. Find the cause: digoxin, potassium, magnesium, inferior MI, recent surgery or sinus node disease.

Common Pitfalls

• Calling a sinus bradycardia junctional. Upright P waves in II say otherwise
• Suppressing a stable escape that keeps the patient perfusing
• Giving digoxin, or another AV nodal blocker, to a patient who is already toxic
• Reading a digoxin level drawn less than 6 hours after the last dose
• Treating an unstable tachycardia without looking for digoxin toxicity, potassium or other causes
• Missing the potassium drop after digoxin immune Fab, or redosing from a post-Fab total digoxin level