Junctional escape rhythm
A protective backup rhythm from the AV junction that emerges when the sinus node fails to pace the heart quickly enough.
Key ECG features
- ✓Narrow QRS
- •Slow, regular rate
- ✓Beats arrive late rather than early
- ±P waves absent, retrograde, or dissociated
✓ required · • typical · ± may be present
ECG characteristics
A narrow QRS - supraventricular in origin - at a slow, regular rate, with P waves absent, retrograde, or dissociated from the QRS. The beats arrive late, at the intrinsic junctional escape rate, rather than early.
This illustration is schematic. Dashed line is a normal rhythm. The grid is not drawn to scale.
Common causes
Failure of the primary pacemaker: sinus arrest, sinus node dysfunction, high-grade AV block, or profound sinus bradycardia.
Why it matters
It should be recognized as a rescue mechanism rather than suppressed. The clinical problem belongs to the failed primary pacemaker, not to the escape rhythm keeping the patient alive.
Differentiate from
- Sinus bradycardiaBoth are slow with a narrow QRS. Sinus bradycardia keeps a normal upright P wave before every QRS.
- Ventricular escape rhythmThe same rescue role from a lower focus: junctional escape is narrow and slightly faster, ventricular escape is wide and slower.
- Atrial standstillIf no P waves appear at all rather than being merely dissociated, the atria may be electrically silent - check potassium.
- Third-degree (complete) AV blockA narrow escape rhythm below a complete block looks identical. The difference is whether dissociated P waves are marching above it.