Criteria for PJCs (Premature Junctional Contractions)
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Article at a Glance
- PJCs are characterized by:
- Regularity: PJC interrupts the underlying rhythm
- Rate: Depends on the rate of the underlying rhythm
- P Wave: P wave preceding the PJC may be before or after QRS or hidden within the QRS
- PR Interval: Normal in underlying sinus rhythm, typically < 0.20 seconds if inverted P wave precedes the QRS; otherwise, no measurable PRI
- QRS Complex: Typically < 0.12 seconds and appears before the next expected beat
A PJC is a premature beat that arises from the atrioventricular (AV) junction of the heart. The “P” stands for premature, so this complex will appear prior to the next expected beat. As the R-waves march out, this complex comes before the next expected complex. The premature junctional contraction (PJC) is marked with a red arrow. The “J” connotes that the beat comes from the junction. The heart’s junction is where the atria and ventricles meet. When the junction fires off, it sends a wave of electricity, retrograde, back through the atrial chamber, creating an inverted P wave. You’ll either have an inverted P wave before the QRS complex, no P wave at all, or an inverted P wave after the QRS complex. Read: Criteria for PACs (Premature Atrial Contractions) During PJC, the conduction starts at the AV node and then moves in both directions simultaneously down through the ventricles and retrograde through the atrial chambers. In a PJC, the conduction starts at the AV node as opposed to the sinoatrial (SA) node. The PJC should have no impact on ventricular conduction, so the QRS complex should appear normal.Premature Junctional Contractions
Related Video – ECG and the Cardiac Cycle Basics
Related Video – ECG Strip: Premature Junctional Complex (PJC)
Summary
A premature junctional contraction arises from the heart’s AV junction. During a PJC, providers will observe either an inverted P wave before or after the QRS complex or no P wave at all. The QRS complex should be normal.
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