A junctional escape rhythm has a rate between 40 bpm and 60 bpm. It is a protective mechanism rather than an arrhythmia. The junctional escape rhythm is a regular rhythm with regular R-R intervals. The P wave is inverted and may occur before, after, or be hidden within the QRS complex. 

The inverted P wave that precedes the QRS complex should have a shortened PR interval < 120 milliseconds. Ventricular conduction is normal, so the QRS complex is < 120 milliseconds.

Characteristics of a Junctional Escape Rhythm

1. A regular rhythm
2. Rate 40–60 bpm
3. An inverted P wave that manifests before, after, or hidden within the QRS complex
4. A shortened PR interval if the P wave is seen before the QRS complex (< 120 milliseconds)
5. A normal QRS complex (< 120 milliseconds)