Which characteristic is found in a junctional escape rhythm?

In a junctional escape rhythm, the characteristic feature is that the P waves are inverted. This occurs because the impulse originates from the area of the heart known as the junction, which is the region around the atrioventricular node, just before it enters the ventricles. Since the atria are depolarized after the ventricles due to the location of the pacemaker, any atrial depolarization that does occur will typically produce inverted P waves in the lead II ECG when the impulse is conducted retrograde to the atria.

The presence of inverted P waves identifies this rhythm as junctional, which is crucial for differentiating it from other types of rhythms such as a sinus rhythm where P waves would usually be upright and follow the QRS complex. In addition, while junctional escape rhythms can sometimes result in absent P waves, the defining characteristic that usually highlights this rhythm is the inverted nature of the P waves when they are present.