This is an example of a junctional rhythm that is slower than what is considered "intrinsic rate" for the junction.  The rate is around 30 bpm.  We know this is a "supraventricular" rhythm because of the narrow QRS.  Junctional beats travel to the ventricles via the bundle branches, which provides very fast conduction, resulting in a narrow QRS complex.  The P waves can be seen at the end of each QRS.  They are upside-down in this Lead II rhythm strip, indicating retrograde conduction from the junctional pacemaker to the atria.

Clinically, the important thing when we encounter such a slow rate is to evaluate the patient's response to the rate.  If the patient is hypoperfused (pale, decreased level of consciousness, low BP), we need to act to increase the rate, regardless of the cause of the bradycardia.