Since the ventricles may depolarize before or after the atria, the P waves in a junctional rhythm may manifest before the QRS complex or be hidden within it. The P wave may also occur after the QRS complex. 

• If the ventricles depolarize before the atria, the QRS complex precedes the P wave. 
• If the ventricles and atria depolarize at the same time, the P wave is hidden within the QRS complex. 
• If the ventricles depolarize after the atria, the P wave appears before the QRS complex. 

An atrial impulse generated very near the AV junction may also cause inverted P waves. The PR interval helps distinguish these impulses from a junctional arrhythmia. An inverted P wave with a normal PR interval of 120–200 milliseconds is likely due to an atrial arrhythmia. Since the junctional impulse is near the ventricle, the PR interval produced by a junctional interval is shorter than normal (< 120 milliseconds).

The junctional pacemaker produces a wide variety of arrhythmias, including premature junctional complexes, junctional escape rhythms, accelerated junctional rhythms, and junctional tachycardia.