What is the characteristic QRS duration in a Premature Junctional Contraction (PJC)?

A Premature Junctional Contraction (PJC) typically presents with a QRS duration that is less than 0.12 seconds. This characteristic is significant because PJCs occur when an impulse originating from the junctional area of the heart (the AV node or nearby tissues) leads to early depolarization of the ventricles. Since the conduction through the ventricles occurs via the normal pathway (the bundle of His and Purkinje fibers), the QRS complex remains narrow, thus measuring less than 0.12 seconds.

In contrast, a QRS duration of 0.12 seconds or greater is indicative of slower conduction through the ventricles, which is not seen in PJCs. Therefore, the QRS duration of a PJC being less than 0.12 seconds reflects its origin and conduction properties, allowing for timely identification of this arrhythmia. Understanding this characteristic aids in distinguishing PJCs from other arrhythmias, such as those that have more pronounced conduction delays.