Which description characterizes premature junctional contractions?

Premature junctional contractions are characterized by the presence of an inverted P wave, which can occur either before or after the QRS complex. This unique feature arises from impulses originating in the junctional tissue of the heart, which is situated between the atria and ventricles. In a typical scenario, when the electrical impulse comes from the junction rather than the atria, the P wave may be inverted due to the different direction of depolarization.

While it's important to note that other symptoms might accompany premature junctional contractions, the key defining characteristic is the inverted P wave. Understanding this feature helps differentiate premature junctional contractions from other types of arrhythmias where P wave morphology and timing would differ. For instance, in the case of atrial contractions, P waves would typically appear upright and occur before the QRS complex, while junctional contractions reflect a different origin of electrical activation.