Final answer:
A premature ventricular contraction is an abnormal heart rhythm originating from the ventricles, which can be transient or lead to more serious conditions if chronic.
Step-by-step explanation:
A premature ventricular contraction (PVC) is classified as an abnormal heart rhythm originating from the ventricles. PVCs fall under the category of ventricular arrhythmias, which are due to issues with the heart's electrical conduction system. These contractions can be the result of an ectopic focus, which may be caused by factors such as localized ischemia, exposure to certain drugs, or elevated autonomic stimulation. While occasional occurrences are typically transient and not life-threatening, chronic conditions may lead to more serious arrhythmias or fibrillation, an uncoordinated beating of the heart.