What is a key feature of premature ventricular contractions (PVCs)?

Premature ventricular contractions (PVCs) are characterized by their wide and bizarre QRS complexes that occur earlier than the next expected heartbeat. This occurs because PVCs originate in the ventricles rather than the atria, leading to a different electrical conduction pathway. The early occurrence disrupts the normal rhythm of the heart, resulting in the characteristic appearance of the QRS complex on an ECG.

The wide and bizarre nature of the QRS complex is due to the abnormal conduction through the ventricles, which does not follow the typical pathways of the heart's conduction system. This gives rise to a prolonged duration of the QRS complex, typically lasting more than 0.12 seconds, in contrast to normal ventricular beats.

Understanding this key feature is crucial for recognizing and interpreting PVCs in clinical practice since they can indicate underlying cardiac issues or be a benign finding, depending on the context and frequency of occurrence.