What defines a PVC?

A PVC, or premature ventricular contraction, is characterized by periodic wide and bizarre QRS complexes. This occurs when an ectopic impulse arises from the ventricles before the normal conduction system has had a chance to initiate a heartbeat. As a result, the QRS complex that follows the PVC is typically wider than normal (greater than 0.12 seconds) and has an unusual morphology.

In this context, the QRS complexes appear bizarre because the electrical activity of the ventricles is not following the typical conduction pathways, leading to a disruption in the usual shape and timing of the heartbeat. The wide QRS complex is a key feature that indicates the ventricle is contracting from an abnormal focus rather than through the normal conduction routes, which results in the characteristic appearance of the PVC. This distinguishes PVCs from other types of arrhythmias that might present with different QRS widths or regularities.