What characterizes premature ventricular contractions (PVCs)?

Premature ventricular contractions (PVCs) are characterized by the presence of a wide QRS complex and the absence of a preceding P wave. This occurs because PVCs originate in the ventricles rather than from the normal conduction pathways in the atria, which is where P waves originate. The QRS complex is widened because the electrical impulse takes longer to travel through the ventricles, leading to a more extensive depolarization process. The absence of a P wave confirms that there was no atrial depolarization associated with the PVC, further indicating that it is a ventricular event. This distinction is crucial in differentiating PVCs from other types of arrhythmias, which may exhibit different characteristics in their waveforms.