How are most premature ventricular complexes (PVCs) typically identified on an ECG?

Premature ventricular complexes (PVCs) are characterized on an ECG by a significant alteration in the usual ventricular depolarization pattern. The most distinguishing feature is the presence of a prolonged QRS duration, which reflects the abnormal conduction through the ventricles. Normally, the QRS complex duration is less than 0.12 seconds, but in the case of PVCs, the QRS is typically wider, often exceeding this duration due to the asynchronous depolarization of the ventricles.

The absence of P waves can often be noted in conjunction with PVCs since the impulse that triggers a PVC originates in the ventricles rather than the atria. However, the defining characteristic of PVCs on an ECG is their wide QRS complex, which can aid in differentiating them from other types of rhythms. The QT interval's length is not typically affected by PVCs, and U waves are not a standard feature of their identification. Thus, the recognition of PVCs primarily hinges on the assessment of the QRS duration during analysis of the ECG.