Which statement is true about a premature ventricular contraction (PVC) on ECG?

• A. It is always preceded by a P wave
• B. It is a narrow QRS
• C. It is an early, wide QRS not preceded by a P wave
• D. It is a wide QRS preceded by a P wave

Answer: (C)

Premature ventricular contractions are ectopic beats that originate in the ventricles, so they fire early in the cycle and appear as a wide, bizarre QRS complex. The defining features on ECG are an early beat with a wide QRS duration (usually >120 ms) that has no preceding P wave. Since the impulse starts in the ventricle, there isn’t atrial conduction triggering it, which is why you don’t see a P wave coming before the PVC. After the PVC, you often get a pause that seems to compensate for the early beat.

This is why the statement describing it as an early, wide QRS not preceded by a P wave is the best fit. A P wave before the beat would imply atrial/or AV nodal origin rather than a ventricular ectopy, and a narrow QRS would indicate a supraventricular origin with intact His-Purkinje conduction. A wide QRS with a preceding P wave would point to a different mechanism, not a PVC.