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

• A. An early ectopic impulse originating in atrial tissue
• B. Widened QRS complexes
• C. Presence of a clear P wave
• D. Normal QRS duration

Answer: (B)

Premature ventricular contractions (PVCs) are characterized by widened QRS complexes. This occurs because PVCs arise from the ventricles rather than the atria, leading to a disruption in the normal conduction pathway. The impulse that causes a PVC originates in the ventricular myocardium and travels through the ventricles in an abnormal manner, resulting in a QRS complex that appears wider than those produced by normal ventricular depolarization.

A widened QRS complex is an important distinguishing feature of PVCs as it indicates that the contraction is occurring outside the usual electrical conduction system, which typically results in a narrow QRS complex. Recognizing this change is crucial for accurately diagnosing PVCs in electrocardiogram (ECG) readings. In contrast, PVCs do not feature a clear P wave since the impulse does not originate from the atria, which is why options highlighting the presence of a P wave or normal QRS duration would not apply to PVCs.