Which statement about P waves during a premature ventricular contraction is correct?

• A. A P wave precedes every QRS
• B. P waves are not associated with the QRS
• C. The QRS is narrow
• D. P waves are absent or dissociated

Answer: (D)

PVCs originate in the ventricular muscle, so the impulse that causes the PVC is not coming from the atria or following the normal atrial–ventricular conduction. Because of this, the atrial activity and the ventricular beat are not in a fixed, coordinated relationship. The result is that P waves are often absent in relation to the PVC or are dissociated from it, while the underlying atrial rhythm may continue separately. The QRS complex during a PVC is typically wide and bizarre because the ventricles are activated by an abnormal, slower route rather than the normal His–Purkinje system. So, P waves are absent or dissociated is the best description of what happens to P waves during a PVC.