How are underlying rhythms typically portrayed on a rhythm strip showing PVCs?

The portrayal of underlying rhythms on a rhythm strip showing Premature Ventricular Contractions (PVCs) is characterized by the presence of underlying patterns that may or may not be affected by the PVCs themselves. In particular, option D accurately reflects that atrial rhythms can be irregular while the underlying ventricular rhythm may remain regular.

When PVCs occur, they interrupt the regularity of the heartbeat as they are early contractions originating in the ventricles. This interruption can make the overall rhythm appear irregular. However, despite these interruptions, the underlying rhythm often maintains a consistent baseline pattern, particularly if originating from the atria or if there's another underlying rhythm driving the heart. This allows for the possibility of observing regular ventricular rhythms alongside irregular atrial rhythms, especially if PVCs are infrequent.

This understanding is crucial for interpreting ECGs, as it helps clinicians distinguish between the effects of irregularities caused by PVCs and the underlying rhythm that guides patient care and treatment decisions.