For which condition would a VVI pacemaker typically be used?

A VVI pacemaker is designed primarily for patients who have a specific need for ventricular pacing and are experiencing an absence of normal atrial activity or influence, such as in chronic atrial fibrillation. In this condition, the electrical signals originating from the atria are disorganized or absent, leading to an irregular ventricular response. The VVI pacing mode allows the pacemaker to deliver impulses to the ventricles in response to their own intrinsic rates while inhibiting pacing based on atrial activity, making it suitable for managing situations where atrial control is not effective or desirable.

In the context of the other choices, patients with heart block typically require pacing to support atrial and ventricular synchronization, making a different pacing mode, such as DDD, more appropriate. Patients with sinus node dysfunction often also benefit from more comprehensive pacing strategies like DDD or AAIR to ensure adequate atrial sensing and pacing. Lastly, patients requiring dual pacing would not be well-served by a VVI pacemaker, as this mode does not provide the necessary atrial and ventricular pacing capabilities. Thus, the choice of B aligns with the specific capabilities and intended use of a VVI pacemaker.