Which of the following is NOT a common pacing mode?

The pacing modes used in cardiac devices are classified based on how they stimulate the heart and respond to its physiology. DDDR, VVIR, and VVI are all recognized modes commonly used in pacemakers.

DDDR stands for Dual Chamber Demand Pacing, which monitors both the atrium and ventricle, providing pacing when necessary, adapting to the patient's physiological needs.

VVIR is a mode that allows ventricular pacing with rate modulation based on intrinsic atrial activity, meaning it paces the ventricles while also allowing for the natural function of the atria when they are beating appropriately.

VVI is a basic mode in which the pacemaker paces the ventricle only when there is no intrinsic ventricular activity, providing a simple and effective solution for certain patients.

On the other hand, VDI is not frequently encountered as a standard pacing mode. It is more of a theoretical or less commonly utilized mode that denotes ventricular pacing with demand sensitivity but does not have the same level of clinical applicability or common use as the other options. Understanding the differences in these pacing modes helps clarify why VDI is not recognized among the standard, commonly used pacing modes in cardiac management.