A knee arthroscopy patient has a VDD pacemaker. Which statement is true?

A knee arthroscopy patient has a VDD pacemaker. Which statement is true?

• A. It senses only the ventricle
• B. It paces only the ventricle
• C. Its response to sensing is always inhibition
• D. It is not useful in AV nodal block

Answer: (B)

In a VDD pacemaker, the device can sense activity from both the atrium and the ventricle, but it paces only the ventricle. This arrangement preserves AV synchrony by waiting for intrinsic atrial activity and then delivering ventricular pacing if the ventricle fails to beat on its own. Therefore the statement that it paces only the ventricle is correct, because atrial pacing is not provided, only atrial sensing. The idea that it senses only the ventricle is incorrect since it actually senses both chambers. Saying its response to sensing is always inhibition isn’t right because the device will pace the ventricle when needed to maintain rate or synchrony, not merely inhibit pacing. And in AV nodal block, the ability to sense atrial activity and pace the ventricle can still be useful to maintain ventricular rate and AV synchrony, so claiming it isn’t useful in AV nodal block isn’t accurate.

In a VDD pacemaker, the device can sense activity from both the atrium and the ventricle, but it paces only the ventricle. This arrangement preserves AV synchrony by waiting for intrinsic atrial activity and then delivering ventricular pacing if the ventricle fails to beat on its own. Therefore the statement that it paces only the ventricle is correct, because atrial pacing is not provided, only atrial sensing. The idea that it senses only the ventricle is incorrect since it actually senses both chambers. Saying its response to sensing is always inhibition isn’t right because the device will pace the ventricle when needed to maintain rate or synchrony, not merely inhibit pacing. And in AV nodal block, the ability to sense atrial activity and pace the ventricle can still be useful to maintain ventricular rate and AV synchrony, so claiming it isn’t useful in AV nodal block isn’t accurate.