Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

Which type of pacing generator paces in both chambers and inhibits QRS complexes?

1. DVI

2. AAI

3. DDD

4. VVI

The correct answer is: DVI

The pacing generator that paces in both chambers and inhibits QRS complexes is the DDD mode. This mode is designed to provide pacing impulses to both the atria and ventricles, allowing for synchronized pacing in the presence of both atrial and ventricular activity. In a DDD pacemaker, the device can pace the atria and the ventricles as necessary, while also being able to sense the electrical activity in both chambers. If a natural QRS complex occurs, the DDD pacemaker can inhibit its pacing output, thus preventing unnecessary pacing spikes that do not correlate with intrinsic cardiac activity. In contrast, the other pacing modes listed have different functionalities: AAI only paces the atrium and senses atrial activity, VVI only paces the ventricle and senses ventricular activity, and DVI is designed to pace the ventricle and the atrium but does not provide the dual sensing capabilities of DDD. Thus, the unique characteristic of the DDD mode is its ability to pace in both the atrial and ventricular chambers while also having the capacity to inhibit based on the heart's own electrical activity.