What pacing mode is indicated when intrinsic conduction is lost?

When intrinsic conduction is lost, the appropriate pacing mode indicated is DDD. This mode is specifically designed to manage situations where there is a loss of natural conduction between the atria and ventricles, allowing for optimal pacing in both chambers.

DDD pacing monitors intrinsic atrial and ventricular activity. If the heart is able to conduct normally, the pacemaker will not initiate pacing. However, if there is a failure in intrinsic conduction, the DDD mode will activate and stimulate the atria and ventricles as needed to maintain an adequate heart rate and rhythm. This dual-chamber pacing is essential in cases where both atrial and ventricular synchronization is crucial to ensure efficient heart function.

While other pacing modes may serve specific purposes—like VVI, which only paces the ventricle and doesn't respond to atrial activity, or AAI, which only paces the atrium—DDD is uniquely suited for conditions of complete atrioventricular block, where both components need to be managed for effective cardiac output. DDD-R, an extension of DDD designed for rate-responsive pacing, is also not necessary if intrinsic conduction is fully lost, as the primary goal is to maintain pacing in both chambers without relying on the intrinsic system.