Which situation can lead to underpacing?

Underpacing occurs when a pacemaker fails to deliver the appropriate electrical impulses, leading to a slower heart rate than intended. Increased motion artifacts can interfere with the sensing capabilities of the pacemaker. When there is excessive movement—such as from exercise, shifts in position, or other activities—it can create false signals or distort the actual heart rhythms. This misinterpretation may lead the device to underpace, as it might not correctly identify when the heart requires pacing or might perceive the natural heart rhythm as sufficient when it is not.

While other options also affect pacing performance, they impact different aspects of the pacemaker's function. Excessive signal noise can disrupt communication but doesn't directly cause a failure to pace. Poor tissue adhesion can lead to lead dislodgment or reduced pacing efficacy but is not solely an issue of timing misinterpretation. Unnoticed arrhythmias may cause the heart to pace at inappropriate rates but again does not relate to the sensing issues created by motion artifacts. Thus, increased motion artifacts is the most direct cause leading to underpacing in this scenario.