What could be a sign of an under-sensing pacemaker during monitoring?

An under-sensing pacemaker refers to a situation where the pacing device fails to detect the heart's intrinsic electrical activity effectively, resulting in inappropriate pacing. One of the clear signs of this malfunction is the presence of irregularly spaced pacing spikes.

In a properly functioning pacemaker, pacing spikes should occur consistently based on the programmed rate and the patient's needs. However, if the pacemaker is under-sensing the heart's natural rhythms, it may deliver pacing spikes at inconsistent intervals. This irregularity suggests that the pacemaker is not appropriately responding to the physiological cues from the heart, thus indicating its failure to sense the ongoing heart activity correctly. Regular monitoring of these spikes aids in identifying this particular issue.

The other options do not directly indicate under-sensing. A rapid heart rate might suggest several other cardiac conditions, while excessive anxiety typically relates more to psychological states than to pacing functions. Inconsistent blood pressure readings can point to various hemodynamic issues but are not specific to the functioning of a pacemaker in a sensing context.