What is a likely cause of high resistance in a pacing lead?

A lead fracture or break is a likely cause of high resistance in a pacing lead because it creates a disruption in the electrical pathway that is necessary for proper pacing function. When the lead is compromised due to a fracture, the conductive material within the lead can be damaged or disconnected, which results in increased resistance to the electrical signal. This increased resistance can lead to suboptimal pacing performance, potentially causing pacing thresholds to rise and affecting the overall effectiveness of the pacemaker.

In contrast, while a loose pacemaker connection can also cause issues, it typically does not directly lead to high resistance in the same way a lead fracture does. Improper programming of the device affects the pacing mode or output settings but does not inherently affect lead resistance. Signal interference can impact the quality of the pacing signal, but it is not a structural issue that would increase resistance in the lead itself. Thus, the condition of the pacing lead itself is critical to understanding the reason behind high resistance, making lead fracture or break the most reasonable source in this context.