What is a unique feature of a unipolar lead compared to bipolar leads?

A unipolar lead has a unique feature that distinguishes it from bipolar leads due to its configuration. In a unipolar system, there is one electrode at the tip of the lead and the return path is provided by the case of the pulse generator, which creates a larger sensing field. This design can lead to a greater risk of oversensing, as it is more susceptible to picking up extraneous electrical signals from surrounding muscle activity or other sources of electromagnetic interference. The wide sensing field and the ability to capture signals from areas beyond the immediate vicinity of the lead can result in misinterpretation of noise as actual cardiac signals, causing inappropriate pacing or sensing events.

Conversely, bipolar leads have two electrodes, which can more effectively differentiate between cardiac signals and noise due to their closer proximity. This characteristic reduces the risk of oversensing, providing a more refined and accurate response to true cardiac activity. Thus, the higher risk of oversensing is a salient feature of unipolar leads when compared to bipolar leads.