If there is an insulation break, what does the impedance value drop to?

When there is an insulation break in a pacing lead, the impedance value significantly drops due to the introduction of a pathway that bypasses the usual high resistance of the lead insulation. An insulation break allows external fluids, such as blood or body tissues, to come into contact with the conductive elements within the lead, thereby reducing the overall impedance.

In cases of insulation failure, the impedance values will typically drop to below 300 ohms. This low value indicates that the lead is no longer functioning optimally, as healthy pacing leads generally maintain much higher impedance values due to their intact insulation.

If the impedance were to drop to values above 300 ohms, it would still suggest some insulation integrity, but a value below 300 ohms strongly indicates a significant issue that requires immediate attention to prevent potential complications such as inappropriate pacing or lead failure. Thus, knowing that a drop to less than 300 ohms signals an insulation break is critical for clinicians when assessing the integrity and functionality of pacing leads.