If lead insulation is fractured, lead impedance will:

• A. Decrease
• B. Increase
• C. No change
• D. Variable

Answer: (A)

When insulation around a lead is fractured, the conductor can come into contact with surrounding body fluids and tissues, creating an extra leakage path for current. Lead impedance measures the opposition to current flow through the entire lead-to-tissue circuit. That leakage path to the conductive environment shunts some of the current away from the intended electrode-tissue interface, effectively lowering the total impedance. If the problem were a true conductor fracture, you’d expect the circuit to open and impedance to rise, which is not the scenario described. So lead impedance decreases with insulation fracture.