What does impedance refer to in electrical circuits?

Impedance refers to the total opposition to current flow in an electrical circuit. This concept encompasses both the resistance and the reactance that a circuit presents to the flow of alternating current (AC). Resistance is the opposition to current flow that is independent of frequency, while reactance is the opposition that varies with frequency due to capacitance and inductance in the circuit. Understanding impedance is crucial when working with pacing devices since they operate with AC signals and need precise impedance measurements to ensure proper function and to assess the integrity and performance of pacing leads. This makes it essential for clinicians and technicians to monitor and evaluate impedance in various applications to maintain optimal device operation.