What does impedance refer to in the context of cardiac devices?

In the context of cardiac devices, impedance specifically refers to the resistance encountered by electrical current flowing through the leads and tissues surrounding a cardiac implantable device, such as a pacemaker or defibrillator. It is an important parameter that can be measured to assess the integrity of the leads and the quality of the electrical connection between the device and the heart.

Monitoring impedance can aid in detecting potential issues such as lead fractures or fibrosis, and changes in impedance can indicate alterations in tissue characteristics or the lead's position. This understanding is critical for the optimal functioning of cardiac devices, ensuring they can effectively deliver electrical impulses or shocks as needed.

The other options provided, such as the strength of electrical signals, battery charge duration, and the rate of pacing, do not specifically define impedance. They refer to other aspects of cardiac devices that are essential but are distinct from the concept of impedance itself.