What does the term "impedance" refer to in a cardiac context?

Impedance in a cardiac context refers to the resistance against current flow within the heart's tissues and its electrical pathways. It is a crucial factor in diagnosing and managing various cardiac conditions, particularly when evaluating cardiac devices such as pacemakers or defibrillators. When these devices deliver electrical impulses, understanding impedance helps clinicians assess how well the device interacts with the body’s tissue, which in turn informs adjustments to lead positioning, pacing thresholds, and overall device function.

The concept of impedance encompasses not only resistance but also the reactance due to capacitance and inductance within the body’s tissues. However, in the context of the choices given, describing it primarily as resistance against current flow captures the essential function of impedance in cardiac applications. This information can be vital for ensuring optimal performance and safety of implanted devices in managing heart rhythm disorders.