What does capture threshold refer to in cardiac pacing?

Capture threshold refers to the minimum electrical stimulus necessary to evoke a cardiac response. In the context of cardiac pacing, this is critical for ensuring that the pacemaker can effectively stimulate the heart to contract. If the pacing pulse is below this threshold, it may not produce any mechanical action from the heart, which could lead to ineffective pacing and potential adverse effects on patient health.

Determining the capture threshold involves systematically adjusting the pacing output until the smallest sufficient electrical impulse is identified that results in depolarization and subsequent contraction of the heart muscle. This value is vital for programming the pacing device to ensure it delivers effective stimulation to the heart while conserving battery life and avoiding unnecessary pacing.

The other options do not accurately describe capture threshold, as they focus on aspects such as maximum voltage, lead resistance, and pacing intervals, which are different concepts integral to understanding the pacing system but do not define the capture threshold itself.