What is capture threshold?

Capture threshold is defined as the minimum electrical stimulus required to consistently achieve depolarization of the heart muscle, thereby resulting in a heartbeat that is initiated by the pacing device. When the electrical impulse delivered by a pacemaker meets or exceeds this threshold, it successfully captures the myocardium and generates a contraction. This concept is essential for ensuring effective pacing, as a stimulus lower than the capture threshold may not effectively activate the heart, leading to intermittent or absent pacing.

In the context of pacing, it plays a crucial role in determining the appropriate settings for pacemakers. Understanding the capture threshold helps clinicians adjust the pacing output to ensure reliable stimulation while maintaining patient safety. It is important because capture must occur consistently, particularly outside the heart's own refractory period, to establish effective and stable cardiac rhythms.

The other options present related concepts but do not specifically define capture threshold as accurately in the context of clinical pacing. For example, while the maximum electrical stimulus and average voltage may be relevant, they do not specifically address the minimum threshold necessary for consistent capture, which is key to effective pacing.