What does the term 'failure to capture' refer to in the context of pacemakers?

The term 'failure to capture' specifically refers to the situation in which the pacemaker generates an electrical impulse (a spike), but this impulse does not lead to effective heart contractions. In essence, the pacemaker is activating, but the heart muscle does not respond as expected. This can occur due to various reasons, such as lead displacement, poor lead contact with the myocardium, or the heart tissue being too diseased or weakened to respond to the pacing stimulus.

In this scenario, the pacemaker's effectiveness is compromised despite it functioning correctly at a basic level, which is to deliver electrical impulses. Thus, recognizing failure to capture is crucial, as it indicates that the pacing therapy is not performing as intended, and further evaluation and adjustment might be necessary to ensure proper cardiac function.