Lack of tissue capture can be caused by which of the following?

• A. Insufficient pacing stimulus or paced during refractory
• B. Lead displacement
• C. Battery depletion
• D. Oversensing

Answer: (A)

Capture depends on delivering a pacing pulse that is above the tissue’s capture threshold and at a moment when the myocardium is excitable. If the pacing stimulus is too weak (insufficient energy) or if the pulse is delivered during the absolute refractory period, the cells won’t respond and no depolarization occurs. That direct failure to depolarize is precisely what “lack of tissue capture” means. Other scenarios can affect pacing in different ways—lead displacement changes the contact with heart tissue, battery depletion can reduce output over time, and oversensing can cause the device to inhibit pacing or misinterpret signals—but they are not the fundamental mechanism of a captured beat being unsuccessful due to insufficient energy or wrong timing.