A patient with a demand pacemaker has telemetry showing a pacing spike with no corresponding QRS complex, and the myocardium elicits a QRS after a delay of several seconds. What interpretation should the nurse conclude?

A patient with a demand pacemaker has telemetry showing a pacing spike with no corresponding QRS complex, and the myocardium elicits a QRS after a delay of several seconds. What interpretation should the nurse conclude?

• A. Oversensing
• B. Failure to pace
• C. Failure to sense
• D. Loss of capture

Answer: (D)

The main idea here is that a pacing spike occurring without a following QRS means the heart did not respond to the electrical stimulus. In a demand pacemaker, a captured beat should produce a depolarization that shows up as a QRS complex right after the spike. When the spike is present but no QRS follows, the impulse failed to depolarize the myocardium—this is called loss of capture. The later appearance of a QRS suggests the heart fired on its own after a longer interval, not in response to the pacemaker’s spike. This situation is distinct from oversensing (where the device withholds pacing because it senses tissue or artifacts and you’d see pacing present or absent inconsistently), failure to pace (no pacing spike at all), or failure to sense (spikes may occur at inappropriate times relative to intrinsic beats). Here, the actionable point is that capture isn’t occurring, so you’d look at pacing thresholds, lead integrity, or adjust the output to restore capture.

The main idea here is that a pacing spike occurring without a following QRS means the heart did not respond to the electrical stimulus. In a demand pacemaker, a captured beat should produce a depolarization that shows up as a QRS complex right after the spike. When the spike is present but no QRS follows, the impulse failed to depolarize the myocardium—this is called loss of capture. The later appearance of a QRS suggests the heart fired on its own after a longer interval, not in response to the pacemaker’s spike.

This situation is distinct from oversensing (where the device withholds pacing because it senses tissue or artifacts and you’d see pacing present or absent inconsistently), failure to pace (no pacing spike at all), or failure to sense (spikes may occur at inappropriate times relative to intrinsic beats). Here, the actionable point is that capture isn’t occurring, so you’d look at pacing thresholds, lead integrity, or adjust the output to restore capture.