When you see pacing spikes falling later than where they should be based on the programmed pacing rate, that is:
Failure to capture
Oversensing
Failure to sense
Failure to pace
The correct answer and explanation is:
The correct answer is Failure to Capture.
Failure to capture occurs when the pacemaker delivers a pacing stimulus, but the heart does not respond to it with a contraction. In other words, the pacing spike is seen on the electrocardiogram (ECG), but there is no corresponding QRS complex or heart beat that follows. This happens when the electrical impulse generated by the pacemaker is not strong enough to stimulate the heart tissue effectively or when the timing of the pacing is not ideal for the heart’s electrical system. In this case, the pacing spikes fall later than expected because the pacemaker attempts to stimulate the heart, but the heart does not respond in a normal way.
The pacing rate may be correctly programmed, but if the heart is not responding as it should, it can cause pacing spikes to appear delayed on the ECG. This indicates that the electrical impulse has not successfully captured the heart’s electrical activity, leading to ineffective pacing. Failure to capture is commonly due to problems like incorrect lead positioning, improper pacing threshold, or issues with the pacemaker’s function.
To differentiate from other options:
- Oversensing refers to the pacemaker detecting non-cardiac electrical signals, such as muscle activity, as heartbeats, which can lead to inappropriate inhibition of pacing.
- Failure to sense means that the pacemaker does not detect the heart’s natural electrical activity when it should, potentially leading to unnecessary pacing or missed pacing attempts.
- Failure to pace means that the pacemaker is not delivering any pacing stimuli at all, resulting in no pacing spikes on the ECG.
In summary, when pacing spikes fall later than expected due to the heart not responding to pacing impulses, this is a clear indication of failure to capture.