Which observation can indicate an ineffective pacing threshold?

An observation of variable capture events can indicate an ineffective pacing threshold. This means that the pacemaker is not consistently stimulating the heart to contract effectively. In a scenario where the pacing is adequate, you would expect to see consistent capture of the heart in response to pacing signals. When capture is inconsistent, it suggests that the electrical impulses generated by the pacemaker are failing to depolarize the heart muscle consistently. This can lead to irregular heartbeats or intervals where the heart fails to respond at all to pacing.

In contrast, an increased heart rate might be related to other factors such as increased activity or metabolic demand, and does not directly indicate problems with pacing. Consistent QRS duration typically signals that the pacing is effective since it indicates stable depolarization of the ventricles. Finally, stable rhythm patterns imply that the heart is responding appropriately to pacing and maintaining a regular rhythm, suggesting effective pacing rather than ineffective. Thus, observing variable capture events is a key indicator of pacing threshold issues.