What does a 'failure to capture' look like on ECG with a pacemaker?

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Multiple Choice

What does a 'failure to capture' look like on ECG with a pacemaker?

Failure to capture means the pacemaker fires a stimulus (a pacing spike) but the heart tissue does not depolarize afterward. On the ECG you’ll see a pacing spike with no following P wave or QRS complex—the spike stands alone because there’s no capture of atrial or ventricular tissue. This distinguishes it from normal capture, where a spike is followed by a P wave (atrial pacing) or a QRS complex (ventricular pacing). Seeing a QRS complex without a preceding pacing spike indicates the heart’s own conduction is producing the beat at that moment, not a failure to capture. A paced rhythm with consistent capture would show spikes reliably followed by P waves or QRS complexes, which is the desired finding. If there were no pacing spikes at all with a normal sinus rhythm, that just means the pacemaker isn’t firing, not that capture has failed.

Failure to capture means the pacemaker fires a stimulus (a pacing spike) but the heart tissue does not depolarize afterward. On the ECG you’ll see a pacing spike with no following P wave or QRS complex—the spike stands alone because there’s no capture of atrial or ventricular tissue. This distinguishes it from normal capture, where a spike is followed by a P wave (atrial pacing) or a QRS complex (ventricular pacing).

Seeing a QRS complex without a preceding pacing spike indicates the heart’s own conduction is producing the beat at that moment, not a failure to capture. A paced rhythm with consistent capture would show spikes reliably followed by P waves or QRS complexes, which is the desired finding. If there were no pacing spikes at all with a normal sinus rhythm, that just means the pacemaker isn’t firing, not that capture has failed.

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