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Pacemaker failure to capture on an ECG strip

Pacing spikes arrive on time, but some have no QRS after them.

What to look for

The pacemaker fires on time, but some spikes have no QRS after them: the stimulus didn't depolarize the ventricles. Every missed capture leaves a pause, and on this strip there's nothing underneath to fill it. A spike with nothing after it is the tell.

Examples

Each strip is 6 seconds of lead II, drawn to scale (25 mm a second, 10 mm a millivolt), so you can count boxes the way you would on paper. Each one is a different example, measured below it.

Example 1 · lead II · 6 seconds
II25 mm/s · 10 mm/mV
Rate
41/min5 QRS complexes in 6 seconds × 10 = 50/min
Rhythm
Regular, except where beats drop
P waves
None: fine fibrillatory baseline
P to QRS
No P waves (atrial fibrillation underneath)
PR
None to measure
QRS
0.19 s, wide
Pacing
VVI at 62/min2 spikes with no QRS after them
Example 2 · lead II · 6 seconds
II25 mm/s · 10 mm/mV
Rate
62/min6 QRS complexes in 6 seconds × 10 = 60/min
Rhythm
Regular, except where beats drop
P waves
None: fine fibrillatory baseline
P to QRS
No P waves (atrial fibrillation underneath)
PR
None to measure
QRS
0.18 s, wide
Pacing
VVI at 87/min3 spikes with no QRS after them
Example 3 · lead II · 6 seconds
II25 mm/s · 10 mm/mV
Rate
60/min6 QRS complexes in 6 seconds × 10 = 60/min
Rhythm
Regular, except where beats drop
P waves
None: fine fibrillatory baseline
P to QRS
No P waves (atrial fibrillation underneath)
PR
None to measure
QRS
0.18 s, wide
Pacing
VVI at 84/min2 spikes with no QRS after them

Don't confuse it with

Want a new strip every time? The ECG Drill in the app draws a fresh, measured example on every try and steers you toward the rhythms you miss. It's part of the Paramedic level, and you can try 5 strips a day free.

Try the ECG Drill

Where the criteria come from

Others in the Paced group