EMS Registry Ready

Pacemaker failure to sense on an ECG strip

Pacing spikes at a fixed rate that ignore the patient's own beats, landing in and just after them.

What to look for

The patient's own rhythm is faster than the pacing rate, so a working pacemaker would stay quiet. This one doesn't sense it. The spikes keep coming at the pacing rate and land in and just after the patient's own QRS complexes and T waves, where they can't capture. It only paces a beat when a spike happens to land after the T wave.

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
99/min underlyingThe whole strip averages 99/min · 10 QRS complexes in 6 seconds × 10 = 100/min
Rhythm
Irregular
P waves
Sinus P waves (the patient's own rhythm)
P to QRS
1:1 for the patient's own beats; the pacing spikes ignore them
PR
0.18 s
QRS
0.07 s, narrow
Pacing
VVI at 55/min2 spikes landing in the patient's own beats
Example 2 · lead II · 6 seconds
II25 mm/s · 10 mm/mV
Rate
90/min underlyingThe whole strip averages 88/min · 9 QRS complexes in 6 seconds × 10 = 90/min
Rhythm
Irregular
P waves
Sinus P waves (the patient's own rhythm)
P to QRS
1:1 for the patient's own beats; the pacing spikes ignore them
PR
0.17 s
QRS
0.10 s, narrow
Pacing
VVI at 55/min2 spikes landing in the patient's own beats
Example 3 · lead II · 6 seconds
II25 mm/s · 10 mm/mV
Rate
87/min underlyingThe whole strip averages 92/min · 9 QRS complexes in 6 seconds × 10 = 90/min
Rhythm
Irregular
P waves
Sinus P waves (the patient's own rhythm)
P to QRS
1:1 for the patient's own beats; the pacing spikes ignore them
PR
0.13 s
QRS
0.09 s, narrow
Pacing
VVI at 58/min3 spikes landing in the patient's own beats

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