Irregular, under 100/min, with three or more different P-wave shapes and a PR that varies.
What to look for
Think of it as multifocal atrial tachycardia at a rate under 100. You'll see at least three P-wave shapes, and the PR and P-P vary as the pacemaker wanders between sites in the atria.
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
Rate
80/min8 QRS complexes in 6 seconds × 10 = 80/min
Rhythm
Irregularly irregular
P waves
Three or more shapes in II, changing from beat to beat
P to QRS
1:1, each P conducted, each with its own PR
PR
Changes beat to beat, 0.13 s to 0.19 s
QRS
0.07 s, narrow
Example 2 · lead II · 6 seconds
Rate
76/min8 QRS complexes in 6 seconds × 10 = 80/min
Rhythm
Irregularly irregular
P waves
Three or more shapes in II, changing from beat to beat
P to QRS
1:1, each P conducted, each with its own PR
PR
Changes beat to beat, 0.13 s to 0.19 s
QRS
0.10 s, narrow
Example 3 · lead II · 6 seconds
Rate
84/min9 QRS complexes in 6 seconds × 10 = 90/min
Rhythm
Irregularly irregular
P waves
Three or more shapes in II, changing from beat to beat
Sinus rhythm with early beats that start with an early P wave of a different shape, then a narrow QRS.
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.
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