Regular wide complexes at 50-100/min: a ventricular focus outpacing the sinus node.
A regular rhythm of wide complexes at 50-100/min. That's faster than a ventricular escape (under 50) and slower than VT (over 100 here, though LITFL puts the line near 110). A ventricular focus is outpacing the sinus node. It classically follows reperfusion of a heart attack and is usually harmless. If the sinus node is still firing, its P waves march through, and one that arrives at the right moment conducts. That gives you a narrow capture beat.
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.
Regular wide complexes at 20-40/min, with no P waves.
Regular, wide and over 100/min, with every complex the same shape.
P waves and QRS complexes each regular but unrelated: no P is conducted, so the PR is all over the place.
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
EMS Registry Ready