How do I tell AFib from atrial flutter with variable conduction?

Flutter shows organized atrial activity (sawtooth flutter waves) at ~300/min; AFib has chaotic fibrillatory baseline. When in doubt, verify with a 12-lead and your clinician.

Is rapid AFib an emergency?

It can be. Rate, hemodynamic stability, and patient symptoms determine urgency. RN PocketPal does not make that call — your clinical judgment and the team do.

What about new-onset AFib?

New-onset AFib has implications for anticoagulation and cardioversion timing — those are clinician decisions. Notify and document.

Atrial fibrillation — an educational nurse reference.

What AFib looks like on a strip, why the rhythm is irregularly irregular, and what to verify clinically before acting.

Recognizing this rhythm at the bedside means matching pattern, intervals, and clinical context. This page covers the educational pattern; calipers and your clinical judgment carry it across the line.

What RN PocketPal does

Identifying traits

Rate: variable; ventricular response can be slow, controlled, or rapid
Rhythm: irregularly irregular (no pattern to R-R intervals)
P wave: absent — fibrillatory waves instead
PR interval: not measurable (no P)
QRS: usually narrow unless aberrancy or pre-existing block

Verify with

Calipers: confirm R-R irregularity has no repeating pattern.
Patient's pulse: irregular and often pulse-deficit relative to apex.
Patient's chart: known AFib history vs. new onset.

Who it’s for

For Nurses and nursing students learning rhythm interpretation.

Ten seconds of this rhythm, from a real recording

115 bpm · 10 seconds · each large grid square is 0.20 seconds. Amplitude is normalised for practice, so the vertical scale is not calibrated millivolts — read rate, regularity, and shape here, not voltage.

What to notice in this strip

No two R-R intervals repeat, and the baseline between complexes is restless rather than flat — there is no P wave to find. Because the rhythm is irregular, the 300-rule does not apply to it; count every QRS across the full ten seconds instead.

Counting the rate on a strip like this

The strip above is exactly ten seconds, so counting every QRS complex across it and multiplying by six gives the rate — the method that works whether the rhythm is regular or not. When the rhythm is regular, you can shortcut it: divide 300 by the number of large squares between two R waves.

Rhythms this gets confused with

Known-answer practice — RN PocketPal does not interpret your patient's monitor. To work through strips with the answer revealed after you commit, open Rhythm Practice.

Strip source: MIT-BIH Atrial Fibrillation Database v1.0.0, record 04015. Channel 0, 10 s window, resampled to 100 Hz, zero-mean/unit-variance normalized for practice use. Used under the Open Data Commons Attribution License v1.0. Goldberger AL, et al. PhysioBank, PhysioToolkit, and PhysioNet. Circulation. 2000;101(23):e215-e220.

Frequently asked questions

How do I tell AFib from atrial flutter with variable conduction?: Flutter shows organized atrial activity (sawtooth flutter waves) at ~300/min; AFib has chaotic fibrillatory baseline. When in doubt, verify with a 12-lead and your clinician.
Is rapid AFib an emergency?: It can be. Rate, hemodynamic stability, and patient symptoms determine urgency. RN PocketPal does not make that call — your clinical judgment and the team do.
What about new-onset AFib?: New-onset AFib has implications for anticoagulation and cardioversion timing — those are clinician decisions. Notify and document.

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Reviewed by RN PocketPal Clinical Team, RN. Last reviewed May 7, 2026.