The 5 ECGs Every New Nurse Should Recognize Before Their First Shift

Your first shift on a cardiac unit will involve rhythms. A lot of them. And while you won't need to interpret a 12-lead like a cardiologist, you absolutely need to recognize a handful of rhythms on the bedside monitor — because some of them are immediately life-threatening and some are completely normal.

These are the five you must know before you start.

1. Normal Sinus Rhythm

What it looks like: Regular rhythm at 60–100 bpm. Upright P wave before every QRS. Narrow QRS complexes (<120 ms). Consistent PR interval between 120–200 ms.

Why it matters: This is your baseline. Every other rhythm you'll see is deviation from this. If you don't have NSR anchored in your visual memory, you can't recognize when it stops.

2. Atrial Fibrillation

What it looks like: Irregularly irregular. No discernible P waves — just a wavy, fibrillating baseline. QRS complexes come at random intervals. Ventricular rate can range from 60 to >150 bpm.

Why it matters: AFib is extremely common on medical units. It's usually not an emergency, but rapid AFib (rate >150) can cause chest pain, shortness of breath, and hemodynamic instability. You need to differentiate "chronic AFib, stable" from "new-onset AFib with RVR, symptomatic."

What to do: Check the patient's chart for known history of AFib. If new onset, notify the physician. If symptomatic (chest pain, hypotension, shortness of breath), it's an urgent notification regardless of rate.

3. Sinus Bradycardia vs. Complete Heart Block

Both rhythms are slow. But one is benign and one requires a pacemaker. Learn the difference.

Sinus Bradycardia

What it looks like: Regular rhythm <60 bpm. Normal P before every QRS. Normal PR interval. Everything looks like NSR, just slower.

Common in: Athletes, patients on beta blockers, elderly at rest, vasovagal episodes.

Complete (3rd Degree) Heart Block

What it looks like: P waves and QRS complexes march completely independently. The atrial rate is often 80–100 (normal), but the ventricles beat at 30–50 bpm because they've taken over pacing themselves. No consistent PR relationship.

Common in: Acute MI (especially inferior), degenerative conduction disease, medication toxicity.

Complete heart block is a true emergency. These patients can deteriorate into asystole. If you see it: transcutaneous pads on the patient, atropine at bedside, physician at the bedside now.

4. Ventricular Tachycardia (VT)

What it looks like: Regular, wide-complex tachycardia. QRS >120 ms. Rate typically 150–250 bpm. May or may not have a pulse.

Why it matters: VT can degenerate into VF within seconds. Even if the patient currently has a pulse, they are minutes (or less) away from cardiac arrest.

What to do: Check responsiveness. Check a pulse. If pulseless, call code blue, start compressions, get the defibrillator. If pulse is present and patient is stable, you still need a physician at the bedside immediately. If unstable (hypotension, chest pain, altered mental status), synchronized cardioversion is the answer.

5. Ventricular Fibrillation (VF)

What it looks like: Chaotic, irregular, no discernible P, QRS, or T waves. The baseline looks like electrical noise. Coarse VF has higher amplitude waves; fine VF has smaller, more flat waves.

Why it matters: VF = cardiac arrest. No effective cardiac output. The patient will die within minutes without defibrillation. Every minute without defibrillation reduces survival by 7–10%.

What to do: This is a code blue. Begin CPR immediately. Get defibrillator pads on. Shock at 200J biphasic. Resume CPR. The speed with which VF is recognized and shocked is the single largest determinant of survival.

A Note on Monitor Artifact

Sometimes what looks like a malignant rhythm is really just artifact — patient moving, loose electrode, shivering, tremor. Before you call a code, do two things:

• Look at the patient. If they're awake, talking, and look fine — they probably are fine.
• Check a pulse. A patient with a strong pulse is not in VF, no matter what the monitor shows.

That said: if you're ever unsure, call for help. Calling a rapid response for what turns out to be artifact is never held against you. Missing VF because you hesitated is.

Practicing in CardioLens

All five rhythms are in the CardioLens ECG Library with interactive waveforms and clinical pearls. The Rhythm Mastery quiz includes 8 questions per rhythm across 36 rhythms — 288 total — so you can test yourself until recognition becomes instant. The free tier includes the core "survival rhythms" you need for day one.