The 5 ECGs Every New Nurse Should Recognize Before Their First Shift
By the CardioLens Team
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 recognise 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 a deviation from this. If you don't have normal sinus rhythm anchored in your visual memory, you can't recognise when it stops.
2. Atrial Fibrillation
What it looks like: Irregularly irregular. No discernible P waves — just a wavy, fibrillating baseline. QRS complexes arrive 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 haemodynamic instability. You need to differentiate "chronic AFib, stable" from "new-onset AFib with RVR, symptomatic."
What to do: Check the chart for a 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 normal sinus rhythm, just slower.
Common in: Athletes, patients on beta blockers, the elderly at rest, and vasovagal episodes.
Complete (Third-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, and 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 the 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 a code, start compressions, get the defibrillator. If a pulse is present and the patient is stable, you still need a physician at the bedside immediately. If unstable (hypotension, chest pain, altered mental status), synchronised cardioversion is the answer.
5. Ventricular Fibrillation (VF)
What it looks like: Chaotic, irregular, with no discernible P, QRS, or T waves. The baseline looks like electrical noise. Coarse VF has higher-amplitude waves; fine VF has smaller, flatter waves.
Why it matters: VF means 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. Begin CPR immediately. Get defibrillator pads on. Shock at 200 J biphasic. Resume CPR. The speed with which VF is recognised 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 — the patient moving, a loose electrode, shivering, or 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.
Key takeaway: Master these rhythms before your first shift — normal sinus, atrial fibrillation, sinus bradycardia, complete heart block, VT, and VF. If you can recognise them, and specifically know which require immediate physician notification or a code, you'll handle 90% of monitor events competently on any medical or surgical unit.
Practicing in CardioLens
All of these 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 in total — so you can test yourself until recognition becomes instant. The free tier includes the core "survival rhythms" you need for day one.
Sources
- AHA/ACC/HRS Guidelines for ECG Interpretation
- Braunwald's Heart Disease, 12th Edition
- Dubin's Rapid Interpretation of EKGs, 6th Edition
For educational purposes only — not a diagnostic tool.