Nursing Field Notes / Cardio · Rhythm recognition

9 ECG Strips on the NCLEX 📈

Recognize them in three seconds · then say the priority out loud

NG-090 CARDIO ADHD-friendly visual edition

The NCLEX does not ask you to read a 12-lead. It shows you one rhythm strip and asks what is it and what do you do first. Nine rhythms cover almost every one of those questions. This page teaches the look of each one and the single distinguishing feature that separates it from its look-alike. For the systematic step-by-step method, pair this with NG-011 · 5-Step EKG Interpretation — that page is the how, this page is the what.

📄 Simple Nursing original — opens in Drive →

❓ 4 questions, every stripP wave? · Regular? · Rate? · QRS wide or narrow? Answer those four and you have named it.

🔢 6-second × 10Count the R waves in a 6-second strip and add a zero. 8 R waves = 80.

⚡ Only 2 rhythms get shockedV-Fib and pulseless V-Tach. Never shock asystole or PEA.

🩺 Always assess the clientThe monitor does not have a pulse. Check the client before you treat the strip.

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READ ANY STRIP

STEP 1 · THE 4 QUESTIONS

Before you memorize nine pictures, learn the four questions that generate the answer.

🤖 Sparky reads every strip the same way

🧠 “P · R · R · W” — P wave? · Regular? · Rate? · Wide? Four letters, and every rhythm on this page falls out of them.

📐 The waves themselves — what each bump actually is

🧠 “P for Pre-game, QRS for the Play, T for the Time-out.” Atria warm up, ventricles do the work, then everyone resets. Lose the P and you have lost the atria; widen the QRS and the beat started in the wrong place.

🔢 Counting the rate — the 6-second rule

Most telemetry paper marks 3-second intervals at the top. Two of those marks = 6 seconds.

🧠 “Count and add a zero.” It works on irregular rhythms too — which is exactly why it is the method the NCLEX expects for A-fib.

🗺️ Where each rhythm is BORN

🧠 “The further down it starts, the worse it gets.” SA node → fine. Atria → uncomfortable and clot-risky. AV node → fast and scary. Ventricles → lethal.

🗂️ Jump to a rhythm

1 · NSRthe reference picture 2 · Sinus brady< 60 · P present 3 · Sinus tach> 100 · P present 4 · A-Fibno P · irregularly irregular 5 · A-Fluttersawtooth 6 · SVTnarrow · 150–250 7 · V-Tachwide · regular · check pulse 8 · V-Fibchaotic · shock it 9 · Asystoleflatline · never shock

🧠 Three green, three blue, three red. Three rhythms you monitor, three you medicate, three you resuscitate.

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THE SINUS THREE

STEP 2 · 1 · 2 · 3

All three have a P wave before every QRS and are regular. The only thing that changes is the rate.

1️⃣ Normal Sinus Rhythm — the picture everything else is measured against

P wave	Regular?	Rate	QRS
Yes — one before every QRS, all the same shape	Yes — R–R spacing is identical	60–100	Narrow < 0.12 s

PR interval 0.12–0.20 s and constant. Learn this strip cold — every other rhythm is described as how it differs from this one.

🧠 “One P, one QRS, one T — evenly, forever.”

2️⃣ Sinus Bradycardia — everything normal, just slow

The distinguishing feature: P before every QRS, regular, rate under 60. Nothing is missing — there is just more space between the beats.

Causes: athletic conditioning · sleep · vagal stimulation (bearing down, vomiting, suctioning) · inferior-wall MI · hypothyroidism · hypothermia · increased intracranial pressure · drugs (beta blockers, calcium channel blockers, digoxin).

What you do:

Asymptomatic → monitor, hold the rate-lowering drug per parameters, look for the cause
Symptomatic (dizzy, confused, hypotensive, chest pain, dusky) → atropine, then transcutaneous pacing — see NG-057
Give oxygen and check the airway first — hypoxia causes bradycardia, especially in children

🧠 “Brady = Big gaps.” Count only 4–5 R waves in 6 seconds and you have your 40–50.

3️⃣ Sinus Tachycardia — a symptom, not a disease

The distinguishing feature: P before every QRS, regular, rate over 100 (usually 100–150). At very fast rates the P wave starts to hide in the previous T wave — that is the boundary with SVT.

Causes: fever · pain · anxiety · hypovolemia / hemorrhage · hypoxia · anemia · dehydration · sepsis · hyperthyroidism · heart failure · caffeine, nicotine, decongestants, cocaine, amphetamines.

What you do: treat the CAUSE.

Fever → antipyretic and cooling
Pain or anxiety → analgesia, reassurance
Hypovolemia → fluids and find the bleeding
Hypoxia → oxygen

Do not slow a compensatory tachycardia with a beta blocker. A bleeding client's fast heart rate is the only thing keeping the blood pressure up.

🧠 “Sinus tach is the smoke alarm, not the fire.” Silencing the alarm does not put out the fire — find what is burning.

📊 Telling the sinus three apart in one glance

Rhythm	P wave	Regular	Rate	First move
Normal sinus	Yes	Yes	60–100	Nothing — this is the goal
Sinus bradycardia	Yes	Yes	< 60	Assess symptoms → atropine if symptomatic
Sinus tachycardia	Yes	Yes	> 100	Find and fix the cause

🧠 The word “sinus” is a promise: the SA node is still in charge, so there is a P wave and the rhythm is regular. Only the speed is in question.

💙

THE ATRIAL THREE

STEP 3 · 4 · 5 · 6

Now the P wave changes or disappears — and clots become the story.

4️⃣ Atrial Fibrillation — no P waves · irregularly irregular

The distinguishing feature: there is no discrete P wave anywhere — the baseline is a chaotic wavy line — and the R–R spacing never repeats. The atria are quivering at 350–600 times a minute; the AV node lets random beats through.

Causes: valvular disease · heart failure · pulmonary hypertension · COPD · after heart surgery · hypertension · hyperthyroidism · alcohol · advancing age.
Why it matters: quivering atria let blood pool and clot → the clot embolises → STROKE. Plus the "atrial kick" is lost, dropping cardiac output.
Assessment: irregular pulse, palpitations, fatigue, dyspnea, and often a pulse deficit — the apical rate is higher than the radial rate because weak beats don't reach the wrist.

🧠 “No P, Floppy and Free — Fibrillation FLOPPING.” No P wave, no pattern, no atrial kick.

✅ A-Fib treatment — three jobs, in this order

RATE control. Slow the ventricles: beta blockers, calcium channel blockers (diltiazem, verapamil), or digoxin. See NG-057 and NG-060.

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ANTICOAGULATE. Warfarin — monitor the INR, antidote is vitamin K, teach a consistent (not zero) intake of green leafy vegetables. Or a DOAC per the provider.

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RHYTHM control if needed. Synchronized cardioversion — but only after a TEE rules out an atrial clot, or after several weeks of therapeutic anticoagulation. Cardioverting a clot-filled atrium throws a stroke.

Digoxin safety before EVERY dose: apical pulse for a full minute — hold and call if it is under 60. Watch for toxicity: visual disturbances (yellow-green halos, blurring), nausea, vomiting, anorexia. Serum level above roughly 2.0 ng/mL is toxic, and potassium under 3.5 makes toxicity far more likely.

🧠 “Rate · Anticoagulate · Rhythm” = R-A-R. Slow it, thin it, then — carefully — reset it.

5️⃣ Atrial Flutter — A-FLUTTER = SAW-TOOTH

The distinguishing feature: instead of a chaotic baseline you get identical, repeating sawtooth "F waves" — one signal racing around a fixed circuit in the right atrium at about 250–350 per minute.

The AV node blocks most of them, so several F waves pass for each QRS — a 2:1, 3:1 or 4:1 pattern.
Because the block ratio is usually fixed, the ventricular rate is often regular — that is the fastest way to tell it from A-fib.
Same causes and same clot risk as A-fib, and the same three treatment jobs: rate control, anticoagulation, cardioversion after a TEE.

A-fib vs A-flutter in one line:

A-Fib	A-Flutter
Baseline is chaotic and wavy	Baseline is a repeating sawtooth
Irregularly irregular	Often regular (fixed ratio)
No two waves look alike	Every F wave is identical

🧠 “A FluTTer = sawTooTh.” Two T's in flutter, two teeth in the saw. A-fib has no T's and no teeth — just noise.

6️⃣ SVT — Super Fast = Supraventricular

The distinguishing feature: narrow QRS, perfectly regular, 150–250 bpm, and you cannot find a P wave — it is buried inside the preceding T wave. It starts and stops abruptly.

Causes: stimulants (caffeine, energy drinks, decongestants, cocaine) · strenuous exercise · hypoxia · fever · anxiety · underlying heart disease.

Narrow is the good news: a narrow QRS proves the impulse traveled down the normal conduction pathway — the problem is above the ventricles.

Treatment, in order:

Vagal maneuver — bear down as if having a bowel movement; ice-cold stimulation to the face
Adenosine — rapid IV push over 1–2 seconds + 20 mL saline flush + elevate the arm; expect a brief pause
Beta blocker or calcium channel blocker
Synchronized cardioversion if unstable

Two classic exam items. ① A client in SVT with HR 200 · BP 78/40 · RR 30 is unstable → the priority is synchronized cardioversion. ② Which drug is held 48 hours before an elective cardioversion for SVT? Digoxin — because of increased ventricular irritability during the shock.

🧠 “Narrow and fast and regular = SVT. Wide and fast and regular = V-Tach.” One letter of difference on the monitor, a completely different emergency.

⭐ Narrow vs wide — the single most useful line on the whole page

🧠 “Three little boxes.” If the QRS spans more than 3 small boxes (0.12 s) the beat did not use the normal wiring — treat it as ventricular until someone proves otherwise.

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THE LETHAL THREE

STEP 4 · 7 · 8 · 9

Stop reading the monitor and touch the client. These three are decided by one finding: is there a pulse?

7️⃣ Ventricular Tachycardia — wide · regular · fast · no P waves

The distinguishing feature: a run of wide, bizarre, identical complexes marching regularly at 100–250. Three or more consecutive PVCs is V-Tach.

Causes: MI / ischemia · cardiomyopathy · low K⁺ · low Mg²⁺ · QT-prolonging drugs · hypoxia · acidosis.

Assessment: may be alert and talking, or pulseless within seconds. The pulse decides the treatment.

Treatment splits three ways:

Pulseless → CPR + DEFIBRILLATE (unsynchronized)
Pulse, unstable → synchronized cardioversion
Pulse, stable → antidysrhythmic (amiodarone, lidocaine) — see NG-062

🧠 “V-Tach: check the neck.” Carotid pulse present → cardiovert or medicate. Absent → shock. Never medicate a pulseless client instead of shocking them.

8️⃣ Ventricular Fibrillation — chaos · no QRS · NEVER a pulse

The distinguishing feature: there is no identifiable QRS at all — just an irregular, wandering squiggle. The ventricles are quivering, not pumping. Coarse V-Fib has large deflections; fine V-Fib is low-amplitude and can be mistaken for asystole.

The client is always unresponsive, pulseless and apneic. If your "V-Fib" client is talking to you, look at the leads — motion artifact and a loose lead mimic it.
Treatment: start CPR immediately and DEFIBRILLATE as soon as the machine is charged. Then continue CPR, give epinephrine, and add amiodarone or lidocaine for shock-refractory V-Fib.
Every minute without defibrillation drops the chance of survival substantially — this is the rhythm where speed is the intervention.

🧠 “Fibrillation = a bag of worms.” A quivering bag of muscle cannot pump. Shock it back into one organized beat.

9️⃣ Asystole — the flatline

The distinguishing feature: a nearly flat line with only a faint drift — no P waves, no QRS, no electrical activity at all.

Before you believe it — confirm it:

Check the client: unresponsive? pulseless? not breathing?
Check the leads — are they attached and connected?
Turn up the gain / amplitude
Confirm in a second lead — fine V-Fib can look flat in one lead

Treatment:

High-quality CPR and epinephrine
Aggressively hunt the reversible cause — the H's and T's
NEVER defibrillate asystole. There is no electrical activity to reorganize, and the shock stuns any remaining pacemaker cells.

🧠 “Flatline = leads, gain, second lead — then CPR.” Confirm before you call it, then compress.

⚡ SHOCKABLE vs NON-SHOCKABLE — the ACLS split you must not miss

🧠 “You can only shock a heart that is still trying.” V-Fib and pulseless V-Tach are disorganized effort — a shock reorganizes them. Asystole and PEA are no effort — there is nothing to reorganize, so you compress and give epinephrine.

🌀 Bonus strip — Torsades de Pointes

Polymorphic V-Tach whose amplitude twists around the baseline — the "Tornado Pointes". Causes: post-MI · hypoxia · low magnesium · low potassium · QT-prolonging drugs.

Treatment: IV magnesium sulfate — Magnesium Mellows out the heart. If it becomes pulseless, defibrillate.

🧠 “A tornado gets MAG.” Nothing else on this page gets magnesium — so if you see the twist, you know the answer.

📊 All nine, side by side

#	Rhythm	P wave	Regular	Rate	QRS	First action
1	Normal sinus	Yes	Yes	60–100	Narrow	Nothing
2	Sinus bradycardia	Yes	Yes	< 60	Narrow	Symptoms? → atropine, pacing
3	Sinus tachycardia	Yes	Yes	> 100	Narrow	Treat the cause
4	Atrial fibrillation	None — wavy baseline	Irregularly irregular	Varies	Narrow	Rate control + anticoagulate
5	Atrial flutter	Sawtooth F waves	Often regular	Atrial 250–350	Narrow	Rate control + anticoagulate
6	SVT	Hidden in the T	Yes	150–250	Narrow	Vagal → adenosine → cardiovert
7	V-Tach	None	Yes	100–250	WIDE	Check pulse → defib or cardiovert
8	V-Fib	None	No — chaotic	Unmeasurable	No QRS	CPR + DEFIBRILLATE
9	Asystole	None	Flat	0	None	CPR + epinephrine — never shock

🧠 Cover the right-hand columns and name each rhythm from the P-wave column alone. If you can do that, you can do the strip questions.

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QUICK RECALL

SAY IT OUT LOUD

❓ P · Regular · Rate · WideFour questions name every rhythm on this page.

🦷 A-FluTTer = sawTooThA-fib = no P, irregularly irregular. SVT = narrow, fast, regular.

⚡ Shock only 2V-Fib & pulseless V-Tach. Asystole and PEA get CPR + epi.

🌀 Tornado gets MAGTorsades → IV magnesium sulfate. Nothing else here gets magnesium.

🎯 Cover & check — 9 rapid-fire questions

Q1: What four questions do you ask of every strip?

Is there a P wave before every QRS? Is it regular? What is the rate? Is the QRS narrow or wide?

Q2: The baseline is chaotic, there are no P waves, and no two R–R intervals match. Name it.

Atrial fibrillation. Priorities: rate control (beta blocker, calcium channel blocker or digoxin) and anticoagulation, because pooled blood in the quivering atria forms clots and causes stroke.

Q3: How do you tell A-flutter from A-fib in three seconds?

A-flutter has repeating, identical sawtooth F waves and the ventricular rate is often regular. A-fib has a chaotic wavy baseline and is irregularly irregular.

Q4: Why is a TEE done before elective cardioversion for A-fib?

To rule out a clot in the left atrium. Cardioverting a heart with an atrial clot can dislodge it and cause a stroke. The alternative is several weeks of therapeutic anticoagulation first.

Q5: Narrow QRS at 210, perfectly regular, no visible P waves. Rhythm and first intervention?

SVT. If stable: vagal maneuvers first, then adenosine — standard adult ACLS dosing is 6 mg rapid IV push with a 20 mL saline flush (12 mg may follow); always confirm the dose against your facility's protocol. If unstable — hypotension, altered LOC, chest pain — synchronized cardioversion.

Q6: Wide, bizarre, regular complexes at 180. What is your very first action?

Check the client and check a pulse. Pulseless V-Tach = CPR and defibrillation. V-Tach with a pulse but unstable = synchronized cardioversion. With a pulse and stable = an antidysrhythmic such as amiodarone or lidocaine.

Q7: Which two rhythms are shockable?

Ventricular fibrillation and pulseless ventricular tachycardia. Asystole and PEA are non-shockable — CPR, epinephrine, and treat the H's and T's.

Q8: The monitor flatlines. Name three things you check before calling it asystole.

Assess the client (responsive? pulse? breathing?), check the leads and connections, turn up the gain, and confirm in a second lead — fine V-Fib can look flat in one lead. Then CPR and epinephrine. Never defibrillate a flatline.

Q9: Which medication is held 48 hours before an elective cardioversion for SVT, and why?

Digoxin — because of increased ventricular irritability during cardioversion.