The 6-step method that keeps you from panicking on test day
An EKG lands in front of you. Your eyes go everywhere at once. Nothing sticks. You pick "normal sinus rhythm" and pray.
Here's the thing — EKGs are pattern recognition, and your visual-spatial brain is built for this. You just need a system so you stop looking at everything and start looking at the right things in the right order.
Every EKG. Every time. Same six questions, same order. The system works because it forces you to check one thing at a time instead of trying to see the whole picture at once.
How fast is the heart going?
Count the number of big boxes between two R waves. Divide 300 by that number.
Normal: 60–100 bpm. Under 60 = bradycardiaSlow heart rate. Can be normal in athletes (high vagal tone) or pathological (AV block, sick sinus).. Over 100 = tachycardiaFast heart rate. Narrow QRS = probably supraventricular. Wide QRS = could be ventricular (dangerous) or SVT with aberrancy..
Is it regular or irregular?
Look at the R-R intervalsDistance between consecutive R waves. If they're all the same distance apart, the rhythm is regular. If they vary, it's irregular.. Same distance apart = regular. Varying = irregular.
Are there P waves? Are they upright in lead II? Is there one before every QRS?
The P wave = atrial depolarization. If you see consistent, upright P waves marching before every QRS, the SA nodeSinoatrial node — the heart's natural pacemaker, sitting in the right atrium. Fires at 60-100 bpm. When it's in charge, you get normal sinus rhythm. is in charge. Good sign.
No P waves at all? → A-fib or junctional rhythm.
Sawtooth P waves? → A-flutter.
P waves present but disconnected from QRS? → 3rd degree heart block.
How long from the start of the P to the start of the QRS?
Normal: 0.12–0.20 seconds (3–5 small boxes).
Too long (>0.20s) = 1st degree AV block (the signal is slow getting through the AV node, but it always makes it).
Getting progressively longer until a QRS drops = 2nd degree Type I (Wenckebach).
Fixed PR but randomly dropped QRS = 2nd degree Type II (dangerous — can progress to complete block).
Is the QRS narrow or wide?
Normal: < 0.12 seconds (< 3 small boxes).
Is the ST segment elevated, depressed, or normal? Are the T waves peaked, inverted, or normal?
ST elevation = STEMI until proven otherwise. This is the one that gets the cath lab activated at 3 AM.
ST depression = ischemia, dig effect, or strain pattern.
Peaked T waves = hyperkalemia. Tall, narrow, tent-like. The potassium is rising and the heart is about to have a very bad time.
Inverted T waves = ischemia, LVH strainLeft ventricular hypertrophy creates asymmetric T-wave inversion in the lateral leads (I, aVL, V5-V6). The thick muscle depolarizes abnormally., or post-MI (Wellens).
These six rhythms cover ~80% of EKG questions on boards. Learn to recognize them on sight.
| Rhythm | Rate | Regularity | P Waves | QRS | The Giveaway |
|---|---|---|---|---|---|
| Normal Sinus | 60–100 | Regular | Upright, 1:1 | Narrow | Everything normal. Boring. Beautiful. |
| A-fib | Variable | Irregularly irregular | None (fibrillatory baseline) | Narrow | No P waves + chaotic rhythm |
| A-flutter | ~150 (with 2:1 block) | Regular | Sawtooth | Narrow | Rate ~150 + sawtooth baseline |
| SVT (AVNRT) | 150–250 | Regular | Hidden in QRS | Narrow | Sudden onset/offset, very regular fast rate |
| V-tach | 100–250 | Regular | Dissociated or absent | Wide | Wide + fast + regular = V-tach |
| V-fib | Chaotic | None | None | None | Chaotic squiggles. Patient is dead. Shock them. |
You see an EKG. Walk through this. One step at a time.
First question: Is the QRS narrow or wide?
A patient walks in. Clues appear one at a time. Eliminate diagnoses as you go. See how few clues you need.
4 questions, pulled from a pool. Different every time.