ECG examples

Every rhythm and finding Squiggler draws, as 29 worked examples — STEMI territories, blocks, tachyarrhythmias, arrest rhythms and the metabolic patterns — each one a synthetic tracing you can open and tune.

Acute coronary syndrome

• Inferior STEMI — Elevation in II, III and aVF with reciprocal depression in aVL.
• Anterior STEMI — A convex dome across the anterior leads in a patient who is tachycardic with it.
• Posterior MI — Nothing is elevated on a standard twelve-lead — the injury points away, so V1–V3 show the depression instead.
• Wellens type A — Biphasic T waves in V2–V3 with no elevation and no pain: a critical LAD stenosis that looks almost well.
• de Winter T waves — Upsloping depression with tall symmetric T waves — an LAD occlusion that never elevates and gets sent home.

Blocks & conduction

• Wenckebach (Mobitz I) — The PR stretches beat by beat until a P wave is not conducted. 4:3 by default.
• Mobitz II — A fixed PR and then a beat simply vanishes — the one that needs a wire, not atropine.
• 2:1 AV block — Every other P conducts, so there is no PR sequence to read — which is why this is the one second-degree block that cannot be called Mobitz I or II.
• Complete block, narrow escape — Third-degree block with a junctional escape — the same diagnosis as a wide escape, a different urgency.
• High-grade block with escape — Only some P waves conduct, and a junctional focus covers the pauses — a complete block is just this with nothing getting through at all.
• Junctional escape over a slow sinus — The sinus node has fallen below the junction, so most complexes are junctional while the P waves march on independently.
• WPW pre-excitation — Short PR with a delta wave: the accessory pathway beats the AV node to the ventricle.
• Left bundle branch block — A changed depolarisation sequence — the wide complex falls out of the projection.

Tachyarrhythmias

• AF with rapid response — Irregularly irregular with no organised atrial activity anywhere on the strip.
• Flutter, variable block — Irregular — but the R–R intervals are multiples of the flutter interval, which is how it is told from the AF it gets called.
• AF, rate-controlled — The same fibrillating atria as above — only the AV node has changed. Still irregularly irregular, which a rate-controlled AF must never stop being.
• Regularised AF — An irregular rhythm that has gone regular: nothing conducts and a junctional focus has taken over. The classic picture of digoxin toxicity.
• SVT — Regular, narrow, fast, and no P wave you can find.
• Monomorphic VT — Wide, regular, and every complex the same shape — twelve leads to prove it.

Arrest rhythms

• Torsades de pointes — Teach your students to reach for the defibrillator and some magnesium.
• Ventricular fibrillation — No organised beat to measure anything against. Shock it.
• Idioventricular / agonal — A slow wide escape with nothing above it — the rhythm of a PEA arrest.

Metabolic & inherited

• Hyperkalaemia — Peaked T waves and a widening QRS — the ECG is faster than the blood gas.
• Pericarditis — Widespread CONCAVE elevation. Compare the ST shape against the anterior STEMI preset — that curve is the whole differential.
• Brugada type 1 — Coved elevation in V1–V2 in a structurally normal heart — a syncope you do not discharge.
• PE pattern (S1Q3T3) — The classic pattern, worth knowing precisely because sinus tachycardia is the common finding.
• Hypothermia (Osborn) — The J wave sitting on the end of every QRS, with a bradycardia to match.
• LVH with strain — Voltage criteria plus the lateral repolarisation change that makes it strain.
• Digoxin effect — The sagging 'reverse tick' ST — an effect at therapeutic levels, not a sign of toxicity.

For education only; not for clinical use. Every tracing on this site is generated, not recorded: there is no patient and no protected health information.