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12-LEAD ECG • CLINICAL VIGNETTES • HIDDEN INTERPRETATION

🫀 ECG Masterclass

Fifty case-based ECG challenges. Read the patient first, inspect the tracing, commit to an interpretation, then reveal the systematic analysis, diagnosis and management.

FREE SAMPLE: Cases 1–5 are public. Cases 6–50 remain visible but greyed and require Members Access. ECGs are served from Wikimedia Commons and each case links to its source/licence page.
ECG tracing case 1
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Case 01 — Crushing pain before breakfast

A 58-year-old man has 45 minutes of crushing retrosternal pain, diaphoresis and nausea. BP 104/68 mmHg.

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ECG tracing case 2
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Case 02 — The irregular pulse

A 72-year-old woman has palpitations and exertional breathlessness. Pulse is irregularly irregular at 132/min.

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ECG tracing case 3
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Case 03 — A young man who fainted at night

A 32-year-old man has recurrent nocturnal syncope and a family history of sudden unexplained death.

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ECG tracing case 4
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Case 04 — The slow pulse before surgery

A 64-year-old asymptomatic man has a pulse of 58/min before surgery; every P wave is followed by QRS but the PR interval is prolonged.

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ECG tracing case 5
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Case 05 — A broad-complex clue

A 66-year-old man with hypertension has an incidental broad QRS complex. Compare V1 and the lateral leads.

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ECG tracing case 6
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Case 06 — Pain with inferior ST elevation

A 61-year-old man develops severe central chest pain with vomiting and diaphoresis; BP is 92/60 mmHg.

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ECG tracing case 7
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Case 07 — Chest pain with an easy-to-miss posterior clue

A 59-year-old man has persistent chest pain; the standard ECG shows horizontal ST depression across V1–V3 with prominent anterior R waves.

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ECG tracing case 8
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Case 08 — Hypotension after an inferior infarct

A 63-year-old man with inferior ST elevation becomes hypotensive; lungs are clear and JVP is elevated.

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ECG tracing case 9
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Case 09 — Rest pain with changing ST depression

A 67-year-old woman has recurrent rest chest pain; serial ECGs show new horizontal ST depression in V4–V6 that improves when pain settles.

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ECG tracing case 10
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Case 10 — Pain-free now, but the T waves are warning

A 54-year-old man had repeated chest pain overnight but is pain-free now; V2–V4 show deeply inverted symmetric T waves.

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ECG tracing case 11
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Case 11 — A STEMI without classic ST elevation

A 48-year-old man has ongoing crushing chest pain; precordial leads show upsloping ST depression at the J point with tall symmetric T waves.

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ECG tracing case 12
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Case 12 — Sharp chest pain that improves sitting forward

A 35-year-old man has pleuritic chest pain relieved by leaning forward after a viral illness.

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ECG tracing case 13
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Case 13 — Weakness with a widening QRS

A 70-year-old man with CKD presents with weakness; potassium is 7.2 mmol/L and the ECG shows peaked T waves with QRS widening.

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ECG tracing case 14
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Case 14 — Palpitations after several days of vomiting

A 46-year-old woman has vomiting, weakness and palpitations; potassium is 2.5 mmol/L.

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ECG tracing case 15
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Case 15 — Syncope after a new medication

A 42-year-old woman faints after starting a QT-prolonging drug; the corrected QT interval is markedly prolonged.

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ECG tracing case 16
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Case 16 — Twisting complexes after a pause

A 56-year-old woman develops recurrent syncope with runs of polymorphic wide-complex tachycardia after QT prolongation.

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ECG tracing case 17
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Case 17 — A regular broad-complex tachycardia

A 68-year-old man with prior MI has palpitations and BP 86/54 mmHg; ECG shows a regular broad-complex tachycardia.

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ECG tracing case 18
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Case 18 — Collapse with changing QRS morphology

A 50-year-old man becomes dizzy with a rapid irregular broad-complex rhythm whose QRS morphology changes beat to beat.

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ECG tracing case 19
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Case 19 — Sudden regular racing heart

A 29-year-old woman has abrupt-onset palpitations at 190/min; ECG shows a regular narrow-complex tachycardia with no obvious preceding P waves.

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ECG tracing case 20
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Case 20 — Palpitations in a patient with an accessory pathway

A 24-year-old man with known pre-excitation develops a regular narrow-complex tachycardia at 210/min.

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ECG tracing case 21
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Case 21 — The short PR with a slurred upstroke

A 22-year-old man has episodic palpitations; resting ECG shows a short PR and slurred initial QRS upstroke.

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ECG tracing case 22
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Case 22 — A regular rate close to 150

A 65-year-old man has persistent palpitations at 150/min; the rhythm appears regular until the baseline is examined carefully.

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ECG tracing case 23
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Case 23 — A slow pulse in an endurance runner

A 28-year-old asymptomatic athlete has a resting pulse of 44/min and normal blood pressure.

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ECG tracing case 24
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Case 24 — Dizziness with pauses

A 74-year-old woman reports fatigue, presyncope and alternating slow pulse with bursts of atrial tachyarrhythmia.

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ECG tracing case 25
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Case 25 — Progressively longer PR, then a dropped beat

A 61-year-old man on an AV-nodal blocker has grouped beating on telemetry.

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ECG tracing case 26
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Case 26 — A dropped QRS without warning

A 70-year-old man with syncope has constant PR intervals but intermittent non-conducted P waves.

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ECG tracing case 27
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Case 27 — P waves and QRS complexes marching independently

A 76-year-old man presents with syncope, HR 32/min and hypotension.

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ECG tracing case 28
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Case 28 — A new broad QRS in a breathless patient

A 69-year-old man with cardiomyopathy has a broad QRS with a dominant S in V1 and broad notched R waves laterally.

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ECG tracing case 29
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Case 29 — Left axis deviation with a narrow-ish QRS

A 67-year-old man has marked left-axis deviation without LVH or inferior infarction.

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ECG tracing case 30
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Case 30 — Syncope with two conduction defects

A 73-year-old man has unexplained syncope; ECG shows RBBB plus marked left-axis deviation.

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ECG tracing case 31
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Case 31 — The hypertensive heart on ECG

A 62-year-old man with long-standing hypertension has high QRS voltages and lateral repolarization abnormalities.

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ECG tracing case 32
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Case 32 — Right-sided forces in a breathless patient

A 55-year-old man with chronic pulmonary hypertension has right-axis deviation and a dominant R wave in V1.

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ECG tracing case 33
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Case 33 — Sudden dyspnoea after immobilisation

A 49-year-old woman develops acute pleuritic chest pain, tachycardia and hypoxaemia after prolonged immobilisation.

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ECG tracing case 34
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Case 34 — Scooped ST segments on chronic therapy

A 78-year-old man taking digoxin has no acute symptoms but an ECG with characteristic downsloping ST depression.

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ECG tracing case 35
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Case 35 — Nausea, confusion and an unusual arrhythmia

An elderly patient on digoxin with AKI develops nausea, confusion and frequent ectopy.

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ECG tracing case 36
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Case 36 — A cold patient with an extra deflection

An 82-year-old man is found outdoors confused with a core temperature of 30°C.

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ECG tracing case 37
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Case 37 — A short QT in a patient with malignancy

A 64-year-old patient with metastatic cancer has calcium 14.2 mg/dL and a shortened QT interval.

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ECG tracing case 38
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Case 38 — A prolonged QT after neck surgery

A 45-year-old woman develops perioral tingling after thyroid surgery; calcium is low and QT is prolonged.

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ECG tracing case 39
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Case 39 — ST elevation in a healthy young adult

A 25-year-old asymptomatic man has stable concave precordial ST elevation on repeated ECGs.

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ECG tracing case 40
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Case 40 — Chest pain after intense emotional stress

A 63-year-old woman develops chest pain after severe emotional stress; ECG shows widespread anterior ST-T abnormalities.

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ECG tracing case 41
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Case 41 — Syncope in a young athlete

A 21-year-old athlete has exertional syncope and a harsh systolic murmur.

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ECG tracing case 42
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Case 42 — T-wave inversion in a young patient with ventricular arrhythmia

A 34-year-old man has palpitations and syncope; ECG shows right-precordial T-wave inversion and ventricular ectopy.

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ECG tracing case 43
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Case 43 — Regular spikes before broad complexes

A 76-year-old man with a pacemaker has regular pacing spikes followed by broad QRS complexes.

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ECG tracing case 44
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Case 44 — Pacing spikes without a QRS

A pacemaker-dependent patient becomes dizzy; pacing spikes are seen but some are not followed by QRS complexes.

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ECG tracing case 45
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Case 45 — Every other beat arrives early

A 58-year-old man notices palpitations; ECG shows a premature broad complex after every sinus beat.

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ECG tracing case 46
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Case 46 — Irregular tachycardia in severe COPD

A 71-year-old man with COPD exacerbation has an irregular narrow-complex tachycardia at 135/min.

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ECG tracing case 47
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Case 47 — A narrow slow rhythm without sinus P waves

A 69-year-old man after inferior MI has a regular narrow-complex rhythm at 45/min with absent/retrograde P waves.

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ECG tracing case 48
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Case 48 — Fast pulse with fever

A 40-year-old man with pneumonia has HR 128/min; each QRS is preceded by a normal P wave.

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ECG tracing case 49
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Case 49 — Alternating QRS amplitude with hypotension

A 56-year-old patient with malignancy has dyspnoea, raised JVP and hypotension; ECG shows beat-to-beat variation in QRS amplitude.

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ECG tracing case 50
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Case 50 — Chest pain after a viral illness with troponin rise

A 27-year-old man develops chest pain and palpitations one week after a viral syndrome; troponin is elevated.

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