Explain 10 common heart diseases with ECG changes and ecg inages of those diseases

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ECG electrocardiogram myocardial infarction ST elevation

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atrial fibrillation ECG irregularly irregular rhythm

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heart block complete AV block ECG bradycardia

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ventricular tachycardia ECG wide complex tachycardia

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hypertrophic cardiomyopathy ECG left ventricular hypertrophy

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pulmonary embolism ECG S1Q3T3 right heart strain

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Wolff-Parkinson-White syndrome delta wave short PR ECG

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pericarditis ECG saddle-shaped ST elevation diffuse

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dilated cardiomyopathy ECG left bundle branch block low voltage

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long QT syndrome torsades de pointes ECG polymorphic ventricular tachycardia

Here is a comprehensive guide to 10 common heart diseases with their characteristic ECG changes and representative ECG images.

10 Common Heart Diseases: ECG Changes & Images

1. 🫀 ST-Elevation Myocardial Infarction (STEMI)

What it is

Acute complete occlusion of a coronary artery causing full-thickness myocardial injury. Most commonly involves the LAD (anterior), RCA (inferior), or LCx (lateral) territory.

ECG Changes

Feature	Finding
ST Segments	Convex (tombstone) ST elevation ≥1 mm in ≥2 contiguous leads
Reciprocal Changes	ST depression in leads opposite to the infarct territory
Hyperacute T-waves	Tall, peaked T-waves in the early phase
Q-waves	Pathological Q-waves develop within hours (>40 ms wide, >25% of R-wave height)
T-wave inversions	Follow ST elevation in the evolutionary phase

Localisation:

Anterior (V1–V4) → LAD occlusion
Inferior (II, III, aVF) → RCA occlusion
Lateral (I, aVL, V5–V6) → LCx occlusion

ECG Image — Anterior STEMI (LAD territory)

Anterior STEMI ECG showing ST elevation in V1-V6

ECG Image — Inferolateral STEMI

Inferolateral STEMI with ST elevation in inferior and lateral leads with reciprocal changes

2. ❤️ Atrial Fibrillation (AF)

What it is

The most common sustained cardiac arrhythmia, caused by chaotic electrical activity in the atria (often originating from pulmonary vein triggers). Associated with hypertension, valvular disease, heart failure, hyperthyroidism, and alcohol use.

ECG Changes

Feature	Finding
P waves	Absent; replaced by fine, irregular fibrillatory (f) waves at 350–600/min
Rhythm	"Irregularly irregular" ventricular response
QRS complex	Narrow (unless aberrant conduction or WPW co-exists)
Rate	Ventricular rate 60–180/min depending on AV node conduction
Baseline	Undulating, no flat isoelectric line

ECG Image

12-lead ECG showing atrial fibrillation with absent P waves and irregularly irregular rhythm

3. 🔵 Complete (Third-Degree) AV Block

What it is

Complete failure of AV conduction — no atrial impulses reach the ventricles. The atria and ventricles beat independently. Caused by inferior MI, fibrosis of the conduction system, medications, or infiltrative disease.

ECG Changes

Feature	Finding
AV Dissociation	P waves and QRS complexes completely independent
Atrial Rate	Regular, usually 60–100/min
Ventricular Rate	Slow escape rhythm: 40–60/min (nodal) or 20–40/min (ventricular)
QRS morphology	Narrow if junctional escape; wide/bizarre if ventricular escape
PR interval	Variable — no fixed relationship

ECG Image

Complete third-degree AV heart block showing complete AV dissociation with slow ventricular escape rhythm

4. ⚡ Ventricular Tachycardia (VT)

What it is

A life-threatening arrhythmia originating below the Bundle of His (≥3 consecutive ventricular beats at ≥100 bpm). Often occurs in the setting of ischaemic heart disease, cardiomyopathy, or electrolyte disturbance.

ECG Changes

Feature	Finding
Rate	100–250 bpm, usually regular
QRS	Wide (>120 ms), bizarre morphology
P waves	AV dissociation — P waves march through independently
Fusion beats	Pathognomonic of VT
Capture beats	Narrow QRS amid wide complex — pathognomonic
Axis	Often extreme left or right axis deviation
Concordance	Positive concordance (all V leads upright) or negative concordance strongly suggests VT

ECG Image

Ventricular tachycardia ECG showing wide complex tachycardia with regular morphology

5. 🫁 Pulmonary Embolism (PE)

What it is

Obstruction of pulmonary vasculature causing acute right ventricular pressure overload. The ECG changes reflect acute right heart strain.

ECG Changes

Feature	Finding
Sinus tachycardia	Most common finding (>100 bpm)
S1Q3T3	Deep S in lead I, Q wave in lead III, T-wave inversion in lead III
RBBB	New incomplete or complete right bundle branch block
T-wave inversions	V1–V4 (right ventricular strain pattern)
Right axis deviation	Shift from baseline
P pulmonale	Tall peaked P waves in inferior leads (right atrial enlargement)
Sinus tachycardia	Most sensitive but least specific finding

ECG Image — Classic S1Q3T3 Pattern

Pulmonary embolism ECG showing S1Q3T3 pattern with sinus tachycardia and right heart strain

ECG Image — Acute RV Strain with T-wave Inversions

PE ECG with S1Q3T3 and precordial T-wave inversions indicating right ventricular strain

6. 🧬 Hypertrophic Cardiomyopathy (HCM)

What it is

Genetic disorder (autosomal dominant, sarcomere protein mutations) causing asymmetric myocardial hypertrophy, most commonly affecting the interventricular septum. Leading cause of sudden cardiac death in young athletes.

ECG Changes

Feature	Finding
LVH criteria	High voltage in precordial leads (Sokolow-Lyon: S-V1 + R-V5 >35 mm)
Strain pattern	ST depression + T-wave inversions in lateral leads (I, aVL, V4–V6)
Deep T inversions	Giant T-wave inversions in V3–V5 (apical HCM variant)
Abnormal Q waves	Deep narrow Q waves in lateral/inferior leads (septal hypertrophy)
Left axis deviation	Common
No septal Q waves	Absence of normal septal Q in V5–V6 (reversed septal depolarisation)

ECG Image — Septal HCM with LVH & Strain

Hypertrophic cardiomyopathy ECG showing LVH, strain pattern, and deep T-wave inversions

ECG Image — Apical HCM (Giant T-wave Inversions)

Apical hypertrophic cardiomyopathy ECG with giant T-wave inversions in V3-V5

7. ❄️ Acute Pericarditis

What it is

Inflammation of the pericardium, most commonly viral in origin. Presents with sharp pleuritic chest pain relieved by sitting forward.

ECG Changes

Feature	Finding
ST elevation	Diffuse, concave (saddle-shaped) in almost all leads except aVR and V1
PR depression	Classic early finding — depression in most leads, elevation in aVR
Spodick's sign	Downsloping TP segment (highly specific)
No reciprocal changes	Unlike STEMI — ST elevation is global, not regional
Temporal evolution	ST→ T-wave flattening → T inversion → normalisation (4 stages)
Electrical alternans	If large effusion with tamponade

ECG Image

Pericarditis ECG showing diffuse saddle-shaped ST elevation and PR depression in multiple leads

8. ⏱️ Long QT Syndrome (LQTS) & Torsades de Pointes

What it is

Disorder of cardiac repolarisation (congenital or acquired) that prolongs the QT interval and predisposes to a dangerous polymorphic VT called Torsades de Pointes ("twisting of the points"), which can degenerate into ventricular fibrillation.

ECG Changes

Feature	Finding
QTc prolongation	QTc >440 ms (men), >460 ms (women); danger threshold >500 ms
T-wave morphology	Notched, bifid, or prolonged T-waves; prominent U waves
Torsades de Pointes	Polymorphic VT with characteristic twisting QRS axis around the isoelectric line
Trigger	Often initiated by a PVC with short-long-short RR sequence
Self-terminating	Paroxysmal episodes of TdP, may degenerate to VF

ECG Image — Long QT + Torsades de Pointes

Long QT syndrome ECG from Harrison's showing prolonged QT interval and polymorphic ventricular tachycardia

ECG Image — Torsades de Pointes

Torsades de pointes ECG showing the classic twisting morphology of polymorphic ventricular tachycardia

9. 🔗 Wolff-Parkinson-White (WPW) Syndrome

What it is

Ventricular pre-excitation via an accessory pathway (Bundle of Kent) that bypasses the AV node, allowing premature ventricular depolarisation. Predisposes to re-entrant tachycardias and, in AF, to life-threatening rapid conduction.

ECG Changes

Feature	Finding
Short PR interval	<120 ms (bypasses normal AV node delay)
Delta wave	Slurred upstroke at the start of QRS — hallmark finding
Wide QRS	Broadened complex (>120 ms) due to pre-excitation
Secondary ST-T changes	Discordant ST/T changes (not ischemic)
Pseudo-infarction	Negative delta waves in inferior leads mimic Q-waves
AF with WPW	Extremely rapid irregular wide-complex rhythm (≥200 bpm) — medical emergency

ECG Image

Wolff-Parkinson-White syndrome ECG showing short PR interval, delta waves, and widened QRS complex

10. 🫀 Dilated Cardiomyopathy (DCM)

What it is

Dilated, poorly contracting left ventricle (EF <40%) due to ischaemic, genetic, viral, alcoholic, or idiopathic causes. The stretched, fibrotic myocardium produces characteristic ECG abnormalities.

ECG Changes

Feature	Finding
LBBB	Most common — broad monophasic R in I, aVL, V5–V6; QS in V1–V3
Left axis deviation	Common
Low voltage	QRS amplitude <5 mm in all limb leads (amyloid, pericardial effusion)
Fragmented QRS	Multiple notches within the QRS — marker of fibrosis
Atrial fibrillation	Very common complication of DCM
Non-specific ST-T changes	Widespread T-wave flattening or inversion
Q waves	May mimic infarction in ischaemic DCM

ECG Image — Dilated Cardiomyopathy with LBBB

Dilated cardiomyopathy ECG showing left bundle branch block and fragmented QRS in context of structural heart disease

Quick Reference Summary Table

#	Disease	Key ECG Hallmarks
1	STEMI	Convex ST elevation, reciprocal depression, Q waves
2	Atrial Fibrillation	No P waves, irregularly irregular, fibrillatory baseline
3	Complete AV Block	AV dissociation, slow escape rhythm, variable PR
4	Ventricular Tachycardia	Wide QRS >120 ms, AV dissociation, fusion/capture beats
5	Pulmonary Embolism	Sinus tach, S1Q3T3, RBBB, RV strain T inversions V1–V4
6	Hypertrophic Cardiomyopathy	LVH, strain, deep T inversions (apical), abnormal Q waves
7	Acute Pericarditis	Diffuse saddle ST elevation, PR depression, Spodick's sign
8	Long QT / TdP	QTc >500 ms, prominent U waves, twisting polymorphic VT
9	WPW Syndrome	Short PR <120 ms, delta wave, widened QRS
10	Dilated Cardiomyopathy	LBBB, low voltage, fragmented QRS, AF, non-specific ST-T changes

Clinical Pearl: Always interpret the ECG in clinical context. Many of these patterns can overlap (e.g., LBBB in DCM can mask STEMI; WPW can mimic VT in AF; pericarditis can mimic STEMI). Rate, rhythm, morphology, and clinical history together guide management.

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normal sinus rhythm 12 lead ECG healthy baseline

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