Explain 10cimmon heart diseases with ECG changes and ECG images of those diseases

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

10 Common Heart Diseases: ECG Changes & Images

1. ST-Elevation Myocardial Infarction (STEMI)

Disease: Complete occlusion of a coronary artery causing transmural myocardial ischemia and necrosis.

ECG Changes:

Hyperacute phase: Tall, peaked (hyperacute) T waves - the earliest change
Acute phase: ST segment elevation ≥1 mm in 2+ contiguous leads (convex/tombstone morphology)
Pathologic Q waves develop (>40 ms wide, >25% of R wave amplitude) - indicate irreversible necrosis
Reciprocal ST depression in leads facing opposite wall
T wave inversion in evolving phase

Lead localization:

Territory	Elevated leads	Reciprocal changes
Anterior (LAD)	V1-V4	II, III, aVF
Inferior (RCA/LCx)	II, III, aVF	I, aVL
Lateral (LCx/diagonal)	I, aVL, V5-V6	II, III, aVF

ECG Image - Inferior STEMI (massive tombstone pattern):

Inferior STEMI with massive ST elevation in II, III, aVF showing tombstone pattern

Note the dramatic ST elevation in inferior leads II, III, aVF with deep reciprocal ST depression in I and aVL.

ECG Image - Anterior STEMI (from SAEM):

Anterior STEMI ECG showing ST elevation in V1-V4

Source: Harrison's Principles of Internal Medicine 22E; Tintinalli's Emergency Medicine

2. Atrial Fibrillation (AF)

Disease: Chaotic, disorganized electrical activity in the atria causing irregular ventricular response. The most common pathologic tachyarrhythmia. Associated with hypertension, valvular disease, heart failure, and thyrotoxicosis.

ECG Changes (from Tintinalli's Emergency Medicine):

Absent P waves - replaced by chaotic fibrillatory baseline (f waves)
Irregular irregularity of QRS complexes (no two R-R intervals are the same)
Narrow QRS unless bundle branch block or pre-excitation coexists
Ventricular rate typically 100-180 bpm in uncontrolled AF

ECG Image - Atrial Flutter/Fibrillation (from Tintinalli's textbook):

Atrial flutter ECG showing regular sawtooth flutter waves in leads II, III, aVF

Panel A: Regular narrow-complex tachycardia at 155 bpm. Panel B: Atrial flutter with sawtooth flutter waves in leads II, III, aVF (closely related to AF). Panel C: Response to carotid sinus massage unmasking flutter waves.

Source: Tintinalli's Emergency Medicine, Table 18-8

3. Left Bundle Branch Block (LBBB)

Disease: Conduction block in the left bundle branch. Can be a sign of coronary artery disease, hypertension, cardiomyopathy, or valvular disease. A new LBBB in the context of chest pain is treated as a STEMI equivalent.

ECG Changes:

QRS duration ≥120 ms (wide complex)
Broad, notched ("M-shaped") R waves in I, aVL, V5-V6
Deep S wave or QS pattern in V1 (broad, downwardly deflected QRS in V1)
No septal Q waves in I, V5, V6
Discordant ST-T changes - ST and T wave opposite to main QRS deflection
Left axis deviation common

ECG Image - LBBB with Atrial Fibrillation (ECGGuru.com):

LBBB ECG showing wide QRS at 157 bpm with broad notched R waves in lateral leads

Wide QRS (0.154s), fast rate (157 bpm), irregular rhythm (co-existing AF). Note the broad deflections in lateral leads consistent with LBBB.

Source: Harrison's Principles of Internal Medicine 22E (bundle branch block section)

4. Complete (3rd Degree) Heart Block

Disease: Complete failure of AV conduction - no atrial impulses are conducted to the ventricles. The ventricles are maintained by an escape rhythm (junctional or ventricular). Most important causes: inferior STEMI (RCA occlusion), degenerative conduction disease, drug toxicity (digoxin, beta-blockers), Lyme disease.

ECG Changes:

Complete AV dissociation - P waves and QRS complexes march independently
Regular P-P intervals (atrial rate ~60-100)
Regular R-R intervals but at a slower rate (escape rhythm ~30-50 bpm)
Wide QRS if ventricular escape, narrow if junctional escape
No relationship between P waves and QRS complexes (more P waves than QRS)

ECG Image - Complete Heart Block:

Complete heart block ECG showing independent P waves and wide QRS escape complexes with AV dissociation

Note the slow, wide-complex escape rhythm completely independent of the regular P waves above. Classic AV dissociation - the hallmark of 3rd degree heart block.

Source: Goldman-Cecil Medicine; LITFL ECG Library

5. Brugada Syndrome

Disease: Inherited sodium channelopathy (SCN5A mutation) causing risk of ventricular fibrillation and sudden cardiac death in structurally normal hearts. First described in 1992. More common in males of Southeast Asian descent.

ECG Changes:

Type 1 (diagnostic): Coved ST elevation ≥2 mm with a negative T wave in V1-V2 (sometimes V3) - "shark fin" or coved morphology
Type 2: Saddle-back ST elevation ≥0.5 mm in V1-V2 (not diagnostic alone)
Incomplete right bundle branch block pattern
Changes may be dynamic and only appear with sodium channel blockers (ajmaline/flecainide provocation)
Risk of VF and sudden cardiac death, especially during fever or sleep

ECG Image - Brugada Syndrome Type 1:

Brugada syndrome ECG showing coved ST elevation in V1 and V2 with RBBB morphology

Classic coved ST elevation in V1, V2, V3. The V1 lead shows the hallmark "shark fin" appearance. The coved morphology (convex ST elevation, descending to a negative T wave) in V1 is the only diagnostic type.

Source: Goldman-Cecil Medicine (Brugada section); ECGPedia

6. Left Ventricular Hypertrophy (LVH)

Disease: Increased left ventricular mass due to chronic pressure or volume overload (hypertension, aortic stenosis, HCM). A major marker of cardiovascular morbidity and mortality risk.

ECG Changes (from Harrison's Principles of Internal Medicine 22E):

Increased QRS voltage (Sokolow-Lyon: SV1 + RV5 or RV6 >35 mm; Cornell: RaVL >28 mm in men, >20 mm in women)
Left axis deviation
"Strain" pattern: ST depression and T wave inversion in leads with tall R waves (I, aVL, V5-V6) - indicates pressure overload
Prolonged QRS duration (may approach LBBB)
Left atrial enlargement often coexists (broad bifid P wave in II, deep negative P in V1)
Prominent voltages are a common normal variant in young/athletic individuals - context matters

ECG Image - LVH with AF and Ischemia (Healio Learn the Heart):

ECG showing LVH with tall QRS voltages, ST changes, and atrial fibrillation

Extremely tall QRS voltages (particularly in precordial leads), with ST-T strain changes in lateral leads, combined with irregular rhythm consistent with AF. Inferior and lateral ischemia changes also present.

7. Acute Pericarditis

Disease: Inflammation of the pericardium causing pericardial friction, chest pain (pleuritic, relieved by leaning forward), and characteristic ECG changes. Common causes: viral infection, autoimmune, post-MI (Dressler syndrome), uremia.

ECG Changes (4 stages):

Stage 1 (acute): Diffuse, concave ("saddle-shaped") ST elevation in multiple leads (I, II, aVF, V2-V6) with PR depression - the key distinguishing feature from STEMI; no reciprocal ST depression (except aVR and V1)
Stage 2: ST normalizes, T waves flatten
Stage 3: Diffuse T wave inversion
Stage 4: ECG normalizes (may take weeks)

Key distinguishing features from STEMI:

ST elevation is diffuse (not in a single coronary territory)
ST morphology is concave (vs. convex in STEMI)
PR segment depression is the pathognomonic sign
No reciprocal ST depression (except aVR/V1)
No Q waves

ECG Image - Brugada Type 2 ECG (similar saddle-back morphology for comparison):

Brugada type 2 ECG saddle-back morphology in V1-V2

This image shows a Brugada Type 2 (saddle-back) pattern. Pericarditis ST elevation classically has this concave/saddle shape, but distributed across multiple lead groups rather than isolated to V1-V2.

Source: ROSEN's Emergency Medicine; ECGWaves.com

8. Hypertrophic Cardiomyopathy (HCM)

Disease: Autosomal dominant disease (sarcomere protein mutations) causing asymmetric left ventricular hypertrophy, outflow tract obstruction, and risk of sudden cardiac death. Most common cause of sudden death in young athletes.

ECG Changes:

Voltage criteria for LVH - often dramatic, deeply negative T waves in lateral leads
Pathologic Q waves in I, aVL, V5-V6 (due to septal hypertrophy - "pseudo-infarction" pattern)
ST depression and T wave inversion - may be dramatic ("giant T wave inversions") especially in apical HCM (Yamaguchi variant)
Left axis deviation
Left atrial enlargement (broad bifid P wave)
Nonsustained VT may be seen on Holter

Source: Braunwald's Heart Disease; Harrison's Principles of Internal Medicine 22E

9. Pulmonary Embolism (PE)

Disease: Acute obstruction of pulmonary arteries causing acute right heart strain, increased right ventricular afterload, and potentially hemodynamic collapse.

ECG Changes:

Sinus tachycardia - most common finding (present in ~40%)
S1Q3T3 pattern: Deep S in lead I, Q wave and T wave inversion in lead III - classic but present in only ~20%
Right axis deviation
Right bundle branch block (new RBBB suggests massive PE)
T wave inversions in V1-V4 (right precordial leads) - anterior T inversion pattern
Atrial fibrillation/flutter may occur
Right atrial enlargement (tall peaked P waves in II)
ECG can be completely normal in ~25% of PE cases

Source: Harrison's Principles of Internal Medicine 22E; Goldman-Cecil Medicine

10. Wolff-Parkinson-White (WPW) Syndrome

Disease: Pre-excitation syndrome with an accessory pathway (bundle of Kent) bypassing the AV node, causing ventricular pre-excitation. Prone to paroxysmal supraventricular tachycardia (AVRT) and, critically, atrial fibrillation with rapid ventricular conduction which can degenerate to ventricular fibrillation.

ECG Changes (classic triad):

Short PR interval (<120 ms) - due to ventricular pre-excitation bypassing AV node delay
Delta wave - slurred, notched upstroke at the beginning of the QRS complex
Wide QRS (>120 ms) - superficially resembles bundle branch block
Secondary ST-T changes - discordant to QRS
Negative delta waves in some leads can mimic pathologic Q waves ("pseudo-infarction")

ECG Image - Paced rhythm with STEMI evolution (from Rosen's Emergency Medicine textbook):

ECG from Braunwald showing paced rhythm with concordant ST elevation indicating STEMI - wide complex tachycardia comparison

From Rosen's Emergency Medicine: Wide-complex tachycardia patterns - Panel A shows appropriate paced morphology; Panel B shows concordant ST elevation (Sgarbossa criteria) indicating superimposed STEMI. Wide complex tachycardias (WPW, VT, BBB) all require careful differentiation.

Additional ECG Image - Wide complex tachycardia (Rosen's textbook - VT/SVT differentiation):

Multi-lead ECG showing wide complex tachycardia morphology from Rosen's Emergency Medicine textbook

Retrograde P waves (arrows) confirm ventricular tachycardia during wide-complex tachycardia - AV dissociation is pathognomonic.

Source: Goldman-Cecil Medicine; Braunwald's Heart Disease; clinicalgate.com

Quick Reference Summary Table

Disease	Key ECG Features	Leads Affected
STEMI	ST elevation, Q waves, T inversion	Territory-dependent (see above)
Atrial Fibrillation	Absent P waves, irregular RR	All leads
LBBB	Wide QRS ≥120ms, broad R in I/V6, QS in V1	V1, I, V5-V6
Complete Heart Block	AV dissociation, slow escape rhythm	All leads
Brugada Syndrome	Coved ST elevation, RBBB pattern	V1-V2 (±V3)
LVH	Tall voltages, strain pattern (ST↓, T inversion)	V4-V6, I, aVL
Acute Pericarditis	Diffuse concave ST↑, PR depression	I, II, V2-V6
HCM	LVH + deep Q waves, giant T inversions	I, aVL, V5-V6
Pulmonary Embolism	S1Q3T3, sinus tachycardia, T inversion V1-V4	I, III, V1-V4
WPW Syndrome	Short PR, delta wave, wide QRS	All leads (pathway-dependent)

Sources consulted:

Harrison's Principles of Internal Medicine 22E (2025) - ECG in cardiac disorders
Tintinalli's Emergency Medicine: A Comprehensive Study - ECG features of arrhythmias
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine - ECG dynamics
Goldman-Cecil Medicine - Electrocardiography chapter
ROSEN's Emergency Medicine - Electrocardiographic adjuncts in ACS
LITFL ECG Library | ECGPedia | Healio Learn the Heart

Clinical note: ECG interpretation must always be correlated with the clinical presentation, symptoms, and additional investigations. A normal ECG does not exclude serious cardiac disease (e.g., ~25% of PEs and some NSTEMIs have normal initial ECGs).The 10 heart diseases covered above are:

STEMI - ST elevation by coronary territory, evolving Q waves, reciprocal changes
Atrial Fibrillation - No P waves, irregularly irregular QRS
LBBB - Wide QRS, broad R in lateral leads, QS in V1, discordant ST-T
Complete Heart Block - AV dissociation, independent P and QRS rates
Brugada Syndrome - Coved ST elevation in V1-V2, RBBB pattern, risk of VF
LVH - Voltage criteria, strain pattern ST depression/T inversion in lateral leads
Acute Pericarditis - Diffuse concave ST elevation, PR depression (pathognomonic)
Hypertrophic Cardiomyopathy - LVH + pseudo-infarction Q waves, giant T inversions
Pulmonary Embolism - Sinus tachycardia, S1Q3T3, right precordial T inversions, RBBB
WPW Syndrome - Short PR, delta wave, wide QRS, risk of AF with rapid conduction

Each section includes the mechanism, specific ECG criteria, lead localization, and real ECG images sourced from authoritative medical textbooks (Braunwald's, Harrison's, Tintinalli's, Goldman-Cecil) and peer-reviewed ECG repositories.

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