Explain me 10 common heart diseases with ecg changes and ecg images

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I now have comprehensive textbook content and ECG images for the major conditions. Let me compile the complete, detailed answer.

10 Common Heart Diseases: ECG Changes and Images

Sources: Harrison's Principles of Internal Medicine 22E, Tintinalli's Emergency Medicine, Fuster and Hurst's The Heart 15E, Ganong's Review of Medical Physiology, Braunwald's Heart Disease, Goldman-Cecil Medicine

1. ST-Elevation Myocardial Infarction (STEMI)

Mechanism: Complete occlusion of a coronary artery causes transmural (full-thickness) ischemia. Infarcted myocytes undergo rapid repolarization, reduced resting membrane potential, and delayed depolarization - all producing "currents of injury" that shift the ST segment upward over the affected zone.

ECG Changes:

Hyperacute T waves - earliest finding (tall, broad, peaked T waves within minutes)
ST elevation - convex (tombstone) morphology; ≥1 mm in limb leads, ≥2 mm in precordial leads
Reciprocal ST depression in leads opposite the infarct zone (indicates larger injury area and worse prognosis)
Pathologic Q waves - develop within hours to days (>40 ms wide, >25% of R-wave amplitude); marker of myocardial necrosis
T-wave inversion - follows ST elevation as infarction evolves

Localisation by leads (Tintinalli's, p. 378):

Territory	ST Elevation Leads
Anterior	V1-V4
Inferior	II, III, aVF
Lateral	I, aVL, V5-V6
Right ventricle	V3R-V6R
Posterior	Tall R in V1-V2 (reciprocal)

ECG Diagram - Subendocardial vs. Transmural Ischemia (current of injury):

Current of injury diagram: subendocardial ischemia causes ST depression, transmural causes ST elevation

Figure: A - Subendocardial ischemia: ST vector directed inward, overlying leads show ST depression. B - Transmural/epicardial injury: ST vector directed outward, overlying leads show ST elevation. (Harrison's, Fig. 247-11)

Anterior STEMI ECG sequence (acute → evolving):

ECG sequence of anterior ST-elevation Q-wave infarction across leads I, II, III, aVR, aVL, aVF, V2, V4, V6

Acute (top row) shows ST elevation with hyperacute T waves. Evolving (bottom row) shows Q-wave development and T-wave inversion. (Harrison's, Fig. 247-13A)

Inferior STEMI ECG sequence:

ECG sequence of inferior ST-elevation Q-wave infarction across leads I, II, III, aVR, aVL, aVF, V2, V4, V6

Inferior MI with ST elevation in II, III, aVF and reciprocal ST depression in I, aVL. (Harrison's, Fig. 247-13B)

2. NSTEMI / Unstable Angina

Mechanism: Partial coronary occlusion or severe subendocardial ischemia without transmural injury. The ST vector shifts inward (toward the subendocardium), producing ST depression in overlying leads.

ECG Changes:

ST depression - horizontal or downsloping ≥0.5-1 mm (more specific and worrisome than upsloping)
T-wave inversion - may be deep or diffuse
No ST elevation (by definition) and no Q waves in NSTEMI
Wellens sign - deep symmetric T-wave inversions in V1-V4 indicates critical LAD stenosis (even without troponin elevation)

Wellens T-wave pattern (critical LAD stenosis):

Six precordial ECG strips V1-V6 showing deep symmetric T-wave inversions - the Wellens sign of LAD stenosis

Wellens T-wave sign: Prominent, deep T-wave inversions in V1-V4 (and sometimes I, aVL) indicating high-grade LAD obstruction. (Harrison's, Fig. 247-12)

3. Atrial Fibrillation (AF)

Mechanism: Chaotic, disorganized atrial electrical activity from multiple reentrant circuits replaces normal sinus node depolarization.

ECG Changes:

Absent P waves - replaced by irregular fibrillatory baseline ("f waves"), best seen in V1 and lead II
Irregularly irregular RR intervals - the hallmark finding
Narrow QRS complexes - unless aberrant conduction or bundle branch block coexists
Variable ventricular rate - typically 100-160 bpm in uncontrolled AF
If associated with WPW: wide, irregular, rapid complex tachycardia (very dangerous)

Key points:

AF with pulmonary hypertension may show right axis deviation and R/S ratio >1 in V1 (Tintinalli's)
AF with mitral stenosis: left atrial enlargement pattern (bifid P waves in sinus rhythm, then no P waves once AF develops)

4. Wolff-Parkinson-White (WPW) Syndrome

Mechanism: An accessory pathway (bundle of Kent) bypasses the AV node and pre-excites part of the ventricle before the normal impulse arrives, creating a "delta wave."

ECG Changes (in sinus rhythm):

Short PR interval (<120 ms) - because the accessory pathway conducts without the AV nodal delay
Delta wave - slurred upstroke at the beginning of the QRS
Wide QRS (>120 ms) - from fusion of pre-excited and normally conducted impulses
Secondary ST-T changes - discordant T waves

During tachycardia:

Orthodromic AVRT (most common, 65%): narrow-complex tachycardia, no delta waves
Antidromic AVRT: wide-complex tachycardia mimicking ventricular tachycardia
AF with WPW: extremely rapid, wide, irregular tachycardia - can degenerate to VF

WPW 12-lead ECG:

12-lead ECG showing Wolff-Parkinson-White syndrome: short PR interval, widened QRS, and delta waves across all leads

WPW in sinus rhythm: short PR interval with widened QRS complexes and delta waves (slurred QRS upstroke). (Tintinalli's, Fig. 130-1)

WPW single complex detail (Symptom to Diagnosis textbook):

Three lead strips (I, II, V1) showing the classic WPW pattern with delta wave and PR shortening

Classic WPW: leads I, II, V1 showing the slurred delta wave (note the prominent onset of the QRS complex) and short PR.

5. Acute Pericarditis

Mechanism: Inflammation of the pericardium causes current spread affecting adjacent myocardium (pericardium itself is electrically silent). This creates diffuse, non-territory-specific changes unlike the focal ST elevation of STEMI.

ECG Changes - Four Classical Stages:

Stage	Timing	Changes
1	Hours to days	Diffuse ST elevation (concave/saddle-shaped) in nearly all leads + PR depression (in all leads except aVR, where there is PR elevation + ST depression)
2	Days	ST and PR return to baseline
3	1-3 weeks	Diffuse T-wave inversions
4	Weeks-months	ECG normalizes

Key distinguishing features from STEMI:

ST elevation is diffuse (not territory-specific), concave upward (not convex/tombstone)
PR depression is present (almost never in STEMI)
No reciprocal ST depression (except aVR)
No Q waves

Acute Pericarditis 12-lead ECG (Stage 1):

12-lead ECG showing stage 1 acute pericarditis with diffuse ST elevation and PR segment depression across most leads, with ST depression and PR elevation in aVR

Stage I acute pericarditis: diffuse ST elevation with concurrent PR segment depression in a non-territory-specific distribution. aVR shows reciprocal ST depression and PR elevation. (Fuster & Hurst's, Fig. 53-3)

6. AV Heart Block (1°, 2°, 3°)

Mechanism: Impaired conduction through the AV node or His-Purkinje system, classified by degree of conduction failure.

ECG Changes:

First-Degree AV Block:

PR interval prolonged >200 ms (5 small squares)
All P waves conduct; no dropped beats
Usually benign; may indicate inferior MI, digoxin toxicity, increased vagal tone

Second-Degree AV Block:

Mobitz Type I (Wenckebach): Progressive lengthening of PR interval until one P wave fails to conduct (dropped QRS); groups of beats; RR shortens before the dropped beat; typically at AV node level; usually benign
Mobitz Type II: Fixed PR interval with sudden dropped QRS (no progressive lengthening); QRS typically wide; infranodal block; high risk of progression to complete block - requires pacing

Third-Degree (Complete) AV Block:

Complete AV dissociation: P waves and QRS complexes march independently
Atrial rate faster than ventricular rate
Ventricular escape rhythm: narrow (nodal, ~40-60 bpm) or wide (ventricular, <40 bpm)
Symptoms: Stokes-Adams attacks (syncope), bradycardia, heart failure

The blood supply to the AV node arises from the right coronary artery in 80-90% of people; inferior MI is the most common cause of acquired complete heart block. (Harrison's, p. block28)

7. Left Ventricular Hypertrophy (LVH)

Mechanism: Increased left ventricular mass (from hypertension, aortic stenosis, HCM) increases the magnitude of LV depolarization vectors.

ECG Changes:

Voltage criteria (Sokolow-Lyon): S in V1 + R in V5 or V6 ≥ 35 mm; or R in aVL ≥ 11 mm; or R in I + S in III ≥ 25 mm
Strain pattern (repolarization abnormality): downsloping ST depression with asymmetric T-wave inversion in I, aVL, V5-V6 (lateral leads)
Left axis deviation (beyond -30°)
Prolonged intrinsicoid deflection in V5-V6 (>50 ms)
Left atrial enlargement: bifid P wave in lead II (P mitrale), terminal negative P in V1

Note: LVH voltage + strain pattern together have higher specificity than voltage alone. ST elevation in V1-V2 in LVH can mimic anterior STEMI.

8. Ventricular Tachycardia (VT)

Mechanism: Reentrant circuit or abnormal automaticity arising from the ventricles, bypassing the normal His-Purkinje system, causing wide-complex depolarization.

ECG Changes:

Wide QRS complexes (>120 ms), regular rhythm, rate typically 100-250 bpm
AV dissociation - P waves march independently through the tachycardia (pathognomonic when visible)
Capture beats - a normally narrow QRS appearing during tachycardia (AV node transiently captures the ventricle)
Fusion beats - hybrid morphology between normal and VT complex
Extreme axis deviation ("northwest axis" or no-man's land: aVR positive, I and aVF both negative)
Concordance: all precordial leads positive or all negative (positive concordance suggests WPW; negative concordance is highly specific for VT)

Distinguishing VT from SVT with aberrancy:

AV dissociation, fusion/capture beats, northwest axis, very wide QRS (>160 ms), and precordial concordance all favor VT
When in doubt, treat as VT (Goldman-Cecil)

Polymorphic VT (Torsades de Pointes):

Occurs with prolonged QT interval (long QT syndrome, drug toxicity)
ECG shows rotating QRS axis that "twists around the baseline"
Associated with drugs that prolong QT (macrolides, fluoroquinolones, antipsychotics, antiarrhythmics - see Table 130-5 in Tintinalli's)

9. Long QT Syndrome (LQTS)

Mechanism: Inherited or acquired dysfunction of cardiac ion channels prolongs ventricular repolarization, creating a substrate for triggered arrhythmias (Torsades de Pointes) and sudden death.

ECG Changes:

Prolonged QTc interval - corrected QT >440 ms in men, >460 ms in women (Bazett formula: QTc = QT / √RR)
Abnormal T-wave morphology - notched T waves, bifid T waves, prominent U waves
T-wave alternans - beat-to-beat variation in T-wave amplitude (precedes TdP)
Long-short RR sequence - short-long-short initiating Torsades (typical of acquired LQTS)

Causes of acquired QT prolongation (Tintinalli's Table 130-5):

Class IA/III antiarrhythmics (quinidine, sotalol)
Macrolide antibiotics (azithromycin, erythromycin)
Fluoroquinolones
Antipsychotics (haloperidol, quetiapine)
Electrolyte abnormalities: hypokalemia, hypomagnesemia

Inherited forms: LQTS1 (KCNQ1 mutation - triggered by exercise/swimming), LQTS2 (KCNH2 - triggered by auditory stimuli), LQTS3 (SCN5A - during sleep)

10. Pulmonary Embolism (PE)

Mechanism: Massive PE causes acute right ventricular pressure overload, right heart dilation, and rightward shift of depolarization vectors. ECG is often nonspecific but reflects acute cor pulmonale.

ECG Changes:

Sinus tachycardia - most common finding (~40% of cases)
S1Q3T3 pattern - S wave in lead I + Q wave in lead III + inverted T in lead III (classic but only in ~20%)
Right bundle branch block (RBBB) - complete or incomplete; RSR' in V1, wide S in V5-V6
Right axis deviation
T-wave inversions in V1-V4 (right heart strain pattern - more sensitive and specific than S1Q3T3)
Atrial fibrillation - in 10-35% of cases
Peaked P waves in lead II (P pulmonale - right atrial enlargement)
Electrical alternans - suggests large pericardial effusion or severe cardiac strain
Low voltage or nonspecific ST-T changes

Normal ECG does NOT exclude PE - approximately 30% of cases have a near-normal ECG.

Quick Reference Summary Table

Disease	Key ECG Findings
STEMI	ST elevation (convex), reciprocal ST depression, Q waves, hyperacute T waves
NSTEMI/UA	ST depression (horizontal/downsloping), T-wave inversions, no Q waves
Atrial Fibrillation	Absent P waves, irregularly irregular rhythm, fibrillatory baseline
WPW	Short PR, delta wave, wide QRS, orthodromic or antidromic tachycardia
Acute Pericarditis	Diffuse concave ST elevation, PR depression (all leads), no reciprocal changes
AV Heart Block	Prolonged PR (1°), dropped beats ± PR lengthening (2°), AV dissociation (3°)
LVH	High voltage, lateral strain pattern, left axis deviation
Ventricular Tachycardia	Wide QRS, regular, AV dissociation, fusion/capture beats, concordance
Long QT Syndrome	Prolonged QTc, notched/bifid T waves, Torsades de Pointes
Pulmonary Embolism	Sinus tachycardia, S1Q3T3, RBBB, right axis deviation, V1-V4 T inversions

Sources:

Harrison's Principles of Internal Medicine 22E (2025), Chapters 247, 252, 256
Tintinalli's Emergency Medicine: A Comprehensive Study, Chapters 49, 130
Fuster and Hurst's The Heart 15E, Chapter 53
Braunwald's Heart Disease, Chapters 7, 12
Goldman-Cecil Medicine, Chapters 49, 51, 52, 62
Ganong's Review of Medical Physiology 26E, Chapter 29

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