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Explain me 10 common heart disease with ECG changes and ECG images of those diseases

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10 common heart diseases ECG changes patterns images cardiology

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10 Common Heart Diseases: ECG Changes & Images

Below are 10 major cardiac conditions, their signature ECG findings, and actual ECG images from Harrison's Principles of Internal Medicine (22nd Ed.), Guyton & Hall Medical Physiology, and Fuster & Hurst's The Heart.

1. ST-Elevation Myocardial Infarction (STEMI)

What happens: Occlusion of a coronary artery causes transmural ischemia. A voltage gradient develops between normal and ischemic zones, producing "currents of injury" seen on ECG.
ECG changes:
  • Hyperacute T waves - the earliest sign (tall, broad, peaked T waves)
  • ST-segment elevation in the territory of the occluded artery (>1 mm in limb leads, >2 mm in precordial leads)
  • Reciprocal ST depression in mirror-image leads
  • Q waves - develop within hours to days (necrosis marker)
  • T-wave inversion - follows ST elevation as infarct evolves
  • R-wave loss in the infarct zone
Localization by leads:
  • Anterior STEMI (LAD): V1-V4
  • Inferior STEMI (RCA): II, III, aVF
  • Lateral STEMI (LCx): I, aVL, V5-V6
  • Posterior STEMI: reciprocal ST depression in V1-V3 (tall R wave in V1)
Acute ischemia current of injury diagram - transmural vs subendocardial
FIGURE: ST vector in acute ischemia. Transmural ischemia directs the ST vector outward (epicardial) -> ST elevation in overlying leads. Subendocardial ischemia directs it inward -> ST depression in overlying leads. (Harrison's, 22E)
Severe anterior wall ischemia with deep T-wave inversions in precordial leads (Wellens sign)
FIGURE: Severe anterior wall ischemia - deep T-wave inversions in precordial leads (Wellens T-wave sign), indicating high-grade LAD stenosis. (Harrison's, 22E)

2. Non-ST-Elevation MI (NSTEMI) / Unstable Angina

What happens: Partial or subendocardial ischemia without full transmural involvement.
ECG changes:
  • ST depression (horizontal or downsloping) in affected leads - the ST vector shifts toward the subendocardium
  • T-wave inversions - deep, symmetric, often in anterior or lateral leads
  • No Q waves (by definition - no full thickness necrosis on ECG)
  • No ST elevation (but aVR may show ST elevation as a reciprocal change)
  • Normal ECG does not exclude NSTEMI - diagnosis depends on biomarkers
Key note: Deep T-wave inversions in V1-V4 (Wellens pattern) signal a critical LAD lesion and impending STEMI even before enzyme rise.

3. Atrial Fibrillation (AF)

What happens: Chaotic, disorganized electrical activity fires from multiple ectopic foci in the atria at 350-600 bpm. The AV node acts as a gatekeeper, allowing only random impulses through.
ECG changes:
  • Absence of distinct P waves - replaced by a fine, irregular, low-amplitude baseline ("fibrillatory waves," sometimes called f-waves)
  • Irregularly irregular RR intervals - the hallmark; no two consecutive RR intervals are equal
  • Ventricular rate typically 100-160 bpm if untreated
  • QRS complexes are normal unless aberrant conduction or pre-existing bundle branch block is present
ECG of Atrial Fibrillation - no P waves, irregular QRS intervals
FIGURE: Atrial fibrillation (Lead II). No P waves visible; only ventricular QRS and T waves with irregular timing. (Guyton & Hall Medical Physiology)

4. Atrial Flutter

What happens: A single, organized macroreentrant circuit in the right atrium (usually around the tricuspid annulus) fires at 250-350 bpm. The AV node blocks most impulses, usually conducting every 2nd or 3rd beat.
ECG changes:
  • "Sawtooth" flutter waves (F waves) at ~250-300 bpm, best seen in leads II, III, aVF, and V1
  • No isoelectric baseline between flutter waves
  • Regular atrial rate ~300 bpm
  • Regular ventricular response with a fixed block ratio (2:1 most common -> ventricular rate ~150 bpm; also 3:1, 4:1)
  • Normal QRS unless aberrant conduction
ECG of Atrial Flutter showing sawtooth pattern at 250 bpm with 2:1 block
FIGURE: Atrial flutter at 250 beats/min with 2:1 AV block, ventricular rate 125 bpm (Lead II). Classic sawtooth flutter waves. (Guyton & Hall Medical Physiology)

5. Ventricular Fibrillation (VF)

What happens: Multiple simultaneous chaotic reentrant wavefronts propagate through the ventricles in all directions - a "chain reaction" mechanism. No coordinated ventricular contraction occurs. This is immediately life-threatening (cardiac arrest).
ECG changes:
  • Chaotic, bizarre, irregular waveforms - no identifiable P waves, QRS complexes, or T waves
  • No repetitive pattern whatsoever
  • Initial coarse VF - larger amplitude irregular waves in first few seconds
  • Degenerates to fine VF - lower amplitude waves as amplitude decays over minutes
  • Voltages decay rapidly: ~0.5 mV initially -> 0.2-0.3 mV after 20-30 seconds
ECG of Ventricular Fibrillation - chaotic irregular waveforms
FIGURE: Ventricular fibrillation (Lead II). Completely chaotic waveforms; no organized electrical activity. (Guyton & Hall Medical Physiology)

6. Left Ventricular Hypertrophy (LVH)

What happens: Increased LV muscle mass amplifies leftward and posterior electrical forces. Common in hypertension, aortic stenosis, hypertrophic cardiomyopathy.
ECG changes:
  • Tall R waves in left precordial leads (V5, V6) and limb leads
  • Deep S waves in right precordial leads (V1, V2)
  • Sokolow-Lyon voltage criterion: SV1 + RV5 or RV6 >35 mm
  • RaVL >20 mm (women) or >28 mm (men) (Cornell voltage criterion)
  • "Strain" pattern: ST depression with T-wave inversion in leads with tall R waves (I, aVL, V5-V6)
  • Left axis deviation
  • Left atrial enlargement (broad, notched P wave - "P mitrale")
  • Can progress to incomplete or complete LBBB
ECG pattern comparison: Normal vs LVH vs RVH with heart diagrams
FIGURE: LVH increases amplitude of forces directed leftward/posteriorly. RVH shifts QRS vector rightward with tall R in V1. Both show repolarization (ST-T) abnormalities. (Harrison's, 22E)

7. Right Ventricular Hypertrophy (RVH)

What happens: Increased RV muscle mass (from pulmonary hypertension, chronic lung disease, congenital heart disease) reverses the normal left-dominant QRS vector.
ECG changes:
  • Tall R waves in V1 (R > S in V1) - reversal of normal pattern
  • Deep S waves in V5, V6 (prominent S wave pattern in left lateral leads)
  • Right axis deviation (QRS axis >+110°)
  • T-wave inversions in V1-V4 ("RV strain" pattern)
  • Incomplete or complete RBBB pattern in atrial septal defects
  • Acute RVH (pulmonary embolism): S1Q3T3 pattern - S wave in lead I, Q wave in lead III, T-wave inversion in lead III; sinus tachycardia; new right bundle branch block
(Image above (Fig 247-9) also shows RVH pattern for comparison)

8. Bundle Branch Block (LBBB / RBBB)

What happens: Delay or block in one bundle branch forces the affected ventricle to depolarize late via slow myocardial conduction rather than fast Purkinje fibers, widening the QRS.
LBBB ECG changes:
  • Wide QRS >120 ms
  • Broad, notched ("M-shaped") R wave in V5, V6, I, aVL
  • Absent septal q waves in lateral leads
  • Deep S wave or QS in V1
  • Secondary ST-T changes: T wave opposite to final QRS deflection (discordant)
  • Left axis deviation
RBBB ECG changes:
  • Wide QRS >120 ms
  • rSR' ("M-shape") in V1, V2 - the second R' representing delayed RV activation
  • Wide, slurred S waves in I, V5, V6
  • T-wave inversion in V1-V3 (secondary repolarization change)
Comparison of RBBB and LBBB QRS-T patterns in V1 and V5
(See Harrison's Fig 247-10 description: "Comparison of typical QRS-T patterns in RBBB and LBBB vs normal in leads V1 and V5. Note secondary T-wave inversions in leads with rSR' complex with RBBB, and in leads with wide R wave with LBBB." - Harrison's 22E)

9. Acute Pericarditis

What happens: Inflammation of the pericardium irritates the underlying epicardium, causing diffuse (non-territory-specific) ST and PR changes. Evolves through 4 classical ECG stages.
ECG changes (4 stages):
  • Stage 1 (acute, days 1-2): Diffuse concave-up ("saddle-shaped") ST elevation in almost all leads EXCEPT aVR and V1 (where ST is depressed); PR depression diffusely (PR elevation in aVR) - this combination is highly specific for pericarditis
  • Stage 2 (days 3-7): ST and PR changes normalize; ECG may be normal
  • Stage 3 (weeks 1-3): Diffuse T-wave inversions across multiple leads
  • Stage 4 (weeks-months): Return to baseline (or persistent T-wave changes in chronic pericarditis)
Key distinguishing features from STEMI:
  • ST elevation is diffuse, not territory-specific
  • PR depression is a unique hallmark
  • No reciprocal ST depression in other leads
  • No Q waves
12-lead ECG showing Stage I acute pericarditis - diffuse ST elevation and PR depression
FIGURE: Stage I acute pericarditis. Diffuse ST-segment elevation with PR-segment depression in a non-territory-specific distribution. aVR shows simultaneous ST depression with PR elevation - the classic reciprocal pattern. (Fuster & Hurst's The Heart, 15E)

10. Complete (Third-Degree) Heart Block

What happens: No electrical impulses conduct from atria to ventricles through the AV node. The atria and ventricles beat completely independently - "AV dissociation." The ventricles are driven by a slow escape pacemaker (junctional or ventricular).
ECG changes:
  • Regular P waves at normal sinus rate (60-100 bpm)
  • Regular QRS complexes at a much slower escape rate:
    • Junctional escape: 40-60 bpm, narrow QRS
    • Ventricular escape: 20-40 bpm, wide QRS (>120 ms)
  • P waves and QRS complexes are completely independent - the PR interval changes constantly; P waves "march through" QRS complexes
  • No relationship between P waves and QRS complexes
  • Slow ventricular rate leads to symptoms: syncope (Stokes-Adams attacks), heart failure, presyncope
Causes: Ischemic heart disease (especially inferior MI affecting the AV node), Lyme disease, drugs (digoxin, beta-blockers, calcium channel blockers), congenital, degenerative disease of the conduction system.

Quick Reference Summary Table

#DiseaseKey ECG FindingRate/Rhythm
1STEMIST elevation + Q waves in territorySinus ± tachycardia
2NSTEMI/UAST depression, T inversions, no Q wavesUsually sinus
3Atrial FibrillationNo P waves, irregularly irregular100-160 bpm
4Atrial FlutterSawtooth F waves, 2:1/3:1 blockAtrial 300, ventricular 150
5Ventricular FibrillationChaotic, no organized waveformNo cardiac output
6LVHTall R waves (V5/V6), strain patternUsually sinus
7RVHTall R in V1, right axis, S1Q3T3 (PE)Usually sinus
8Bundle Branch BlockWide QRS >120 ms, RSR' (RBBB) or M-wave (LBBB)Depends on underlying
9Acute PericarditisDiffuse saddle ST elevation + PR depressionUsually sinus tachycardia
10Complete Heart BlockAV dissociation, slow ventricular escape20-60 bpm escape
Sources: Harrison's Principles of Internal Medicine 22E (2025) - Chap. 247; Guyton and Hall Textbook of Medical Physiology 14E - Chap. 13; Fuster and Hurst's The Heart 15E - Chap. 53; Goldman-Cecil Medicine - Chap. 42.

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