Explain me common 10 heart diseases with ECG changes and ECG images of those diseases
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ECG images STEMI atrial fibrillation heart block ventricular tachycardia LVH example
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10 Common Heart Diseases - ECG Changes with Images
Here is a complete guide to the 10 most clinically important heart diseases, their ECG changes, and real ECG examples.
1. ST-Elevation Myocardial Infarction (STEMI)
Pathophysiology: Complete occlusion of a coronary artery causes transmural ischemia, producing a sequence of ECG changes.
ECG Changes (by stage):
- Hyperacute phase (minutes): Tall, broad, peaked "hyperacute" T waves - earliest sign
- Acute phase (hours): ST elevation ≥ 1 mm in ≥ 2 contiguous leads ("tombstone" appearance in severe cases)
- Evolving (hours-days): T wave inversion, development of pathological Q waves (≥ 40 ms wide, ≥ 25% of QRS height)
- Chronic/old MI: Persistent Q waves, T wave normalization
Localization by leads:
| Territory | Leads | Artery |
|---|---|---|
| Anterior | V1-V4 | LAD |
| Inferior | II, III, aVF | RCA |
| Lateral | I, aVL, V5-V6 | LCx |
| Posterior | Tall R in V1-V2, ST depression V1-V3 | RCA/LCx |
Reciprocal changes: ST depression in leads opposite to the infarct zone
ECG - Inferior STEMI (ST elevation in II, III, aVF with reciprocal changes in I, aVL):
2. Atrial Fibrillation (AF)
Pathophysiology: Chaotic, disorganized atrial electrical activity from multiple micro-reentrant circuits. No organized P waves, irregular ventricular response.
ECG Changes:
- Absent P waves - replaced by irregular fibrillatory baseline (f waves) at 350-600/min
- Irregularly irregular RR intervals - the hallmark finding
- Narrow QRS (unless aberrant conduction or BBB present)
- Ventricular rate typically 100-180/min if uncontrolled
- Fibrillatory baseline is best seen in V1
ECG - Atrial Fibrillation (note irregular RR intervals and absent P waves):
3. Complete Heart Block (3rd Degree AV Block)
Pathophysiology: Complete failure of impulse conduction from atria to ventricles. The atria and ventricles beat independently - AV dissociation.
ECG Changes:
- Regular P waves at normal atrial rate (60-100/min)
- Regular QRS complexes at a slower escape rate
- No relationship between P waves and QRS - they "march through" each other
- Escape rhythm: Junctional escape = narrow QRS at 40-60/min; Ventricular escape = wide QRS at 20-40/min
- PR intervals appear to vary randomly
ECG - Complete Heart Block (P waves dissociated from QRS; ventricular rate ~40 bpm independent of atrial rate):
4. Ventricular Tachycardia (VT)
Pathophysiology: Fast, life-threatening rhythm originating in the ventricles, often from areas of scar (post-MI) or cardiomyopathy.
ECG Changes:
- Wide QRS ≥ 120 ms (usually ≥ 140 ms), bizarre morphology
- Regular rhythm at rate 100-250/min
- AV dissociation - P waves independent of QRS (when visible)
- Fusion beats and capture beats - pathognomonic for VT
- Concordance in precordial leads: all positive (R) or all negative (QS) = strongly suggests VT
- Left axis deviation common
- Brugada criteria: If any one of LBBB morphology + right axis, or RBBB morphology with negative concordance = VT
ECG - Ventricular Tachycardia (wide QRS tachycardia with AV dissociation visible):
(Above shows wide complex tachycardia pattern with bizarre QRS morphology)
5. Left Ventricular Hypertrophy (LVH)
Pathophysiology: Thickened LV myocardium (from hypertension, aortic stenosis, hypertrophic cardiomyopathy) generates increased electrical forces seen as tall voltages.
ECG Changes (Sokolow-Lyon criteria):
- S in V1 + R in V5 or V6 > 35 mm (voltage criteria)
- R in aVL > 11 mm (alternative criteria)
- LV strain pattern: ST depression + asymmetric T wave inversion in lateral leads (I, aVL, V5-V6) - the "hockey stick" pattern
- ST elevation in right precordial leads V1-3 (discordant to the deep S waves)
- Left axis deviation common
- Prolonged QRS (0.09-0.11 s) due to delayed depolarization
ECG - Left Ventricular Hypertrophy (deep S in V2, tall R in V5 - exceeds 35 mm combined; ST-T changes laterally):
6. Acute Pericarditis
Pathophysiology: Inflammation of the pericardium causes diffuse epicardial irritation and concurrent subepicardial myocarditis - producing widespread ST changes and PR depression.
ECG Changes (4 stages):
- Stage 1 (acute): Diffuse saddle-shaped (concave up) ST elevation in most leads EXCEPT aVR and V1 + PR depression in same leads + PR elevation in aVR - the key differentiator from STEMI
- Stage 2 (days): ST returns to baseline, T waves flatten
- Stage 3: Diffuse T wave inversions
- Stage 4 (weeks): ECG normalizes (or T inversions persist = constrictive pericarditis)
Key differentiators from STEMI:
- ST elevation is concave-up (saddle-shaped) vs convex in STEMI
- Diffuse (not territory-specific)
- PR depression present
- No reciprocal ST depression (except in aVR)
ECG - Acute Pericarditis (diffuse saddle-shaped ST elevation + PR depression):
7. Pulmonary Embolism (PE)
Pathophysiology: Acute right heart strain from elevated pulmonary artery pressure causes RV dilatation and right ventricular ischemia.
ECG Changes:
- S1Q3T3 pattern: Deep S wave in I + Q wave in III + T wave inversion in III - classic but only present in ~20% of cases
- Right ventricular strain: T wave inversions in V1-V4 (and sometimes inferior leads II, III, aVF)
- Right axis deviation
- RBBB (new, incomplete or complete) due to RV pressure overload
- Sinus tachycardia - most common finding
- Clockwise rotation - persistent S wave in V6
- T inversion in both lead III AND V1 = most specific finding (specificity up to 99%)
ECG - Pulmonary Embolism (S1Q3T3 + T wave inversions V1-V4 from RV strain):
8. Hyperkalemia
Pathophysiology: Elevated extracellular potassium depolarizes resting membrane potential, slowing conduction. Progressive ECG changes correlate with rising K⁺ levels.
ECG Changes (progressive with rising K⁺):
| K⁺ Level | ECG Change |
|---|---|
| 5.5-6.5 mEq/L | Tall, narrow, peaked (tented) T waves - earliest sign |
| 6.5-7.5 mEq/L | Prolonged PR interval, widened P wave, then P wave flattening/disappearance |
| 7.0-8.0 mEq/L | Wide QRS (> 120 ms), bizarre morphology, right axis shift |
| > 8.5-9.0 mEq/L | "Sine wave" pattern - QRS merges with T wave |
| > 9-10 mEq/L | Ventricular fibrillation or asystole |
ECG - Hyperkalemia (tall, peaked T waves + widened QRS + bizarre morphology at K⁺ ~9.3):
9. Wolff-Parkinson-White (WPW) Syndrome
Pathophysiology: An accessory pathway (Bundle of Kent) bypasses the AV node and pre-excites the ventricle, creating the delta wave. Risk of life-threatening arrhythmias if AF conducts rapidly down the pathway.
ECG Changes (classic WPW triad):
- Short PR interval (< 120 ms) - fast conduction through accessory pathway
- Delta wave - slurred upstroke at the beginning of QRS (ventricular pre-excitation)
- Wide QRS (> 120 ms) - fusion of normal and pre-excited depolarization
- ST-T changes discordant (opposite) to the QRS polarity
- Pseudo-infarct pattern - negative delta waves can mimic Q waves in inferior leads
WPW + AF = DANGER: Rapid pre-excited AF with wide complex, irregular, extremely fast (> 250/min) rhythm - can degenerate to VF
ECG - WPW with Atrial Fibrillation (rapid pre-excited AF - broad, irregular, bizarre QRS):
10. Heart Failure / Dilated Cardiomyopathy (DCM)
Pathophysiology: Dilated, poorly contracting ventricles cause multiple non-specific ECG abnormalities from chamber enlargement, conduction delays, and fibrosis.
ECG Changes:
- Left bundle branch block (LBBB): QRS > 120 ms, broad notched R in I/V5-V6, broad QS in V1 - present in ~25% of HF patients; indicates dyssynchrony
- Low voltage QRS (if pericardial effusion, amyloid, or severe cardiomyopathy)
- Left axis deviation
- Atrial fibrillation - very common in heart failure
- Ventricular ectopy / PVCs
- Non-specific ST-T changes throughout
- QTc prolongation due to electrolyte disturbances or medications
- Poor R wave progression in precordial leads
Note: LBBB in a heart failure patient is an indication for cardiac resynchronization therapy (CRT/biventricular pacing) when EF ≤ 35%.
Quick Reference Summary Table
| Disease | Key ECG Feature | Rate | Rhythm |
|---|---|---|---|
| STEMI | ST elevation + Q waves | Variable | Regular |
| Atrial Fibrillation | No P waves, irregular RR | 100-180 | Irregularly irregular |
| Complete Heart Block | P waves dissociated from QRS | Atria 60-100; Ventricles 20-40 | Regular (2 independent rhythms) |
| Ventricular Tachycardia | Wide QRS ≥ 120 ms, AV dissociation | 100-250 | Regular |
| LVH | Voltage criteria + strain pattern | Normal | Regular |
| Acute Pericarditis | Diffuse saddle ST elevation + PR depression | Normal | Regular |
| Pulmonary Embolism | S1Q3T3, RV strain (TWI V1-V4) | Tachycardia | Regular |
| Hyperkalemia | Peaked T waves → wide QRS → sine wave | Bradycardia | Progressive |
| WPW | Delta wave + short PR + wide QRS | Variable | Variable |
| DCM/Heart Failure | LBBB, low voltage, AF | Variable | Often irregular |
For an excellent visual overview of killer ECG patterns across multiple conditions, the LITFL ECG Library is a top-tier free resource. The Rhesus Medicine ECG patterns video also covers all these rhythms with clear explanations:
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