Explain 10 ecg changes with pictures
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ECG electrocardiogram changes patterns
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ST elevation myocardial infarction STEMI ECG
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atrial fibrillation ECG irregularly irregular rhythm
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ventricular fibrillation tachycardia ECG wide complex
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heart block complete AV block third degree ECG
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prolonged QT interval ECG Wolff-Parkinson-White delta wave
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left bundle branch block right bundle branch block ECG
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hyperkalemia peaked T waves ECG electrolyte changes
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pericarditis diffuse ST elevation saddle-shaped ECG
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left ventricular hypertrophy Sokolow-Lyon ECG criteria voltage
Here are 10 key ECG changes explained with images:
1. ST-Elevation Myocardial Infarction (STEMI)
What it is: Acute transmural myocardial injury causing convex (tombstone) ST-segment elevation ≥1 mm in ≥2 contiguous leads (≥2 mm in V1–V3).
ECG features:
- Convex/tombstone ST elevation in the territory of the occluded artery
- Reciprocal ST depression in opposing leads (e.g., inferior STEMI → ST depression in aVL)
- Hyperacute T waves early on; pathological Q waves develop later (indicating necrosis)
- Lead localization: Anterior (V1–V4) = LAD; Inferior (II, III, aVF) = RCA; Lateral (I, aVL, V5–V6) = LCx
2. Atrial Fibrillation (AF)
What it is: Chaotic, disorganized atrial electrical activity with irregular ventricular conduction. The most common sustained cardiac arrhythmia.
ECG features:
- Absent P waves — replaced by fine fibrillatory (f) waves, best seen in V1 and lead II
- Irregularly irregular R-R intervals — the hallmark
- Narrow QRS (unless aberrant conduction or bundle branch block co-exists)
- Rate can be slow, normal, or rapid depending on AV nodal conduction
3. Complete (Third-Degree) AV Block
What it is: Total failure of conduction through the AV node — the atria and ventricles beat completely independently.
ECG features:
- AV dissociation — P waves and QRS complexes march through each other with no fixed PR relationship
- Regular P-P intervals (faster atrial rate) and regular R-R intervals (slower escape rate)
- Wide QRS (>120 ms) if escape focus is ventricular; narrow QRS if junctional escape
- Requires urgent pacemaker implantation
4. Wolff-Parkinson-White (WPW) Syndrome
What it is: An accessory pathway (Bundle of Kent) bypasses the AV node, causing ventricular pre-excitation.
ECG features (classic triad):
- Short PR interval (<120 ms) — conduction bypasses the AV node delay
- Delta wave — slurred upstroke at the start of the QRS complex
- Wide QRS (>120 ms) — fusion of normal + accessory pathway conduction
- Secondary ST-T changes discordant to QRS direction
- Can precipitate life-threatening AF with rapid ventricular response
5. Left Bundle Branch Block (LBBB)
What it is: Failure of the left bundle branch causes abnormal, slow left ventricular depolarization via cell-to-cell spread.
ECG features (WiLLiaM):
- Wide QRS (≥120 ms)
- Dominant R wave (broad, monophasic, notched) in lateral leads I, aVL, V5–V6
- QS or rS complex in V1 (predominantly negative)
- Discordant ST-T changes — ST and T wave point opposite to QRS direction
- New LBBB + chest pain = presumed STEMI equivalent (Sgarbossa criteria apply)
6. Right Bundle Branch Block (RBBB)
What it is: Failure of the right bundle branch delays right ventricular depolarization.
ECG features (RaBBiT):
- Wide QRS (≥120 ms)
- rSR' ("rabbit ears") pattern in V1 — the classic finding
- Wide, slurred S waves in I, aVL, V5–V6
- T-wave inversion in V1–V3 (secondary repolarization change)
- Can be a normal variant or indicate pulmonary embolism, RV strain, or cardiac disease
7. Torsades de Pointes (Polymorphic VT)
What it is: A potentially lethal polymorphic ventricular tachycardia associated with prolonged QT interval. The QRS complexes appear to "twist" around the isoelectric baseline.
ECG features:
- Wide, rapidly changing QRS morphology — amplitude and axis shift cyclically
- "Twisting of the points" — complexes appear to rotate around the baseline
- Often initiated by a "short-long-short" RR interval sequence
- Triggered by QT-prolonging drugs, electrolyte disturbances (hypokalemia, hypomagnesemia)
- Can degenerate into ventricular fibrillation → cardiac arrest
8. Hyperkalemia
What it is: Elevated serum potassium (K⁺ >5.5 mEq/L) progressively disrupts cardiac membrane potential.
ECG changes are sequential with rising K⁺:
| K⁺ Level | ECG Change |
|---|---|
| 5.5–6.5 | Tall, peaked ("tented") T waves — narrow base, symmetric |
| 6.5–7.5 | PR prolongation + P wave flattening/loss |
| 7.5–9.0 | QRS widening → sine wave pattern |
| >9.0 | Ventricular fibrillation / asystole |
9. Acute Pericarditis
What it is: Inflammation of the pericardium causing diffuse myocardial epicardial irritation.
ECG features (4 stages):
- Stage 1 (acute): Diffuse concave ("saddle-shaped") ST elevation in nearly all leads (except aVR and V1) + PR depression (pathognomonic) + PR elevation in aVR
- Spodick's sign: Downsloping TP segment
- Stage 2: ST normalizes, T waves flatten
- Stage 3: T wave inversion
- Stage 4: ECG returns to normal
- Key distinction from STEMI: diffuse (not territorial), concave morphology, PR depression, no reciprocal ST changes
10. Left Ventricular Hypertrophy (LVH)
What it is: Increased LV muscle mass (from hypertension, aortic stenosis, HCM) generates exaggerated electrical voltages.
ECG features:
- Sokolow-Lyon criteria: S in V1 + R in V5 or V6 ≥35 mm
- Cornell criteria: R in aVL + S in V3 >28 mm (men) or >20 mm (women)
- "Strain pattern": ST depression + T-wave inversion in lateral leads (I, aVL, V5–V6) — indicates pressure/volume overload
- Left axis deviation
- Broad, notched P wave (P mitrale) if left atrial enlargement coexists
Quick Reference Summary
| # | ECG Change | Key Finding |
|---|---|---|
| 1 | STEMI | Convex ST elevation, reciprocal depression, Q waves |
| 2 | Atrial Fibrillation | Absent P waves, irregularly irregular |
| 3 | Complete Heart Block | AV dissociation, P & QRS independent |
| 4 | WPW | Short PR, delta wave, wide QRS |
| 5 | LBBB | Wide QRS, monophasic R in V5–V6, QS in V1 |
| 6 | RBBB | rSR' in V1, wide S in I/V6 |
| 7 | Torsades de Pointes | Twisting polymorphic VT, long QT |
| 8 | Hyperkalemia | Peaked T waves → wide QRS → sine wave |
| 9 | Acute Pericarditis | Diffuse saddle ST elevation, PR depression |
| 10 | LVH | High voltage, lateral strain pattern |
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