10 Common Heart Diseases — ECG Changes & Images

1. 🫀 ST-Elevation Myocardial Infarction (STEMI)

ECG Changes:

• ST elevation ≥1 mm in ≥2 contiguous leads (≥2 mm in precordial leads)
• Hyperacute T-waves (tall, peaked) — earliest finding
• Reciprocal ST depression in opposite leads
• Pathological Q-waves develop within hours (irreversible necrosis)
• T-wave inversions in the post-infarct stage
• Localization by leads:
  • Anterior (V1–V4): LAD occlusion
  • Inferior (II, III, aVF): RCA or circumflex
  • Lateral (I, aVL, V5–V6): circumflex artery

ECG Image — Anterior STEMI (LAD occlusion):

Massive anterolateral STEMI: convex ST elevation in V1–V6 and leads I/aVL, with reciprocal ST depression in II/III/aVF. Proximal LAD occlusion.

ECG Image — Inferolateral STEMI:

ST elevation in II, III, aVF and V4–V6 (green circles) with reciprocal depression in I, aVL and V2–V3 (yellow arrows).

2. 💓 Atrial Fibrillation (AF)

ECG Changes:

• Absent P-waves — replaced by fine fibrillatory (f) waves (best seen in V1)
• Irregularly irregular R-R intervals — the hallmark
• Narrow QRS complexes (unless aberrant conduction/WPW)
• Ventricular rate varies widely (slow, controlled, or rapid response)
• Baseline undulation rather than flat isoelectric line

ECG Image:

Classic AF: complete absence of P-waves, fine fibrillatory baseline (visible in V1), narrow QRS with irregular R-R intervals throughout all 12 leads.

3. 💔 Complete (Third-Degree) AV Block

ECG Changes:

• P-waves and QRS complexes are completely dissociated — no fixed PR interval
• Atrial rate is faster than ventricular rate
• Escape rhythm: narrow QRS (junctional, ~40–60 bpm) or wide QRS (ventricular, ~20–40 bpm)
• Profound bradycardia
• Prolonged QT may occur with ventricular escape rhythm

ECG Image:

Third-degree AV block: P-waves (black arrows in rhythm strip) occur regularly but bear no relationship to the wide QRS escape complexes at ~33 bpm. QTc 560 ms.

4. 🫁 Pulmonary Embolism (PE)

ECG Changes:

• Sinus tachycardia — most common finding
• S1Q3T3 pattern (McGinn-White sign): deep S in I, Q-wave in III, T-wave inversion in III
• T-wave inversions V1–V4 — right ventricular strain
• Incomplete or complete RBBB — acute RV dilatation
• Rightward axis deviation
• P pulmonale (peaked P in II) in massive PE

ECG Image:

Acute PE: Sinus tachycardia with classic S1Q3T3 (S-wave lead I, Q-wave lead III, inverted T lead III) and deep T-wave inversions V1–V6 indicating severe RV strain.

5. 🏥 Acute Pericarditis

ECG Changes (Stage I — Acute):

• Diffuse concave (saddle-shaped) ST elevation in almost all leads EXCEPT aVR and V1
• PR-segment depression in most leads (highly specific) — aVR shows reciprocal PR elevation
• Spodick's sign: downward sloping TP segment
• No reciprocal ST changes in a typical vascular territory (unlike STEMI)
• ST:T-wave amplitude ratio in V6 >0.25 favors pericarditis

ECG Image:

Acute pericarditis: diffuse concave ST elevation in I, II, III, aVF and V2–V6; PR-segment depression in II, aVF and V4–V6; reciprocal ST depression and PR elevation in aVR.

6. 🧬 Hypertrophic Cardiomyopathy (HCM)

ECG Changes:

• Left ventricular hypertrophy voltage criteria (Sokolow-Lyon: S in V1 + R in V5/V6 >35 mm)
• Deep T-wave inversions — especially in apical HCM (Yamaguchi syndrome): giant negative T-waves in V3–V5
• ST depression with lateral strain pattern
• Absence of septal Q-waves in I, aVL, V5, V6 (due to abnormal septal depolarization)
• Left axis deviation
• Atrial fibrillation common

ECG Image — Apical HCM (Yamaguchi syndrome):

Apical HCM: Normal sinus rhythm with LVH voltage, deep symmetric T-wave inversions across virtually all leads (V2–V6, I, II, aVF). Hallmark of Yamaguchi syndrome.

ECG Image — HCM Variants (Composite):

Composite showing HCM variants: Panel A = concentric hypertrophy (high R-wave voltage), B = septal hypertrophy, C = apical (giant T-wave inversions 12 mm in V5), each correlated with cardiac MRI.

7. ⚡ Wolff-Parkinson-White (WPW) Syndrome

ECG Changes:

• Short PR interval (<120 ms) — AV node bypassed
• Delta wave — slurred initial upstroke of QRS (pre-excitation)
• Widened QRS (>120 ms) — fusion of normal and accessory conduction
• Secondary ST-T changes — discordant to QRS
• Accessory pathway location estimated by delta wave polarity:
  • Negative delta in inferior leads (II, III, aVF) → posteroseptal pathway
  • Positive in V1 → left-sided pathway

ECG Image:

Classic WPW: Short PR interval, prominent delta waves in leads II and III (red arrows), widened QRS, consistent with an anteroseptal accessory pathway. Risk of sudden death via AF with rapid ventricular conduction.

8. 💥 Ventricular Tachycardia (VT)

ECG Changes:

• Wide QRS complexes (≥120 ms), regular, rate 100–250 bpm
• AV dissociation — P-waves unrelated to QRS (if visible)
• Fusion beats and capture beats (pathognomonic)
• Concordance in precordial leads (all positive or all negative)
• NW ("no man's land") axis — extreme right axis deviation
• Brugada criteria (RBBB-type) or Josephson's sign (notching near S-wave nadir)

ECG Image:

Monomorphic VT: High-rate, wide-complex rhythm with positive concordance across precordial leads V1–V6. No visible P-waves. Superior axis. Associated with structural heart disease.

9. 🧬 Brugada Syndrome

ECG Changes:

• Type 1 (Diagnostic) — "Coved" pattern in V1–V2 (or V1–V3 with high precordial placement):
  • J-point elevation ≥2 mm
  • Convex (downward) ST segment
  • Negative (inverted) T-wave
• Type 2 & 3 are "saddle-back" patterns (not diagnostic alone)
• Features may be dynamic — unmasked by fever, sodium channel blockers, autonomic changes
• Arrhythmias: polymorphic VT, ventricular fibrillation

ECG Image:

Type 1 Brugada pattern: Classic "coved" morphology in V1–V2 — J-point elevation with downsloping convex ST segment terminating in inverted T-wave. Diagnostic hallmark of Brugada syndrome.

10. 📏 Long QT Syndrome (LQTS)

ECG Changes:

• Prolonged QTc: ≥450 ms (men), ≥460 ms (women); ≥500 ms = high risk
• Abnormal T-wave morphology by subtype:
  • LQT1: broad-based, smooth T-wave
  • LQT2: bifid/notched T-wave (most visible)
  • LQT3: long flat ST segment with late-peaked T-wave
• T-wave alternans — beat-to-beat T-wave variation; marker of high instability
• Torsades de Pointes: polymorphic VT with "twisting" QRS complexes around isoelectric line
• Triggered by "R-on-T" phenomenon, bradycardia, or pause (short-long-short sequence)

ECG Image — Prolonged QT with Torsades de Pointes:

Severe LQTS: Marked QT prolongation with R-on-T PVC triggering Torsades de Pointes — the classic "twisting" polymorphic VT. Life-threatening arrhythmia requiring urgent management.

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