10 Common Heart Diseases: ECG Changes & Images

1. 🫀 ST-Elevation Myocardial Infarction (STEMI)

ECG Changes

• Anterior (LAD): V1–V4
• Inferior (RCA): II, III, aVF
• Lateral (LCx): I, aVL, V5–V6
• aVR elevation → left main / proximal LAD occlusion

Classic anterior STEMI: convex ST elevation V1–V6 with hyperacute T-waves and reciprocal changes in inferior leads

2. 🫀 Atrial Fibrillation (AF)

ECG Changes

• Absent P waves — replaced by fine fibrillatory (f) waves (best seen in V1)
• Irregularly irregular R-R intervals — hallmark finding
• Narrow QRS (unless aberrant conduction or pre-excitation)
• Ventricular rate variable: bradycardic, normal, or tachycardic
• No fixed PR interval

AF with rapid ventricular response: absent P-waves, irregular R-R intervals, fine f-waves on baseline

3. 🫀 Complete (Third-Degree) AV Block

ECG Changes

• Complete AV dissociation — P-waves and QRS complexes march through each other with NO relationship
• P-P intervals regular; R-R intervals regular — but at completely different rates
• Atrial rate > Ventricular escape rate (atria ~70–90 bpm; ventricles 20–40 bpm)
• Escape QRS morphology:
  • Narrow (junctional escape) if block is at AV node
  • Wide/bizarre (ventricular escape) if block is infra-Hisian
• No fixed PR interval — PR interval randomly varies

Third-degree AV block: P-waves (faster) march independently through wide-complex ventricular escape rhythm

4. 🫀 Ventricular Tachycardia (VT)

ECG Changes

• Wide QRS tachycardia (QRS ≥ 120 ms), rate 100–250 bpm
• AV dissociation (P-waves unrelated to QRS) — most specific sign for VT
• Capture beats — occasional narrow QRS (sinus captures ventricles)
• Fusion beats — hybrid narrow+wide QRS
• Concordance in precordial leads (all positive or all negative V1–V6)
• Brugada criteria and Vereckei algorithm help differentiate from SVT with aberrancy
• May degenerate into ventricular fibrillation

Monomorphic VT: rapid wide-complex tachycardia with positive concordance V1–V6 and AV dissociation

5. 🫀 Left Ventricular Hypertrophy (LVH)

ECG Changes

• S in V1 + R in V5 or V6 > 35 mm
• R in aVL > 11 mm

• ST depression + T-wave inversion in I, aVL, V5–V6 (lateral leads)
• Left axis deviation
• Prolonged QRS duration (may approach 110 ms)
• Broad, notched P-wave in II suggesting left atrial enlargement

LVH: deep S-waves V1–V2, tall R-waves V5–V6 exceeding voltage criteria, with lateral strain pattern (ST depression + T inversion)

6. 🫀 Wolff-Parkinson-White (WPW) Syndrome

ECG Changes

1. Short PR interval < 120 ms (accessory pathway bypasses AV node delay)
2. Delta wave — slurred upstroke at the beginning of QRS (slow conduction through myocardium)
3. Widened QRS > 120 ms (fusion of normal + accessory conduction)

• Secondary ST-T changes (discordant to QRS vector)
• Pseudo-Q waves in some leads (mimicking old MI)
• Accessory pathway localization by delta wave polarity (negative in inferior leads → posteroseptal pathway)
• Risk of rapid AF with antegrade accessory conduction → ventricular fibrillation

WPW syndrome: short PR interval, delta waves (arrows in II, III), widened QRS complexes throughout

7. 🫀 Acute Pericarditis

ECG Changes (evolve over 4 stages)

• ST elevation is diffuse (not limited to one coronary territory)
• Concave morphology (vs convex in STEMI)
• PR depression in II, V4–V6 (PR elevation in aVR) — very specific
• Spodick's sign: downsloping TP segment
• No reciprocal ST depression (except aVR)
• No Q-waves

Acute pericarditis: diffuse saddle-shaped ST elevation, PR depression in II (arrows), reciprocal changes in aVR

8. 🫀 Hypertrophic Cardiomyopathy (HCM)

ECG Changes

• Left ventricular hypertrophy by voltage criteria
• "Giant" deep symmetric T-wave inversions in lateral/precordial leads (especially V4–V6) — hallmark of apical variant (Yamaguchi)
• Septal Q waves — deep narrow Q-waves in I, aVL, V5–V6 (due to septal hypertrophy causing abnormal septal depolarization)
• ST-segment depression in lateral leads (strain pattern)
• Left axis deviation
• Prolonged QTc (~460 ms)
• Abnormal P-waves (left atrial enlargement)
• ECG is abnormal in ~95% of symptomatic HCM patients

HCM: high-amplitude R-waves V2–V4, deep T-wave inversions V2–V6 and lateral leads, ST depression, absence of septal Q waves

9. 🫀 Pulmonary Embolism (PE)

ECG Changes

Acute PE: sinus tachycardia, S1Q3T3 pattern, T-wave inversions V1–V3, incomplete RBBB

10. 🫀 Long QT Syndrome (LQTS)

ECG Changes

• Prolonged QTc interval:
  • Normal: ♂ < 440 ms; ♀ < 460 ms
  • Borderline: 440–470 ms (♂), 460–480 ms (♀)
  • Abnormal: > 470 ms (♂), > 480 ms (♀)
  • High risk: > 500 ms
• T-wave morphology abnormalities by subtype:
  • LQT1: Broad-based T-waves (absent "notch")
  • LQT2: Low-amplitude, notched/bifid T-waves
  • LQT3: Normal T-wave, prolonged isoelectric ST segment before T
• T-wave alternans (beat-to-beat T-wave changes in amplitude/polarity) — marker of high arrhythmic risk
• Degeneration into Torsades de Pointes (polymorphic VT with twisting QRS around isoelectric line)

LQTS: Panel (a) baseline ECG with prolonged QTc = 478 ms; Panel (b) rhythm strips showing degeneration into Torsades de Pointes

Quick Reference Summary

Clinical note: ECG interpretation must always be correlated with the patient's clinical history, symptoms, examination findings, and other investigations. No single ECG finding is pathognomonic in isolation.Here's a summary of what was covered across all 10 conditions, each with a real clinical ECG image:

1. STEMI — Convex ST elevation in a vascular territory, reciprocal changes, evolving Q-waves
2. Atrial Fibrillation — No P-waves, irregularly irregular rhythm, fibrillatory baseline
3. Complete AV Block — Full AV dissociation with independent P-wave and escape rhythms
4. Ventricular Tachycardia — Wide-complex tachycardia, AV dissociation, concordance pattern
5. LVH — Voltage criteria (SV1+RV5 >35 mm), lateral strain pattern (ST depression + T inversion)
6. WPW Syndrome — Short PR interval, delta wave, widened QRS, pre-excitation triad
7. Acute Pericarditis — Diffuse concave ST elevation, PR depression, Spodick's sign
8. Hypertrophic Cardiomyopathy — Giant T-wave inversions, deep narrow Q-waves, LVH voltage
9. Pulmonary Embolism — Sinus tachycardia, S1Q3T3 pattern, right ventricular strain signs
10. Long QT Syndrome — Prolonged QTc >480 ms, T-wave morphology subtypes, Torsades de Pointes