Top 10 Heart Diseases & Their ECG Findings

1. 🫀 ST-Elevation Myocardial Infarction (STEMI)

• ST-segment elevation ≥1 mm in ≥2 contiguous leads (convex "tombstone" morphology)
• Hyperacute (peaked) T-waves — earliest change
• Pathological Q-waves — develop within hours (indicate transmural necrosis)
• Reciprocal ST-depression in opposite leads
• T-wave inversion in the evolving phase

Goldman-Cecil Medicine — "Acute MI is classified based on whether the ECG shows ST-segment elevation (STEMI) or not (NSTEMI)."

2. 💓 Atrial Fibrillation (AF)

• Absent P waves — replaced by chaotic fibrillatory (f) waves (best seen in V1)
• Irregularly irregular R-R intervals — hallmark finding
• Narrow QRS complexes (unless aberrant conduction)
• Rapid ventricular response (>100 bpm) if uncontrolled

Braunwald's Heart Disease — "New atrial fibrillation or flutter" is a classic ECG manifestation of structural cardiac disease.

3. 🫁 Acute Pericarditis

• Stage I: Diffuse concave ST elevation in nearly all leads (except aVR & V1) + PR depression (pathognomonic)
• Stage II: ST normalises, PR depression persists
• Stage III: T-wave inversions
• Stage IV: ECG normalises

• ST elevation is diffuse (not regional)
• PR depression is present
• No reciprocal ST depression (except in aVR)
• No Q-waves

Washington Manual — "Classic ECG findings are diffuse ST-segment elevation with PR depression." Mulholland Surgery — "The EKG classically shows diffuse ST elevations without Q waves or T-wave inversion. PR depression can also be seen."

4. 💗 Hypertrophic Cardiomyopathy (HCM)

• Left ventricular hypertrophy (LVH) — Sokolow-Lyon criteria: deep S in V1 + tall R in V5 (sum >35 mm)
• Deep, broad Q-waves in lateral leads (I, aVL, V5–V6) — "septal Q-waves" (pseudoinfarction pattern)
• "Giant" symmetric T-wave inversions — especially in apical HCM (Yamaguchi syndrome) V3–V5 (up to 15 mm deep)
• Left axis deviation
• Atrial fibrillation common

Tintinalli's Emergency Medicine — "Deep S-wave voltage (28 mm S in V2) and deep broad Q-waves are characteristic HCM ECG findings."

5. 🔁 Wolff-Parkinson-White (WPW) Syndrome / Pre-Excitation

• Short PR interval (<120 ms) — accessory pathway bypasses AV node delay
• Delta wave — slurred upstroke at the beginning of the QRS (pre-excitation of ventricles)
• Widened QRS (>120 ms) — due to fusion of normal and accessory conduction
• Pseudo-ST/T changes (secondary repolarisation abnormalities)
• Can mimic LBBB or RBBB patterns depending on pathway location

Washington Manual — "WPW syndrome: short PR and a delta wave on the upstroke of QRS. Can have AVRT (orthodromic or antidromic) as the mechanism of SVT." Miller's Anesthesia — "WPW: characterised by a shortened PR interval and a delta wave (i.e., early activation/"pre-excitation" of the His–Purkinje system)."

6. ❤️ Heart Failure with LV Hypertrophy / Hypertensive Heart Disease

• LVH voltage criteria (Sokolow-Lyon, Cornell criteria)
• LV strain pattern — ST depression + T-wave inversion in lateral leads (I, aVL, V5–V6)
• Left atrial enlargement — broad, bifid P-wave (P-mitrale) in lead II; biphasic P in V1
• Left axis deviation
• LBBB in advanced disease
• Atrial fibrillation (from left atrial dilatation)

Robbins Pathology — "ECG or echocardiographic findings of left ventricular hypertrophy. The disease comes to attention with the onset of atrial fibrillation (secondary to left atrial enlargement)."

7. 📉 AV Heart Block (2nd & 3rd Degree)

Goldman-Cecil — "Complete heart block is usually preceded by abnormal baseline ECG findings, such as bundle branch block or second-degree AV block." Washington Manual — "Mobitz II 2nd-degree AV block carries a higher risk of progression to complete heart block than Mobitz I."

8. 🫀 Non-ST Elevation ACS (NSTEMI / Unstable Angina)

• ST depression ≥0.5–1 mm (horizontal or downsloping) in ≥2 contiguous leads
• T-wave inversions (deep, symmetric)
• Transient ST elevation that resolves
• ECG may be normal in ~20–30% of cases
• No pathological Q-waves (subendocardial infarction)

Goldman-Cecil — "MI is classified based on whether the ECG shows ST elevation (STEMI) or not (NSTEMI). NSTEMI shows no ST elevation but elevated biomarkers."

9. 🔴 Aortic Stenosis

• LVH — high voltage (pressure overload pattern)
• LV strain — ST-depression and T-wave inversion in V5–V6, I, aVL
• Left axis deviation
• Left atrial enlargement (P-mitrale)
• Left bundle branch block (advanced disease)
• Atrial fibrillation (late)

Tintinalli's — "ECG findings are generally nonspecific. The most common abnormality is left ventricular hypertrophy."

10. 🔶 Dilated Cardiomyopathy (DCM)

• Sinus tachycardia — compensatory
• Left bundle branch block (LBBB) — very common; QRS >120 ms, broad notched R in I/V5–V6
• LVH or low voltage (in end-stage)
• Pathological Q-waves — pseudoinfarction pattern (fibrosis)
• Left atrial enlargement
• Atrial fibrillation, ventricular ectopics, ventricular tachycardia

Quick Reference Summary Table

• Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine
• Goldman-Cecil Medicine
• Harrison's Principles of Internal Medicine, 22nd Ed. (2025)
• Tintinalli's Emergency Medicine
• Washington Manual of Medical Therapeutics
• Robbins & Kumar Basic Pathology
• Miller's Anesthesia