---

20 Common Heart Diseases: ECG Changes & Images

---

1. 🫀 Acute ST-Elevation Myocardial Infarction (STEMI)

ECG Changes:

• Hyperacute T waves (earliest finding — tall, peaked, symmetric)
• ST-segment elevation ≥1 mm in ≥2 contiguous leads (convex/tombstone morphology)
• Reciprocal ST depression in opposite leads
• Pathological Q waves (>40 ms wide, >25% QRS amplitude) — develop after hours
• T-wave inversion in the evolutionary phase
• New LBBB is treated as STEMI equivalent

Anterior STEMI — Tombstone pattern:

Anterolateral STEMI:

Inferior STEMI with reciprocal changes:

---

2. 🫀 Non-ST-Elevation Myocardial Infarction (NSTEMI) / Unstable Angina

ECG Changes:

• ST-segment depression (horizontal or downsloping) in ischemic leads
• T-wave inversion (symmetric, deep)
• No ST elevation and no Q waves
• Dynamic ECG changes (worsen with symptoms)
• Leads may be normal in 1–6% of NSTEMI

Evolutionary Inferior MI (post-PCI changes):

---

3. 🫀 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 or pre-excitation)
• Ventricular rate variable (60–200+ bpm depending on AV node)
• Baseline chaotic, undulating

---

4. 🫀 Atrial Flutter

ECG Changes:

• "Sawtooth" flutter (F) waves at ~300 bpm — best seen in II, III, aVF, V1
• Regular ventricular response — typically 2:1 (150 bpm), 3:1, or 4:1
• No isoelectric baseline between flutter waves
• Narrow QRS complexes
• Counter-clockwise flutter (typical) = negative F-waves in inferior leads

---

5. 🫀 Third-Degree (Complete) AV Block

ECG Changes:

• Complete AV dissociation — P waves and QRS complexes occur independently
• Bradycardia — ventricular rate 20–40 bpm (escape rhythm)
• Wide QRS if ventricular escape (>120 ms); narrow if junctional escape
• P rate > QRS rate (atrial rate normal ~60–100 bpm)
• No relationship between P waves and QRS complexes

---

6. 🫀 First-Degree AV Block

ECG Changes:

• Prolonged PR interval >200 ms (>5 small squares)
• Every P wave followed by a QRS — 1:1 conduction maintained
• QRS complexes narrow and morphologically normal
• Benign finding; commonly caused by vagal tone, medications, or inferior MI

---

7. 🫀 Second-Degree AV Block (Mobitz Type I & II)

ECG Changes:

• Progressive PR prolongation → dropped QRS
• Grouped beating pattern
• Site of block: AV node (usually benign)

• Constant PR interval → sudden dropped QRS (no warning)
• Often with bundle branch block
• Site of block: His-Purkinje (more dangerous, can progress to complete block)

---

8. 🫀 Right Bundle Branch Block (RBBB)

ECG Changes:

• RSR' pattern ("M pattern") in V1–V3 — rabbit ears
• Wide, slurred S waves in I, aVL, V5–V6
• QRS duration ≥120 ms (complete RBBB)
• Secondary ST-T changes — ST depression + T-wave inversion in V1–V3
• Normal axis usually

---

9. 🫀 Left Bundle Branch Block (LBBB)

ECG Changes:

• Broad, notched ("M-shaped") R waves in I, aVL, V5–V6
• Deep QS or rS in V1–V3 (no septal Q waves in lateral leads)
• QRS duration ≥120 ms
• Discordant ST-T changes (ST/T opposite to QRS)
• Left axis deviation common
• New LBBB = STEMI equivalent until proven otherwise (Sgarbossa criteria)

---

10. 🫀 Hypertrophic Cardiomyopathy (HCM)

ECG Changes:

• Left ventricular hypertrophy (LVH) voltage criteria — tall R in V4–V6, deep S in V1–V3 (Sokolow-Lyon >35 mm)
• Deep, giant, symmetric T-wave inversions in V2–V6 (especially apical HCM / Yamaguchi syndrome)
• Lateral ST depression and T-wave inversions (strain pattern)
• Pathological Q waves in inferior and lateral leads (septal hypertrophy)
• Left axis deviation
• Atrial enlargement (broad, notched P waves in II)

---

11. 🫀 Dilated Cardiomyopathy (DCM)

ECG Changes:

• Low voltage QRS in limb leads (<5 mm) or precordial leads (<10 mm)
• LBBB pattern (very common)
• Non-specific ST-T wave changes
• Sinus tachycardia (compensatory)
• Atrial fibrillation (common complication)
• Pathological Q waves (pseudo-infarct pattern)
• Left atrial enlargement

---

12. 🫀 Acute Pericarditis

ECG Changes (4 classic stages):

1. Stage I — Diffuse saddle-shaped (concave up) ST elevation in most leads + PR depression (most specific sign); ST elevation in aVR with PR elevation
2. Stage II — ST normalises, T waves flatten
3. Stage III — T-wave inversions (without Q waves)
4. Stage IV — Normalisation (weeks later)

• ST changes are diffuse (not territorial)
• No reciprocal depression (except aVR/V1)
• PR depression is hallmark
• No Q waves develop

---

13. 🫀 Pericardial Effusion / Cardiac Tamponade

ECG Changes:

• Sinus tachycardia
• Low QRS voltage (fluid dampening electrical signals)
• Electrical alternans — beat-to-beat alternation in QRS amplitude/axis (pathognomonic for large effusion/tamponade)
• P wave alternans may also occur

---

14. 🫀 Pulmonary Embolism (PE)

ECG Changes:

• Sinus tachycardia (most common finding, ~44%)
• S1Q3T3 pattern: Deep S in I + Q wave in III + T-wave inversion in III
• Incomplete or complete RBBB
• T-wave inversions in V1–V4 (right ventricular strain)
• Right axis deviation
• P pulmonale (peaked P in II >2.5 mm)
• New AF or flutter possible

---

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

ECG Changes:

• Short PR interval <120 ms (accessory pathway bypasses AV node delay)
• Delta wave — slurred upstroke at start of QRS (pre-excitation)
• Wide QRS (>120 ms) due to delta wave
• Secondary ST-T changes discordant with QRS
• Pseudo-infarct Q waves possible
• Risk: AF with rapid ventricular response through accessory pathway → VF

---

16. 🫀 Brugada Syndrome

ECG Changes:

• Type 1 (diagnostic): "Coved" ST elevation ≥2 mm with descending ST → negative T-wave in V1–V2 ("shark fin" or "ski slope")
• Type 2: "Saddleback" morphology — ST elevation ≥2 mm, rises then dips, upright T-wave (not diagnostic alone)
• Changes in right precordial leads V1–V3
• PR prolongation possible
• Normal QT interval
• Risk: ventricular fibrillation and sudden cardiac death (especially at rest/fever)

---

17. 🫀 Long QT Syndrome (LQTS)

ECG Changes:

• Prolonged QTc interval >450 ms (males), >460 ms (females), >480 ms pathological
• Corrected using Bazett formula: QTc = QT / √RR
• T-wave abnormalities — notched, biphasic, broad T waves
• Risk: Torsades de Pointes (TdP) — polymorphic VT with twisting QRS axis around baseline → VF → sudden death

Torsades de Pointes (complication of long QT):

---

18. 🫀 Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVC)

ECG Changes:

• Epsilon wave — small positive deflection at end of QRS in V1–V3 (pathognomonic — fibrofatty RV infiltration)
• T-wave inversions in V1–V4 (right precordial leads)
• Localised QRS prolongation >110 ms in V1–V3
• RBBB pattern (complete or incomplete)
• Ventricular tachycardia with LBBB morphology (arises from RV)
• S-wave upstroke >55 ms in V1–V3

---

19. 🫀 Heart Failure with Left Ventricular Hypertrophy (LVH)

ECG Changes (Sokolow-Lyon criteria):

• S in V1 + R in V5 or V6 >35 mm
• R in aVL >11 mm
• LV strain pattern: ST depression + T-wave inversion in I, aVL, V5–V6
• Left axis deviation
• Broad, notched P waves (P mitrale) → left atrial enlargement
• LBBB pattern in severe disease

---

20. 🫀 Ventricular Tachycardia (VT)

ECG Changes:

• Wide complex tachycardia — QRS ≥120 ms, rate >100 bpm
• AV dissociation — P waves independent of QRS (key feature)
• Fusion beats and capture beats (diagnostic when present)
• Concordance — all precordial leads same polarity (positive or negative)
• Extreme axis deviation ("northwest axis")
• LBBB morphology VT = RV origin; RBBB morphology VT = LV origin
• Can degenerate into ventricular fibrillation (VF)

---

21. 🫀 Ventricular Fibrillation (VF)

ECG Changes:

• Chaotic, irregular, baseline oscillations — no identifiable P waves, QRS, or T waves
• Variable amplitude and frequency
• Completely disorganized electrical activity
• Medical emergency — requires immediate defibrillation

---

22. 🫀 Hyperkalemia

ECG Changes (progressive with rising K⁺):

• K⁺ 5.5–6.5 mmol/L: Tall, peaked ("tented") T waves (narrow base)
• K⁺ 6.5–7.5 mmol/L: Prolonged PR interval, widened QRS
• K⁺ >7.5 mmol/L: Flattened/absent P waves, sine wave pattern
• K⁺ >8–9 mmol/L: VF or asystole

---

23. 🫀 Hypokalemia

ECG Changes:

• Flattened or inverted T waves
• Prominent U waves (positive deflection after T wave, best seen V2–V3)
• ST depression
• Prolonged QT interval (when U wave merges with T wave)
• PR prolongation
• Risk of VT/TdP with severe hypokalemia

---

24. 🫀 Mitral Stenosis

ECG Changes:

• P mitrale — broad, notched P waves ≥120 ms in lead II (bifid P) = left atrial enlargement
• Biphasic P wave in V1 — terminal negative component (LA abnormality)
• Right ventricular hypertrophy signs if pulmonary hypertension develops: right axis deviation, dominant R in V1
• Atrial fibrillation (very common complication — LA dilation)
• P pulmonale in severe PAH

---

Quick Reference Table

---

Clinical Note: ECG changes should always be interpreted alongside clinical history, symptoms, and other investigations. A single ECG finding is rarely diagnostic in isolation — serial ECGs and troponin measurements are essential for ischemic syndromes.