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10 Heart Diseases & Their ECG Changes

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1. 🫀 ST-Elevation Myocardial Infarction (STEMI)

ECG Changes

• Anterior (LAD): ST elevation in V1–V4
• Inferior (RCA): ST elevation in II, III, aVF
• Lateral (LCx): ST elevation in I, aVL, V5–V6
• Posterior: Dominant R in V1–V3 + ST depression anteriorly

ECG Image — Acute Anterior STEMI

ECG Image — Inferior STEMI with Posterior Extension

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2. 💓 Atrial Fibrillation (AF)

ECG Changes

ECG Image — Atrial Fibrillation with RVR

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3. 🚫 Complete (Third-Degree) AV Heart Block

ECG Changes

ECG Image — Complete (Third-Degree) AV Block

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

ECG Changes

• Negative delta in V1–V3: left-sided pathway
• Negative delta in inferior leads: posteroseptal pathway

ECG Image — WPW Syndrome

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5. 🫁 Pulmonary Embolism (PE)

ECG Changes

ECG Image — Pulmonary Embolism (S1Q3T3)

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6. 🔥 Acute Pericarditis

ECG Changes

ECG Image — Acute Pericarditis

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7. 💪 Left Ventricular Hypertrophy (LVH)

ECG Changes

ECG Image — Left Ventricular Hypertrophy with Strain

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8. ❤️ Hypertrophic Cardiomyopathy (HCM)

ECG Changes

ECG Image — Hypertrophic Cardiomyopathy

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9. ☠️ Brugada Syndrome

ECG Changes

ECG Image — Brugada Syndrome Type 1

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10. ⚡ Ventricular Tachycardia (VT)

ECG Changes

ECG Image — Ventricular Tachycardia

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Quick Reference Summary Table

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Clinical Pearl: ECG interpretation requires integration with clinical context (symptoms, history, exam). A single ECG feature is rarely diagnostic alone — pattern recognition across multiple leads is essential.

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🩺 ABG Analysis in the Emergency Ward

A Comprehensive Lecture — Professor of Emergency Medicine

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"Good morning, students. Welcome to the Emergency Ward. ABG interpretation is one of the most powerful tools you have at 3 AM when your patient is deteriorating. Master this, and you will save lives. Let us begin."

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📌 What Is an ABG?

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🩸 Step 1: How to Collect an ABG

Radial Artery — The Standard Site

1. Perform the Allen test (confirm ulnar collateral circulation)
2. Hyperextend the wrist ~60° over a rolled towel
3. Palpate the radial pulse, insert needle at 45°, aspirate ~1–2 mL bright red pulsatile blood
4. Remove air bubbles, cap immediately — transport on ice, analyze within 15 minutes

💡 Professor's Tip: Bright red, pulsatile blood = arterial. Dark venous blood filling the syringe passively = you're in a vein. Start again.

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🧭 The 5-Step Systematic Approach to ABG Interpretation

"Students, you MUST follow a systematic approach every single time. Never jump to conclusions."

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STEP 1 — Look at the pH: Is the Patient Acidemic or Alkalemic?

pH < 7.2 = Life-threatening emergency. Act NOW.

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STEP 2 — Identify the Primary Disorder (PaCO₂ vs HCO₃⁻)

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STEP 3 — Is There Appropriate Compensation?

💡 If PaCO₂ ≠ expected → mixed disorder is present!

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STEP 4 — Calculate the Anion Gap (if Metabolic Acidosis)

Causes of High-Anion Gap Metabolic Acidosis (Harrison's):

💡 Mnemonic — MUDPILES: Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates

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STEP 5 — Assess Oxygenation

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📊 The Acid-Base Nomogram

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🔬 The 4 Primary Acid-Base Disorders — In Depth

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1. 🔴 Metabolic Acidosis

• High AG: DKA, lactic acidosis (sepsis, shock), uremia, toxic ingestions
• Normal AG: Severe diarrhea, RTA, saline excess

"When you see pH < 7.0 with AG > 15 — that patient needs ICU immediately. Do not wait."

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2. 🔵 Respiratory Acidosis

• Opiate overdose / sedative poisoning → respiratory depression
• Acute severe asthma / COPD exacerbation
• Neuromuscular failure (Guillain-Barré, myasthenia crisis)
• Tension pneumothorax
• Laryngospasm, foreign body

"PaCO₂ > 60 with pH < 7.25 → consider intubation or BiPAP. The patient is tiring out."

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3. 🟡 Metabolic Alkalosis

• Vomiting / NG suction (loss of HCl)
• Diuretic use (thiazides, loop diuretics — Cl⁻ and K⁺ loss)
• Antacid excess / NaHCO₃ therapy
• Hyperaldosteronism (Conn's syndrome)

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4. 🟢 Respiratory Alkalosis

• Hypoxemia driving hyperventilation (PE, pneumonia, early sepsis)
• Anxiety / panic attack
• Liver failure (hyperammonemia stimulates breathing)
• Salicylate toxicity (early phase)
• Pregnancy
• Mechanical over-ventilation

"Respiratory alkalosis in a non-anxious patient = screen for PE, sepsis, and liver failure. Always."

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🆘 Common Emergency ABG Scenarios

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⚡ Mixed Acid-Base Disorders

• pH 7.00 | PaCO₂ 60 | HCO₃⁻ 12
• Respiratory acidosis (↑PaCO₂) + Metabolic acidosis (↓HCO₃⁻) simultaneously
• → Double acidosis — most dangerous ABG pattern

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🫁 Assessing Oxygenation — Beyond PaO₂

PaO₂/FiO₂ Ratio (P/F Ratio)

A P/F ratio < 300 in a mechanically ventilated patient = acute lung injury. A P/F < 100 = severe ARDS, consider prone positioning.

The 6 Mechanisms of Hypoxemia

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🧠 Professor's Mnemonics — Never Forget

ROME (Primary Disorders)

Respiratory Opposite (pH and PaCO₂ move opposite) Metabolic Equal (pH and HCO₃⁻ move same direction)

MUDPILES (High AG Metabolic Acidosis)

Methanol | Uremia | DKA | Propylene glycol | Isoniazid/Iron | Lactic acidosis | Ethylene glycol | Salicylates

CLEVER PD (Normal AG Metabolic Acidosis)

Carbonic anhydrase inhibitors | Loss of HCO₃⁻ (diarrhea) | Expansion (saline) | Vertical (ureterosigmoidostomy) | Endocrine (hyperaldosteronism) | Renal tubular acidosis | Pancreatic fistula | Drugs (cholestyramine)

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🗒️ Quick Reference — ABG Normal Values

pH:       7.35 – 7.45
PaCO₂:    35  – 45   mmHg
PaO₂:     80  – 100  mmHg
HCO₃⁻:   22  – 26   mEq/L
SaO₂:     95  – 100  %
BE:       −2  to +2  mEq/L
Anion Gap: 8  – 12   mEq/L
A-a gradient: < (Age/4 + 4) mmHg on room air

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🏥 5-Step ABG Cheat Sheet for the Emergency Ward

1. pH → Acidosis (<7.35) or Alkalosis (>7.45)?
2. PaCO₂ / HCO₃⁻ → Respiratory or Metabolic primary?
3. Is compensation appropriate? (Use Winter's / rules)
4. If metabolic acidosis → Calculate Anion Gap → MUDPILES?
5. Oxygenation → PaO₂, A-a gradient, P/F ratio → Mechanism?

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"Remember, students — the ABG doesn't give you the diagnosis. It gives you the physiology. Your job is to marry that physiology to the clinical picture. A pH of 7.10 in a DKA patient and a pH of 7.10 in a COPD patient require completely different treatments. The numbers mean nothing without the bedside."

— Your Professor, Emergency Medicine

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