EASY ECG – Notes for Students

ECG Basics

Electrocardiogram (ECG) records the electrical activity of the heart over time.

Key Components

• P wave – Atrial depolarization
• QRS complex – Ventricular depolarization
• T wave – Ventricular repolarization

ECG Paper

• 1 small square = 0.04 sec
• 1 large square = 0.20 sec
• Heart rate = 300 ÷ number of large squares between R waves

Leads

• Limb leads: I, II, III
• Augmented leads: aVR, aVL, aVF
• Chest leads: V1–V6

How to Analyze a Rhythm

1. Check Rate
2. Check Rhythm (regular/irregular)
3. Look for P waves
4. Measure PR interval (0.12–0.20 sec)
5. Check QRS duration (< 0.12 sec)
6. Check relationship between P and QRS

Normal Sinus Rhythm

• Rate: 60–100 bpm
• Regular rhythm
• P wave before each QRS
• Normal PR interval
• Narrow QRS complex

Heart Arrhythmias 1

• Sinus Bradycardia – Rate less than 60 bpm
• Sinus Tachycardia – Rate more than 100 bpm
• Atrial Fibrillation – No clear P waves, irregular rhythm
• Atrial Flutter – Sawtooth pattern

Heart Arrhythmias 2

• PVC – Early wide QRS complex
• Ventricular Tachycardia – Fast wide complex rhythm
• Ventricular Fibrillation – Chaotic rhythm
• SVT – Rapid narrow complex rhythm

Heart Arrhythmias 3

• 1st Degree AV Block – Prolonged PR interval
• 2nd Degree AV Block – Dropped QRS complexes
• 3rd Degree AV Block – Complete dissociation

Acute Myocardial Infarction

• ST Elevation – Acute injury
• ST Depression – Ischemia
• Pathological Q waves – Old infarction
• T wave inversion – Ischemia

Localization

• Inferior: II, III, aVF
• Anterior: V1–V4
• Lateral: I, aVL, V5–V6

Advanced 12-Lead Interpretation

• Cardiac axis determination
• R-wave progression
• Hypertrophy patterns (LVH, RVH)

Reading 12-Lead ECGs 1

1. Rate and rhythm
2. Axis
3. Intervals (PR, QRS, QT)
4. Wave morphology
5. ST-T changes

Lead Groups

• Inferior: II, III, aVF
• Anterior: V1–V4
• Lateral: I, aVL, V5–V6

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Reading 12-Lead ECGs 2

• Interpret ECG with clinical symptoms
• Identify ischemia, arrhythmias, electrolyte imbalance

Electrolyte Changes

• Hyperkalemia – Tall peaked T waves
• Hypokalemia – U waves, flat T waves

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Summary

• ECG is an important diagnostic tool
• Follow a step-by-step method
• Practice regularly