ECG Interpretation Basics (Nursing & Medical Students Notes)
Introduction:
Electrocardiography is a diagnostic method used to record the electrical activity of the heart. It
helps in detecting heart rhythm, rate, and abnormalities.
An ECG (Electrocardiogram) is essential in emergency, cardiac, and clinical settings.
1. Basic Principle of ECG:
The heart produces electrical impulses that travel through:
•SA node (natural pacemaker)
•AV node
•Bundle of His
•Purkinje fibers
These impulses are recorded as waves on ECG paper.
2. ECG Paper Basics:
Small Box:
•0.04 seconds
•1 mm
Large Box:
•0.20 seconds
•5 small boxes
Important:
, •Horizontal axis = time
•Vertical axis = voltage (mV)
3. ECG Waves & Their Meaning:
Wave Meaning
P wave Atrial depolarization
QRS complex.Ventricular depolarization
T wave Ventricular repolarization
PR Interval:
Time from atrial to ventricular activation
•Normal: 0.12 – 0.20 sec
QRS Duration:
•Normal: < 0.12 sec
QT Interval:
•Represents total ventricular activity
4. Heart Rate Calculation:
Method (300 Rule):
•Count large boxes between R waves
Large Boxes Heart Rate
1 300 bpm
Introduction:
Electrocardiography is a diagnostic method used to record the electrical activity of the heart. It
helps in detecting heart rhythm, rate, and abnormalities.
An ECG (Electrocardiogram) is essential in emergency, cardiac, and clinical settings.
1. Basic Principle of ECG:
The heart produces electrical impulses that travel through:
•SA node (natural pacemaker)
•AV node
•Bundle of His
•Purkinje fibers
These impulses are recorded as waves on ECG paper.
2. ECG Paper Basics:
Small Box:
•0.04 seconds
•1 mm
Large Box:
•0.20 seconds
•5 small boxes
Important:
, •Horizontal axis = time
•Vertical axis = voltage (mV)
3. ECG Waves & Their Meaning:
Wave Meaning
P wave Atrial depolarization
QRS complex.Ventricular depolarization
T wave Ventricular repolarization
PR Interval:
Time from atrial to ventricular activation
•Normal: 0.12 – 0.20 sec
QRS Duration:
•Normal: < 0.12 sec
QT Interval:
•Represents total ventricular activity
4. Heart Rate Calculation:
Method (300 Rule):
•Count large boxes between R waves
Large Boxes Heart Rate
1 300 bpm
