ECG its definition, basis, leads placement and nurses responsibility

1. ECG
Srividhya. N

2. Introduction
The contraction of any muscle is associated with electrical changes called
“depolarization” and these changes can be detected by electrolytes attached to
the surface of the body

3. History of ECG
Willem Einthoven is the father of ECG.

4. Definition
An ECG is a graphic record of the electrical impulses that are generated by
depolarization and repolarization of the myocardium

5. Indications
● Coronary artery disease
● Angina
● Myocardial infarction
● Cardiac dysrhythmias
● Cardiac enlargement
● Electrolyte imbalances
● Inflammatory heart disease
● Effects of drugs on heart

6. ECG machine
It is a
galvanometer and
electrodes with six
limb leads and six
chest leads
recorded on a
graph paper

7. ECG paper
Each small square is 0.04 seconds
One large square is 0.20 seconds

8. ECG pattern
Baseline : isometric line
Positive deflection - above the baseline
Negative deflection - below the baseline

9. Leads
Bipolar limb leads - LI, LII,LIII
Unipolar Augmented leads - AVR,AVL,AVF
Chest leads- V1,V2,v3,V4,V5,V6

10. Einthoven’s triangle
It is an imaginary equilateral triangle formed by connecting the points and
junctions of right and left superior extremities and left inferior extremity

11. Leads positioning
Limb leads

12. Leads positioning - Chest leads
● V1- 4rth intercostal space right sternal border
● V2- 4rth intercostal space left sternal border
● V3- Midway between V2 and V4
● V4- 5th intercostal space left midclavicular line
● V5- 5th intercostal space left anterior axillary line
● V6- 4rth intercostal space left mid axillary line

13. Normal ECG
● P wave - Atrial contraction
● QRS complex- ventricular depolarization
● T wave - ventricular repolarization- usually
positive
● ST segment Normally not elevated >1mm
or depressed >0.5mm
● PR interval - 0.12 to 0.20 sec (time taken
for impulses to move from atria to
ventricles)
● QT interval - 0.36 to 0.45 (Time required
for ventricular depolarization and
repolarization)

14. Heart rate
Heart rate can be calculated by looking at a 6 second ECG strip(in regular
rhythms)
The heart rate can be calculated when R R interval is regular
HR = 1500/ Number of small squares in one RR interval
Or 300 / Number of big squares

15. Nurses responsibilities
● No preparation needed
● Explain procedure and reassure the client
● Nurses must be able to detect abnormal rhythm
● Abnormal rhythms are recorded and reported immediately
● Ensure good contact between skin and electrodes by applying gel
● Client should lie flat and relaxed . avoid any movements
● Bystanders should be kept away from the patients
● Leads should not come in contact with ornaments or gadgets
● Machine should be checked for proper working condition
● Machine should be properly grounded
● Nurse should ensure proper placements of leads
● No other electrical equipments should work during the procedure.