12 - Practical ECG methods

Question 1

What are the electrodes on an ECG?

Answer 1

the sticky pads on the chest or limbs

Question 2

What are the leads?

Answer 2

digital representations of depolarisation in the heart

a view of electrical heart activity

Question 3

What does a flat line mean on an ECG?

Answer 3

no electrical activity

DOESN’T mean the heart has stopped, may be perpendicular (not moving towards either electrode)

Question 4

What do normal deflections look like?

Answer 4

up or down

Question 5

What 2 things do the shape and amplitude of the wave on an ECG tell us?

Answer 5

• speed of conduction

- how much muscle mass is present

Question 6

What is the base line called?

Answer 6

the isoelectric line

Question 7

How many leads are there in an ECG?

Answer 7

12

this allows us to get different perspectives of the heart and see any blood vessel damage

Question 8

What are bipolar leads?

Answer 8

directly compare between the electrodes on the limbs (both are physical electrodes)

Question 9

What are unipolar leads?

give the names of the ones used in ECG

Answer 9

augmented and chest leads
aVR, aVL, aVF
use 1 electrode as 1 point of comparison and the other is a virtual electrode (made by averaging 2 other points)

Question 10

How is the QRS axis calculated?

Answer 10

• requires 2 leads - the angle of the leads needs to be 90°
• calculate the net deflection of each lead
• use displacement and trig to calculate the angle
• the result is the angle of the triangle NOT the cardiac axis angle

Question 11

What is the normal QRS axis range?

Answer 11

-30° to 90°