ECG

Question 1

Do ECGs measure electrical voltage inside or outside the cell

Answer 1

outside

Question 2

What is a lead?

Answer 2

tracings that measure the electrical currents from 1 electrode to another

Question 3

How many leads are needed for a standard ECG?

Answer 3

12

Question 4

Why do we need 12 leads for an ECG? why not less?

Answer 4

to give a better 3D view of the electrical current in the herat

Question 5

How many electrodes are needed for an ECG? How many can we find on the limbs and how many on the chest?

Answer 5

10 total
4 on the limbs and 6 on the chest

Question 6

Does the electrical current go from + to - OR - to + ?

Answer 6

• to +

Question 7

What is a Bipolar lead? A Unipolar lead?

Answer 7

bipolar = the lead that exist between 2 physical electrode
unipolar = the lead that exist between 1 physical electrode (the + end) and the central terminal

Question 8

What is the central terminal?

Answer 8

The average of the right arm, left arm and foot electrodes

Question 9

How many Limb leads are there? How many Chest leads?

Answer 9

6 of each

Question 10

On this image, identify the leads

Answer 10

Question 11

Which limb leads are bipolar and which are unipolar?

Answer 11

bipolar = I II III
unipolar = aVR aVF aVL

Question 12

What is the Hexaxial reference system?

Answer 12

it is the system that happens when we overlay all the 6 limb leads

Question 13

True or false?
The limb leads allow us to see the frontal plane as well as the transverse plane whereas the chest plane only allows to visualize the frontal plane

Answer 13

false, the opposite is true

Question 14

What are the names of the 6 chest leads?

Answer 14

v1-6

Question 15

In each of these scenarios, explain how the voltmeter (ECG) would look like at that point in time

Answer 15

Question 16

When the depolarization is in the direction of the lead (from - to +) will the ECG curve be pointed upwards of downwards?

Answer 16

upwards

Question 17

In this scenario, how should the ECG curve look like?

Answer 17

Question 18

If the lead is perpendicular to the flow of current how will the ECG look like?

Answer 18

it will be flat, no deflection

Question 19

During repolarisation, why is the T wave upright and not upside down?

Answer 19

Because repolarisation happens backwards, from the apex to the atrium

Question 20

Associate the lead with the proper ECG

Answer 20

Question 21

What does the P wave represent?
The QRS complex?
The T wave?

Answer 21

P wave = atrium depolarisation
QRS = Ventricle depolarisation
T wave = ventricle repolarisation

Question 22

What is the sequence of depolarization in the heart

Answer 22

SA - AV - fibers

Question 23

True or false, there can be variations in the QRS complex

Answer 23

True

Question 24

name these QRS complexes

Answer 24

Question 25

Where can we find the ST segment?

Answer 25

between the S and T

Question 26

Where can we find the PR interval?

Answer 26

From before the P to before the QRS

Question 27

Where is the QT inteval

Answer 27

From the beginning of th QRS to the end of T

Question 28

On an ECG, what is the vertical axis? the horizontal axis?

Answer 28

vertical = voltage (1mm = 0.1mV) horizontal = time (1 small box = 40ms)

Question 29

What is an example of sequence of analysis on how to read an ECG

Answer 29

Question 30

Which lead is the best one to use and why?

Answer 30

Lead 2, since is face the direction of depolarization since the heart is oriented towards the left foot

Question 31

What does it mean when the P wave is upside down?

Answer 31

the ECG electrodes were put on backwards or there is an abnormal rhythm

Question 32

What is bradycardia? Tachycardia?

Answer 32

bradycardia = less than 60 beats/min tachycardia = more than 10 beats/min

Question 33

What are the 3 ways to measure heart rate on an ECG?

Answer 33

1) 1500/number of mm between beats 2)count off (300-150-100-75-60-50) on each of the big lines after and R peak 3) Counts the number of beats in a 3 sec marker, than do times 20