CVS - ECGs

Question 0

What is the spread of depolarisation called?

Answer 0

Electrical axis

Question 1

What is the contraction of each cell triggered by?

Answer 1

Action potential

Question 2

What do the chest electrodes detect?

Answer 2

A change in membrane potential - ie during depolarisation or repolarisation

Question 3

What does depolarisation spreading towards an electrode look like in the ECG?

Answer 3

Upwards deflection

Question 4

What does depolarisation AWAY a from a positive electrode look like?

Answer 4

Downwards deflection

Question 5

What does repolarisation spreading towards a positive electrode look like?

Answer 5

Downwards deflection

Question 6

What does repolarisation away from a positive electrode look like on ECGs?

Answer 6

Upwards deflection

Question 7

What does the amplitude of the deflection depend on?

Answer 7

No of cells changing and how fast

How directly the wave is moving towards the electrode

Question 8

What does the p wave show?

Answer 8

Atrial depolarisation

Question 9

What does the QRS complex show?

Answer 9

Q = septal depolarisation (away from lead II electrode) 
R= main ventricle depolarisation (towards lead II electrode)
S = end ventricular depolarisation (away from lead II electrode)

Question 10

What does the T wave show on the ECG?

Answer 10

Repolarisation of the myocardium (away from lead II electrode)

Question 11

What is an amplifier?

Answer 11

They take the incoming signal on the negative electrode and invert it to positive before combing the two to form the view.

Question 12

Where does lead I,II And III view?

Answer 12

I - left side
II - apex view
III - bottom view

Question 13

What is an augmented lead?

Answer 13

A lead with two negative electrodes and one positive

So they convert the two -ves to a single one then invert it.

Question 14

How many leads in a full ECG?

Answer 14

12

Question 15

Where are the positions of the 10 electrodes in a 12 lead ECG?

Answer 15

One on each limb - RYGB (right arm, left arm, left leg, right leg) 
Then Remember Your Great Big Black Purse 
1- 4th ICS right side
2 - 4th ICS left side
3 - inbetween 2 and 4
4 - 5th ICS mid clavicular
5- between 4-6
6- 5th ICS mid Axilla

Question 16

How is rate seen in ECGs?

Answer 16

Each square - 0.2s

300 squares per minute

Question 17

When is the p wave absent?

Answer 17

In atrial fibrillation

Question 18

When is the P-R interval altered?

Answer 18

Prolonged in 1st degree heart block
Erratic in 2nd degree heart block
No relationship between this and QRS complex in 3rd

Question 19

What does the direction of main ventricular depolarisation (electrical axis) show?

Answer 19

It shows if there is any left/right Hypertrophy
Left axis deviation (left hypertrophy)- larger lead 1
Right axis deviation (right hypertrophy) larger lead 3

Question 20

What does the shape of the QRS complex show?

Answer 20

Tells you about any damage to the conducting pathway

I.e bundle branch block

Question 21

What does an ST depression show?

Answer 21

Partial coronary artery occlusion

Question 22

What does an ST elevation show?

Answer 22

Dying myocardium (MI)

Question 23

When are pathological Q waves seen?

Answer 23

Present in MI and remain even after resolve