L15 - ECG and Heart Blocks Flashcards Preview

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Flashcards in L15 - ECG and Heart Blocks Deck (59)
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1

Machine to measure ECG

Electrocardiograph

2

Read out of the ECG machine

Electrocardiogram

3

What does the ECG rely on

The summation of the cells repolarisation and depolarisation which gives resultant vectors

4

What about the hearts electrical activity can be sensed by predators

The small ammount which reaches the surface of the skin

5

Where are the three limb leads placed
What is this known as

Right arm, left arm, left leg
Einthovens triangle

6

Where is lead I

Right arm to left arm (+)

7

Where is lead II

Right arm to left leg (+)

8

Where is lead III

Left arm to left leg (+)

9

At rest what can be said about current flow
What is this point known as

No net current flow toward an electrode so no deflection on the ECG

10

What would net current flow toward an electrode cause

Upward deflection of the ECG trace

11

What deflection is seen when the atria depolarise

Net current movement toward II
Upward deflection in lead II

12

What deflection is seen when the septum is depolarised

Upward deflection in lead II
As current is moving in the same direction as lead II

13

What deflection is seen when the ventricles depolarise

Downward deflection in lead II
As current is moving in the opposite direction of lead II

14

Describe what is occuring at the P wave

Atrial depolarisation

15

Why is the p wave a relatively small deflection

Atria = small muscle mass = small deflection of the ECG trace

16

What does the flat line after the p wave represent

That atrial depolarisation is complete

17

Describe the QRS complex

Ventricular depolarisation begins at the apex
Large deflection as large muscle mass

18

Why is no wave seen for the repolarisation of the atria

Because it is masked by the QRS complex

19

What does the flat line after the QRS complex represent

Completion of ventricular depolarisation

20

What is happening to the blood at the flat line after the QRS complex

Blood being ejected from the ventricles into pulmonary and systemic circulations

21

What is shown by the t wave

Ventricular repolarisation - beginning at the apex
Occurs in the same direction as depolarisation so has an upward deflection

22

What is shown by the flat line after the t wave

Ventricular repolarisation is complete
Heart is ready for the next cycle

23

Normal PR interval

0.12-0.2

24

Normal QRS interval

0.08-0.1

25

Normal QT interval

0.4-0.43

26

Normal st interval

Average of about 0.32

27

What is shown by the U wave

Possible repolarisation of the purkinje fibres/papilalry muscles

28

What would a high P wave be indicative of

Atrial hypertrophy
(greater muscle mass of the atria so more t depolarise)

29

What would a low T wave be indicative of

Ventricular hypoxia (not enough O2)

30

What would a prolonged ST interval be indicative of

Acute myocardial infarction