CVS 7 (ECG) Flashcards Preview

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Flashcards in CVS 7 (ECG) Deck (45):
1

Name the tissue which electrically connects the atria, allowing an action potential to travel from the SAN to the left atria:

Bachmann's Bundle

2

Which surface of the heart tissue repolarises first?

Epicardial surface

3

How many electrodes are attached for a standard 12-lead ECG?

10 electrodes

4

How many leads are used for a standard ECG?

12 leads

5

Which limb lead looks from the apex of the heart to the right atria? Where are the electrodes placed?

Lead II
Right arm
Left leg

6

Why does depolarisation appear as a positive deflection from the baseline of an ECG?

Depolarisation moves towards positive electrode = positive deflection

7

Depolarisation moving away from an electrode would appear as what kind of deflection in an ECG?

Negative deflection

8

Repolarisation moving away from an electrode would appear as what kind of deflection in an ECG?

Positive deflection

9

What are the chest leads used in an ECG?

V1-6 (medial to lateral)

10

What does the P wave show?

Atrial depolarisation

11

What does the QRS complex show?

Ventricular depolarisation

12

What point of the ECG shows atrial repolarisation?

Lost in QRS complex

13

What does the T wave show?

Ventricular repolarisation

14

List some possible confounders for an incorrect ECG:

- Lead misplacement
- Sweat
- Hair
- Muscle contraction
- Interference

15

What is the name given to the normal rhythm of the heart?

Sinus rhythm

16

What is meant by 'sinus rhythm'?

The normal rhythm of the heart

17

Why does atrial depolaristaion produce a much smaller deflection in an ECG compared to ventricular depolarisation?

Atria have much less muscle compared to the ventricles, so less electrical activity needed to depolarise the muscle.

18

If electrical activity started at the AVN instead of the SAN, how would the P wave appear in an ECG?

Negative deflection (rather than positive deflection), as depolarisation moving away from electrode.

19

The muscle in the interventricular septum depolarises in which direction?

From left to right

20

What part of an ECG should be used to assess heart rhythm?

Rhythm strip

21

Which lead is used for the rhythm strip of an ECG?

Lead II

22

What is the constant speed an ECG runs at?

25 mm/s

23

How many large squares of an ECG corresponds to 1 sec?

5 large squares = 1 sec

24

How many large squares of an ECG corresponds to 1 min?

300 large squares = 1 min

25

How can you calculate heart rate from an ECG with a regular rhythm?

HR = 300 / number of large squares between 2 QRS complexes

26

How can you calculate heart rate from an ECG with an irregular rhythm?

Count number of QRS complexes in 6 sec (30 large squares) and x 10

27

How do you measure the RR interval?
What is the normal range of an RR interval?

Measure between peaks of R waves
0.6-1.2 secs

28

If the RR interval is decreased below the normal range, what can you tell about the heart rate?

Heart rate is increased above normal - tachycardic

29

How do you measure the QRS interval?
What is the normal length?

From start of Q wave to end of S wave
< 3 small boxes, or 0.12 secs

30

Wide QRS waves indicate that the ventricular depolarisations are not going through the normal purkinje system. List some causes of this:

- Left or Right bundle branch block
- Hyperkalaemia
- Na+-channel blockade
- Pacemaker

31

How do you measure the PR interval?
What is the normal length?

From start of P wave to start to Q wave
Between 3-5 small boxes, or 0.12 - 0.2 secs

32

What is indicated by a short PR interval?

Either:
- Atria have been depolarised from area close to AV node
- Abnormally fast conduction from atria to ventricles

33

What is the diagnosis if PR interval > 5 small squares, but normal P wave and QRS complex?

1st degree heart block

34

How do you measure the ST segment?

From the end of S wave to start of T wave

35

Elevated ST segment indicates:

- Acute MI
- Pericarditis

36

Depressed ST segment indicates:

- Ischaemia

37

How do you measure the QT interval?

From start of Q wave to end of T wave

38

List some causes of Long QT syndrome:

Medication - diuretics, anti-arrhythmics, cholesterol-lowerers etc
Hypokalaemia - excessive vomiting/diarrhoea, EDs, thyroid dysfunction

39

Torsades de pointes is a complication of which heart syndrome?

Long QT syndrome

40

How does Torsades de pointes lead to sudden syncope?

- Ventricular tachycardia
- Decreased CO
- Decreased blood to brain
- Sudden syncope

41

How can you diagnose atrial fibrillation from an ECG trace?

- Absent P waves
- Irregularly irregular QRS complexes

42

Name the 4 types of heart block:

- 1st degree
- Mobitz type 1 2nd degree
- Mobitz type 2 2nd degree
- Complete AV 3rd degree

43

Which type of heart block is characterised by progressive lengthening of the PR interval (leading to loss of a QRS complex)?

Mobitz type 1 2nd degree

44

Which type of heart block is characterised by a sudden dropped QRS complex (normal PR interval)?

Mobitz type 2 2nd degree

45

What type of heart block is characterised by the lack of relationship between the P waves and QRS complexes?

Complete AV 3rd degree