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CVS > 8. ECG > Flashcards

8. ECG Flashcards

1
Q

In what direction do the ventricles depolarise? What does this enable?

A

Endocardium to epicardium

Coordinated contraction of atria and ventricles

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2
Q

Where in the heart has the fastest rate of depolarisation?

A

Sinoatrial node

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3
Q

Depolarisation occurs from the SA node, through atria, AV node, bundle of his, purkinje system from apex to base of ventricles. What order does repolarisation occur in?

A

Reverse order

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4
Q

What does an ECG record?

A

Changes on the extracellular surface of cardiac myocytes during wave of depolarisation and repolarisation

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5
Q

If depolarisation is moving directly towards the electrode, what is seen on an ECG tracing?

A

Tall positive complex

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6
Q

If depolarisation is moving at 90 degrees to the electrode, what is seen on an ECG tracing?

A

Biphasic or no complex

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7
Q

If depolarisation is moving directly away from the electrode, what is seen on an ECG tracing?

A

Deep negative complex

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8
Q

If repolarisation is moving directly towards the electrode, what is seen on an ECG tracing?

A

Deep negative complex

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9
Q

If repolarisation is moving directly away from the electrode, what is seen on an ECG tracing?

A

Tall positive complex

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10
Q

Do you see SA node depolarisation on an ECG?

A

No, is insufficient signal to register on surface ECG

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11
Q

What happens in atrial depolarisation? What wave does this produce on an ECG?

A

Spreads along atrial muscle fibres and intermodal pathways, towards AV node.
P wave

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12
Q

What is the AV node

A

Fibrous ring between atria and ventricles, which is only crossed by the bundle of His

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13
Q

What is seen on an ECG in depolarisation of the AV node?

A

Isoelectric (flat line) segment

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14
Q

In what direction does the septum depolarise? So what does this produce on an ECG?

A

Left to right

Small downward deflection, Q wave

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15
Q

What is seen on an ECG during depolarisation of the apex and free ventricular wall?

A

Tall positive complex - R wave

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16
Q

What will happen to the R wave on an ECG if the LV is hypertrophied

A

R wave will be correspondingly taller

17
Q

What happens at the end of depolarisation? What does this produce on an ECG?

A

Depolarisation spreads up towards the base of the ventricles

Small downward deflection, S wave

18
Q

What happens in ventricular repolarisation? What is seen on an ECG tracing?

A

Begins on epicardial surface in opposite direction of depolarisation.
Upward wave as repolarisation is moving away from electrode, T wave

19
Q

What components of an ECG may not be seen in all leads?

A

QRS

20
Q

What 3 views in the vertical place (limb leads) look at the inferior surface of the heart? What are they best to detect?

A

II, III and aVF

Problems in inferior heart surface eg muscle necrosis due to inferior MI

21
Q

What 2 views in the vertical plane (limb leads) look at the left side of the heart?

A

I and aVL

22
Q

What 1 view in the vertical place (limb leads) looks at the right side of the heart?

A

aVR

23
Q

What do the V1 and V2 chest leads (horizontal plane) look at?

A

RV and septum

23
Q

What do the V3 and V4 chest leads (horizontal plane) look at?

A

Apex and anterior ventricle walls

24
Q

What do the V5 and V6 chest leads (horizontal plane) look at?

A

LV

25
Q

How much time does one large square on an ECG represent?

A

0.2 seconds

26
Q

How much time does one small square on an ECG represent?

A

0.04 seconds

27
Q

How would you calculate the heart rate if the rhythm is irregular on an ECG?

A

Count number of QRS complexes in 6 seconds (30 large squares) and then multiple by 10

28
Q

How long should the PR interval (time from start of P to R) normally be?

A

0.12-0.2 seconds

29
Q

How long should the QRS interval normally be?

A

Less than 0.12 seconds

30
Q

How long should the QT interval normally be on an ECG?

A

Depends on heart rate, approx 0.45 seconds

31
Q

What should you think about when considering if an ECG shows normal sinus rhythm?

A 
Regular?
HR?
P waves? Are they upright in leads I and II?
PR normal?
Every P followed by a QRS?
Every QRS preceded by a P?
QRS normal?
32
Q

What is sinus bradycardia?

A

Sinus rhythm with rate less than 60/min

33
Q

What is sinus tachycardia?

A

Sinus rhythm with rate over 100/min

CVS (14 decks)

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