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Study Notes - Cardiology > *ECG > Flashcards

*ECG Flashcards

1
Q

What is the name for a recording of the potential differences between distant sites on the body surface?

A

Electrocardiogram (measured by an electrocardiograph)

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2
Q

What is the wave of depolarisation across the heart and what does this create?

A

Positive charge moving towards the ventricles leaving behind a negative charge
Creates an electric dipole (which generates an electrical field) - the dipole represents an electrical vector

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3
Q

In terms of leads, when is the measured potential difference greater?

A

When lead axis is parallel to the direction of the dipole- zero when perpendicular

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4
Q

What determines the magnitude of the electrical vector?

Direction?

A 
Magnitude = mass of cardiac muscle
Direction = overall activity of the heart
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5
Q

Where does each of the standard limb leads (I, II, III) run?

At what degree does each lead look at the heart?

A 
I = RA (-)  - LA (+) (0 degrees = 3 o'clock)
II = RA (-) - LL (+) (+60 degrees = 5 o'clock)
III = LA (-) - LL (+) (+120 degrees = 7 o'clock)
RL = earthed
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6
Q

In terms of depolarisation, what causes an upwards deflection on the ECG and what causes a downwards deflection?

A 
Upwards = deflection moving towards recording electrode
Downwards = deflection moving away from recording electrode
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7
Q

What causes the P wave? Duration?

A

Action potential upstroke through the atrial muscle

0.08 - 0.1 secs

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8
Q

What causes QRS complex? duration

What causes each of the separate waves?

A

Action potential upstroke throughout the ventricular muscle

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9
Q

T wave cause?

A

Ventricular repolarisation moving in a direction opposite to that of depolarisation accounts for the usually observed upwards deflection

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10
Q

What causes the PR interval? Duration

A

Largely AV nodal delay (0.12 - 0.2 secs) - different from PR segment

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11
Q

What causes the ST segment?

A

Maintained ventricular depolarisation

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12
Q

What causes the TP interval?

A

Diastole

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13
Q

What are the augmented limb leads and where does each link?

A 
aVR = RA (+) to [LA and LF] (-)
aVL = LA to [RA and LF]
aVF = LF to [RA and LA]
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14
Q

What cause the direction of the Q wave on an ECG?

A

Left to right depolarisation of the inter-ventricular septum moving slightly away from the recording electrode

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15
Q

What causes the direction of the R wave on an ECG?

A

Depolarisation of the main ventricular mass moving towards the recording electrode

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16
Q

What causes the direction of the S wave on an ECG?

A

Depolarisation of ventricles at the base of the heart moving away from the recording electrode

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17
Q

What causes the direction of the T wave on an ECG?

A

Ventricular repolarisation moving in a direction opposite to that of depolarisation

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18
Q

What is another name for the standard limb leads?
What is another name for augmented limb leads?
What is another name for chest (precordial) leads?

A

Bipolar limb leads
Unipolar limb leads
Unipolar leads (wilson’s leads)

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19
Q

What type of polarity do the augmented limb leads have?

A

Goldberger’s method: one +ve electrode, 2 others linked as -ve electrodes

20
Q

How do the augmented limb leads differ in direction to the standard limb leads?

A

30 degrees away

21
Q

What is the name given to the normal triangle that the standard limb leads are arranged in?

A

Einthoven’s triangle

22
Q

How does the appearance of II and aVR compare?

A

aVR is practically an upside down version of II

23
Q

What degrees are classified as a normal axis for the heart? (between)

A

-30 - +90

24
Q

What range of degrees are classified as a left axis?

A

-30 to -90

25
Q

What range of degrees are classified as a right axis?

A

+90 to 180

26
Q

What range of degrees are classified as a far right axis?

A

-90 o 180

27
Q

At what degree is aVL present at?

A

-30

28
Q

At what degree is aVR present at?

A

-150

29
Q

At what degree is aVF present at?

A

+90

30
Q

Where is V1 placed?

A

Right sternal edge, 4th intercostal space

31
Q

Where is V2 placed?

A

Left sternal edge, 4th intercostal space

32
Q

Where is V3 placed?

A

Halfway between V2 and V4

33
Q

Where is V4 placed?

A

Apex beat

34
Q

Where is V5 placed?

A

Anterior axillary line

35
Q

Where is V6 placed?

A

Mid-axillary line

36
Q

What lead are the ECG waves best seen in?

A

Lead II

37
Q

What happens during the ST segment?

A

Ventricles contract (systole)

38
Q

What happens during the TP segment?

A

Ventricles relax (diastole)

39
Q

What is the normal QT interval?

A

0.36-0.44 seconds at a heart rate of 60 (needs to be corrected for heart rate)

40
Q

How many seconds does each small block represent when the paper speed = 25mm/sec?

A

0.04 seconds (and 1mm of amplitude)

41
Q

Equation for calculating HR from ECG?

A

300/number of large squares between beats

42
Q

What is the ECG strip?

A

Prolonged recording of one lead (usually lead II) which allows you to detect rhythm disturbances

43
Q

How many wires does an ECG have?

A

10 (despite there being 12 leads)

44
Q

What test should be done if stable angina is suspected?

A

An exercise ECG (ECG changes are usually absent during rest)

45
Q

How to calculate the heart rate from an ECG if the heart rate is irregular?

A

Count the number of QRS complexes in 30 large squares and multiply by 10

Study Notes - Cardiology (25 decks)

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