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My Cardiovascular > ECG > Flashcards

ECG Flashcards

1
Q

What is an ECG?

A

ECG is an indirect measurement of the electrical activity of the heart. Currents that are generated in the heart cause local currents in the surrounding tissues that can be picked up

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2
Q

What does an ECG give signals from?

A

ECG only gives a signal from large masses of tissue such as the atria and the ventricles but not the SA or AV nodes

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3
Q

What can an ECG also provide information about?

A

cardiac rate and rhythm, chamber size, electrical axis and myocardial infarction

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4
Q

What is the purpose of gap junctions?

A

gap junctions carry the electrical activity so there is current flow within the heart and within the surrounding tissues that generates tiny changes in potential which is what is recorded at the surface of the body

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5
Q

What is a dipole?

A

a vector which has magnitude and direction

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6
Q

What is the separation of charges in the heart?

A

negative in the atria and positive in the ventricles

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7
Q

What is the magnitude of the vector determined by?

A

mass of cardiac muscle involved in generation of the signal

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8
Q

What is direction of the vector determined by?

A

overall activity of the heart

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9
Q

What is an ECG lead vs a wire?

A

the lead is the imaginary line and the wire connects the electrode to the recording device

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10
Q

Which is the seeing electrode?

A

the positive electrode

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11
Q

What causes an upward movement in the ECG?

A

when depolarisation moves towards the recording electrode

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12
Q

What causes a downward movement in the ECG?

A

depolarisation moving away from the recording electrode

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13
Q

What causes no movement on the ECG?

A

no movement towards or away there will be no movement on the ECG so it is isopotential

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14
Q

What are the various lead of the ECG?

A

3 standard limb leads (1,2 and 3) which are bipolar
3 augmented voltage leads (aVR, aVL and aF) which are unipolar
Six chest leads (V1-V6) or precordial leads

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15
Q

Why are 12 leads needed?

A

Using 12 leads builds a picture of the heart so vertical (frontal/coronal) from leads 1-3 and aVR/L/F and horizontal with leads V1-6

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16
Q

Explain the views of the first three leads?

A

Lead 1 is RA (-) to LA (+)
Lead 2 is RA (-) to LL (+)
Lead 3 is LA (-) to LL (+)

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17
Q

What is the purpose of lead 2?

A

used to measure rhythm and is from an inferior direction

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18
Q

What is the P wave and what is its length?

A

P wave will have value less than 0.12s and is the depolarisation of the atria

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19
Q

What is the QRS complex and what is its length?

A

QRS complex normally has a duration of 0.1s and is the ventricles depolarising

20
Q

What is the direction of the Q wave? (L2)

A

The Q wave is from right to left causing the down Q wave

21
Q

What is the direction of the R wave? (L2)

A

The R wave is from left to right and down as the ventricles depolarise causing a tall and narrow R wave

22
Q

What is the direction of the S wave? (L2)

A

The S wave is from right to left and up so there is a downward movement as the depolarisation moves up toward the base

23
Q

What is the T wave?

A

upward movement as the ventricles repolarise (this is a negative signal moving away from the recording lead which is equivalent to positive moving towards the wire so the wave is upwards)

24
Q

What is the flat line on the ECG called?

A

the isoelectric line

25
Q

What is the PR interval?

A

The PR interval is from the start of the P wave to the start of the QRS complex and is the time it takes the SA node impulse to reach ventricles. It is determined by the AV node delay. It is normally around 0.12-0.2s.

26
Q

What is the ST segment?

A

The ST segment is the end of the QRS complex to the end of the T wave and is flat and isoelectric but, if it isn’t this is diagnostically important.

27
Q

What is the QT interval?

A

The QT interval is the time from the start of the QRS complex to the end of the T wave and is the time for the ventricles to depolarise and repolarise completely, if this is prolonged then this disturbance in cardiac rhythm could be due to drugs.

28
Q

Where do the augmented leads view from?

A

the corners of Einthoven’s triangle forming a hexaxial reference system with the other three leads

29
Q

Where do the precordial leads view the heart from?

A

a horizontal position

30
Q

What happens to the R wave as the Vs get bigger?

A

The R wave increases in size as the Vs get bigger until 4 because the vector lines up correctly with the lead

31
Q

Where are the V leads placed?

A

V1 is in fourth intercostal space immediately right of sternum
V2 is fourth intercostal space immediately left of sternum
V3 is midway between V2 and V4
V4 is in the fifth intercostal space in the midclavicular line
V5 in in the same horizontal level as V4 in the anterior axillary line
V6 is in the same horizontal level as V4 and V5 is the mid-axillary line

32
Q

How do you calculate the heart rate from an ECG?

A

Heart rate is 300/ number of large squares between beats so between R-R

33
Q

How many seconds are the large and small squares on an ECG?

A

Big square is 0.2s and small square is 0.04s

34
Q

Why is lead 2 recorded for a longer time?

A

allows you to calculate heart rate and cardiac rhythm

35
Q

Why are 12 leads necessary?

A

to determine the axis of the heart, look for any ST or T wave changes in relation to specific regions (ischaemic heart disease diagnosis) and any voltage criteria changes (chamber hypertrophy diagnosis)

36
Q

What is the process of checking if an ECG is normal? (6 steps)

A
  1. Verify name and date of birth
  2. Check date and time ECG was taken
  3. Check calibration of the ECG paper
  4. Determine the axis if possible
  5. Look at rhythm strip and ask:
    - Is electrical activity present?
    - Is the rhythm regular or irregular?
    - What is the heart rate?
    - P-waves present?
    - What is the PR interval?
    - Is each P-Wave followed by a QRS complex?
    - Is the QRS duration normal?
    1. Look at individual leads for voltage criteria changes or any ST or T-wave changes
37
Q

What does a normal ECG not exclude?

A

MI, intermittent rhythm disturbance or stable angina

38
Q

In what leads are the P waves most obvious?

A

lead 2 and V1

39
Q

How do you calculate the rate of an irregular rhythm?

A

count the number of QRS complexes in 30 squares and times by 10

40
Q

What are the inferior leads?

A

2,3 and aVF

41
Q

What are the anterior leads?

A

chest

42
Q

What are the leads to look at for axis?

A

1 and aVF

tea-pot

43
Q

How many seconds is one little square?

A

0.04

44
Q

How many seconds is a big square?

A

0.2

45
Q

What electrolyte imbalance is associated with QT interval prolongation?

A

Hypocalcemia

My Cardiovascular (13 decks)

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