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Cardio > ECG > Flashcards

ECG Flashcards

1
Q

How does an ECG detect the excitation of the heart?

A

The wave of depolarisation and repolarization moves across the heart and sets up electrical currents which can be detected by surface electrodes

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2
Q

What is an ECG a record of?

A

Depolarisation and repolarisation cycle of cardiac muscle obtained from skin surface, the potential differences between distant sites on the body surface are detected by electrodes and coupled to the electrocardiograph

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3
Q

What are the 3 limb leads?

A
  • lead I RA-LA
  • lead II RA-LL
  • lead III LA-LL
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4
Q

What is the P wave?

A

Atrial depolarisation

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5
Q

What is the QRS complex?

A

Ventricular depolarisation (masks atrial repolarisation)

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6
Q

What is the T wave?

A

ventricular repolarisation

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7
Q

What is the PR interval?

A

Largely AV node delay

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8
Q

What is the ST segment?

A

Ventricular systole

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9
Q

What is the TP interval?

A

diastole

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10
Q

When do the atria contract?

A

between the P wave and QRS complex

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11
Q

What is the difference between the electrocardiograph and the electrocardiogram?

A

The electrocardiograph is the machine which the electrodes are coupled to and the electrocardiogram is the recording of the potential differences

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12
Q

What is meant by a dipole?

A

charges which are separated - a vector with components of magnitude and direction

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13
Q

What information is provided by an ECG?

A 
information on:
cardiac rate 
cardiac rhythm
chamber size
the electrical axis of the heart 
- main test for myocardial ischaemia and infarction
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14
Q

How is the magnitude of the electrical vector determined?

A

by the mass of cardiac muscle involved in the generation of the signal

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15
Q

How is the direction of the electrical vector determined?

A

the overall activity of the heart at any instant in time and varies over the cardiac cycle

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16
Q

What does the word lead refer to in an ECG?

A

an imaginary line between 2 or more electrodes, one of which electrodes is the recording (+ve) or seeing electrode

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17
Q

What happens on the electrocardiogram when the depolarisation moves towards the recording electrode?

A

Deflection is upwards

deflection downwards when depolarisation moves away

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18
Q

What 12 leads comprise a 12 lead ECG?

A

3 standard limb leads (I, II, III) these are bipolar
3 augmented voltage (aV) leads (aVR, aVL and aVF) these are unipolar
6 chest leads (V1 - V6) the precordial leads

19
Q

What view of the heart do the precordial leads provide?

A

A horizontal view

20
Q

What view of the heart do the limb leads and augmented voltage leads provide?

A

A vertical view

21
Q

In lead I which electrode is which?

A

RA is negative

LA is positive (recording)

22
Q

In lead II which electrode is which?

A

RA is negative

LL is positive (recording)

23
Q

In lead III which electrode is which?

A

LA is negative

LL is positive (recording)

24
Q

What direction does lead II see the heart from?

A

it looks at the heart from the inferior left position so is well placed as the depolarisation of the heart moves in this direction as well

25
Q

What is the normal duration of the P wave?

A

less than 0.120s

26
Q

What is the downward deflection before the R wave?

A

The Q wave

27
Q

What is the large upwards deflection?

A

R wave

28
Q

What is the downward deflection following the R wave?

A

S wave

29
Q

What is the T wave?

A

The wave of re polarisation moving away from the recording electrode

30
Q

What does the PR interval indicate?

A

From start of P wave until start of QRS
time for the SA node impulse to reach the ventricles
0.12-0.2s is normal duration

31
Q

What is the ST segment?

A

end of QRS to start of T wave should be isoelectric

32
Q

What does the QT interval indicate?

A

from start of QRS to end of T wave primarily reflects time for ventricular depolarisation and repolarisation

33
Q

How do augmented limb leads observe the heart?

A

there is one positive electrode viewing the others which are linked as -ve, the augmented leads see the heart from different angles than just the standard limb leads

34
Q

What is the hexaxial reference system?

A

The 6 different views of the heart seen in the vertical plane in a 12 lead ECG

35
Q

Where is the -ve electrode for the precordial leads?

A

Due to the way the electrodes on the precordium link up the -ve electrode is essentially in the centre of the heart

36
Q

What view do V1 and V2 look at the heart from?

A

from the right at the interventricular septum

37
Q

What view do V3 and V4 look at the heart from?

A

anterior view

38
Q

What view do V5 and V6 look at the heart from?

A

look at the lateral aspect - left ventricle

39
Q

Where do you position the chest leads?

A

V1 - 4th intercostal space, right sternal edge
V2 - 4th intercostal space, left sternal edge
V3 - midway between V2 & V4
V4 - 5th intercostal space, midclavicular line
V5 - same horizontal position as V4, anterior auxillary line
V6 - same horizontal level as V4, mid auxillary line

40
Q

What cardiac event is indicated by the ST segment?

A

ventricular systole

41
Q

What cardiac event is indicated by the TP segment?

A

Ventricular diastole

42
Q

Why are 12 leads used when 1 lead can determine rate and rhythm?

A

it allow us to
determine the axis of the heart in the thorax
look at ST segment and T wave changes in relation to specific heart regions
look at voltage criteria changes - to diagnose chamber hypertrophy

43
Q

6 steps to looking at an ECG

A
  1. Verify patient details: name and date of birth
  2. Check date and time ECG was taken
  3. Check the calibration of the ECG paper
  4. Determine the axis (if possible)
  5. Workout the rate and rhythm
  6. Look at individual leads for voltage criteria changes OR any ST or T-wave changes
44
Q

What are the 7 questions to workout rate and rhythm from the rhythm strip of the ECG?

A
  1. Is electrical activity present?
  2. Is the rhythm regular or irregular?
  3. What is the heart rate?
  4. P-waves present?
  5. What is the PR interval?
  6. Is each P-Wave followed by a QRS complex?
  7. Is the QRS duration normal?

Cardio (36 decks)

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