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Cardiology > ECG theory and practice > Flashcards

ECG theory and practice Flashcards

1
Q

Where does depolarisation spread?

A

From the endocardium to the epicardium

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2
Q

Where does repolarisation spread?

A

From the epicardium to the endocardium

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3
Q

What is an ECG?

A

The ECG is a recording of potential changes, detected by electrodes positioned on the body surface, that allows the electrical activity of the heart to be monitored in a manner that is simple to perform

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4
Q

What is needed to generate detectable potential changes?

A

Large masses of cardiac tissue

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5
Q

What is extracellular current?

A

What generates the changes in potential which we can record on the body surface

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6
Q

What is an electrical vector?

A

the separation of charge with particular direction

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7
Q

Where does the wave of depolarisation spread in terms of the AV node?

A

Away from the AV node. Spreading to the left of the heart

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8
Q

What allows us to approximate the electrical axis of the heart?

A

The direction of the vector

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9
Q

What are the components of the electrical vector?

A

Magnitude and direction

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10
Q

What defection on the ECG does depolarisation generate moving towards the recording electrode?

A

upward deflection

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11
Q

What deflection on the ECG does depolarisation generate moving away from recording electrode?

A

downward deflection

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12
Q

What is the lead axis?

A

The imaginary line between two electrodes

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13
Q

What deflection on the ECG does depolarisation generate when there is no movement away or from recording electrode?

A

no deflection. Isopotential

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14
Q

What does the 12 lead ECG comprise of?

A
  • three standard limb leads
  • three augmented voltage leads
  • six chest leads
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15
Q

Which plane of the heart is seen in chest leads?

A

horizontal

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16
Q

What plane of the heart is see in limb and augmented leads?

A

vertical

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17
Q

What is lead I

A

RA to LA

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18
Q

What is lead II

A

RA to LL

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19
Q

What is lead III

A

LA to LL

20
Q

How is the P wave formed?

A

Atrial depolarization spreads from the SA node inferiorly and to the left - depolarization is moving towards the recording electrode (+ve) in lead II producing a (normally) upward deflection in this lead – the P wave

21
Q

What is a Q wave?

A

a downward (negative) deflection preceding an R wave is called a Q wave

22
Q

What is an R wave?

A

a deflection upwards (positive) is called an R wave, irrespective of whether, or not, it is proceeded by a Q wave – this can be confusing

23
Q

What is an S wave?

A

a downward (negative) deflection following an R wave

24
Q

How is a Q wave formed?

A

ventricular depolarization starts in the interventricular septum and spreads from left to right causing the small and narrow Q wave

25
Q

How is an R wave formed?

A

subsequently the main free walls of the ventricles depolarize causing a tall and narrow R wave

26
Q

How is an S wave formed?

A

finally, the ventricles at the base of the heart depolarize, producing a small and narrow S wave

27
Q

How is a T wave formed?

A

It is an upward (positive) deflection because the wave of repolarization is spreading away from the recording electrode (think of it as negative charge moving away from the recording electrode which is the equivalent of positive charge moving towards it!)

28
Q

What is a T wave?

A

ventricular repolarisation

29
Q

What is the normal length for the PR interval?

A

0.12-1.2 s

30
Q

What is the PR interval strongly influenced by?

A

the delay in conduction through the AV node. If conduction from AV node is fast, the PR interval decreases and vice versa

31
Q

True/False. the ST segment is normally isoelectric

A

True

32
Q

What is the normal length for the QT interval?

A

0.44 in males and 0.46 in females

33
Q

What is the recording electrode in augmented leads?

A

One recording lead other two linked.

34
Q

How mamy views of the heart do we have with a 12 lead ECG?

A

12 views, 6 from limbs and augmented and 6 from chest

35
Q

What are V1 and V2 looking at?

A

interventricular septum

36
Q

What are V3 and V4 looking at?

A

anterior of the heart

37
Q

What are V5 and V6 looking at?

A

lateral aspect (left ventricle) of the heart

38
Q

What is the first positive deflection in the QRS complex in V1?

A

R wave immediately followed by an S wave

39
Q

What happens to the R ad S wave as you move from V1 to V6?

A

progressive increase in R wave and progressive decrease in S wave

40
Q

How long does the P wave last?

A

0.08-0.1 s

41
Q

How long does the QRS complex last?

A

less than 0.1 s

42
Q

What is the ECG rhythm strip?

A

Prolonged recording of one lead. Usually lead II. It allows you to detect rhythm disturbance

43
Q

What are the 6 steps in analysing the ECG?

A 
1- verify patients name and DOB
2-check time and date when ECG was taken
3-Check the calibration of the ECG paper
4- determine the axis if possible
5-work out the rhythm 
6- look at individual leads for voltage criteria changes or any ST or T wave changes
44
Q

What are the 7 steps in determining rhythm?

A
  1. 1 Is electrical activity present?
  2. 2 Is the rhythm regular or irregular?
  3. 3 What is the heart rate?
  4. 4 P-waves present?
  5. 5 What is the PR interval?
  6. 6 Is each P-Wave followed by a QRS complex?
  7. 7 Is the QRS duration normal?
45
Q

true or False. Always use ECG over clinical judgement

A

False clinical judgment comes first

Cardiology (32 decks)

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