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ESA 2 CVS > Electrocardiogram (7) > Flashcards

Electrocardiogram (7) Flashcards

0
Q

What is an electrocardiogram?

A
  • Electrodes on the body’s surface that are able to detect the changing electrical field in the myocardium.
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1
Q

What is meant by the myocardium?

A
  • Large mass of muscle undergoing electrical changes at the same time which generates a large changing electrical field.
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2
Q

What does a depolarisation and repolarisation look like on an ECG?

A
  • Depolarisation: upwards signal

- Repolarisation: downwards signal

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3
Q

What are the 4 main rules regarding ECGs?

A
  • Depolarisation towards an electrode: upwards going signal
  • Depolarisation away from electrode: downwards going signal
  • Repolarisation towards an electrode: downwards going signal
  • Repolarisation away from electrode: upwards going signal
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4
Q

What affects the amplitude of signals?

A
  • How much the muscle’s depolarising

- How directly towards the electrode the excitation is moving

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5
Q

What is the P wave?

A
  • Atrial depolarisation: small upwards deflection
  • Small as little muscle involved
  • Upwards as moving towards electrode
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6
Q

What is meant by the Q wave?

A
  • Excitation spreads halfway down the septum then out across the axis of the heart: small downwards deflection
  • Downwards as moving away
  • Small as not moving directly away
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7
Q

What is meant by the R wave?

A
  • Depolarisation spreads through the ventricular muscle along an axis slightly to the left of the septum: produces a large upward deflection
  • Upward because moving towards electrode
  • Large as lots of muscle
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8
Q

What is a S wave?

A
  • Depolarisation spreads upwards to the base of the ventricles: small downwards deflection
  • Downwards as mainly away
  • Small as not directly away
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9
Q

What is meant by T wave?

A
  • Ventricular repolarisation spreads through the ventricular myocardium in the opposite way to depolarisation: medium upwards deflection
  • Upwards because moving away
  • Medium as turning in different cells dispersed
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10
Q

What has happened to the atrial repolarisation deflection?

A
  • Lost in QRS complex
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11
Q

What happens to the signals as you move the electrodes to different positions?

A
  • Directions and amplitude of waves change predictably
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12
Q

Why do we need to put electrodes in different positions?

A
  • Allows detection and localisation of abnormal patterns of electrical activity.
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13
Q

How are signals amplified?

A
  • Invert negative input
  • Adds to positive input
  • Then amplifies total
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14
Q

What are the positions of the positive and negative electrode, equivalent positive, and the total for lead 1

A
  • Positive electrode top left
  • Negative electrode top right
  • Equivalent positive of negative bottom left
  • 2 together = looking from left side.
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15
Q

What are the positions of the positive, negative, equivalent positive and total for lead 2?

A
  • Positive electrode bottom left
  • Negative electrode top right
  • Equivalent positive of negative bottom left
  • Total: 2 views from bottom left (apex)
16
Q

What are the positions of the positive, negative and equivalent positive and total for lead 3?

A
  • Positive bottom left
  • Negative top left
  • Equivalent positive bottom right
  • Total: straight up/from bottom
17
Q

What is the best way of getting a picture of the ECG?

A
  • 12 leads

- 12 different views

18
Q

What is meant by an augmented lead?

A
  • 2 negatives connected
  • Convert 2 negatives to one first
  • Then convert to a positive and add to a real positive to give one view
19
Q

What are the 6 different limb leads in order starting from top right.

A
  • AVL
  • Lead 1
  • Lead 2
  • AVF
  • Lead 3
  • AVR
20
Q

What are the chest leads and how are they arranged?

A
  • V1 to V6
  • V1: right 4th rib
  • V2: left 4th rib
  • V3: slightly below V2
  • V4-V6 across rest of chest to left axilla
21
Q

What are the main things that you look for in an ECG?

A
  • Rate
  • Rhythm
  • Axis
  • P wave
  • P-R segment
  • QRS complex
  • Q-T interval
  • T wave
22
Q

At what rate does an ECG run at?

A
  • Each large square is equivalent to 0.2s

- 300 squares per minute

23
Q

What is the rhythm related to?

What are the different components that should be looked out for in an ECG?

A
  • Relates to the timing of components of ECG
  • Rhythm is regular/irregular
  • Relationship between atrial and ventricular depolarisation
24
Q

When may the P wave be absent in an ECG?

A
  • Atrial fibrillation
25
Q

What is the P-R interval and how long should it last?

A
  • Time taken for impulse to reach ventricles

- (0.12-0.2s)

26
Q

How is the P-R interval affected in 1st/2nd/3rd degree heart block?

A
  • 1st: prolonged
  • 2nd: erratic (sometimes absent, sometimes not)
  • 3rd: no relationship between p wave and QRS complex
27
Q

What does the QRS complex tell us?

A
  • Tells us about the axis of heart and pattern of conduction through ventricles
28
Q

What is the electrical axis of the heart?

A
  • Relates to main spread of depolarisation through ventricle wall: R wave
29
Q

If there’s hypertrophy in a ventricle wall what may this cause?

A
  • More muscle in left: left shift

- More muscle in right: right shift

30
Q

How do you find the electrical axis?

A
  • Lead with smallest and most equiphase deflection
  • So net deflection’s 0 indicating that electrical axis must run at right angles to the view.
  • Normally lead 2
31
Q

Why may the QRS complex change shape?

A
  • Determined by route of spread of depolarisation
  • Damage to conducting pathways alters route of spread
  • Example: Bundle branch block
32
Q

Why may perfusion problems occur?

A
  • Partial occlusion of coronary arteries

- Acute occlusion by thrombus

33
Q

What may a partial occlusion of coronary arteries lead to?

A
  • Intermittent poor myocardial perfusion

- Angina - pain during exercise

34
Q

What is acute occlusion of thrombus?

A
  • Death of part of myocardium

- Myocardial Infarction

35
Q

What may show that an MI is in process on an ECG?

A
  • S-T elevation
  • Pathological Q waves
  • Inverted T waves
36
Q

What would a Q wave look like in an MI?

A
  • More than 0.04s (1 small square) wide
  • x>2mm
  • Remains after other changes resolve

ESA 2 CVS (16 decks)

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