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Cardiographer > Electrocardiographic Instrumentation, Technique and ECG Interpretation > Flashcards

Electrocardiographic Instrumentation, Technique and ECG Interpretation Flashcards

1
Q

The standard recording speed for an ECG is…

A

25mm per second

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2
Q

Each large square represents… seconds

A

0.2s

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3
Q

Each small square represents… seconds

A

0.04s

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4
Q

How many small squares are there per large square?

A

5

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5
Q

5 large squares is equal to… seconds + cm

A

1 second (2.5cm of trace)

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6
Q

1 large square is equal to… cm

A

0.5cm

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7
Q

1 small square is equal to… mm

A

1mm

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8
Q

A signal of 1mV should cause the graph to rise…

A

1cm (2 large squares)

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9
Q

Events of the electrical activity of the heart:

A
  1. SA node initiates atrial depolarisation
  2. Wave of depolarisation spreads across both atria
  3. AV node slows the signal, from the atria to ventricles
  4. The wave of depolarisation spreads to the bundle of His, down the bundle branches to both ventricles
  5. Depolarisation spreads throughout the myocardium of the heart via the purkinje fibres
  6. Once depolarisation has occurred repolarisation of the ventricles begins
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10
Q

PR interval is from…

A

the start of the P wave to the start of the R wave

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11
Q

PR interval represents…

A

atrial depolarisation and the time it takes for the electrical activity to pass from the SA node, through the AV node and various bundles, to the ventricular muscle

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12
Q

The normal PR interval is…

A

0.12 – 0.20 seconds (3-5 small squares)

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13
Q

QRS duration is from…

A

the start of the QRS complex to the end of the QRS complex

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14
Q

QRS duration represents…

A

the amount of time taken for signal to spread throughout ventricles

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15
Q

The normal QRS duration is…

A

0.10 seconds (2.5 small squares)

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16
Q

QT interval is from…

A

the start of the QRS complex to the end of the T wave

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17
Q

QT interval represents…

A

The time it takes the electrical activity to depolarise the ventricles and repolarise the ventricles

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18
Q

The normal QT interval duration is…

A

0.35-0.45s (should not be more than half of the R-R interval)

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19
Q

ST segment is from…

A

the end of the S wave to the start of the T wave

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20
Q

When rhythm is regualar, heart rate can be calculated by…

A

Counting the number of large squares between two consecutive R waves, and divide 300 by this number

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21
Q

When the rhythm is irregular, heart rate can be calculated by…

A

counting the number of intervals between QRS complexes in 10 seconds (25 cm of recording paper = the rhythm strip) and multiplying by six

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22
Q

Leads that view the inferior surface =

A

II, III and aVF

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23
Q

Leads that view the anterior surface =

A

V1 – V4

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24
Q

Leads that view the lateral surface

A

I, aVL, V5 and V6

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25
Q

V1 and aVR look through…

A

the right atrium into the cavity of the left ventricle

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26
Q

Lead I views…

A

the lateral wall of the left ventricle

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27
Q

Lead II views…

A

the diaphragmatic surface (inferior)

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28
Q

Lead III views…

A

the diaphragmatic surface (inferior)

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29
Q

Lead aVR views…

A

lateral wall of the right atrium

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30
Q

Lead aVL views…

A

lateral wall of left ventricle

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31
Q

Lead aVF views…

A

the diaphragmatic surface (inferior)

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32
Q

Lead V1 views…

A

the septal wall of the ventricles

33
Q

Lead V2 views…

A

the septal wall of the ventricles

34
Q

Lead V3 views…

A

the anterior surface

35
Q

Lead V4 views…

A

the anterior surface

36
Q

Lead V5 views…

A

the lateral wall of the left ventricle

37
Q

Lead V6 views…

A

the lateral wall of the left ventricle

38
Q

When the R wave is greater than the S wave, this means the signal is generally ………, and therefore moving ……. the lead.

A

positive

towards

39
Q

When the S wave is greater than the R wave, it means the signal is ………. and moving ……… from the lead.

A

negative

away

40
Q

When the depolarisation wave is moving at right angles to the lead, then R and S waves will be….

A

equal size

41
Q

voltage gain is set to…

A

10mm/mV

42
Q

Cardiac axis:

A

Direction of spread of the signals flows along lead II = mostly positive signal wave. whilst signal travels away from aVR so signal in mostly negative

Can determine direction of the cardiac axis by looking at leads I-III. A normal cardiac axis will cause a positive signal in all 3 of these leads (because signal is travelling laterally and inferiorly, which is measured by these leads). Deflection is greatest in lead II.

43
Q

The heart valves:

A

dictate when blood flows and in which direction blood flows in the heart

valves ensure the blood flows in the correct direction

44
Q

Valve from right atrium to right ventricle =

A

tricuspid valve

45
Q

Valve from left atrium to left ventricle =

A

mitral valve

46
Q

valve from right ventricle to pulmonary artery =

A

pulmonary valve

47
Q

valve from left ventricle to aorta =

A

aortic valve

48
Q

left side of heart carries…

A

oxygenated blood (from the lungs via the pulmonary vein and goes out to the rest of the body via aorta)

49
Q

right side of heart carries…

A

deoxygenated blood (from the body via the vena cava and going to lungs via pulmonary artery)

50
Q

Aortic valve is composed of:

A

Aortic annulus
Aortic root
Cusps/Leaflets
Commissures

51
Q

Coronary arteries =

A

Supply blood to the heart muscle

Originate from the ascending aorta

The coronary arteries wrap around the outside of the heart and small branches dive into the heart muscle to bring it blood

52
Q

Left main coronary artery:

A

supplies blood to the left side of the heart muscle (the left ventricle and left atrium).

The left main coronary divides into branches:

  1. The left anterior descending artery branches off the left coronary artery and supplies blood to the front of the left side of the heart.
  2. The circumflex artery branches off the left coronary artery and encircles the heart muscle. This artery supplies blood to the outer side and back of the heart.
53
Q

Right coronary artery:

A

supplies blood to the right ventricle, the right atrium, and the SA and AV nodes

The right coronary artery divides into smaller branches, including the right posterior descending artery and the acute marginal artery.

Together with the left anterior descending artery, the right coronary artery helps supply blood to the middle or septum of the heart.

54
Q

Vena cava

A

carries oxygen-depleted blood into right atrium from body

The superior vena cava carries blood from the upper body (head and arms) to the heart.
The inferior vena cava brings blood up from the lower body (stomach, pelvis and legs) to the heart.

55
Q

Pulmonary artery

A

carries oxygen-depleted blood out of the right ventricle (via the pulmonary valve)

56
Q

Pulmonary vein

A

carried oxygenated blood from the lungs into the left atria

57
Q

Aorta

A

carries oxygenated bloodroot of the left ventricle to the body, via the aortic valve

It starts at the heart and travels up the chest (ascending aorta) and then down into the stomach (descending aorta).

58
Q

Capillaries

A

These blood vessels connect very small arteries (arterioles) and veins (venules).

Capillaries have thin walls that allow oxygen, carbon dioxide, nutrients and waste products to pass into and out of cells.

59
Q

Pericardium is…

A

a protective, fluid-filled sac that surrounds the heart and helps it function properly.

60
Q

The pericardium also covers…

A

the roots of the major blood vessels as they extend from the heart (aorta, pulmonary artery, pulmonary veins, superior and inferior vena cava)

61
Q

Functions of the pericardium:

A

Cushioning heart from outside forces and pressure

Holding heart in place

Keeping heart from expanding too much and filling with too much blood

Protecting heart from infections

Providing lubrication to reduce friction between heart and surrounding tissues

62
Q

What are the layers of the pericardium?

A

Fibrous pericardium = outermost layer of the pericardium (attaches to the great vessels (at the top of heart) and to the central tendon of the diaphragm (at the bottom of heart), at the front of the chest, ligaments connect this layer to the breastbone)

Serous pericardium = inner layer of the pericardium (produces pericardial fluid that lubricates the heart as it beat)

63
Q

The pericardial cavity:

A

the space between the two layers of the serous pericardium

This space holds the pericardial fluid.

64
Q

Conditions and disorders that affect the pericardium include:

A

Pericarditis: Inflammation of the pericardium.

Constrictive pericarditis: A condition in which the pericardium becomes too thick or stiff.

Pericardial effusion: A build-up of fluid in the pericardium.

Cardiac tamponade: A dangerous condition that happens when fluid builds up and puts pressure on the heart = prevents it from filling properly.

65
Q

Right side of heart supplies blood to the…

A

lungs

66
Q

Left side of heart supplies blood to the…

A

body = works at higher pressure = left ventricle wall is thicker

67
Q

Cardiac cycle:

A
  1. Ventricular diastole (ventricular filling)
  2. Atrial systole (ventricular filling)
  3. ventricular systole (iso-volumetric contraction phase)
  4. ventricular systole (ejection phase)
  5. ventricular diastole (iso-volumetric relaxation phase)
68
Q
  1. Ventricular diastole (ventricular filling)
A

Blood flows from the vena cava/pulmonary vein into the atria. The tricuspid and mitral valves are open, so blood then flows into the ventricles (most of the blood that goes into the ventricles does not require atrial contraction). This causes the heart to swell up.

69
Q
  1. Atrial systole (ventricular filling)
A

Blood flow from the atria to the ventricles is aided by the contraction of the atria. There is a delay between atrial contraction and ventricular contraction.

70
Q
  1. Ventricular systole (isovolumetric contraction phase)
A

When the ventricles are filled with blood (high ventricular pressure), they start to contract. As all valves are now closed there is no change in volume in the heart.

71
Q
  1. Ventricular systole (ejection phase)
A

Eventually as the pressure in the ventricles exceeds that in the aorta and pulmonary veins, blood is ejected from the ventricles as the aortic and pulmonary valves are open.

72
Q
  1. Ventricular diastole (isovolumetric relaxation phase)
A

As the blood leaves the heart the ventricles relax. As all valves are now closed there is no change in volume in the heart.

73
Q

Regulation of contraction is dependent on…

A

cellular mechanisms, in particular the activity of ion channels in the membrane of cardiac cells and smooth muscle cells.

74
Q

SA node

A

Collection of specialised (pacemaker) cells in the top of the right atrium (just beneath the epicardium) close to the entrance point of the superior vena cava.

The pacemaker region spontaneously fires action potentials which spread through the atria them to contract.

These cells generate a cardiac rhythm at a rate of between 60-100bpm.

75
Q

AV node

A

Specialised cells bundled together to form a node within the wall of the interatrial septum (between the atria and the ventricles).

Responsible for transmitting impulses that originate in the SA node to the ventricles

Act as an electrical gatekeeper between the atria and ventricles by introducing a delay between atrial and ventricular excitation, allowing for efficient ventricular filling.

Has the ability to slightly delay electrical signals, thus coordinating the contraction firstly of the atria and secondly of the ventricles. The delay ensures sufficient time for the atria to empty before the contraction of the ventricles.

The cells can also generate their own electrical impulses: functions as a backup pacemaker in case of SA node dysfunction or advanced AV block = protects the ventricles from rapid atrial arrhythmias

76
Q

Bundle of His

A

The AV node is connected to a network of fibres that run down the interventricular septum and then through the walls of the ventricles. The initial segment of this pathway is called the bundle of His.

Takes the impulse through to the ventricles – divides into bundle branches.

77
Q

Left and right bundle branches

A

The bundle of His divides into the left and right bundle branches.

Both the left and right bundle branches give off numerous branches known as Purkinje fibres that supply the ventricular myocardium.

78
Q

Purkinje Fibres

A

At the end of the bundle branches there are smaller electrical conducting fibres that take the electrical current into the heart muscle cells.

Cardiographer (5 decks)

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