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Term 1 > Week 113: Syncope > Flashcards

Week 113: Syncope Flashcards

1
Q

What happens during diastole?

A

The heart fills

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2
Q

What happens during systole?

A

The heart contracts

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3
Q

Where does the cardiac cycle start?

A

The electrical activation of the sino-atrial node

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4
Q

Where is the sino-atrial node located?

A

High in the right atrium

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5
Q

What does the activation of the sino-atrial node do?

A

Initiates a wave of depolarisation that spreads over the right atrium and into the left atrium via the Bundle of Bachmann

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6
Q

How does the wave of depolarisation initiated by the sino-atrial node go into the left atrium?

A

Via the bundle of Bachmann

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7
Q

What does the electrical activation of the atria lead to?

A

Coordinated atrial pumping

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8
Q

Where else does the electrical impulse from the sino-atrial node travel?

A

To the atrioventricular node

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9
Q

What is special about the atrioventricular node?

A

It is the only electrical connection between the atria and the ventricles

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10
Q

What does the AV node do once the signal has reached it?

A

Delays the electrical impulse

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11
Q

Why does the AV node delay the electrical impulse?

A

To allow the atrial systole to finish before ventricular systole starts

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12
Q

How long is the delay at the AV node?

A

150-200ms

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13
Q

What happens after the delay at the AV node?

A

The electrical impulse crosses the AV node and enters the specialised conducting tissue of the ventricles

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14
Q

What are the specialised conducting tissues of the ventricles?

A

The bundle of His, bundle branches, and their divisions

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15
Q

How long does it take the specialised conducting tissue to distribute the electrical impulse throughout the ventricle?

A

50-60ms

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16
Q

What does the electrical signal spreading through the ventricles do?

A

Go into the myocytes and initiate contraction

Myocyte-myocyte spread of signal is much slower than through the specialised conducting tissue

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17
Q

What are myocytes?

A

Muscle cells or fibre found in muscle tissue

Develop from myoblasts by myogenesis

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18
Q

What accounts for most leads observing the left ventricle having a positive deflection?

A

The specialised conducting tissue is sub-endocardial so the wave of excitation spreads endocardially to epicardially and then onto an observing electrode

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19
Q

What happens after depolarisation?

A

The action potential of the myocytes has a prolonged plateau phase, during which the ventricular myocytes are contracted and a little current flows

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20
Q

What happens after the plateau phase?

A

Repolarisation: the intracellular level of calcium falls rapidly and the myocytes relax, starting diastole

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21
Q

Where does repolarisation start and end?

A

Starts: sub-epicardially
Ends: sub-endocardially

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22
Q

Where are the four limb leads in an ECG positioned?

A

Red: right arm
Yellow: left arm
Green: left leg
Black: right leg

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23
Q

Where is VI placed?

A

Red: fourth intercostal space, right sternal border

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24
Q

Where is V2 placed?

A

Yellow: fourth intercostal space, left sternal border

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25
Q

Where is V3 placed?

A

Green: midway between V2 and V4

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26
Q

Where is V4 placed?

A

Brown: fifth intercostal space, left mid-clavicular line

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27
Q

Where is V5 placed?

A

Black: level with V4, left anterior axillary line

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28
Q

Where is V6 placed?

A

Violet: level with V4, left mid-axillary line

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29
Q

What is lead I?

A

The voltage between the positive left arm electrode and right arm electrode

I = LA - RA

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30
Q

What is lead II?

A

The voltage between the positive left leg electrode and right arm electrode

II = LL - RA

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31
Q

What is lead III?

A

The voltage between the positive left leg electrode and left arm electrode

III = LL - LA

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32
Q

What is the aVR lead?

A

aVR = - (I + II)/2

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33
Q

What is the aVL lead?

A

aVL = I - II/2

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34
Q

What is the aVF lead?

A

aVF = II - I/2

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35
Q

How long is each large square recording?

A

200ms

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36
Q

How long is each small square recording?

A

40ms

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37
Q

How do you work out the heart rate from an ECG?

A

300/number of squares = rate

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38
Q

How do you work out the axis deviation?

A
  • aVF +ve, lead I +ve: normal
  • aVF -ve, lead I +ve: left axis deviation
  • aVF +ve, lead I -ve: right axis deviation
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39
Q

What does it mean when there is a bifid P-wave?

A

M shaped P-wave implies mitral valve (lead II)

  • Left atrial enlargement/hypertrophy
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40
Q

What does an increased QRS amplitude imply?

A

Right ventricular hypertrophy

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41
Q

What does left axis deviation imply?

A
  • Left ventricular hypertrophy: more ventricular muscle to depolarise
  • Damage to conducting tissue: delaying depolarisation
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42
Q

What does right axis deviation imply?

A
  • Right ventricular hypertrophy

- Disease in left ventricular conducting tissue

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43
Q

What can cause PR interval lengthening?

A

Sleep

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44
Q

What can cause PR interval shortening?

A

Exercise (high heart rate)

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45
Q

What causes a prolonged (>200ms) but regular PR interval?

A

First degree heart block

> 200ms

46
Q

What happens in third degree heart block?

A

A complete dissociation between the P-wave and QRS complex

AV dissociation

47
Q

What are the two types of second degree heart block?

A

Mobitz I - Wenckebach’s Phenomenon

Mobitz II

48
Q

What happens in Wenckebach’s Phenomenon/Mobitz I?

A

The PR interval becomes gradually longer each beat until a QRS is dropped then the pattern restarts

49
Q

What happens in Mobitz II?

A
  • Prolonged PR interval

- Absent QRS at regular intervals

50
Q

How does atrial fibrillation appear on an ECG?

A

Like a blunt saw

51
Q

What causes a shortened PR interval?

A

Wolff-Parkinson-White Syndrome

Lown-Ganong-Lavine Syndrome

52
Q

How does ventricular tachycardia appear?

A

Very fast high waves

53
Q

What produces a prolonged QRS of around 160ms?

A

Right bundle branch block

  • Often a RSR pattern too
54
Q

What produces a long QRS of around 200ms?

A

Left bundle branch block

55
Q

Give four causes of bradycardia

A

Athlete
Cold
Beta blockers
Hyperthyroidism

56
Q

Give two examples of tachycardia

A

Beta agonists

Fear

57
Q

Which X-ray is best for the heart?

A

PA chest xray

58
Q

What is the RR interval and what is its length?

A

The interval between an R wave and the next R wave

  • Usually 60-100 bpm
  • 600-1200ms
59
Q

What is the P wave and what is its length?

A

During normal atrial depolarisation the main electrical vector is directed from the SA node to the AV node and spreads between the atria

80ms

60
Q

What is the PR interval and what is its length?

A
  • Beginning of the P wave to the beginning of the QRS complex
  • Reflects the time the electrical impulse teak to travel from the SA node through the AV node and entering the ventricles
  • PR interval is a good estimate of AV node function

120-200ms

61
Q

What is the PR segment and what is its length?

A
  • Connects the P wave and QRS complex
  • The impulse vector is from the AV node to the bundle of His to the bundle branches then Purkinje fibres

50-120ms

62
Q

What is the QRS complex and what is its length?

A
  • Reflects the rapid depolarisation of the right and left ventricles
  • More muscle in ventricles than atria therefore QRS complex has higher amplitude than P wave

80-120ms

63
Q

What is the ST segment and what is its length?

A
  • Connects the QRS complex and the T wave
  • Represents the period when the ventricles are repolarised

80-120ms

64
Q

What is the T wave and what is its length?

A
  • Represents depolarisation of the ventricles
  • Beginning or QRS complex to the apex of the T wave is the refractory period
  • Final half of T wave is the relative refractory period

160ms

65
Q

What is the ST interval and what is its length?

A
  • End of the S triangle to the T wave

320ms

66
Q

What is the QT interval and what is its length?

A
  • Beginning of QRS complex to the end of the T wave

Up to 420ms in a heart rate of 60 bpm

67
Q

What is TLOC?

A

Transient loss of consciousness due to not getting blood to the brain

68
Q

What is syncope?

A

Unusual heart rhythm

69
Q

What are the main causes of TLOC?

A

Reflexes
Orthostatic (postural hypertension)
Cardiac arrhythmia (syncope)
Structural cardiac diseases

70
Q

What is vasovagal syncope?

A
  • Reflex TLOC
  • To do with the vagus nerve
  • Getting too warm
71
Q

What is situational syncope?

A
  • Reflex TLOC
  • Post cough
  • Post micturition/defecation
72
Q

What is orthostatic syncope?

A

Nervous system failures

73
Q

Give three structure disease examples of causes of TLOC?

A
  • Aortic stenosis: not good blood flow
  • Myocardial ischaemia: can be longer term
  • Aortic dissection: blood stops going in the right direction
74
Q

What options for monitoring TLOC are there?

A
  • Lying/standing BP: check immediately on standing and then 3 minutes later
  • Halter monitor
75
Q

How does blood flow through the heart?

A
  • The atria contract and the tricuspid and mitral valves open
  • Blood flows into the ventricles
  • Ventricles start to contract and the tricuspid and mitral valves close
  • Aortic and pulmonary valves open and blood shoots into the aorta and pulmonary artery
76
Q

How does the sympathetic system regulate the heart?

A

It speeds the heart up

77
Q

How does the parasympathetic system regulate the heart?

A

It slows down the heart

78
Q

What is the mean arterial pressure?

A

Diastolic (low BP) + (systolic-diastolic)/3

79
Q

What is the central venous pressure?

A

Usually quite low as the vein are expanded and act as a blood reservoir

80
Q

What happens to the pressure in veins and arteries when the heart beats?

A
  • Reduction in venous pressure
  • Increase in arterial pressure

Increase is higher than the decrease

81
Q

Why does the increase in arterial pressure occur when the heart beats?

A

Because the arterial system cannot expand as well as veins to cope with the volume

82
Q

What is the compliance of arteries?

A

20% that as of the veins

83
Q

What is the mean arterial pressure - what is trying to be measured?

A

cardiac output x peripheral resistance

84
Q

Where does the main drop in blood pressure occur?

A

Arterioles

85
Q

What are the vasa vasorum?

A
  • A network of small blood vessels that supply blood to larger blood vessels
  • They supply oxygen to the blood vessel
  • Supply the tunica interna/externa
86
Q

What are conduit arteries?

A

Arteries that don’t kink easily

87
Q

What is a major vessel that gives the Windkessel effect?

A

The aorta and its immediate branches (are elastic)

88
Q

Where does the major control of arterial flow occur?

A

Arterioles

89
Q

What passes through cell membranes and what has to go through cell junctions?

A
  • Oxygen and carbon dioxide can diffuse through cell membranes
  • Glucose has to pass through cell junctions
90
Q

What are veins?

A
  • Capacitance vessels that hole ⅔ of blood volume

- Become collapsed when blood is lost so as to get the arterial system to deal with blood loss

91
Q

How does venous return occur?

A
  • Mainly through muscle pumps: as exhale the lung collapses which sucks blood up towards the heart through creation of negative pressure in the thoracic cage
92
Q

What is a function syncytium?

A

A group of joined up cells that can communicate directly with one another

93
Q

What is an example of cells that are a function syncytium?

A

Cardiac myocytes

94
Q

What two things control the firing of the SA node?

A
  • Background sodium current and funny current: both currents result in gradual depolarisation of the heart
  • Central nervous system
95
Q

How does the cardiac action potential work?

A
  • Resting membrane potential -90mV
  • At -60mV, Na+ enters
  • Na+ channel closes at +20
  • Brief depolarisation
  • Plateau phase where Ca2+ released
  • K+ leaves
  • Ca2+ channels close and K= brings about depolarisation
  • Absolute refractory period
96
Q

What is a β1/β2 blocker?

A

Propranolol

97
Q

Give 3 β1-adrenoceptor antagonists

A

Atenolol
Metoprolol
Bisoprolol

98
Q

How do β-adrenoceptor antagonists work?

A
  • Produce a fall in blood pressure by decreasing cardiac output (initially)
  • After continuous treatment cardiac output returns to normal but blood pressure stays low
99
Q

What are common side effects of beta blockers?

A
  • Cold hands
  • Fatigue
  • Provocation of asthma
100
Q

What is propranolol used for?

A

Hypertension
Angina
Arrhythmias

101
Q

What are bisoprolol and metoprolol used for?

A

Hypertension

Heart failure

102
Q

What are diuretics used for?

A

Hypertension

103
Q

Give 3 examples of thiazide diuretics

A

Bendroflumethiazide
Chlortalidone
Spironolactone

104
Q

What is doxazosin and what is it used for?

A

α1-adrenoceptor agonist

Used in hypertension

105
Q

Give 2 examples of calcium channel blockers and how they work and what they are used for

A

Nifedipine
Amlodipine

Vascular smooth muscle tone is determined by the cytosolic calcium concentration

Used in hypertension and angina

106
Q

How do ACE inhibitors work?

A
  • Decrease circulating angiotensin II (a vasoconstrictor)

- Use results in a fall in peripheral resistance and a lowering of blood pressure

107
Q

What are ACE inhibitors used for?

A

Hypertension

108
Q

Give two examples of ACE inhibitors

A

Lisinopril

Enalapril

109
Q

What are common side effects with ACE inhibitors?

A
  • Dry cough
110
Q

What does adenosine do?

A
  • Stimulate A1-adenosine receptors

- Antiarrhythmic

111
Q

What does digoxin do?

A
  • Stimulate vagal activity causing release of Acetylcholine

- Antiarrhythmic

Term 1 (14 decks)

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