20. Coronary Heart Disease Flashcards

1
Q

How does coronary artery disease present?

A

1) Sudden cardiac death
2) Acute coronary syndrome (acute MI, unstable angina)
3) Stable angina pectoris
4) Heart failure
5) Arrhythmia

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2
Q

Patients who present with sudden onset chest pain fall into what two categories?

A

Myocardial infarction

Progressive (unstable) angina

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3
Q

What can coronary artery disease lead to?

A

Heart failure

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4
Q

What does damage to the heart muscle lead to?

A

scar tissue formation within the myocardium

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5
Q

What does scar tissue in the myocardium a substrate of?

A

arrhythmia which in turn is the main substrate for sudden cardiac death

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6
Q

What is the number one cause of death world wide?

A

CVD

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7
Q

What type of angina has its incidence increasing?

A

Stable agina

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8
Q

How many cases of stable angina are there in the UK?

A

2 million

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9
Q

How many deaths per year are caused by CVD?

A

17 million

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10
Q

Define myocardial ischaemia

A

The mismatch between myocardial oxygen supply and demand. There is a primary reduction in blood flow where there is an inability to increase blood flow to match an increase in metabolic demand.

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11
Q

What are the main conductance vessels of the coronary circulation

A

Epicardial coronary arteries

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12
Q

What is the main function of the coronary circulation?

A

1) To make sure that over a wide range of perfusion pressures, flow remains constant -autoregulation
2) To make sure that coronary blood flow matches myocardial demand

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13
Q

How is coronary resistance divided in the large arteries?

A

50%

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14
Q

How is the coronary resistance divided in the smaller arteries and capillaries

A

50%

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15
Q

What is the resistance in the smaller arteries in the myocardium compared to the larger arteries outside?

A

Equal

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16
Q

What happens to the epicardial component when there is stenosis?

A

The resistance in the epicardial component increases

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17
Q

What happens to the intramyocardial resistance vessels when there is epicardial stenosis?

A

There is an increase in the diameter of the intramyocardial resistance vessels - thus decreasing the resistance in the intramyocardial component in maintain flow

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18
Q

What happens when the stenosis increases?

A

The resting blood flow remains unchanged up until a stenosis of greater than 70%.

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19
Q

What is the coronary flow reserve?

A

The ratio of

Resting blood flow:Blood flow achieved under maximal stress

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20
Q

Define coronary flow reserve

A

The ability to the coronary circulation to adapt to an increasing demand in the face of an increasing epicardial coronary stenosis

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21
Q

When does resting blood flow start to decrease?

A

At a stenosis of greater than 70% the coronary blood flow decreases rapidly

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22
Q

At what stage does the ability to maintain the requisite amount of flow needed under stressful conditions start to become impaired?

A

50% stenosis

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23
Q

Describe the symptoms of angina pectoris?

A

Tight feeling in the chest which can diffuse across the jaw, shoulders, back or arms

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24
Q

What can provoke angina pectoris?

A

Physical exertion, emotional stress or anxiety

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25
Q

How can you treat angina pectoris?

A

Use of an inorganic nitrate vasodilator which acts as a vasodilator. Reduces coronary resistance = increasing blood flow
It can also be relieved by rest

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26
Q

What is an example of a inorganic nitrate vasodilator?

A

glyceryl trinitrate

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27
Q

How would you perform a functional test for coronary artery disease?

A

Demonstrating that there is an imbalance between supply and demand

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28
Q

How would you perform a anatomical test for coronary artery disease?

A

Look at anatomical severity of the narrowing within the artery then make an inference about how it is compromising flow

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29
Q

Give examples for functional non-invasive tests for CHD?

A

Exercise ECG

Stress echo/cardiac MRI

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30
Q

Give examples for functional invasive tests for CHD?

A

CFR
Pressure wire

Both require ionising radiation

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31
Q

Give examples for anatomical non-invasive tests for CHD?

A

CT coronary calcium store
CT coronary angiogram

Both require ionising radiation

32
Q

Give examples for anatomical invasive tests for CHD?

A

Coronary angiogram

Both require ionising radiation

33
Q

How would you investigate stable CHD?

A

1) Confirm the clinical diagnosis
2) Assess the risk of future adverse cardiovascular events
3) Test for Coronary artery disease

34
Q

What do anatomical tests for CHD look for?

A

They look for narrowing of the arteries

35
Q

Describe how a catheter can be used to identify stenoses

A

The catheter can be inserted into the radial or femoral artery and moved along to the left main coronary artery to identify stenoses

36
Q

What are the three main strategies to treating coronary heart disease?

A

1) Prevent atherosclerosis progression and risk of death/MI
2) Reduce myocardial oxygen demand
3) Improve blood supply

37
Q

What are the ways of preventing atherosclerosis progression?

A

Education
Lifestyle modification
Asprin, statins, ACE inhibitors

38
Q

What are the ways of reducing myocardial oxygen demand?

A

Decreasing HR (beta blockers, Ca antagonists)
Decreasing wall stress (ACE inhibitors, Ca antagonists)
Metabolic modifiers

39
Q

What are the ways of improving blood supply?

A

Vasodilators (nitrates, Ca antagonists)

Revascularisation (PCI, CABG)

40
Q

What is the main medication used to treat CHD?

A

Aspirin
Statins
ACE inhibitors

41
Q

What is idea behind treating the symptoms of chest pain in CHD?

A

To improve symptoms you have to attend to the mismatch between supply and demand = Decrease the heart rate

42
Q

What is the result of increasing the time in diastole?

A

Improve coronary perfusion - this can be done with beta blockers

43
Q

How could you reduce the demand in terms of the myocardium?

A

Reduce the amount of work it has to do by using ACE inhibitors

44
Q

What does myocardial cell death arise from?

A

Interrupted blood flow to the heart

45
Q

What can cause interrupted blood flow to the heart?

A

Coronary plaque rupture
Coronary plaque erosion
Coronary dissection

46
Q

What are the mechanisms of myocardial death?

A

Oncosis

Apoptosis

47
Q

Define Oncosis

A

A form of accidental or passive cell death that is often considered a lethal injury

48
Q

In terms of thrombosis what can cause abnormal blood flow?

A

Artery stenosis

49
Q

What are the types of thrombus

A

White thrombus

Red thrombus

50
Q

Describe a white thrombus

A

o Platelet rich
o Common in arterial thrombosis (high pressure/turbulent circulation)
o Benefit from anti-platelet therapy

51
Q

Describe a red thrombus

A

o Fibrin rich with trapped erythrocytes
o Common in venous or low pressure situations (stasis)
o Benefit from anti-coagulant or anti-fibrinolytic therapy

52
Q

What is the shear stress in the narrow section of of the stenosis?

A

High shear stress - blood accelerates as you go through the stenosis

53
Q

What is shear stress of the areas before and after the narrow section of the stenosis?

A

Before the stenosis - Low shear stress

After the stenosis - Oscillatory shear stress

54
Q

What are low and oscillatory shear stress important for?

A

Mediating endothelial dysfunction nd acceleratign atherogenesis

55
Q

What is a key factor that triggers coagulation?

A

Tissue Factor

56
Q

How can tissue factor be made?

A

1) The cellular constituents of the atherosclerotic plaque
2) The heart muscle
3) Circulating inflammatory cells (humoral source)

57
Q

How does coronary thrombosis occur?

A

Tissue factor triggering a cascade of factor activation

58
Q

What is the universal definition of acute MI?

A

Detection of a rise or fall in a biomarker (troponin) with at least one value > 99th percentile reference limit and at least one of:

o Symptoms suggestive of ischaemia
o New or presumed new ST-T changes or LBBB on ECG
o Development of pathological Q waves on ECG
o Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
o Identification of intracoronary thrombus or angiography or autopsy

59
Q

What are the three isoforms of troponin?

A

I,T and C

60
Q

What isoforms of troponin specific to cardiac muscle?

A

I and T

61
Q

What happens to cardiac troponin during myocardial ischaemia?

A

It is released due to proteolytic cleavage hence it can be related to cardiac cell death

62
Q

After the onset of symptoms of MI what are the changes in troponin levels?

A

There is a rise and fall after a period of time

63
Q

After MI how long can troponin be detected for?

A

2 weeks

64
Q

What is the principle biomarker for MI?

A

Troponin

65
Q

What are types of acute coronary syndrome?

A

1) Complete blockage of a coronary artery due to an occlusive thrombus. These people present with ST elevation
2) Partial occlusion which embolises distally into the microcirculation resulting in myocardial cell death and troponin elevation. These people present with no ST elevation

66
Q

What is PPCI?

A

Primary Percutaneous Coronary Intervention.

67
Q

What is PPCI used for?

A

ST elevation acute coronary syndrome

68
Q

When there is an acute coronary arterial occlusion describe the spread of the necrosis

A

The myocardial necrosis zone will start at the inner layers of the myocardium and progress as a wave to the front.

69
Q

What is the main working layer of the heart?

A

subendocardium

70
Q

Describe the arterial flow starting from the outside of the heart

A

The arterial inflow is on the outer surface of the heart. It runs through the myocardium to get to the endocardium

71
Q

What is the pressure difference between the intramyocardial pressures and subepicardial pressures?

A

The intramyocardial pressures are greater than the subepicardial pressures

72
Q

What is reperfusion injury?

A

Is the tissue damage caused when blood supply returns to tissue after a period of ischemia or lack of oxygen

73
Q

What remodelling occurs post MI in the left ventricle?

A

Expansion of the heart muscle, thinning of the scar and impairment of heart function

74
Q

What are the risks of having left ventricular remodelling?

A

Increased risk of heart failure and arrhythmias

75
Q

Define embolism

A

An obstruction in a vessel due to a thrombus or other foreign material that gets stuck while travelling through the blood stream