20 Coronary Heart Disease, Angina, MI, Embolism

Question 1

How does coronary artery disease present

Answer 1

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

Question 2

What are the lifestyle risk factors and how do they increase the risk of coronary artery disease

Answer 2

Smoking
Alcohol
Physical inactivity
Unhealthy diet
These contribute to hyperlipidaemia, obesity, diabetes and hypertension which contribute to 80% of CHD

Question 3

What is the world mortality rate caused by CHD

Answer 3

17 million per year

Question 4

True or false: CHD is the leading cause of death in developing countries but not developed countries

Answer 4

False, it is the world leading cause of death in both

Question 5

What is the incidence of CHD

Answer 5

88,000 CHD deaths / year

Question 6

True or false: The death rate of CHD in the UK is decreasing

Answer 6

True, but the UK has higher death rates than the rest of Europe

Question 7

Is the incidence of angina in the UK increasing or decreasing

Answer 7

Increasing

Question 8

What is the pathophysiology of myocardial ischaemia

Answer 8

Mismatch between myocardial oxygen supply and metabolic demand. The heart is unable to increase flow to match increased demand

Question 9

What are prearteriols and arterioles sensitive to

Answer 9

Prearterioles: flow/BP
Arterioles: metabolites

Question 10

What is the role of coronary arteries and how does the coronary circulation ensure this

Answer 10

Maintains flow under a range of perfusion pressure

Epicardial artery and intramyocardial arteries are in concert. If there is coronary stenosis in the epicardial region, intramyocardial arteries will dilate to maintain flow under the control of autonomic nervous system

Question 11

At what extent of stenosis will the coronary flow be affected and severely reduced

Answer 11

50% stenosis will cause a small reduction in flow

70% stenosis will cause a huge disruption in flow

Question 12

Define coronary flow reserve

Answer 12

The ratio between resting coronary flow rate to the flow rate under maximal stress

Question 13

State the stages of ischaemic cascade

Answer 13

Normal function
Perfusion abnormality
Regional diastolic dysfunction
Regional systolic dysfunction
Ischaemic ECG changes
Angina pectoris

Question 14

What is angina pectoris

Answer 14

Caused by exertion or emotional stress
Discomfort in shoulder, chest, jaw, arms and back
Treatment: rest

Question 15

Why is investigation of angina important

Answer 15

To confirm diagnosis
To calculate the risk of future adverse CVD
Choice of test dependent on clinical probability of CHD

Question 16

What are the investigations for CHD

Answer 16

Non-invasive/functional: exercise ECG
Non-invasive/anatomical: CT coronary angiogram
Invasive/functional: CFR
Invasive/anatomical: coronary angiogram

Question 17

What is the management for CHD

Answer 17

1. Prevent progression of atherosclerosis
   - education
   - lifestyle modification
   - statins, aspirin
2. Reduce myocardial oxygen demand
   - HR: beta blocker, Ca2+ channel antagonist
   - Wall stress: ACE inhibitor (captopril)
3. Improve blood supply
   - Vasodilators: nitrates
   - Revascularisation (PCI and CABG)

Question 18

What are the mechanisms underlying MI

Answer 18

1. Disrupted blood flow: coronary plaque erosion and rupture, dissection
2. Myocardial cell death by: apoptosis and oncosis

*plaque rupture more frequently seen

Question 19

Differentiate between two types of thomboses

Answer 19

White thrombus:
- Occurs in arteries/higher pressure
- Platelet rich
- Benefit from antiplatelet therapy
Red thrombus:
- Occurs in veins/lower pressure
- Fibrin rich and trapped erythrocytes
- Benefit from anticoagulant

Question 20

What is the universal definition of acute MI

Answer 20

Rise or fall of cTn I/T AND one of the below:

• symptoms suggestive of ischaemia
• New ST-T changes or LBBB on ECG
• Development of pathological Q wave
• Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
• Identification of intracoronary thrombus on angiography or at autopsy

Question 21

State two types of acute coronary syndromes and how are they differentiated

Answer 21

Acute MI: ST elevation due to complete blockage of coronary artery

Unstable angina: No ST elevation (ST depressoin or T inversion or even normal ECG) due to partial occlusion which embolises distal capillaries

Question 22

How does acute MI develop

Answer 22

Necrotic zone initiates from intramyocardium. Particularly, subendocardium is most at risk and is important in heart function

Question 23

Differentiate between transmural endocardial infarction and sub-endocardial infarction

Answer 23

Transmural endocardial infarction: entire muscle

Sub-endocardial infarction: only inner muscle wall

Question 24

How much cell death does reperfusion injury account for

Answer 24

40%

Question 25

What is the mechanism of left ventricular wall remodelling

Answer 25

1. Infarct thinning, elongation, expansion
2. LV dilatation
   – Minimise the increase in wall tension
   – Maintains cardiac output
3. Non-infarcted myocardium
   – LVH + myofilament dysfunction
   – Altered electromechanical coupling
   – Myocardial fibrosis
   – Apoptosis
   – Inflammation

Question 26

What are the consequences of left ventricular remodelling

Answer 26

• Increased wall tension
• Increased myocardial oxygen demand
• Reduce myocyte shortening
• Dysynchronous depolarisation/contraction
• Reduced subendocardial perfusion
• Mitral regurgitation

Question 27

What is the management to stabilise plaque

Answer 27

Mechanical: stent
Drug: ACE inhibitor (captopril) and statins

Question 28

What is are the drugs for LV remodelling

Answer 28

Beta blockers
ACE inhibitors
Angiotensin receptor blockers
Aldosterone receptor antagonists

Question 29

What is the management for thrombolytic burden

Answer 29

Thrombectomy
Anti-coagulent (Factor Xa inhibitor)
Anti-platelets

Question 30

What is the management for embolism

Answer 30

Thrombectomy
Fibrinolysis
Antiplatelet