Week 10 - Chest Pain and Ischaemic Heart Disease

Question 1

Which muscle is most vulnerable to ischaemia?

Answer 1

Sub-endocardial muscle - last part of heart muscle to receive blood supply (most vulnerable to ischaemia)

Question 2

When does coronary blood flow occur? Why?

Answer 2

Diastole - coronary arteries compressed during systole

Question 3

Outline what factors determine myocardial oxygen supply.

Answer 3

1. Coronary blood flow: perfusion pressure (diastolic BP), coronary artery resistance
2. O2 carrying capacity of blood

Question 4

Outline what factors determine myocardial oxygen demand.

Answer 4

1. Heart rate
2. Wall tension: pre-load, after-load
3. Contractility

Question 5

State the modifiable risk factors for coronary artery disease.

Answer 5

1. Hyperlipidaemia
2. Cigarette smoking
3. Diabetes mellitus
4. Hypertension
5. Lack of exercise, obesity, diet low in fruit and veg, psychosocial factors

Question 6

Outline the steps involved in thrombus formation.

Answer 6

1. Vulnerable/unstable plaques: fibrous cap can undergo fissuring or rupturing
2. Exposing blood to thrombogenic material in necrotic core
3. Platelet “clot” followed by fibrin thrombus

Question 7

Outline the exercise stress ECG Test.

Answer 7

1. Patient connected to ECG machine
2. Graded exercise on a treadmill until target HR reached (i.e. max exercising) OR
3. Chest pain/ECG changes/other problems: arrhythmias, drop in BP

Question 8

What amount of ST depression is sufficient for a positive stress exercise ECG test?

Answer 8

ST depression if greater than or equal to 1 mm (horizontal/down sloping)