2.1 Cardiac Ischaemia and Angina

Question 1

What is the difference between MI and unstable angina?

Answer 1

MI: Areas of myocardium have undergone infarction (death)
Unstable angina: Areas of the heart are ischaemic, meaning starved of oxygen, but not necessarily dead

Question 2

A patient’s cardiomyocytes increase in oxygen demand due to light exercise. How will this affect coronary flow, arterial oxygen saturation, and venous oxygen saturation?

Answer 2

Coronary Flow: Increase
Arterial O2: Remains roughly the same
Venous O2: Decerases (because consumption has increased)

Question 3

Would a 50% stenosis be likely to have clinical consequences on coronary flow?

Answer 3

No; however, larger obstructions (such as ~70% or greater) would increase flow by a much greater margin.

Question 4

What factors determine the haemodynamic significance of a stenotic lesion?

Answer 4

• Length of lesion and extent of narrowing
• Myocardial oxygen demand
• Degree of compensatory vasodilation

Question 5

How can endothelial dysfunction contribute to myocardial ischaemia (besides long-term atherogenesis)?

Answer 5

• Impaired vasodilator release
• Decline in antithrombotic properties of vasodilators

Question 6

List some structural abnormalities than can cause coronary artery dysfunction

Answer 6

• Decreased vasodilatory capacity
• Abnormal vascular remodelling
• Extrinsic vascular compression

Question 7

List some functional abnormalities than can cause coronary artery dysfunction

Answer 7

• Microvascular spasm
• Endothelial dysfunction

Question 8

What is the predominant substrate for energy production normally used by the myocardium?

Answer 8

Fatty acids

Question 9

Explain, in reasonable detail, the metabolic disruption that occurs during myocardial ischaemia

Answer 9

• Decreased oxygen
• Oxidative phosphorylation decreased
• Accumulation of pyruvate, which is converted into lactate
• Lactic acid builds up
• Stimulation of pain pathways

Question 10

Define stable coronary artery disease

Answer 10

A pathological process characterised by atherosclerotic plaque accumulation in the epicardial arteries, whether obstructive or non-obstructive.

Question 11

Explain referred pain

Answer 11

These spinal nerves carry sensory information from somatic receptors in the chest, neck, and arm. The visceral sensory neurons in the heart are connected to these somatic sensory neurons, and so - when the heart produces nociceptive input - a patient will feel this pain in the corresponding external surface locating to the specific spinal nerve.