Microvascular angina

Question 1

Define Angina

Answer 1

Angina is defined as central chest pain Or discomfort that occurs for less than 10 minutes.
- upon exertion or emotional stress
- relieved by nitroglycerin
- typically angina is suggestive of obstructive coronary artery disease

Question 2

What is the current paradigm around ischemic heart disease

Answer 2

The current paradigm around ischemic heart disease is that obstructive atherosclerotic plaques are the main cause of myocardial ischemia.

Treatment of ischemic heart disease revolves around this paradigm.

but there is evidence to suggest that myocardial ischemia occurs in the absence of coronary artery disease.

there is a high prevalence of myocardial ischemia that is not caused by obstructive CAD

Question 3

Based on the current understanding, what are the main cause of angina

Answer 3

• Angina occurs when there is an increase in myocardial oxygen demand and reduced coronary blood flow (occurs due to coronary artery narrowings) —- leads to myocardial ischemia.
• Mainly: Obstructive: atherosclerotic plaques
• Functional problem: coronary artery spasms

Question 4

What is the other proposed mechansism of angina

Answer 4

Problems with the coronary microvasculature:

• increased resistance to blood flow in the coronary microvasculature can trigger myocardial ischemia.

1. Structural factors
   - arteriole remodelling
   - capillary rarefaction
2. Myocardial factors
   - LV hypertrophy
   - reduced diastolic time
   - amyloidosis

Question 5

why is the proposed coronary microvasculature not seriously considered as a mechanism for angina

Answer 5

• The coronary microvasculature has been elusive to conventional imaging for decades
• A normal angiogram does not exclude ischemia that is caused by the coronary microvessels

Question 6

What are the functional causes of microvascular angina?

Answer 6

1. Impaired vasodilation: - exertional angina
   caused by endothelial dysfunction (ED risk factors, CAD, oestrogen deficency, chronic inflammation)
   can also be due to endothelium indp. factors.
2. Inc. Vasoconstriction:
   endothelin-1
3. Microvascular spasms- rest angina

Question 7

What is the diagnostic criteria for microvascular Angina?

Answer 7

1. signs and symptoms of angina
2. Absence of obstructive coronary artery disease
3. Objective evidence of myocardial ischemia
4. Evidence that the coronary microvessels undergo spasm or are unable to dilate

Question 8

What are the treatment targets for Microvascular angina

Answer 8

1. Increased Microvascular oxygen demand- treat the HBP & tachycardia - Beta blockers
2. Microvascular spasms- Nitrates
   (we know if angina is due microvascular spasm if the angina happens at rest)
3. Impaired microvascular vasodilation - Nitrates.
   (we know if angina is due to impaired vasodilation if the angina happens upon exertion)
4. Heart metabolic abnormalities
5. effects of Ischemia: metformin
6. Inflammation: statins