Myocardial Ischaemia (pathology)

Question 1

What is the definition of Mycordial ischaemia?

Answer 1

oxygen supply and demand mismatch due to reduction in coronary artery blood flow to myocardium due to obstructive coronary atheroma (obstructive plaque >70% lumen)

Question 2

What causes myocardial ischaemia (5)?

Answer 2

Atherosclerosis
Embolism
Coronary thrombosis
Aortic dissection
Arteritides (inflammation of arteries)

Question 3

What are arteritides?

Answer 3

Inflammation of arteries:
(Giant cell arteritis, Kawasakis disease, Syphilis) —> can affect ascending aorta
Clinically looks like angina

Question 4

What are the non-modifiable risk factors of myocardial ischaemia (5)?

Answer 4

Male sex
Age
Caucasian 
Post-menopausal female
Existing peripheral vascular disease

Question 5

What are the modifiable risk factors of myocardial ischaemia (6)?

Answer 5

Smoking 
Lifestyle (diet exercise)
Diabetes mellitus 
Hypertension
Hyperlipidaemia 
Previous CAD

Question 6

What are the symptoms of myocardial ischaemia?

Answer 6

Stable angina:
	- retrosternal pain
	- tightness, pressure, heaviness
	- radiation to neck, jaw, left arm
	- aggravated by exertion, emotional stress, heavy meal, cold weather
	- relieved by GTN or rest
Other symptoms on exertion (no pain)
	- SOB
	- excessive fatigue 
	- near syncope 
	- in elderly

Question 7

What are the signs of myocardial ischaemia (6)?

Answer 7

Tar stained fingers (smoker)
Obesity 
Xanthelasma & corneal Arcus
Arterial bruits of AAA
Absent/reduced peripheral pulses
Diabetic or hypertensive retinopathy

Question 8

What are the signs of conditions aggravating myocardial ischaemia (5)?

Answer 8

Pallor of anaemia
Tachycardia, tremor
Ejection systolic murmur (aortic stenosis)
Pansystolic murmur (mitral regurgitation)
Basal crackles, raised JVP, peripheral oedema (heart failure)

Question 9

What are the non-invasive diagnosis/investigations of myocardial ischaemia?

Answer 9

Bloods:
- FBC, lipids, fasting glucose, LFT, thyroid
CXR:
- show pulmonary oedema, rule out other causes of chest pain
12 lead ECG:
- normal >50% cases
- prior MI = pathological Q waves
- left ventricular hypertrophy = ST depression, high voltage
ETT:
- ECG at rest/on exertion
Myocardial perfusion imaging:
- radionuclide imagining at rest/under exercise or pharma stress (normal myocardium takes up tracer)
CT coronary angiography: GOLD standard
Echo stress ultrasound

Question 10

What are the invasive diagnosis/investigations of myocardial ischaemia?

Answer 10

Cardiac catheterisation/ coronary angiography:

- local anaesthetic 
- cannula in femoral/radial artery 
- catheter in coronary artery + IV contrast = x-ray visualisation

Question 11

What is the general treatment/ management for myocardial ischaemia?

Answer 11

Address the risk factors

Question 12

What is the medical treatment/ management to reduce O2 demand for myocardial ischaemia, in order to reduce progression?

Answer 12

Reduce progression:

- statins (atorvastatin, simvastatin)
- aspirin - 75mg-150mg/(clopidogrel, ricagrelor, prasugrel) - if allergic to aspirin
- ACEi (-pril) or ARBs (-sartan)

Question 13

What is the medical treatment/ management to reduce O2 demand for myocardial ischaemia, in order to relieve symptoms?

Answer 13

Symptom relief:

- Nitrates (GTN) - vasodilators which reduce preload & afterload
- beta blockers (Bisoprolol, atenolol) - reduce HR & contractility 
- Ca+ channel blocker:
	- central action (Diltiazem, Verapamil) - lower HR and preload
	- peripheral acting (Amlodipine, felodipine) - vasodilation, 		   lower BP & afterload
- IF channel blockers (ivabradine) - reduce HR
- K channel activators (nicorandil)
- INa blockers - Ranolazine

Question 14

What is the surgical treatment/management options to increase O2 supply for myocardial ischaemia?

Answer 14

PCI - stenting

CABG

Question 15

What is follow up of PCI stenting to increase O2 supply

Answer 15

PCI - stenting:

- Aspirin & clopidogrel 6months post op
- no prognostic benefit (only symptom management)
- continue to reduce progression meds

Question 16

What is process of CABG to increase O2 supply? What are requirements?

Answer 16

CABG

- multivessel disease
- left main stem disease
- disease not amendable to PCI
- may confer prognostic benefit?
- improves QOL
- reverse saphenous vein - free graft 
- LIMA - fixed arterial graft 
- radial arteries if varicose veins 
- (LIMA>saphenous vein)
- especially vein graft - continue reduce progression meds

Question 17

What is stenotomy? what do you need to watch out for?

Answer 17

Operation where incision made along sternum and chest ‘cracked open’
E.g. Cardiopulmonary bypasses

Watch out for:

- tamponade
- haemorrhage 
- wire infection
- sternal dehiscence 
- malunion

Question 18

What is tamponade? What are the signs?

Answer 18

Extra fluid building up around the heart

Tamponade signs:

• ↑ CVP, HR
• ↓ BP
• oliguria (low urine output)
• ↑↑ O2 demand
• metabolic acidosis
• > re-open chest

Question 19

What is a stenosis?

Answer 19

Narrowed vessel (often due to atherosclerosis)

Question 20

Where can the stenosis be relieved (4)?

Answer 20

Origin of coronary arteries
Coronary orifices at aortic root - OSTIAL STENOSIS
Downstream within coronary arteries
Discrete single point = stenting