Ischaemic heart disease and atherosclerosis Flashcards
What is atherosclerosis?
The build-up of plaque in arteries
Give 7 risk factors for atherosclerosis
- Increasing age
- Tobacco smoking
- High serum cholesterol
- Obesity
- Diabetes
- Hypertension
- Family history
Describe the distribution of atheroscleroic plaques
- Within peripheral and coronary arteries
- Focal distribution along the artery length
- Distribution may be governed by haemodynamic factors
- The LAD and right coronary arteries commonly develop atherosclerosis
Describe the structure of a plaque
It is a complex lesion with a mixture of cell types - lipid, necrotic core, connective tissue, fibrous ‘cap’
How do atherosclerotic plaques form?
- Endothelial injury leads to endothelial dysfunction
- Chemoattractants attract leukocytes
- Leukocytes accumulate and migrate into the vessel wall so inflammation occurs
- LDLs can pass through the arterial wall in excess and accumulate in the intima
Name the inflammatory cytokines found in plaques
• Interleukins IL-1 (key one) IL-6 IL-8 • Interferons IFN-γ (a very strong pro-inflammatory agent) • TGF-β (involved in wound healing) • C reactive protein (linked with IL-6)
Describe the steps in the adhesion cascade of leukocyte recruitment
- Capture – 1st interaction of the leukocyte with the vessel wall/endothelial cell
- Rolling – cell slows down as it rolls along the vessel wall
- Firm adhesion to the vessels wall
- Transmigration across endothelial cells
In the adhesion cascade, what do selectins mediate?
The initial steps of the rolling stage
In the adhesion cascade, what do integrins and chemoattractants mediate?
Firm adhesion to the vessels wall and transmigration across endothelial cells
What are the key steps in the disease progression of atherosclerosis?
- Fatty streaks
- Intermediate lesions
- Fibrous plaques/advanced lesions
- Plaque rupture
When do fatty streaks appear in atherosclerosis?
At a very early age (<10yrs)
What do fatty streaks consist of?
Aggregations of lipid-laden macrophages and T lymphocytes within the intimal layer of the vessel wall
What are intermmediate lesions composed of?
- Foam cells
- Vascular smooth muscle cells
- T lymphocytes
What are foam cells?
Lipid laden macrophages
What are fibrous plaques/advanced lesions composed of?
- Smooth muscle cells
- Lipid core
- Necrotic debris
- Macrophages and T lymphocytes
- Foam cells
- RBCs
- Fibrin
What is the dense fibrous cap of atherosclerotic plaques made of?
Extracellular matrix proteins including collagen (strength) and elastin (flexibility)
How does plaque rupture occur?
- The plaque is constantly growing and receding
- The fibrous cap needs to be resorbed and redeposited in order to be maintained
- If balance shifts e.g. in favour of inflammatory conditions (increased enzyme activity) then the cap becomes weak and the plaque ruptures
- Basement membrane, collagen and necrotic tissue exposure as well as haemorrhage of vessel within the plaque
How would you treat coronary artery disease?
- Percutaneous coronary intevention (PCI)
- Aspirin
- Statins
- Antiplatelets e.g. clopidogrel/ticagrelor
Define angina
A condition marked by severe chest pain due the mismatch of oxygen supply and demand to the heart
Give 3 reasons for oxygen demand and supply imbalance to the heart
- Impaired blood flow by proximal arterial stenosis
- Increased distal resistance e.g. left ventricular hypertrophy
- Reduced oxygen-carrying capacity of blood e.g. anaemia
How is Ohm’s law applied relating to the biology of IHD and angina?
Pressure driving blood = blood flow x resistance from plaques and vessels
How is Poiseuille’s equation applied relating to the biology of IHD and angina?
- Change in pressure is inversely proportional to the 4th power of the radius
- Nothing happens until the diameter of stenosis reaches 70% then there is rapid demand
Give some predisposing factors to IHD and angina
- Smoking
- Sedentary lifestyle
- Obesity
- Hypertension
- Diabetes mellitus
- Family history
- Genetics
- Age
- Hypercholesterolaemia
Give 6 supply conditions which would exacerbate IHD/angina
- Anaemia
- Hypoxemia
- Polycythaemia
- Hypothermia
- Hypovolaemia
- Hypervolaemia
Give 5 demand conditions which would exacerbate IHD/angina
- Hypertension
- Tachyarrhythmia/tachycardia
- Valvular heart disease
- Hyperthyroidism
- Hypertrophic cardiomyopathy
Give 3 environmental factors which would exacerbate IHD/angina
- Cold weather
- Heavy meals
- Emotional stress
Give 5 cardiac symptoms which may suggest angina/IHD
- Chest pain
- Breathlessness
- Fluid retention
- Palpitations
- Syncope/pre-syncope
Describe features which suggest ischaemic heart pain
- Character = heavy, crushing
- Location = in the middle of the chest
- Provoking factors = cold weather, big meal, exercise
- Relieving factors = rest, GTN spray
- Associated symptoms = breathlessness
- Associated risk factors = smoking, etc.
Give 7 differential diagnoses of IHD/angina
- Pericarditis/myocarditis
- PE
- Chest infection/pleurisy
- Dissection of the aorta
- Gastro-oesophageal problems e.g. reflux, spasm, ulceration
- MSK problems
- Psychological – anxiety
How would you treat angina/IHD?
- Reassure patient
- Tackle key lifestyle factors e.g. smoking, weight
- Advice for emergency situations
- Medication and drugs
- Revascularisation
Name some types of drugs/medication that you might give in IHD/angina
- Aspirin
- Beta blockers (most effective)
- Nitrate (GTN spray)
- Calcium channel blockers
- Statins
- ACE inhibitors
What types of revascularisation may be used in IHD/angina?
- Percutaneous coronary intervention (PCI)
* Coronary artery bypass graft (CABG)
How would you diagnose IHD/angina?
- Exercise testing - Monitor ECG when the patient walks on a treadmill
- Myoview scan (aka perfusion scan) - IV radiolabelled agent is injected and dark spots indicate ischaemia/infarction
- CT coronary angiogram
- Stress echo (rare to do as it requires a highly skilled person to perform in)
- Perfusion MRI
- Invasive coronary angiography
What is unstable (crescendo) angina?
- Either: Angina of recent onset (<24hrs)
* Or: Cardiac chest pain with crescendo pattern