Atherosclerosis (atheroma, Thrombosis & Embolism, Myocardial Infarction, Ischaemic Heart Disease & Angina, ACS & SCAD) Flashcards
(50 cards)
What is an atheroma? Where does it form?
Atheroma = formation of focal elevated lesions (plaques)
Forms in the intima (innermost membrane) of large and medium-sized arteries
What are the consequences of arteromatous plaques in coronary arteries?
Plaques narrow the lumen —> ischaemia
Serious consequences:
- angina (chest pain due to reduced blood flow to heart muscles) due to myocardial ischaemia
- complications due to thromboembolism
What is the 2-step process of development of atheromatous plaque?
- Injury to endothelial lining of artery
2. Chronic inflammatory and healing response of vascular wall to agent causing injury
How does the endothelium get injured(2)? What are the consequences of this(3)?
Many causes including:
• Haemodynamic disturbances (turbulent flow)
• Hypercholesterolaemia (impairs endothelial function, lipoproteins can aggregate in intima and are modified by free radicals)
Consequences:
- accumulation of lipoproteins in vessel wall
- monocytes migrate into intima and transform into foamy macrophages
- platelets adhere
What are the 4 stages of atherogenesis?
Fatty streak:
- earliest significant lesion
- found in young children
- no clinical significance (may disappear)
Early atheromatous plaque:
- found in young adults and onwards
- smooth yellow patches in intima
Fully developed atheromatous plaque:
- central lipid core with fibrous tissue cap, covered by arterial endothelium
- inflammatory cells reside in fibrous cap
- highly thrombogenic (forms thrombus or clot when in contact with blood)
Complicated atheroma:
- haemorrhage into plaque (calcification)
- plaque rupture/fissuring
- thrombosis
Causes/risk factors of atheroma (6)
Hypercholesterolaemia is most important risk factor (causes plaque formation in absence of other known risk factors) Smoking Hypertension Diabetes mellitus Male Elderly
What are the signs of Hyperlipidaemia(3)?
Corneal Argus - deposit of cholesterol, phospholipds, triglycerides in arc on the iris
Tendon xanthomata - cholesterol deposits in tendons (often on knuckles and Achilles)
Xanthelasmata - yellow deposits of cholesterol underneath skin (usually on/around eyelids)
What are high grade plaque stenosis? What is stenoses atheromatous coronary artery? (What if its severe?)
Stenosis of 50-75% of vessel lumen —> critical reduction of blood flow in distal arterial bed —> reversible tissue ischaemia
E.g. stenoses atheromatous coronary artery = stable angina
Severe stenosis = unstable angina (ischaemic pain at rest)
What is acute atherothrombotic occlusion?
Ruptured plaque exposes thrombogenic plaque contents to blood stream —> coagulation cascade and thrombotic occlusion short time
What is a total atherothrombotic occlusion? With examples
Total occlusion —> irreversible ischaemia —> necrosis (infarction) of tissues
Examples:
- myocardial infarct (coronary artery) - stroke (carotid, cerebral artery) - lower limb gangrene (ileal, femoral, popliteal artery)
What is embolisation of the distal arterial bed?
Detachment of small thrombus fragments from thromboses atheromatous arteries —> embolise distal to ruptured plaque
Embolism occlusion of small vessels —> small infarcts in organs
(Common cause of stroke - cerebral infarct/TIA)
What is a ruptured atheromatous abdominal aneurysm?
Aneurysm - bulge in blood vessel
Media beneath atheromatous plaques gradually weakened —> gradual dilation of vessel
Vessel suddenly ruptures —> massive retroperitoneal haemorrhage (high mortality)
What are primary prevention measures for atheromatous plaques (5)?
Stop smoking Control blood pressure Weight loss Regular exercise Dietary modification
What are secondary prevention measures for atheromatous plaques?
Cholesterol lowering drugs (inhibits platelet aggregation to decrease risk of thrombosis on established atheromatous plaques)
What defects can occur in blood flow (2)?
Stasis - stagnation of flow
Turbulence - forceful, unpredictable flow
What is Virchow’s triad?
- Changes in blood vessel wall - e.g. atheromatous of coronary artery
- Changes in blood constituents - e.g. hyperviscosity
- Changes in pattern of blood flow - e.g. stasis (post-operatively), turbulence (atheromatous plaque)
What is a thrombosis
formation of a solid mass from the constituents of blood within the vascular system during life
What are common clinical scenarios of thrombosis (3)?
Deep vein thrombosis - blood clot developing in deep vein in body (usually leg)
Ischaemic limb - sudden decrease in limb perfusion that threatens viability of limb
Myocardial infarction
What are the 2 types of embolus?
Systemic thromboembolus
- travel to wide variety of sites: often lower limbs, brain - consequences dependent on: vulnerability of affected vessel to ischaemia, calibre of occluded vessel
Venous thromboembolus
- originate from deep venous thromboses - travel to pulmonary arterial circulation - consequences dependent on size of embolus - multiple over time —> pulmonary hypertension & right ventricular failure
Risk factors for DVT and pulmonary thromboembolism (7)
Cardiac failure Severe trauma/burns Post-op/post-partum (time after baby birth) Nephrotic syndrome Old age Oral contraceptive Bed rest/immobile
What are the types of embolus (9)
Fat (after major fractures)
Gas (decompression sickness - N bubbles lodge in capillaries)
Air (head and neck wounds, surgery, central venous catheter)
Tumour (spread of tumour)
Septic material (infective endocarditis)
Amniotic fluid (cause of collapse in childbirth)
Bone marrow (fractures - CPR)
Foreign bodies (sutures)
What is ischaemia?
Relative lack of blood supply to tissue/organ leading to inadequate O2 supply to meet needs of tissue/organ
4 types of hypoxia
- Hypoxic - low inspired O2 level/normal inspired O2 but low PaO2
- Anaemic - normal inspired O2 but abnormal blood
- Stagnant - normal inspired O2 but abnormal delivery (occlusion of vessel)
- Cytotoxic - normal inspired O2 but abnormal at tissue level
What are the supply (5) and demand (2) causes of ischaemic heart disease?
Supply: Coronary artery atheroma Cardiac failure (flow) Pulmonary function (e.g. pulmonary oedema) Anaemia Previous MI Demand: Heart has high intrinsic demand Exertion/stress
