Atheroma, Thrombosis & Embolism (13) Flashcards
Atherosclerosis
Degeneration of arterial walls characterised by fibrosis, lipid disposition and inflammation which limits blood circulation and predisposes to thrombosis
Commonly affected vessels
Bifurcations (turbulent flow), abdominal aorta, coronary arteries, popliteal arteries, carotid vessels, circle of willis
What are non modifiable risk factors?
Age, male, FH, genetic
What are modifiable risk factors?
Hyperlipidaemia (LDL:HDL), hypertension, smoking, diabetes, CRP, increased homocysteine, stress
Pathophysiology
Due to chronic injury and repair of endothelium, in presence of hyperlipidaemia - lipid accumulates in intimate, monocytes migrate (VCAM1) and ingest lipid > foam cells (fatty streak) - secrete chemokines attracting more monocytes/macrophahes, lymphocytes, smooth muscle cells > proliferate and secrete connective tissue (atherosclerotic plaque)
Causes of endothelial injury
Haemodynamic injury, chemicals, immune complex deposition, irradiation
Plaque - fibrous cap
Smooth muscle cells, macrophages, foam cells, lymphocytes, collagen, elastin, proteoglycans, neovascularisation
Plaque - necrotic centre
Cell debris, cholesterol crystals, foam cells, calcium
After athersclerosis
Occlusion, wearing of vessel walls (aneurysm), erosion (thrombosis)
Thrombosis
Solidification of blood contents formed in vessel during life
Blood clot
Stagnant blood, enzymatic process, elastic, adopts shape of vessel
Thrombus
Within the body during life, dependent on platelet, firm
What are platelets?
Fragments of megakaryocytes in bone marrow, circulate in blood stream
How do platelets become activated?
Bind to collagen exposed by endothelial damage
What do platelets secrete?
Alpha granules - fibrinogen, fibronectin, PDGF (platelet derived growth factor)
Dense granules - chemotactic chemicals
Virchow’s triad
Thrombus formations requires changes in
- Intimal surface of vessel
- The pattern of blood flow
- Blood constituents
Plaque rupture causes
Turbulent flow and intimal change
Hyperlipidaemia causes
Change in blood constituents
Arterial thrombus formation
- Lipid-filled cells
- Loss of endothelial cells and exposure to collagen
- Platelet adherence and activation
- Thrombus formed of alternating layers of platelets, fibrin and RBCs
Venous thrombosis
Intimal change - valves
Change in blood flow - immobile
Change in blood constituents - inflammatory mediators (infection, malignancy), factor V leiden, Oestrogen
Cardiac thrombosis
Mural thrombi, occur in MI, myocarditis, arrhythmias, cardiomyopathy (areas of injury)
Sequelae of thrombosis
Occlusion, resolution, incorporation into vessel wall, recanalisation and EMBOLISATION
Embolus
A mass of material in vascular system able to lodge in a vessel and block it (endo/exogenous, sold, liquid/gas)
Pulmonary emboli
Most common, common cause of hospital mortality
