Vascular Disease Flashcards
Define arteriosclerosis
Thickening and hardening of the wall of an artery
Define Artheroma
Important disease of medium and alrge arteries in high-pressure systems, never venous
Define artherosclerosis
Arteriosclerossis due to artheroma
Development of hypertensive arteriosclerosis
- Hypertrophy of media
- Fibro-elastic thickening of smooth muscle intima
- Elastic lamina reduplication
Development of hypertensive Arteriolosclerosis
Replacment of wall structures by amourphous hyaline material causing decreased lumen size and lessening response to endocrine stimulus
Consequences of hypertensive vascular changes
- Reduction of vessel lumen; reduced flow; ischaemia
- Increased rigidity of vessel walls; loss of elasticity and contractility; unresponsive to control agents e.g. vasodilators
Stages of artheroma
Initially effects tunica intima, later tunica media, worsens with age
- Blood lipids enter intima by damaged epithelium
- Macrophages phagocytose lipids to make araise fatty streak
- Some lipid released forming a lipid plaque. M secrete cytokines, stimulate myofibroblasts to secre collages-> early damage of elastic lamina
- Collagen covers plaque forming fibrolpid plaque, muscle fibres replaced by collagen
- Lipids in intima calcified. plaque surface ulcerates, initates coagulation cascade leading to blood clot
How does ischaemic damage occur by artheroma?
Intima expansion; reduced lumen size; reduced blood flow; reduced oxygenation; ischaemic damge
Coronary arteries - Angina
Legs - Intermittent claudation
Mesenteric - Iscaehmic colitis
Cerebral/vertebral - Cerebral sichaemic event
Layers of artery from inner to outer
Lumen
Intima - connective tissue
Internal elastic lamina
Media
Adventia
Dietary cause of Artheroma
High LDL diet
Mechanism for developing aneurysms from artheroma
= Abnormal permanent focal dilation of an artery
- Enlarging intimal artheroma plaque leads to atrophy of media, elastic fibres replasced by collagen
- Collagen incapable of elastic recoil; arterial wall stretches with systolic pulse
- Most common in abdominal aorta
Main cause of mycotic aneurysm
Endocaritis or bacterial sepicaemia
Risk factors for artheroma
- High fat diet
- High LDL:HDL ration
- Smoking
- High BP
- Diabets
- Obesity
Define Thrombosis
The process leading to formation of a thrombus
Can be physiological; preventing bleeding in breached vessel wall. Limited by fibrinolysis
Or pathological: not limited by fibrinolysis
Define thrombus
A solid mass composed of blood constituents which have aggregated together in flowing blood in the lumen
Events in physiological thrombosis
- Vessel wall is breached
- Circulating plateletes aggreagte and plug
- Platelets release factors which trigger coag cascade
- Cascade converts fibrinogen to large molecule sof insolube fibrin
- Fibrin binds platelets together and traps RBC/WBCs
Fibrinolysis
- Plasminogen activated
- Converted to plasmin
- Fragments fibrin; dissolves thrombus
Events in pathological thrombus
- Normal thrombosis
- Reduced fibrinolysis
- Thrombus continues to enlarge over capacity of fibrinolysis
- Red/brown mass produced in lumen
Virchows triangle
3 categories contributing to thrombosis
-
Vessel: Disturbance/damage of the blood vessel
- Exposes collagen in intima
- Blood Flow: Reduction in blood flow/stasis
-
Blood: Disturbance of blood properties/character
- Increased platelets, RBS numbers, Viscosity
Consequences of arterial thrombosis
Stops flow of blood; cuts off oxugen; infarction
Consequence of venous thrombosis
Prevents drainage; blood pools; congestion(+infarction)
e.g. DVT
Define Thromboembolism
Thrombus fragments or detaches completely (breaks off) and travels elsewhere in the circulation (passes into bloodstrem) to a distal site where it occludes the vessel
Circumstances under which a pulmonary thromboembolism can occur
- Thromboembolism in a systemic vein
- Eventually embolises to a pulmonary artery branch
- large enough embolus will cause sudden death
Risk factors in venous thromboembolism
- Active cancer treatment
- 60+
- Dehydration
- Obesity
- HEart disease
- hormone replacement therapy
- Oestrogen contraception
Other material than thrombosis that can embolise
Cancer cells/tumour
Air
Nitrogen(diving)
Amniotic fluid
Define Infarct
An area of ischaemic necrosis due to abrubt cessation of the arterial supply
Stages of venous infarction
- Veins become obstructed
- Tissues become congested with blood
- Pressure rises in capillariea and venules
- Rupture
- Pressure too highg for arterial blood to enter
e.g. hernial strangulation
Causes of arterial infarction
- 95% thrombotic or embolic
- Arterial spasm
- Arterial trauma
Stages of arterial infarction
- 0-12H Swelling of cells; some death
- 12-24 Necrotic muscle fibres apparent
- 24-72 AIR to dead muscle
- 3-14D Macrophagic removal of debris
- Vascular granulation
- Fibrous grnulation
- Scar formation by mature fibrous tissue
Common cause of renal infarct
Emboli from left side of heart
Cerebral infarction
Emolisms
Liquefactive necrosis, heals by astrocytic gliosis
Commonly death
Complication of MI
early
- Sudden death by LV failure or dysrhytmia
- Ruoture of myocardium
- Rupture of papillary muscle; acute valve failure
Late
- Chronic LVF
- Ventricular aneurysm
