Cardiovascular pathology 3 (2) Flashcards
(186 cards)
What is a thrombus ?
solid mass formed from the constituents of blood which is found within the vascular system
Where can a thrombus be found?
Blood vessels or the heart
What causes a thrombus to from ?
change to Virchow’s triad
what is Virchow’s triad ?
Stasis (change in flow), endothelial damage (change in wall structure) and hypercoagulability (change in contents of the blood).
Describe the formation of a thrombus in the arteries
Arterial thrombosis is mainly caused by the rupture of an atheroma plaque which is an example of endothelial damage. Endothelial damage however can be caused by other things such as high cholesterol, smoking, trauma and hypertension. When a atheroma ruptures it causes a thrombus (mainly platelets and fibrin and is therefore white in colour) to form on the surface and this happens through the activation of the clotting cascade (See diagram). Lines of Zahn will then develop, where a thrombus causes a layer of clot to form which then causes a layer of thrombus to form etc.
What can the consequences of a arterial thrombus be ?
This thrombus can then embolise to the coronary vessels to cause a acute coronary syndrome or to the brain to cause a ischemic stroke.
Describe the clotting cascade
Damage occurs to the tissue.
Through a series of steps a clotting factor is produced which converts prothrombin to thrombin which then converts fibrinogen to fibrin
Describe thrombus in the veins
Venous thrombosis is mainly caused by a change in the stasis or hyperstability of the blood. Stasis/flow is altered when there is immobility i.e. when you are bed bound or on a long haul flight. Hypercoagulability can be caused by pregnancy, cancer, sepsis or genetics. In the veins the stasis or hypercoagulability result in a clot forming (mainly fibrin and red blood cells which is red in colour). Venous thrombosis often occurs in the deep veins of the legs and is called DVT. These clots can then embolise and often goes to the lungs and causes a PE. Some thrombus don’t embolise however some will resolve themselves or with medication or they will become organised and shrink over time.
Examples of things which cause stasis
immobility i.e. when you are bed bound or on a long haul flight.
Examples of things which cause hypercoagubility
pregnancy, cancer, sepsis or genetics.
What are the outcomes of venous thrombosis ?
These clots can then embolise and often goes to the lungs and causes a PE.
Some thrombus don’t embolise however some will resolve themselves or with medication
or they will become organised and shrink over time.
Describe normal flow through a vessel
laminar where the cells move in the centre of the vessel and the plasma flows around it.
What is blood flow controlled by ?
changing the pressure gradient, the resistance, the velocity and the compliance
What are the two main ways in which blood flow can be unusual
The first is stasis where there is stagnation of the blood flow i.e. the blood flows slowly (lack of movement due to sitting too long or not moving i.e. after an operation or in a aeroplane etc). The second is where there is turbulent blood flow i.e. flow is forceful and unpredictable.
What is a thromboembolism ?
When a thrombus or clot embolises
Name some other things which can cause an embolism
Fat gas tumours bone marrow foreign bodies parts of the trophoblast etc from the baby in pregnancy
How does fat cause embolism ?
Embolisms can be beads of fat caused when there are bone fractures and fat from the bone enters to the blood and causes confusion (if it enters the brain) or can lodge go to the kidneys or the skin.
How does gas cause embolism ?
Embolism can also be beads of gas. This is commonly caused when a driver rise to the surface to quickly and it causes N2 bubbles to form and lodge in the capillaries, this is called decompression sickness. Gas embolise can also be caused by injury to the head and neck, from surgery or from CV lines
How does bone marrow cause an embolism ?
Bone marrow can embolise after a bone fracture or even after CPR
Describe embolism in pregnancy
. In pregnant ladies an embolism is also caused when part of the Trophoblast from the baby, some Amniotic fluid embolism or foetal skin cells and keratin from the baby get into he maternal circulation.
What are the signs and symptoms of arterial thrombosis ?
Sudden onset
Signs of embolism i.e. strokes, ACS etc
What are the signs and symptoms of venous thrombosis ?
Slow onset
Signs of embolism i.e. PE
Evidence of DVT i.e. unilateral limb swelling, persistent discomfort, calf tenderness and to a lesser extent warmth, redness, prominent collateral veins and unilateral pitting oedema
What investigations should be carried out into thrombosis ?
The wells score
A D-dimer blood test
What is D-Dimer ?
the breakdown product of cross linked fibrin produced during fibrinolysis