2: Pathology of thrombosis & embolism Flashcards
What is the difference between a clot and a thrombus?
Clot - outside the vessel
Thrombus - inside the vessel
Clot often used colloquially.
What is Virchow’s Triad?
Site of endothelial injury
Turbulent blood flow
Hypercoagulable blood
all favour thrombus formation.
Thrombus is formed by intravascular coagulation. What are the two main steps of this?
1) Platelet activation
2) Fibrin production & coagulation cascade
Activated platelets are more “___”.
sticky
Platelets attract and aggregate with other __ and __.
platelets , fibrin
Which chemical is the endpoint of the coagulation cascade?
Fibrin
What activates platelets and how is it exposed?
Collagen of connective tissue
Exposed because of endothelial damage
What chemical on platelets do collagen and vWF bind to?
Glycoprotein Ia/IIb
What does glycoprotein IIb/IIIa bind to?
Fibrinogen
Activated platelets release chemicals (granules) to attract other platelets - what are some examples?
vWF, PAF, Thromboxane A2, ADP
The coagulation effect is also known as a ___.
cascade
The coagulation cascade has a lot of opportunities for inhibition and stimulation, which can all be targeted by __.
drugs
What chemical is important in the formation of specific factors?
Vitamin K
(II, XII, IX and X)
Why does liver disease inhibit the coagulation cascade?
Vitamin K stored in the liver
So body can’t produce factors II, VII, IX and X
Which drug stops the body’s production of II, VII, IX and X?
Warfarin
If someone has been given too much warfarin, what can you do?
Give them Vitamin K injections
Which condition can cause endothelial injury in the arteries?
Hypertension
Why doesn’t high arterial flow damage the arteries?
Pro-coagulant materials (e.g platelets) are washed away before they stick
When may high pressure arterial flow cause thrombosis?
If there is underlying atherosclerosis
What is atherosclerosis?
Arterial hardening and thickening, formation of plaque at sites of endothelial damage
Fibrous plaque caps which form during atherosclerosis are prone to ___.
rupture
Arterial stenosis tends not to occur unless there is underyling ___.
atherosclerosis
Stable angina tends to occur on __.
exertion
Unstable angina is associated with __ and can occur at __.
rupture , rest
What is the main factor affecting blood flow through a vessel?
Radius
What are other causes of endothelial injury?
Toxins (e.g tobacco)
Infectious agents
Autoimmune disease (inflammation)
What is a historic risk factor for DVT?
Having had DVT already
What are two effects of turbulent blood flow on a vessel?
- Swirling of blood (imagine getting stuck in a swirly pool at the bottom of a waterfall)
- Stasis
Blood flow is usually laminar. If it becomes turbulent, platelets move to the edge of the vessel - what is this called?
Margination
In marginated blood flow, platelets are more likely to come into contact with?
Endothelial wall (or lack thereof)
Where is blood flow most likely to slow down and produce stasis?
Deep venous system (low pressure, faulty valves etc.)
Where do DVTs develop?
Calf veins
Femoral veins
Thrombi from __ veins tend to circulate further in the blood.
smaller
A thrombus is only as wide as the vein it started in
What is the name of the process which regulates, amongst other things, clotting and clot lysis in the body?
Homeostasis
Hypercoagulability may be associated with __ disorders.
inherited
If someone has developed a DVT on a long haul flight, they probably have…
an inherited mutation.
Name some causes, other than genetic disorders, of clotting / DVT.
Prolonged immobility
Significant tissue injury - burns, RTA
Autoimmune diseases
MI
Atrial fibrillation - blood clots in atria
What is an embolus?
A dislodged thrombus which travels around the vascular system until it gets stuck
What would you see on an X-ray if a patient had suffered a pulmonary embolism?
Wedge-shaped infarcs
What is ischaemia?
Insufficient blood supply
What is infarction?
Tissue death as a result of ischaemia
Turbulent blood flow occurs anywhere a vessel __.
branches
Branching vessels are a common site of __ __.
endothelial damage
The most common cause of thromboembolic stroke is embolism where?
Bifurcation of carotid arteries
Name some anti-clotting proteins produced by the body.
Protein C, S and antithrombin III
What is a natural clot buster produced by the body?
Plasmin
Name an inherited genetic disorder causing hypercoagulability of the blood.
Factor V Lieden
___ increases the production of TNF, which causes hypercoagulability of the blood.
Cancer
Which particular drug may increase the coagulability of the blood?
Contraceptive pill
Give two examples of branching vessels which are vulnerable to embolism.
Coronary vessels
Bifurcation of aorta
Bifurcation of the carotids
Renal arteries
Superior mesenteric artery
What may happen following embolism which blocks…
1) Bifurcation of carotids
2) Superior mesenteric artery?
1) Stroke
2) Small bowel infarction