Circulation 2- Pathological Thrombosis + Embolism Flashcards
When does pathological thrombosis occur?
Occurs in the absence of a cut or traumatic injury.
What 3 disposing situations does Pathological thrombosis occur in?
Virchow’s triad:
- Change in the intimate surface of a vessel
- Changes in the pattern of blood flow
- Changes in the blood constituents
What are the consequences of partial of complete interruption in arterial blood supply?
Ischaemia, hypoxia, necrosis/infarction
What is an example of pathological thrombosis?
Coronary Artery Thrombosis- all three situations occur.
Describe coronary thrombosis in detail.
Change in blood constituents- Smoking cigarettes:
- Smoking cigarettes increases the “stickiness” of platelets.
- “Stickier” platelets make it more likely that a thrombosis occurs.
- This alteration in the properties of blood is a change in blood constituents.
Change in the pattern of blood flow:
- Cigarette smoking and other things such as high lipid in the blood, can also predispose to atheroma in the coronary arteries.
- Atheroma is a disease of coronary arteries which results in a build-up of lipid and scar tissue under the intimal surface and forms deposits.
- The lipid can result in abnormal blood flow- can get both slow and turbulent flow.
- Slowed blood flow predisposes to fibrin and platelet clumping
Change in intimate surface of vessel:
- Platelets and fibrin are now exposed to an abnormal substance (lipid and collagen) and turbulent and are deposited as a thrombus.
- (The platelets are also sticky because this patient smokes. )
- The thrombus blocks the LUMEN of the coronary artery.
- Clot can now form in the stagnant blood behind the thrombus.
What happens in reality?
It is usually more complex- multiple layers of thrombus and clot (the lines of Zahn)
- First layer= thrombus (platelets and fibrin)
- Then red blood cells are trapped in fibrin meshwork so second layer of clot.
- This complex structure now protrudes even further into the lumen so causes more turbulence/slow and third layer of thrombus forms.
What are the consequences of a thrombus blocking an artery?
- Complete obstruction leading to no flow beyond the blockage.
- Partial obstruction leading to decreased flow beyond the blockage. The tissue supplied by this artery receives less blow flow= ischaemia.
How does ischaemia lead to hypoxia?
- Ischaemia=If it is severe enough ischaemia leads to decreased oxygenation of tissues (hypoxia)
- This tissue is said to be ischaemic.
- Localised area of tissue dies- this is called an infarct.
What organ is highly susceptible to ischaemia?
The brain exhibits the highest sensitivity to ischaemia.
What is necrosis?
Process of any tissue dying in any manner.
What is an infarct?
Name reserved for necrosis as a result of ischaemia (ischaemic necrosis)
When can infarcts occur?
Can occur in other tissue supplied by other arteries:
- Coronary artery thrombosis- infarct in heart
- Cerebral artery thrombosis- infarct in brain
- Mesenteric artery thrombosis- infarct in gut
What is embolism?
- The process of a mass of material (usually thrombosis/clot) breaking off and moving from one part of a circulation to another.
- It becomes lodged in a vessel and block its lumen.
How does pulmonary embolism occur?
When thrombi/clot embolise= thromboembolism= Pulmonary embolism.
Describe pulmonary embolism in detail
- Sluggish flow in leg veins leads to thrombosis and clot formation.
- Part of thrombus and clot breaks off and travels up the vein.
- Embolus passes into inferior vena cava, right heart, then pulmonary trunk and lodges in pulmonary artery branch.
- Embolus blocks pulmonary artery and get pulmonary infarct
