thrombosis Flashcards
how does thrombosis presents as
characterised by the lines of Zahn (platelets and red blood cells held together by fibrin)
and attachment to vessel walls
what are the 3 risk factor of thrombosis called
Virchow’s triad
1st point of Virchow’s triad (1) D_ o_ B_ F_
Disruption of blood flow
- immobilisation (flight/bedrest)
-cardiac wall dysfunction
-Aneurysm
-atrial fibrillation
2nd of Virchow’s traid (2) E_ C_ D_
Endothelial cell damage
-Atheroscelrosis (reptured plaque)
-vasculitis
-high levels of homocysteine (low B12)
-turbulent blood flow of arterial bifurcation
-oxidised LDL
-cigarrette smoke
-cytokines
3rd of Virchow’s traid (3) H_ S_
Hypercoaguable states
-due to excessive procoagulant factors /defective anticoagulants
-may be inherited (AT3 deficiency), acquired (DIC)
(classic presentation is recurrent DVT or DVT at early age)
what is the most common cause and site of venous thrombosis
Stasis of blood
most common site is deep vein of lower limbs
what is the presentation of DVT
Red swollen painful legs with skin discolouration
what can happen if a person has DVT
can dislodge to the lungs and cause a pulmonary embolism
Arterial thrombosis is commonly due to what - and what is an rare cause
common = endothelial damage related to turbulent blood flow at bifurcation or over atherosclerotic plaque in high velocity vessels
rare = hypercoagulabilty + stasis
Arterial thrombosis causes -(3)
myocardial infarctions
small bowel infarction
strokes
what is INR
International normalised ratio
what is normal INR
1
what is INR used for
montiter warfarin therapy
what is INR=2.5
treatment of DVT, pulmonary/arterial embolsim, atrial fibrillation, myocardial infraction
what is INR=3.5
treatment of recurrent DVT or pulmonary embolism
describe Prothrombin time (PT)
-evaluates the extrinsic coagulation system to formation of the fibrin clots
-monitored person taking warfarin + liver synthesis function
what is normal PT
11-15 second
Time is prolonged when clotting factor level is
30-40% of normal PT
what is a pulmonary embolism
An intravascular mass that travels and occludes pulmonary blood vessels
Most common cause is a dislodged thrombus (thromboembolus) – 95%
what is used to treat AIS
Alteplase
Aspirin (24h after thrombolysis)
what is used to treat venous thrombosis
Rivaroxaban + Apixaban
what is used to treat arterial thrombosis
inhibitor of platelets aggregation prevent formation - Aspirin
what is thrombin
acts on fibrinogen to produce fibrin monomers
activates fibrin stabilising factor 13 (13a)
thrombin (extensive mechanims)
- converts these monomers to cross linked fibrin which strengthens blood clots
- acts on a feedback loop to activates several other coagulation factors and is therefore pivitol in the amplification system
what switches off thrombin
natural anticoagulant antithrombin 3 - limits clot formation
What does plasmin does
- breaks down clots, cleave fibrin & fibronigen into degradation products (fragments known as D-dimers)
- degrades some clotting factors + blocks platelet aggregation
what are the three stages of platelet activation
adhesion, release reaction, aggregation
platelet undergo shape changes and degranulation which causes -
-release mediator ADP (from dense core granules)
-ADP induces the expression of GP2b/3a (GPIIb/IIIa) another essential receptor of aggregation and and fibrinogen which acts as a linker molecule in the developing clot
- production thromboxane A2 (TXA2)(a derivative of platelets cyclooxygenases) its a vasocontrictor that also promotes platelets aggregation
-releases calcium
Plaque formation (using LDL and anti-inflammatory systems)
-Circulating LDL gains access to subendothelial spaces where their oxidised
-cytokines IL-1 and MCP-1 attract circulating monocytes
macrophages phagocytose LDL to form _ in plaque formation
foam cells
what happens after foam cells formation
smooth muscle cells migrate and proliferate under the influence of smooth muscle mitogens
A primative plaque is formed of
Foam cells, smooth muscle cells, lipids & necrotic cells
how does plaques mature
the plaque enlarged, develops a fibrous capsule and protrudes in vessel lumen
