Thrombosis/Emboli

Question 1

What is a thrombus?

Answer 1

A solid mass formed from the constituents of blood in the vessels or heart

Question 2

What is thrombosis?

Answer 2

The process of forming a thrombus

Question 3

What are the changes in the triad of virchow?

Answer 3

1) Vascular wall - injury
2) Blood flow - slow/turbulent
3) Blood - hypercoaguable

Question 4

Which part of virchows triad is most important in DVT?

Answer 4

Slow blood flow -stasis

Question 5

Which part of virchows triad is most important in cardiac/arterial thrombi

Answer 5

Turbulent flow/injury due to plaque rupture

Question 6

How does pregnancy predispose to thrombosis?

Answer 6

Stasis - pressure of babies head on arteries/veins

Hypercoaguable - more blood

Question 7

Why does slow flow predispose to thrombosis?

Answer 7

Gives more chance for platelets to adhere and clotting factors to accumulate

Question 8

Why are veins more predisposed to thrombus than arteries?

Answer 8

Slower flow

Valves form pockets were stagnant blood can sit

Question 9

How does surgery, fractures or burns increase chance of thrombosis?

Answer 9

Hypercoaguable due to increased fibrinogen and factor VIII

Question 10

What else causes hypercoaguability?

Answer 10

Smoking
Cancer
Contraceptive pill
DIC

Question 11

Why are platelets likely to congregate behind vein valves?

Answer 11

Because they are the smallest particles in blood so flow along the peripheries where they can catch onto the vein valves

Question 12

What are lines of Zahn?

Answer 12

Layers of a thrombus with varying amounts of RBC platelets fibrin fibrinogen etc

Question 13

What are the 5 outcomes of a thrombus?

Answer 13

1) Resolution
2) Propagation
3) Embolisation
4) Recanalisation
5) Organisation

Question 14

How does resolution occur?

Answer 14

Fibrinolysis - happens often when thrombus is small

Question 15

How does propagation occur?

Answer 15

Blood around thrombus is stagnant and therefore predisposed to forming more - so thrombus enlarges. Also flow around a thrombus is likely to be turbulent further predisposing

Question 16

How does embolisation occur?

Answer 16

Part of embolus of thrombus can come off and travel in the blood and dislodge at a site distant to it’s original

Question 17

How does recanalisation occur? What is the risk here?

Answer 17

One or more small holes may form for blood flow to resume through - can be seen e.g. in coronaries

Risk of more thrombus as flow is turbulent

Question 18

How does organisation occur?

Answer 18

Attempts to repair - fibroblasts and new capillaries -> lumen still obstructed

Question 19

What are some common clinical outcomes of thrombosis (3)?

Answer 19

Occlusion of artery at site of thrombus e.g. coronary - ischamia - MI

Emboli - e.g. DVT to PE/CVA

Ulcers - from DVT, congestion and oedema in venous bed

Question 20

What is an embolus?

Answer 20

A solid liquid or gas that is carried by the blood and lodges in a distant site

Question 21

What is embolism?

Answer 21

Sudden blocking of an artery by a thrombus or foreign material that has traveled to a distant site via the blood

Question 22

Why can’t embolisation occur in veins? Where does it end up?

Answer 22

Because flow is from small to large vessels - flows up till it reaches the pulm arteries

Question 23

Where is the most common location of DVT causing a PE?

Answer 23

Politeal/femoral vein

Question 24

What are some complications of PE?

Answer 24

Death
Pulmonary hypertension
RH failure

Question 25

How can fat emboli occur? What are 2 symptoms?

Answer 25

E.g. from fracture of bones - respiratory distress and confused patient can sometimes be a symptom

Question 26

What are thrombi more commonly see in LV than RV (3)?

Answer 26

1) MI often affect LV - so thrombi can develop where there is necrosis
2) AF - causing LA in particular to become large - thrombi in atrial appendage
3) Vegetations are more common on LHS due to the greater pressure and therefore micro trauma

Question 27

What is the treatment for thromboembolic disease?

Answer 27

Warfarin and Heparin

Vena cava filters to prevent PEs forming from DVTs

Question 28

What is prophylaxis for VTE?

Answer 28

Compression stockings
Mobilise soon after surgery
Calf muscle exercises
Long term anticoagulation
Aspirin - antithrombogenic (blocks platelets)

Question 29

What occurs in an amniotic fluid embolism?

Answer 29

Amniotic fluid enters the maternal circulation through a tea in the amniotic membranes. Resp distress, hypotension, seizures and DIC (because amniotic fluid is prothrombotic)