Thrombosis and Embolism

Question 1

Define thrombosis

Answer 1

Formation of a solid mass WITHIN the circulatory system

Question 2

Define what a thrombus is

Answer 2

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

Question 3

What is a clot?

Answer 3

Mass of blood OUTSIDE vessel wall

Question 4

Describe Virchow’s triad

Answer 4

Three factors that explains how a thrombus forms

1) Vessel wall = endothelial damage
2) Blood flow problems = stasis and turbulent flow
3) Problems with blood components = hypercoagulable states (sticky blood)

Question 5

What increases in hypercoagulable states and who are more likely to be in this state?

Answer 5

-increased fibrinogen or factor 8

• smokers
• pregnancy
• post-op patients
• cancer
• trauma
• burns

Question 6

Describe arterial thrombus (appearance)

Answer 6

• pale
• granular
• lines of Zahn visible
• lower cell content

Question 7

Describe venous thrombus (appearance)

Answer 7

• deep red colour
• gelatinous
• soft
• higher cell content

Question 8

How are lines of Zahn formed?

Answer 8

1) small platelets clump up with fibrin as they get trapped
2) red blood cells go atop of this layer as they get caught as well forming red layer
3) more platelets and fibrin forms a lighter white layer
4) cycle continues

Question 9

What are the outcomes/consequences of thrombosis (5)?

Answer 9

1) Lysis = complete dissolution of thrombus
2) Propagation = thrombus grows and progressively spreads
3) Organisation = thrombus undergoes fibrous repair forming a scar on vessel wall
4) Recanalisation = new smaller channels in occluding thrombus forms
5) Embolism = part of thrombus breaks off and lodges at a distant site

Question 10

Clinical effects of thrombosis

Answer 10

• occlusion of artery = ischaemia and infarction

- occlusion of viens = congestion, oedema, ischaemia and infarction

Question 11

Define embolism

Answer 11

The blockage of a blood vessel by solid, liquid or a gas at a site distant from its origin

Question 12

What is a thromboemboli?

Answer 12

Emboli that arise from thrombus

Question 13

Where do emboli in the veins go to?

Answer 13

Right heart and lead to embolisation in pulmonary arteries

Question 14

Where do emboli in the arteries go to?

Answer 14

Emboli from left heart and aorta can go anywhere in systemic circulation

Question 15

List some predisposing factors for a deep vein thrombosis

Answer 15

• immobility/bed rest
• post-op
• pregnancy
• oral contraceptives
• severe burns
• cardiac failure

Question 16

Describe the general prophylaxis for embolism

Answer 16

• prevention of venous stasis = encourage movement after operation, compression stockings, calf muscle stimulation
• prevention of hypercoagulability = anticoagulants

Question 17

How does Heparin work as an anticoagulant?

Answer 17

Forms irreversible complexes with antithrombin 3 = activates it

Question 18

How does Warfarin work as an anticoagulant?

Answer 18

Interferes with vitamin K metabolism (blocks formation of vitamin k dependent clotting factors e.g. 2, 7, 9, 10)

Question 19

Treatments for embolism

Answer 19

• clot busters e.g. streptokinase
• new generation NOAC (noval oral anticoagulants) e.g. dabigatran, rivaroxaban, apixaban, edoxaban
• insert a filter in the inferior vena cava
• embolectomy