89 - Venous Thrombosis and Pulmonary Thromboembolism

Question 1

Most common preventable cause of death in hospitalised patients

Answer 1

Pulmonary thromboembolism

Question 2

Clot

Answer 2

A solid mass composed of blood components which forms after death

Question 3

Thrombus

Answer 3

Solid mass composed of blood components formed in an artery of vein during life

Question 4

Where do thrombi often form?

Answer 4

Deep veins of the lower limbs

Question 5

Deep veins of lower limb 
1
2
3
4

Answer 5

Distal to proximal:

Anterior, posterior tibial veins
Popliteal vein
Femoral vein
Iliac vein (in the pelvis)

Question 6

Most important venous plexus in lower limb

Answer 6

In soleus muscle

Question 7

Superficial veins of the lower limb

Answer 7

Great and small saphenous veins

Question 8

Location of formation of venous thrombi

Answer 8

Form upstream of valve.

Become more occlusive, thicker.

Question 9

Feature of growth of venous thrombi

Answer 9

Can propagate up- and downstream of where thrombus began forming.

Question 10

Why are venous thrombi red?

Answer 10

Form in an environment of low flow.

Have lots of RBCs.

Question 11

Structure of venous thrombi

Answer 11

Lines of Zahn.

Alternating layers of red (RBC) and pink (platelets and fibrin)

Question 12

Thrombi that are often occlusive

Answer 12

Venous thrombi

Question 13

When are venous thrombi more likely to embolise?

Answer 13

When recently-formed.

Question 14

Examples of changes to vessel wall that can predispose to thrombi

Answer 14

Trauma from catheterisation.

Bacterial infection of vessel wall.

Question 15

Polycythaemia

Answer 15

Condition where too many RBCs are produced.
Can’t be cured, only can control symptoms.
Predisposes to thrombosis.

Question 16

Things that can lead to non-laminar flow, causing thromboses
1
2
3
4
5

Answer 16

Prolonged immobilisation
Dehydration
Hypotension
Congestive cardiac failure
Polycythaemia

Question 17

What cause most arterial thromboses?

Answer 17

Complications of atherosclerosis.

Question 18

Example of a genetic hypercoagulable state

Answer 18

Factor V Leiden

Question 19

Factor V Leiden

Answer 19

Point mutation in factor V prevents activated protein C (natural anticoagulant) from binding to a cleavage site.

Question 20

Proportion of patients with DVT that have factor V Leiden

Answer 20

50%

Question 21

Uncommon genetic predispositions to hypercoagulable state
1
2
3

Answer 21

(1) Antithrombin III deficiency
(2) Protein C deficiency
(3) Protein S deficiency

Question 22

Common genetic predispositions to hypercoagulable state
1
2

Answer 22

Factor V Leiden

Prothrombin III deficiency

Question 23

Examples of secondary predisposing factors to hypercoagulability
1
2
3
4
5
6
7
8

Answer 23

• Surgery
• Massive trauma and burns
• Malignancy – release of thrombogenic substances from
tumours especially mucinous adenocarcinomas
• Obesity – mechanism unknown
• Smoking – probably
• Hyper-oestrogenic states (pregnancy and the OCP)
• Nephrotic syndrome (both cause and effect of renal
vein thrombosis)
• Anti-phospholipid antibody syndrome

Question 24

Fates of venous thrombi
1
2
3
4

Answer 24

1) Lysis of thrombus
2) Organisation of thrombus (can form scar tissue, forming a stricture on the vessel wall)
3) Recanalisation (most common fate. New blood vessels form, restoring blood flow around thrombus)
4) Embolism (most dangerous outcome)

Question 25

Embolus

Answer 25

An embolus is a mobile mass of material within the | vascular system able to lodge within a vessel, occlude its lumen and obstruct blood flow.

Question 26

Thromboembolus

Answer 26

A detached piece of thrombus

Question 27

What do clinical effects of pulmonary thromboemboli depend on?

Answer 27

Size of occluded vessel

Question 28

Pulmonary thromboembolus that can cause sudden death

Answer 28

'Saddle embolus' | Thromboembolus lodges at the bifurcation of the pulmonary artery.

Question 29

'Saddle embolus'

Answer 29

Thromboembolus lodges at the bifurcation of the pulmonary artery.

Question 30

Features of a saddle embolus

Answer 30

Red, with some pale areas. Lodged at the bifurcation of the pulmonary artery. Coiled shape, reflecting vein of origin. Occlusive.

Question 31

Clinical effects of a saddle embolus

Answer 31

Sudden death - Cardiac arrest with electromechanical dissociation.

Question 32

Electromechanical dissociation

Answer 32

Electrical activity of heart is continuing in normal fashion, but mechanical activity of heart is prevented from thromboembolus.

Question 33

``` Clinical effects of a thromboembolus in a right or left pulmonary artery 1 2 3 4 ```

Answer 33

Sudden death. Dyspnoea. Chest pain. Circulatory failure mimicking myocardial infarction

Question 34

Thoracic catastrophes presenting with central chest pain, SOB

Answer 34

MI. Pulmonary thromboembolus Aortic dissection

Question 35

``` Clinical features of a small pulmonary thromboembolus 1 2 3 4 5 6 ```

Answer 35

``` Share features with other solid-organ infarcts Sharply demarcated infarct Wedge-shaped infarct Pleural base. Red Occluded artery at apex ```

Question 36

Clinical features of a small pulmonary thromboembolus 1 2 3

Answer 36

Dyspnoea Haemoptysis Pleuritic chest pain

Question 37

Why are lung infarcts red and not pale?

Answer 37

Dual blood supply (pulmonary circulation and bronchial circulation from descending aorta)

Question 38

Clinical features of a small pulmonary thromboembolus without infarct

Answer 38

Unexplained tachycardia in a patient with risk factors for pulmonary thromboembolism

Question 39

What could be occurring if a patient has an unexplained tachycardia, and has risk factors for venous thromboses.

Answer 39

Small pulmonary thromboembolism without an infarct