S5) Thrombosis and Embolism Flashcards
What is a thrombosis?
A thrombosis is the formation of a solid mass from the constituents of the blood, within the circulatory system
There are three fundamental predisposing factors to thrombosis.
What is this called?
Virchow’s triad
Identify the three predisposing factors to thrombosis as outlined in Virchow’s triad
- Abnormalities of the flow of blood
- Abnormalities of the blood vessel wall
- Abnormalities of the constituents of the blood
State two possible abnormalities in the flow of blood
- Stagnation
- Turbulence
State three causes for abnormalities in the blood vessel wall
- Atheroma
- Direct injury
- Inflammation
State three causes for abnormalities in the constituents of the blood
- Smoking
- Post-partum
- Post-operation
Describe the appearance of arterial thrombi
- Pale
- Granular
- Lines of Zahn
- Lower cell content
Describe the appearance of venous thrombi
- Soft
- Gelatinous
- Deep red
- Higher cell content
What are the 5 possible outcomes of a thrombosis?
- Lysis
- Propagation
- Organisation
- Re-canalisation
- Embolism
In three steps, describe the following outcome of a thrombosis: lysis
⇒ Complete dissolution of thrombus (small)
⇒ Fibrinolytic system active
⇒ Blood flow re-established
In three steps, describe the following outcome of a thrombosis: propagation
⇒ Progressive spread of thrombosis
⇒ Spreads distally in arteries
⇒ Spreads proximally in veins
In two steps, describe the following outcome of a thrombosis: organisation
⇒ Ingrowth of fibroblasts and capillaries (similar to granulation tissue)
⇒ Lumen remains obstructed
In two steps, describe the following outcome of a thrombosis: re-canalisation
⇒ Blood flow re-established but usually incompletely
⇒ 1/more channels formed through organising thrombus
In three steps, describe the following outcome of a thrombosis: embolism
⇒ Part of thrombus breaks off
⇒ Travels through bloodstream
⇒ Lodges at distant site
What are the arterial effects of thrombosis?
Depends on site and collateral circulation:
- Ischaemia
- Infarction
What are the venous effects of thrombosis?
- Congestion
- Oedema
- Ischaemia
- Infarction
What is an embolism?
An embolism is the blockage of a blood vessel by solid, liquid or gas at a site distant from its origin
What is the most common type of embolism?
Over 90% of emboli are thrombo-emboli
What are other types of embolism?
- Air
- Amniotic fluid
- Nitrogen
- Medical equipment
- Tumour cells
Outline the four different pathways for thromboemboli
- From systemic veins → lungs (pulmonary emboli)
- From the heart (via aorta) → renal, mesenteric and other arteries
- From atheromatous carotid arteries → brain
- From atheromatous abdominal aorta → leg arteries
Identify common areas where emboli can occur
- Pulmonary embolism
- Coronary embolism
- Cerebral embolism
What is a deep vein thrombosis?
- A deep vein thrombosis is the formation of a thrombus within a deep vein, most commonly the deep calf veins
- It produces an inflammatory response (calor, dolor, rubor, tumor, functio laesa)
Identify 5 predisposing factors to deep vein thrombosis
- Immobility
- Post-operative
- Pregnancy and postpartum
- Oral contraceptives
- Severe burns
How does one prevent DVT?
- Prophylaxis for high-risk patients
- Heparin sub-cutaneously
- Leg compression during surgery
I. TED stockings
II. ‘Flowtron’ boots
What is the treatment for DVT?
- Intravenous heparin
- Oral warfarin
What is a pulmonary embolism?
- A pulmonary embolism is a sudden blockage of a pulmonary artery in the lung, usually due to a deep vein thrombosis
- It presents with chest pain, shortness of breath, coughing and blood stained sputum
Identify and describe the three forms of pulmonary embolism
- Massive PE – >60% reduction in blood flow (rapidly fatal)
- Major PE – medium-sized pulmonary vessels blocked (SOB ± cough, blood stained sputum)
- Minor PE – small peripheral pulmonary arteries blocked (asymptomatic/SOB)
What is the effect of recurrent minor pulmonary emboli?
Recurrent minor PEs lead to pulmonary hypertension
