Thrombosis Embolism and Infarction

Question 1

What is a thrombus?

Answer 1

A solidification of blood contents that forms in the vascular system during life. (Blood clots at wounds do not count)

Question 2

Name the three pathological features that lead to the development of a thrombus?

Answer 2

Endothelial Injury, Abnormal blood flow and hypercoagulation

Question 3

Endothelial damage in important formation of thrombi where? and name some examples

Answer 3

• In heart and aorta.
• Some examples are thrombi developed of the left ventricle at sites of myocardial infarction and on ulcerated plaques in advanced atherosclerosis.

Question 4

How can the endothelial become damaged?

Answer 4

Radiation Injury,
Both endogenous and exogenous chemical agents,
Bacterial toxins/endotoxins,
Immunological Injuries,
Neoplastic involvement (tumours)

Question 5

Describe the role of platelets after injury to vessel

Answer 5

• Adhesion (to exposed collagen with help of von Williebrand’s factor)
• Secretion (of granules such as ADP, thromboxane A2 and Pf4 which recruits more platelets)
• Aggregation (fibrin helps adhesion)
  WBC’s and RBC’s can become trapped in thrombus causing occlusion

Question 6

Name some disorders that occur with deficiency of GpIIb-IIIa and GpIb

Answer 6

GpIIb-IIIa - Glanzmann’s Thromboasthenia
GpIb - Bernard-Soulier Syndrome
Results in inability to form clots

Question 7

What are the two abnormal types of blood flow and what to they contribute to?

Answer 7

Turbulence (blood flow in all directions, not linear) - development of arterial and cardiac thrombi
Stasis (low blood flow) - venous thrombosis

Question 8

Describe how the turbulence and stasis blood flow contribute to formation of thrombi

Answer 8

• Disrupt laminar flow
• Prevent dilution of coagulation factors
• Retard the inflow of inhibitors of clotting factors
• Promote endothelial cell activation

Question 9

Define hypercoagulation

Answer 9

Alternation of the blood coagulation mechanism that in some way predisposes thrombosis

Question 10

What is primary hypercoagulation?

Answer 10

Its genetic and can be because of;

• Mutation in factor V gene
• Antithrombin III deficiency
• Protein C and S deficiency

Question 11

What is secondary hypercoagulation?

Answer 11

It is acquired and can be;
High risk - Result of bed rest, myocardial infarction, tissue damage, DIC
Lower risk - AF, cardiomyopathy, oral contraceptive, sickle cell anaemia and smoking.

Question 12

What are the three different morphology of thrombi?

Answer 12

Mural thrombi (chambers of heart or aorta),
Arterial Thrombi,
Venous Thrombosis (Phlebothrombosis

Question 13

Describe some of the features of arterial thrombi

Answer 13

• Usually occlusive, may be mural and are frequently seen (in order of commonality) Coronary, cerebral and femoral. Grey-white

Question 14

Describe the histological appearance of a thrombus

Answer 14

Key - Lamination’s called lines of Zahn. These are pale bands of fibrin and platelets with red bands of RBC’s

Question 15

Describe some of the features of venous thrombosis (Phlebothrombosis)

Answer 15

• Can be occlusive and are dark red.

- 90% of time effect veins of lower limbs (deep calf, femoral, popliteal and illiac)

Question 16

What is Thrombophelbitis

Answer 16

When a vein becomes very inflamed and then thrombosed

Question 17

Describe the fate of thrombi

Answer 17

• Resolved (using drugs)
• Embolization to lungs
• Incorporated into wall, narrowing lumen
• Organisation and recanalization

Question 18

Describe the clinical appearance of arterial thrombosis

Answer 18

Importance - Obstruction and sources of emboli
Presentation - Lose of pulses distal to thrombus, 5P’s (pulseless, perishing cold, pale, painful and parasthesia) and tissue eventually dies and gangrene results

Question 19

Describe the clinical correlations of venous thrombosis

Answer 19

Superficial - Congestion, swelling, pain and tenderness but rarely embolise.
Deep - Foot and ankle oedema, Homans’ sign but also could be asymptomatic until it embolised.

Question 20

Describe some of the treatments for thrombosis

Answer 20

Prevention - Stockings (squeeze deep veins)
Anticoagulant drugs - Warferin (oral) or Heparin (i.v or s.c). Warfarin takes a day to start working so given as after treatment, heparin used for quick effects.

Question 21

What is an embolus? What percent arise from thrombi?

Answer 21

The detachment of intravascular solid, liquid or gaseous mass carried by blood to a site distant from origin. 99% arise from thrombi so unless otherwise stated, it usually means thromboembolism.

Question 22

Rare forms of emboli include fragments of what?

Answer 22

Bone/bone marrow
Atheromatous debris
Fat
Bits of tumour
Bubbles of air/nitrogen

Question 23

Describe the classifications of embolism

Answer 23

Pulmonary embolism,
Systemic embolism
Amniotic fluid embolism
Air embolism
Fat embolism

Question 24

Describe some of the features of a pulmonary embolism

Answer 24

Occlusion of a large/medium pulmonary artery is embolic until proven otherwise. Over 95% of pulmonary emboli arise from thrombi from large deep leg veins.

Question 25

What is a saddle embolus?

Answer 25

A large embolism that bifurcation of the main pulmonary artery - causes instant death.

Question 26

Pulmonary embolism results in what?

Answer 26

Respiratory compromise and haemodynamic compromise. It is one of the few things that cause instantaneous death.

Question 27

Smaller pulmonary emboli may cause?

Answer 27

Acute respiratory and cardiac problems;

Chest pain, dyspnoea (difficulty breathing), shock, increased LDH and haemoptysis (coughing up blood)

Question 28

How can you diagnose pulmonary emboli?

Answer 28

X-ray, X-ray with radionucleotides and some occlusion can put strain on the heart which is picked up on ECG

Question 29

Describe some of the features of Systemic Embolism

Answer 29

• Emboli that travels through arterial circulation.
• 80%ish arise from thrombi within heart
• Less common sources include ulcerated atherosclerotic plaque and aortic aneurysm etc
• Most common sites of lodgement are lower extremities (70-75%), brain (10%), viscera and then upper limb

Question 30

Describe some of the features of air embolism

Answer 30

• Presence of bubbles within circulation that obstruct vascular flow and damage tissue (barotrauma)
• Can occur; In delivery or abortion, performance of a pneumothorax, injury to chest wall or decompression sickness (Caisson disease)

Question 31

Describe some of the features of Caisson disease

Answer 31

• Rapid decompression causes helium and nitrogen to persist and form a gaseous emboli. Effects scuba divers.
  Treatment - Recompression chamber

Question 32

Describe some features of fat embolism

Answer 32

• Small globules of fat in circulation
• Can occur with long bone fractures and less common soft tissue trauma and burns.
  Pathenogenesis - Mechanical obstruction (microagregates of neutral fat causing occlusion) and chemical injury (free fatty acids released from fat cause toxic injury to endothelium)

Question 33

Describe some of the clinical features of fat embolisms

Answer 33

Characterised by; Pulmonary insufficency, neurological symptoms (irritability, restlessness which progresses to delerium and coma) and anaemia and thrombocytopenia.
Symptoms only appear 24-72hrs after injury.

Question 34

Describe some of the features of amniotic fluid embolism

Answer 34

Rare complication but cause of maternal mortality. Caused by infusion of amniotic fluid into mother’s circulation.
Patients pulmonary micocirculation at postmortem contains - Epithelial squames, lanugo hair, fat from vernix caseosa and mucin from baby respiratory/GI

Question 35

what is the clinical presentation of amniotic fluid embolism

Answer 35

Resp difficulty (deep cyanosis and cardiovascular shock), followed by convulsions and the coma.

Question 36

What is infarction and what are the main causes and some other causes

Answer 36

Occlusion of vascular supply to tissue causing cell death. Main causes are thrombosis or embolism (99%). Other causes can be vasospasm, expansion of atheroma, compression of vessel etc

Question 37

What are some of the factors that influence development of an infarct?

Answer 37

Nature of vascular supple (kidneys and spleen have single blood supply)
Rate of development of occlusion
Vulnerability to hypoxia (brain can only last 3-4mins without air, where are myocardial cells are up to 30mins)
Oxygen content of blood

Question 38

Describe the different types of infarct

Answer 38

Red (haemorrhagic) - venous occlusion
White (anaemic) - arterial occlusions
Septic/bland - collection of bacteria causing blockage of BV.

Question 39

Describe the histology of infarction

Answer 39

Ischaemic coagulation necrosis (mins-days)
Inflammatory response (hours-7 days)
Reparative response (1-2 weeks)
Scaring (2weeks-2 months)