L1: Thrombosis & Embolism

Question 1

What is the definition of thrombosis?

Answer 1

Formation of a compact mass composed of the circulating blood elements inside a vessel or a heart cavity during life.

Question 2

What are the causes and pathogenesis of thrombosis?

Answer 2

(Virchow’s triad)

1. Roughness of the intima (Endothelial injury).
2. Slowing of blood flow (stasis). “Bed rest”
3. Changes in the composition of blood (hypercoagulability). “Inherited or acquired (due to cancer)”

Question 3

What is the morphology of thrombosis?

Answer 3

Grossly and microscopically apparent laminations called lines of Zahn, which are pale platelet and fibrin deposits alternating with darker red cell-rich “RBCs and WBCs” layers.

Question 4

What are the types of thrombosis?

Answer 4

A) According to site:
1. Venous thrombosis (phlebothrombosis): deep vein thrombosis in the lower limb

2. Arterial thrombi: As in coronary, cerebral, & femoral arteries
3. Heart chambers or in the aortic lumen are mural thrombi

B) Presence or absence of organism (infection): Septic “due to infection at the site of thrombosis” or Aseptic

Question 5

What are the fate and complications of thrombosis?

Answer 5

1) Septic thrombus: fragmented by proteolytic enzymes → septic emboli → pyaemic abscesses.
2) Aseptic thrombus: fate depends upon its size
a. if small in size: Dissolution: dissolved and absorbed.

b. if large in size: (PEOC)
1. Propagation: Thrombi accumulate additional platelets and Fibrin
2. Embolization: Aseptic emboli → ischemia.
3. Organization “Replaced by fibrous tissue” & Recanalization
4. Calcification.

Question 6

What is the definition of embolism?

Answer 6

It is the circulation of insoluble material (solid, liquid, or gaseous) in the blood and its sudden impaction in a narrow vessel.

Question 7

What are the types of emboli?

Answer 7

1- Thrombo-embolism. 
2- Fat embolism.
3- Tumor emboli.
4- Parasitic emboli.
5- Air embolism.
6- Amniotic fluid embolism.

Question 8

What is the origin of thromboembolism?

Answer 8

A detached thrombus may originate from:

1. Systemic veins reach the right side of the heart, then lungs → pulmonary embolism
2. Cardiac thrombi: Usually originate in the left side of the heart. They are carried by the systemic arterial circulation to impact any organ (spleen, kidney, brain…etc.)
3. Portal vein or its branches passes to the liver (portal embolism).

Question 9

What are common sites for fat embolism? “Injury in BV + Fat source”

Answer 9

Common in sites containing fat such as; Bone fractures & abdomen due to acute pancreatitis

Question 10

What do fat globules enter through?

Answer 10

ruptured veins

Question 11

What is the definition of tumor emboli?

Answer 11

Malignant “not just neoplastic” cells pass as emboli in the circulation and give metastases in the organs.

Question 12

What forms parasitic emboli?

Answer 12

Bilharzial ova and worm

Question 13

Is amniotic fluid “contains epithelium” embolism rare or common? And when does it occur?

Answer 13

Rare

Occurs during delivery→ fatal pulmonary embolism.

Question 14

What is the definition of air embolism?

Answer 14

Sudden admission of 100 cc air in the bloodstream —->sudden death.

The air may block the right ventricle or pulmonary arteries —> acute heart failure.

Question 15

What are the causes of air embolism?

Answer 15

• Injury of large neck veins → gaping (because they are embedded in the fascia that prevents their collapse) → air is sucked into the vessels then the heart.
• Faulty technique during blood transfusion.
• Criminal abortion (air passes into uterine veins). “Using a tool that damages the BV”
• Caisson’s disease

Question 16

What is caisson’s disease?

Answer 16

 A type of air embolism occurs when deep divers work under high atmospheric pressure, where their nitrogen gas is dissolved in the tissues and blood.

 Sudden decompression i.e. sudden ascent produces nitrogen bubbles which act as gas emboli.

Question 17

What is the effect of embolism?

Answer 17

emboli lodge in vessels too small to permit further passage —-> partial or complete vascular occlusion ——>ischemic necrosis (infarction) of the tissue supplied by this vessel.

Question 18

What does the effect of embolism depend on?

Answer 18

1- Size of embolus.
2- Nature of the embolus: septic (pyemic abscess) or aseptic (infarction).
3- State of the collateral circulation in the affected organ.

Question 19

What are the sources of pulmonary embolism?

Answer 19

• Mainly arises from recent thrombi of calf veins in lower limbs (Most common).
• Thrombi in the Rt. side of the heart e.g. in cases of Rt. sided heart failure.

Question 20

What are the effects of pulmonary embolism?

Answer 20

Depends on the size of the embolus

Question 21

What are the effects of pulmonary embolism in the case of large embolus?

Answer 21

Occludes the pulmonary trunk or one of its main branches produces sudden death (no time for infarction)

Question 22

What are the effects of pulmonary embolism in the case of a medium-sized embolus?

Answer 22

If the lung is healthy, no effect will occur as the lung has a double blood supply (pulmonary and bronchial arteries).

If the lung suffers from chronic venous congestion, lung infarct occurs. “ And the patient needs observation as he has hypercoagulability”

Question 23

What are the effects of pulmonary embolism in the case of recurrent small-sized embolus?

Answer 23

Produce pulmonary hypertension due to lung fibrosis “resists blood flow” and right-sided heart failure “higher work done to overcome resistance” (cor-pulmonale).