Thrombosis and Embolism

Question 1

What causes fibrin production?

Answer 1

Fibrin production occurs when the coagulation cascade is triggered from contact with damaged epithelium or atheromatous plaque. Fibrinogen is converted to fibrin polymer.

Question 2

What are the 2 substances that platelets contain?

Answer 2

alpha granules which are adhesion substances.

dense granules which are aggregation substances.

Question 3

What are the 3 factors that promotes thrombosis? What are they collectively known as?

Answer 3

Endothelial damage, abnormal blood flow, hypercoagulability. Known as the Virchow’s Triad

Question 4

There are alternating pale and dark red zones (lines of Zahn). Is this seen in a thrombus or a clot?

Answer 4

A thrombus

Question 5

What is a mural thrombus?

Answer 5

A mural thrombus can release fragments which can travel in blood to block distant vessels.

Question 6

Where do embolism to organs and limbs originate from?

Answer 6

From the heart or large arteries

Question 7

Where do embolism to the lungs (pulmonary arteries) originate from?

Answer 7

From deep veins

Question 8

Where is a rare source of pulmonary thromboemboli?

Answer 8

Right atrium

Question 9

Define thrombus, clot and embolus

Answer 9

Thrombus is a blood clot that is formed within the vascular system in a living person.

Clot is a coagulation formed within or outside the vascular system, in a living or dead person.

Embolus is a mass of material in blood that can be trapped in a blood vessel and block its lumen.

Question 10

What is usually given to reduce the risk of thrombosis in surgery?

Answer 10

Heparin

Question 11

What is cardiac thrombosis?

Answer 11

Thrombosis of cardiac valves and chambers

Question 12

Which sites can be affected by atheroma?

Answer 12

Any arteries that are larger than 1mm in diameter can be affected.
But maximum atheroma occurs at sites of bifurcation with haemodynamic stress.

Question 13

In which type of atheroma is there weakened vessel walls? What can result from the weakened vessel wall?

Answer 13

In Type IV - Complicated lesion

Weakened vessel wall can lead to aneurysm

Question 14

Lumenal narrowing results in?
Lumenal occlusion results in?
Embolism results in?
Give examples of conditions caused in each case.

Answer 14

Lumenal narrowing results in ischaemia. Example is angina (chest pain on exertion).
Lumenal occlusion leads to infarction. Example is myocardial infarction due to thrombosis of a coronary artery.
Embolism results in Ischaemia and infarction. Example is transient cerebral ischaemic attacks due to embolism from carotid atheroma.

Question 15

What can cause transient cerebral ischaemic attacks? What are the symptoms leading to it?

Answer 15

Transient cerebral ischaemic attacks results from embolism. Symptoms include transient neurological deficit or loss of consciousness.

Question 16

Describe the symptoms of ischaemic colitis and ischaemic enteritis.

Answer 16

Ischaemic colitis: Lack of blood supply to the colon leading to ischaemia, short of infarction (no infarction)
Patient has bloody diarrhoea and pain.
Ischaemic enteritis: Thrombosis develops over an atheromatous plaque in one of the mesenteric arteries, resulting in infarction. Gut infarction results.

Question 17

Which arteries are usually spared from severe atheroma?

Which artery is most susceptible to aneurysm?

Answer 17

Renal arteries are usually spared from severe atheroma.

Infrarenal abdominal artery is most susceptible to aneurysm.

Question 18

Describe how atheroma can lead to hypertension.

Answer 18

Renal arteries are usually spared from severe atheroma, but sometimes, especially in diabetic patients, the origin of the of the renal arteries may be affected. The kidney becomes gradually atrophic due to ischaemia. The underperfused kidney will release renin which results in renal hypertension.

Question 19

Explain how does injury to the endothelium lead to atheroma formation.

Answer 19

Injury to the endothelium triggers monocyte adhesion, a loosening of endothelial cell junctions, and migration of monocytes beneath the endothelium into the sub-endothelial space, where they differentiate into macrophages.
The more permeable endothelium also allows LDL to enter the intima of the artery. Macrophages engulf LDL and become laden with lipids, now called macrophage foam cells. Collection of these leads to fatty streak lesions.
T-lymphocytes also release cytokines which will trigger smooth muscle cells to migrate from the media to the intima and proliferate (under the influence of growth factors).

Question 20

What leads to a dissection?

Answer 20

Tear in intima, leading to extravasation of blood into the intima of blood vessel wall.

Question 21

Necrosis began in the tissue areas furthest away form the obstructed artery or nearest to the obstructed artery?

Answer 21

Necrosis first begin in tissue regions furthest from the affected artery.