Thrombosis and Embolism Flashcards
What causes fibrin production?
Fibrin production occurs when the coagulation cascade is triggered from contact with damaged epithelium or atheromatous plaque. Fibrinogen is converted to fibrin polymer.
What are the 2 substances that platelets contain?
alpha granules which are adhesion substances.
dense granules which are aggregation substances.
What are the 3 factors that promotes thrombosis? What are they collectively known as?
Endothelial damage, abnormal blood flow, hypercoagulability. Known as the Virchow’s Triad
There are alternating pale and dark red zones (lines of Zahn). Is this seen in a thrombus or a clot?
A thrombus
What is a mural thrombus?
A mural thrombus can release fragments which can travel in blood to block distant vessels.
Where do embolism to organs and limbs originate from?
From the heart or large arteries
Where do embolism to the lungs (pulmonary arteries) originate from?
From deep veins
Where is a rare source of pulmonary thromboemboli?
Right atrium
Define thrombus, clot and embolus
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.
What is usually given to reduce the risk of thrombosis in surgery?
Heparin
What is cardiac thrombosis?
Thrombosis of cardiac valves and chambers
Which sites can be affected by atheroma?
Any arteries that are larger than 1mm in diameter can be affected.
But maximum atheroma occurs at sites of bifurcation with haemodynamic stress.
In which type of atheroma is there weakened vessel walls? What can result from the weakened vessel wall?
In Type IV - Complicated lesion
Weakened vessel wall can lead to aneurysm
Lumenal narrowing results in?
Lumenal occlusion results in?
Embolism results in?
Give examples of conditions caused in each case.
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.
What can cause transient cerebral ischaemic attacks? What are the symptoms leading to it?
Transient cerebral ischaemic attacks results from embolism. Symptoms include transient neurological deficit or loss of consciousness.
Describe the symptoms of ischaemic colitis and ischaemic enteritis.
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.
Which arteries are usually spared from severe atheroma?
Which artery is most susceptible to aneurysm?
Renal arteries are usually spared from severe atheroma.
Infrarenal abdominal artery is most susceptible to aneurysm.
Describe how atheroma can lead to hypertension.
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.
Explain how does injury to the endothelium lead to atheroma formation.
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).
What leads to a dissection?
Tear in intima, leading to extravasation of blood into the intima of blood vessel wall.
Necrosis began in the tissue areas furthest away form the obstructed artery or nearest to the obstructed artery?
Necrosis first begin in tissue regions furthest from the affected artery.
