Pathophysiology of Thrombosis & Embolism Flashcards
What is Laminar blood flow?
It is the normal condition for blood flow throughout most of the circulatory system.
- It is characterized by concentric layers of blood moving in parallel down the length of a blood vessel.
What is blood stasis?
The slowing or pooling of blood
What occurs when blood flow becomes turbulent?
- Blood does not flow linearly and smoothly in adjacent layers, but instead the flow can be described as being chaotic.
Defects in blood flow
- Thromboembolism common
Other causes: - Atheroma
- Hyperviscosity, spasm, external compression, vasculitis, vascular steal
The 3 features of Virchow’s Triad
- Changes in the blood vessel wall
- Changes in the blood constituents
- Changes in the pattern of blood flow
What is Virchow’s triad (meaning)?
Factors causing thrombosis
What is the difference between a blood clot and a thrombus?
Blood clots are clumps that occur when blood hardens from a liquid to a solid.
- A blood clot that forms inside one of your veins or arteries is called a thrombus.
- A thrombus may also form in your heart.
-A thrombus that breaks loose and travels from one location in the body to another is called an embolus.
Features of pathogenesis of Thrombosis
- Atheromatous coronary artery
- Turbulent blood flow (fibrin deposition, platelet clumping)
- Loss of intimal cells, denuded plaque
- Collagen exposed, platelets adhere
- Fibrin meshwork, RBCs trapped
- Alternating bands: lines of Zahn
- Further turbulence and platelet deposition
- Propagation
- Consequences
What do the consequences of Thrombosis depend on?
- Site
- Extent
- Collateral circulation
What does propagation of thrombosis lead to?
Embolism
What is an embolism?
Movement of abnormal material in the bloodstream and its impaction in a vessel, blocking its lumen
Features of an embolus
- Detached intravascular solid, liquid or gaseous mass
- Most emboli are dislodged thrombi (thromboembolism)
- Factors causing embolism depend on type of embolus
Types of embolus
- Systemic/Arterial thromboembolus
- Venous thromboembolus
- Fat
- Gas
- Air embolus
- Tumour
- Trophoblast
- Septic material
- Amniotic material
- Bone marrow
- Foreign bodies
Features of Rheumatic fever
- Disease of disordered immunity
- Inflammatory changes in the heart and joints, sometimes neurological symptoms.
- Commonly affects children 5-15 years, boys > girls
- Pancarditis (inflammation affecting endocardium, myocardium, pericardium) in the acute phase; heart murmurs are common
What are presenting features of rheumatic fever?
-Presenting feature: “flitting” (painful) polyarthritis of large joints (wrists, elbows, knees, ankles) plus skin rashes and fever.
Why do most patients have a recent sore throat in rheumatic fever?
Usually due to group A beta-haemolytic streptococcal infection
What is damage to heart tissue in rheumatic fever caused by?
May be caused by combination of antibody-mediated and T cell-mediated reactions
What are Aschoff bodies?
Nodules found in the heart of individuals with acute rheumatic fever.
- Focus of chronic inflammatory cells, necrosis and activated macrophages (Anitschkow cells)
- They result from inflammation in the heart muscle.
What is Valvular heart disease?
It is any disease process involving one or more of the four valves of the heart
- (the aortic and bicuspid on the left side of the heart and the pulmonary and tricuspid valves on the right side of the heart)
What are pathological problems that cause valvular heart disease?
- Valvular stenosis: valve thickened/calcified and obstructs normal blood flow into chamber/vessel.
- Valvular incompetence/regurgitation/incompetency: valve loses normal function and fails to prevent reflux of blood after contraction of cardiac chamber.
- Vegetations: infective or thrombotic nodules develop on valve leaflets impairing normal valve mobility; may embolise.
What can Pancarditis in acute rheumatic fever progress to?
It can progress over time to chronic rheumatic heart disease, mainly manifesting as valvular abnormalities.
What does inflammation of the endocardium and left-sided valves result in?
It results in fibrinoid necrosis of the valve cusps/chordae tendinae, over which (and along line of closure) form small vegetations.
What is rheumatic heart disease mainly characterised by?
It is characterised principally by deforming fibrotic valvular disease, particularly involving the mitral valve: typically leaflet thickening, commissural fusion and shortening, thickening and fusion of chordae tendinae.
What can Rheumatic heart disease cause?
- Virtually the only cause of mitral stenosis
- Can cause mitral regurgitation but now most comonly due to ischaemic heart disease.
- Now only rarely causes aortic stenosis: most due to calcific aortic valve disease.
- Potntially still causes aortic regurgitation /incompetence.
- Tricuspid valve involvement infrequent: pulmonary valve involvement rare.
What is the typical thing seen in rheumatic heart disease?
Mitral stenosis
