class notes 8 - flashcards

Flashcards for exam review.

What is Virchow's triad related to?

Predisposition to thrombosis

Name one factor that can cause injury to the vascular wall, predisposing to thrombosis.

Trauma, Infection, Immune-mediated disease, or Degenerative/metabolic

What does vascular wall injury expose, leading to thrombosis?

Underlying collagen or causes release of tissue factor from the endothelium

What are two consequences of altered blood flow (stasis or turbulence) in relation to thrombosis?

Platelets settle and contact the endothelium; activated clotting factors are not swept away.

Name two conditions that cause stasis.

Shock, cardiac arrhythmia (e.g. atrial fibrillation), prolonged immobility, focal myocardial fibrosis, abnormally shaped erythrocytes

How does turbulence disrupt laminar flow?

Allows platelets to contact the endothelium

Give two examples of what causes turbulence

Cardiomyopathy, arterial aneurysms, stenotic or insufficient cardiac valves, erythrocyte abnormalities

Name two acquired hypercoagulable conditions.

Nephrotic syndrome, increasing age, vasculitides, certain cancers

What deficiencies are associated with inherited hypercoagulable conditions?

Deficiencies of anticoagulant proteins: AT-III, Protein C, Protein S

What is the effect of aspirin in preventing platelet aggregation?

Reduces production of the platelet activator TXA2 from Arachidonic Acid

Are arterial thrombi often occlusive or non-occlusive?

Occlusive

What does occlusive thrombosis cause in tissues with endarterial blood supply?

Infarction

What is the usual direction of growth for arterial thrombi?

Retrograde

What are the components of the lines of Zahn?

Alternating laminae of pale fibrin and platelets, and darker erythrocytes

How can venous thrombi be distinguished from post-mortem clots at necropsy?

Venous thrombi should be adhered to the vascular wall, while post-mortem clots are not.

What are the two portions of a post-mortem clot?

A dark red dependent portion and a clear or tan, gelatinous superficial portion

What is propagation of a thrombus?

Enlargement of a thrombus until it becomes occlusive

What is embolization in the context of thrombi?

Release of fragments into the blood stream

Which enzyme can dissolve clots in the early stages?

Plasmin

What does FSF do to a clot?

Stabilizes it and makes plasmin digestion more difficult

Describe organization and recanalization of a thrombus.

The thrombus may be incorporated into one side of the vessel wall, with blood flow re- established around it, or an occlusive thrombus may undergo fibrosis, and multiple small vascular channels may be formed through it

Why are thrombi considered fertile soil for bacteria?

Bacteria can lodge easily

What is the difference between septic and bland thrombi?

Septic thrombi contain bacteria, bland do not

What pattern of thrombi/infarcts suggests vegetative valvular endocarditis?

Multiple thrombi or multiple infarcts in the kidneys

Besides thrombi, name two other materials that can form emboli.

Foreign material, gasses, cartilage, lipid

Where do mural thrombi often form in feline dilated cardiomyopathy?

Left heart

What is a saddle thrombus?

An embolus lodged in a vascular bifurcation

What is an infarct?

An area of necrosis caused by occlusion of blood flow

Name the two types of thrombosis that can cause Infarcts

Arterial or venous

What is the appearance of acute arterial infarcts?

May be grossly inapparent or poorly defined

What color does necrotic tissue appear over time

Pale

What causes the red rim around an infarct over time?

Vasodilation and neovascularization

What happens to infarcted tissue histologically?

It is necrotic

What shape do many infarcts have?

Wedge-shaped or symmetrical

In what organs do white infarcts occur most often?

Solid organs with an endarterial blood supply (e.g. kidney, spleen, heart)

What are some causes of a red infarct?

Haemorrhage occurs in loose tissues, in tissues that have a dual blood supply, or as a result of venous infarction

Why are organs with a single venous outflow at the greatest risk of venous infarction?

Lack of collateral vessels

How can pale infarcts become red infarcts?

After lysis of the occluding thromboembolus

Describe septic and bland infarcts

Infarction may result from occlusion by a septic embolus, thrombosis may be predisposed by septicaemia, or bacteria may invade thrombi and necrotic tissue

What do septic infarcts usually become?

Abscesses