2 - Thrombosis, Embolism, Infarction Flashcards
What is the term for the normal physiologic process of maintaining blood in a fluid, clot-free state in normal vessels while inducing a rapid and localized hemostatic plug at sites of vascular injury?
Hemostasis
What are the three major players in the process of hemostasis?
(1) Vascular endothelium (2) Platelets (3) The coagulation cascade
“Which of the following is/are not especially relevant in the process of hemostasis? (a) Albumin (b) Coagulation cascade (c) Fibroblasts (d) Platelets (e) Red blood cells (f) Vascular endothelium “
“(a) Albumin (c) Fibroblasts [remember that fibroblasts have NOTHING to do with fibrin or fibrinogen] (e) Red blood cells”
What is the correct term for a blood clot?
A thrombus
What are the components of a thrombus?
(1) Platelets
(2) Fibrin [circulating fibrinogen, produced by the liver, is polymerized during clotting to insoluble fibrin]
(3) Trapped red and white blood cells [mainly red cells, because they’re more numerous]
What is another term for a blood clot?
A thrombus
What is a thrombus?
A permanent hemostatic plug composed of a mesh of intermingled platelets, fibrin and entrapped blood cells. A “blood clot.”
What does the term thrombosis mean?
Inappropriate activation of blood clotting in an uninjured vessel or after minor injury
What is the term for inappropriate activation of blood clotting in an uninjured vessel or after minor injury?
Thrombosis
What are the three primary influences or inciting causes of thrombosis that comprise Virchow’s triad?
“(1) Endothelial injury (2) Alterations in normal blood flow (3) Hypercoagulability”
Of the three primary influences or inciting causes of thrombosis that comprise Virchow’s triad, which is the most important?
Endothelial injury
“Of the three components of Virchow’s triad, below, which is the most important? (1) Alterations in normal blood flow (2) Endothelial injury (3) Hypercoagulability”
(2) Endothelial injury
Give an example of something that could cause endothelial injury and predispose to thrombosis.
“There are many causes of endothelial injury such as: (1) Trauma [e.g., faulty IV injection] (2) Vasculitis [infectious organisms, immune-mediated] (3) Metabolic disorders [e.g., vitamin E deficiency] (4) Neoplasia (5) Toxins [e.g., bacterial endotoxin]”
“Of the three components of Virchow’s triad, below, which is the SECOND most important? (1) Alterations in normal blood flow (2) Endothelial injury (3) Hypercoagulability”
(1) Alterations in normal blood flow
Is STASIS of blood a more common cause of thrombosis in arteries or in veins?
Veins
Is TURBULENCE of blood a more common cause of thrombosis in arteries or in veins?
Arteries
List FOUR ways in which abnormal blood flow in a vessel can predispose to thrombosis.
“Both stasis and turbulence: (1) disrupt laminar flow, bringing platelets into contact with endothelium (2) prevent dilution of activated clotting factors by fresh flowing blood (3) retard the inflow of clotting factor inhibitors and permit build-up of thrombi (4) promote endothelial cell activation (which makes endothelial cells “sticky”)”
What is the most common cause of hypercoagulability?
Inflammation
What is the definition of hypercoagulability?
Any alteration of the coagulation pathways that predisposes to thrombosis
Which type of thrombus (arterial or venous) is more likely to be occlusive (i.e., fully block a vessel)?
Venous
Which type of thrombus (arterial or venous) is more likely to be red and gelatinous?
Venous
Which type of thrombus (arterial or venous) is more likely to be pale and grey-tan?
Arterial
Which type of thrombus (arterial or venous) is more likely to have its “tail” extend downstream?
Arterial
Which type of thrombus (arterial or venous) is more likely to have its “tail” extend upstream?
Venous
Which type of thrombus (arterial or venous) is more likely to have lines of Zahn?
Arterial
Which type of thrombus (arterial or venous) is more likely to be laminated?
Arterial
Which type of thrombus (arterial or venous) is more likely to contain many red blood cells?
Venous
Which type of thrombus (arterial or venous) is more likely to contain relatively few red blood cells?
Arterial
Which type of thrombus (arterial or venous) is more likely NOT to be attached to the vessel wall?
Neither; this is a trick question. Thrombi arise on vessel walls and are attached to them. If it’s not attached to a vessel wall then a “plug” in a vessel is either a post mortem blood clot or is a fragment of a thrombus that broke free and lodged downstream (i.e., a thromboembolus).
What are the four typical components of a heart valve vegetation in a domestic animal?
“The three components of a thrombus plus bacteria (or less commonly fungi). That is: (1) Fibrin (2) Platelets (3) Entrapped blood cells (4) Bacteria (or less commonly fungi)”
What is the term for irregular nodular masses composed of thrombi and bacteria or fungi found on heart valves?
Vegetations
Why are thromboemboli typically more dangerous than thrombi?
Thrombi tend not to be occlusive (i.e., they still allow some blood to pass around them in the vessel) whereas thromboemboli lodge at bottlenecks downstream and therefore often fully block vessels.
What does “D.I.C” stand for?
Disseminated intravascular coagulation
What is the term for the syndrome of diffuse activation of coagulation in the microcirculation?
Disseminated intravascular coagulation or D.I.C.
What is disseminated intravascular coagulation?
“D.I.C. is not a primary disease, but rather a complication of diffuse activation of coagulation in the microcirculation “
What are two serious clinical consequences of disseminated intravascular coagulation?
(1) CIRCULATORY INSUFFICIENCY in vital organs (brain, heart, lungs, kidney) caused by widespread microthrombosis; (2) WIDESPREAD HEMORRHAGE caused by consumption of clotting factors by the formation of so many thrombi.
What is the most common gross lesion seen in animals that have died from disseminated intravascular coagulation?
Widespread hemorrhage
What is the pathogenesis of the hemorrhage seen in animals that have died from disseminated intravascular coagulation?
“Widespread clotting / thrombosis in microvasculature -> consumption of clotting factors -> hemorrhage “
What is the term for the passage of any intravascular solid, liquid or gaseous mass by the blood to a site distant from its origin?
Embolism
What does the term embolism mean?
The passage of any intravascular solid, liquid or gaseous mass by the blood to a site distant from its origin
What is the origin/source of the material that composes more than 95% of emboli?
Fragments that have broken off thrombi. In comparison, embolism of air, fat, neoplasms, intervertebral disc material or parasites is relatively rare.
What is the typical outcome of thromboembolism?
Infarction of the tissues supplied by the blood vessel in which the embolus lodges
Where do venous thromboemboli tend to lodge?
The lungs
Are thromboemboli that lodge in the lungs more likely to be of venous or arterial origin?
Venous
Where do thromboemboli detached from cardiac thrombi in cats tend to lodge?
At the termination of the abdominal aorta into the iliac arteries, causing feline aortic thromboembolism (FATE or “saddle thrombus)
What is the term for ischemic necrosis of an area caused by obstruction of its (most commonly) arterial supply?
Infarction
What does the term infarction mean?
Ischemic necrosis of an area caused by obstruction of its (most commonly) arterial supply
What is the most common reason for infarction to occur?
Almost all infarction is due to vascular occlusion by thrombosis or thromboembolism. [Other causes are vascular compression or torsion.]
Infarcted organs and tissues tend to undergo what type of necrosis?
Coagulative (except the brain, which undergoes liquefactive necrosis)
Name three major factors that can influence the effects of infarction due to arterial obstruction.
“(1) Tissue/organ supplied. [E.g., the brain is much more susceptible to ischemia than a ligament.] (2) Amount of collateral circulation. [Organs with good collateral circulation (e.g., intestines) are less susceptible to infarction than those without (e.g., testis, spleen, kidney …)] (3) Speed of onset. [Rapid arterial obstruction is more serious than gradual because it does not allow time for collateral circulation to develop.] “
What is the typical shape of the area of infarcted tissue that results from arterial obstruction in a solid organ (e.g., kidney, spleen, skin)?
Wedge-shaped, with the apex/point at the site of blockage, and widening to a base that extends to the capsule of the organ.
Which is more likely to cause severe congestion and edema in addition to infarction, and why: arterial obstruction or venous obstruction?
Venous obstruction. Since the arterial supply often remains intact to an organ that has suffered venous obstruction (e.g., organ torsions or displacements), congestion and edema are often seen. This does not happen in cases of arterial obstruction, in which the tissue is deprived of its blood supply.
What are three major categories of shock?
“(1) Cardiogenic shock (2) Hypovolemic shock (3) Shock caused by blood maldistribution”
