Path XII: Thrombosis

Question 1

What is a thrombus?

Answer 1

solid mass or plug composed of blood constituents in the heart or blood vessels. forms as a consequence of inappropriate activation of normal hemostatic processes.

Question 2

What is Virchow’s triad?

Answer 2

3 factors that predispose someone to thrombus formation:

1. endothelial injury
2. stasis and turbulence
3. hypercoagulatiblity

Question 3

How does endothelial injury lead to thrombus formation?

Answer 3

endothelial injury exposes platelets to collagen in the basement membrane. Tissue factor is also released. There is a local depletion of prostacyclin and plasminogen activators.

Question 4

What are some examples of endothelial injury?

Answer 4

ulcerated athersclerotic plaques
trauma
hypertension
inflammatory or immune-mediated injury (vasculitis plus complement)

Question 5

How does stasis and turbulence contribute to thrombus formation?

Answer 5

Stasis and turbulence leads to a disruption of laminar flow.
With this disruption, platelets can come into conact with the endothelium. Dilution of activated clotting factors is prevented. Accumulation of platelet aggregates is permitted. And the endothelium can be injured.

Question 6

What are some examples of stasis and turbulence contributing to thrombus formation?

Answer 6

DVT after inactivity
atrial fib or dilation (mural thrombi)
aneurysm
atherosclerotic plaque.

Question 7

What are some mechanisms by which someone might be in a hypercoagulable state?

Answer 7

incr. levels of clotting factors
decreased levels of clotting inhibitors
abnormal clotting factors
release of thromboplastin-like factors from malignant cells
incr. or abnormal platelets

Question 8

What are some examples of hypercoaguable states?

Answer 8

neoplasia
thrombophilic states
pregnancy
post partum
OCP

Question 9

Where do arterial and cardiac thrombi occur? Of what are they composed?

Answer 9

at the site of endothelial injury, esp. in system with rapid blood flow. mostly a white thrombus composed of platelets and fibrin.

Question 10

What are some characteristics of mural thrombi?

Answer 10

attached to the wall of a large vessel or cardiac chamber
usually non-occlusive
symptoms due to embolization, not obstruction

Question 11

What are some examples of mural thrombi?

Answer 11

atrial thrombi, ventricular thrombi after MI, ulcerated aortic atherosclerotic plaques, aneurysms

Question 12

What are the characteristics of occlusive thrombi? What are the common sites?

Answer 12

associated with atherosclerosis in small arteries. coronary> cerebral> femoral > iliac> >popliteal > mesenteric

Question 13

What are some genetic risk factors for arterial thrombosis?

Answer 13

sickle cell anemia and familial hypercholesterolemia

Question 14

What are some acquired risk factors for arterial thrombosis?

Answer 14

age, antiphospholipid antibody syndrome, malignancy, vasculitis, heparin-induced thrombocytopenia, hyperviscosity syndromes, smoking, and tissue damage

Question 15

What are some mixed risk factors for arterial thrombosis?

Answer 15

atherosclerosis
diabetes
hyperhomocysteinemia

Question 16

What are some causes and associations with venous thrombosis?

Answer 16

associated with stasis and turbulence.

formed in a system with sluggish blood flow- contain more RBCs.

Question 17

Where do you see laminations/lines of Zahn, and where not?

Answer 17

seen lines of Zahn in arterial thrombosis but not in venous thrombi

Question 18

What is the typical clinical significance of venous and arterial thrombi?

Answer 18

emoblization

Question 19

What are some causes of superficial venous thrombosis? What are some physical signs?

Answer 19

causes- IV drug use, varicose veins
physical signs- tenderness, local inflammation
rarely embolize

Question 20

What are some genetic factors that predispose for venous thrombosis?

Answer 20

antithrombin, protein C, Protein S deficiency. Factor V Leiden (factor V not inactivated)

Question 21

What are some acquired risks of venous thrombosis?

Answer 21

age, immobilization, surgery, malignancy, pregnancy, OCP, hormone replacement, antiphospholipid antibody syndrome, myeloproliferative syndromes

Question 22

What are some mixed risk factors for venous thrombosis?

Answer 22

hyperhomocysteinemia
increased VIII levels
dysfibrogenemia

Question 23

What are the 2 biggest genetic risk factors for venous thrombosis?

Answer 23

Factor V Leiden homozygote- 70X as likely. followed by antithrombin, protein S or C deficiencies (10X)

Question 24

What are the biggest acquired risk factors for venous thrombosis?

Answer 24

hospitalization/immobilization- 10X
surgery- 6X
pregnancy and OCPs- 4X.

Question 25

What is disseminated intravascular coagulation?

Answer 25

coagulation involving small vessels and capillaries.

complication of an underlying process which activates the clotting system and gives rise to multiple thromboses.

Question 26

What is seen in DIC?

Answer 26

minute platelet and thrombi in multiple capillaries and venules. paradoxical hemorrhagic diathesis due to rapid consumption of coagulation factors and activation of the fibronolytic system.

Question 27

When might you see DIC?

Answer 27

gram negative sepsis, shock, carcinoma, amniotic fluid embolism

Question 28

What might happen to the thrombi of DIC?

Answer 28

destruction by fibrinolysis
organization and recanulization
propagation
obstruction
embolization