Coagulation

Front 1

What is the pentasaccharide form of heparin? How is it different?

Back 1

There are 5 specific residues from the heparin molecule that can bind ATIII without inducing a FULL allosteric change. The change that does occur opens the inhibitory bait site adequately enough for Factor Xa to bind but it won’t fit the thrombin active site.
Specificity of ATIII while bound to heparin pentasaccharide: Almost a specific inhibitor of Factor Xa.

Front 2

What is the role of Kallekrein in hemostasis?

Back 2

It serves several roles:
1. Pro-coagulant: initiates the intrinsic pathway (from pre-kalekrein)
2. Fibrinolytic: Activates prourokinase to urokinase

Front 3

What is urokinase? How does it work?

Back 3

Urokinase is an enzyme that activates plasminogen to plasmin which degrades fibrin. Urokinase requires a cell receptor as a cofactor for plasminogen activation; this prevents non-specific systemic activation of plasminogen. Urokinase can degrade extracellular matrix components as well.

Front 4

What is t-PA? How does it work?

Back 4

t-PA is tissue plasminogen activator which is an enzyme that converts plasminogen to plasmin. t-PA is released from endothelial cells and is only active when bound to fibrin thereby isolating its activity to the location of a clot (no systemic degradation of plasminogen)

Front 5

What is d-dimer?

Back 5

A degradation product of clots that is SPECIFIC to the degradation of FIBRIN.

Front 6

What does it mean if there is a normal d-dimer but degradation products are present?

Back 6

It is usually indicative of excessive breakdown of fibrinogen (in circulation) due to systemic activation of plasminogen with subsequent plasmin formation.

Front 7

What does it mean if both PT and PTT are abnormal?

Back 7

It most likely indicates that there is a problem where the two cascades (intrinsic and extrinsic) converge (post-factor Xa), however it can also mean that there is a separate deficiency in BOTH pathways.

Front 8

What is PAI-1? What is its significance?

Back 8

PAI-1: Activated protein C inhibitor 1: it inhibits BOTH urokinase and t-PA.

Front 9

What is the role of alpha-2-AP in hemostasis?

Back 9

Alpha-2-Antiplasmin: the primary enzyme involved in fibrinolysis regulation; delays the dissolution of the clot. It INHIBITS PLASMIN which degrades fibrin. Alpha-2 AP is normally present in circulation which means that it is harder for it to get to plasmin that is present in clots (where it is supposed to be), and therefore is more specific for plasmin that is free floating in circulation (where it is NOT supposed to be)

Front 10

What are the enzyme deficiencies involved in the major hemophilias?

Back 10

Factors IXa and VIIIa

Front 11

Why does a deficiency in factor IXa result in a bleeding disorder while deficiency in factor XII does not?

Back 11

Because factor IXa is required for the activation of Factor X.
Both thrombin and TF-VIIa serve to activate the early portion of intrinsic cascade but they BOTH act at the same location: The activation of IXIXa. If there is no Factor IX then all of these redundant activators still cannot activate the cascade and the patient will have a bleeding disorder.

Front 12

What is the role of thrombin in hemostasis?

Back 12

(I may have already asked this q…)
It converts fibrinogen to fibrin thereby allowing for formation of the soft clot in coagulation
ALSO it can go back and serve as an activator of Factor IXFactor IXa. This also means that tissue factor is NOT required for activation of the intrinsic pathway even if there is deficiency in Factor XII or HMWK-PK; even when TFPI is present and active, the intrinsic pathway can continue and a clot will form.

Front 13

Following vessel injury, what are the different platelet responses?

Back 13

1.Adhesion: the shape of the platelet changes and pseudopods form when the platelet interacts with areas of denuded endothelium thereby revealing the subendothelial matrix. vWF helps bind the platelet to subendothelial matrix. Glycoproteins Ib and gp IIbIIIa are also involved.
2.Aggregation: mediated by adhesion proteins on the platelet, fibrinogen and vWF
3. Secretion: release of granules containing multiple clotting factors. Also the release of other cytoplasmic contents which are involving in the healing/clotting process.
4. Expression of PF3: platelet factor 3 leads to a change in the platelet surface which allows it to support reactions in the blood clotting process. (also found on endothelial cells and macrophage)
5. Negatively charged phosphatidylserine is normally found on the intracellular envelope of the platelet membrane, but following cell injury there is an increase in intracellular Ca+2 which activates a pathways resulting in the switching of the membrane envelopes. This results in the phosphatidylserine being displaced to the extracellular layer where these anionic phospholipids support the assembly of pro-coagulants at the site of denuded epithelium. (Scott syndrome: cannot flip the layers of the platelet membrane: cannot support the coag pathway.

Front 14

What interactions occur between the platelet and injury site components?

Back 14

1. Rxn with collagen in the subendothelial matrix
2. Rxn with vWF for the platelet aggregation process. vWF is released from damaged endothelial cells: it serves to bind together the collagen matrix and the platelet cell surface.

Front 15

What is the role of ADP in hemostasis?

Back 15

ADP: platelet agonist: recruits more platelets to the site of injury and it facilitates the aggregation process which serves to stabilize the clot

Front 16

What is the role of PDGF?

Back 16

PDGF = platelet-derived growth factor: promotes healing response

Front 17

What is the role of platelet factor 4 in hemostasis?

Back 17

Same as PDGF
promotes healing response

Front 18

What is the role of thrombin in hemostasis?

Back 18

It serves to DIRECTLY activate platelets for aggregation as well as convert fibrinogen to fibrin.

Front 19

What are the important antagonists of platelet aggregation? Where do they come from?

Back 19

Prostacyclin (PGI2): release from the endothelium

Front 20

What is the role of ADPase in hemostasis? Where is it found?

Back 20

HEALTHY endothelial cell express surface ADPase in order to prevent the activation of platelets by ADP (platelet agonist)

Front 21

Where is tissue factor located? How is it activated?

Back 21

TF is a cell surface molecule but it is NOT found on endothelial cells. It is found on stromal and smooth muscle cells that make up the subendothelial tissue.

Front 22

What is the role of factor VIIIa in the coagulation cascade?

Back 22

Factor VIIIa is a coenzyme for factor IXa (+Ca+2, and phosopholipid) which converts factor X to Xa.

Front 23

How is factor Va different from factor VIII?

Back 23

Factor Va also serves as a cofactor (similar to factor VIIIA) but it is a coenzyme for factor II (prothrombin). This rxn also requires Ca+2 and phospholipids.

Front 24

What is factor XIIIa? Why is it necessary in the coagulation cascade?

Back 24

Factor XIIIa is a transglutaminase which serves to cross-react/link fibrin strands in order to create a stable clot. Without these covalent bonds between fibrin strands, the clot is soft and unstable; it is susceptible to the natural physiologic forces of blood flowing through the vessel. The transglutaminase cross-links specific lysine side chains on fibrin strands with nearby glutamine residues on other, adjacent fibrin strands. This slows the process of fibrinolysis as well.

Front 25

What is the intrinsic coagulation pathway?

Back 25

Also known as the contact pathway.
1. HMWK-PK and Factor XII are involved in the first step: XII gets activated to XIIa
2. XIIa activates factor XI  XIa
3. XIa + Ca+2 activates factor IX  IXa
4. IXa + VIIIa + Ca+2 + phospholipid activate factor X  Xa
5. Xa + Va+ Ca+2 + phospholipid activates Factor II (prothrombin)  Thrombin
6. Thrombin (IIa) converts fibrinogen  fibrin
7. Fibrin strands form a loose, soft clot
8. Factor XIIIa + Ca+2 convert the loose clot into a stable clot

Front 26

What is the extrinsic coagulation pathway?

Back 26

Also known Tissue Factor pathway
1. Tissue factor + Factor VII form a complex: TF-VII which becomes activated to TF-VIIa
2. TF-VIIa + Ca+2 + phospholipid activates Factor X  Xa
3. Xa + Va + Ca+2 + phospholipid activates factor II (prothrombin)  Thrombin
4. Thrombin (IIa) converts fibrinogen  fibrin
5. Fibrin strands form a loose, soft clot
6. Factor XIIIa + Ca+2 convert the loose clot into a stable clot

Front 27

What is prothrombin time (PT)? What does it measure?

Back 27

PT is a way to measure the extrinsic pathway. A blood sample is collected and the Ca+2 is chelated out (citrate). To measure the PT, tissue factor, phospholipid, and Ca+2 are added to the blood sample and the amount of time for a clot to form is measured. A normal PT is ~10-12 sec. By adding tissue factor it stimulates the extrinsic pathway.

Front 28

What is PTT? What does it measure?

Back 28

PTT is partial thromboplastin time: it measures the intrinsic pathway clotting time. A citrated blood sample is collected (chelates out the Ca+2) and cells are removed by centrifugation. PTT reagent is added (contains Ca+2, phospholipids, initiating agent) to the remaining blood sample which is put into a container that has an artificial surface. The time for a clot to form is measured (normally ~40-50 sec).
You can shorten this time by doing an activated PTT in which you add everything but the Ca+2 and allow the blood sample +reagent to incubate. This allows for the accumulation of factor XIa (there’s no Ca+2 available for the activation of IXIXa by XIa. Then Ca+2 is added and it drives the rxn to completion.
PTT is prolonged whenever any of the factors in the intrinsic pathway are missing.

Front 29

What is the role of Vitamin K in the coagulation cascade?

Back 29

Vitamin K serves as a cofactor in an enzymatic reaction that is a part of the post-translational modification of certain Factors in the intrinsic/extrinsic coagulation cascades. The post-translational modification is the addition of an extra carboxyl group to a glutamic acid found at the N-terminus of the Factor proteins which forms a gabba-carboxyglutamic acid. This modification is necessary for the Factors to bind Ca+2 and phosphatidyl-choline rich areas on the platelet surface. Some people do not run this reaction as efficiently as others (allelic differences).

Front 30

What drug interferes with Vitamin K and its role in the coagulation cascade?

Back 30

WARFARIN

Front 31

What components of the coagulation system require vitamin K?

Back 31

Factors VII, IX, X, Prothrombin (factor II), Protein C and Protein S.

Front 32

What is INR? How is it calculated? Why do we have it?

Back 32

INR: international normalized ratio. A way to normalize patient PT times between different labs which use different machines/reagents ect. It is often used to evaluate the effectiveness of warfarin (to follow a pt over time).
INR = [Patient PT/Normal PT] ISI where ISI is the international standardized index (a value assigned to thromboplastic reagents. It varies between companies and amongst batches of thromboplastin that each company makes)

Front 33

Physiologically how are the intrinsic and extrinsic coagulation cascades intertwined?

Back 33

They both share a common pathway once factor X is activated to Xa.
ALSO: In the intrinsic pathway, the activation of Factor IX to IXa requires factor XIa and Ca+2, but TF-VIIa can also activate factor IX.

Front 34

What happens if a patient has a deficiency in HMWK-PK or Factor XII?

Back 34

HMWK: high-molecular weight kininogen
PK: Prekallekreinin
These patients will have a prolonged PTT because a component of the intrinsic pathway will be missing but they will not have any bleeding problems and this is because the intrinsic and extrinsic pathways over-lap in the intrinsic pathway (see above question). Since TF-VIIa is still able to activate the step that requires products from these deficient proteins, the cascade will still proceed to completion.

Front 35

What is the role of TF pathway inhibitor in hemostasis?

Back 35

It inhibits two points in the initiation of the coagulation cascade:
1. DIRECT effect: Binds factor Xa and inhibits it by forming a TFPI-Xa complex
2. INDIRECT effect: The TFPI-Xa complex is capable of blocking TF-VIIa complex (forms a TF-VII-TFPI-Xa

Front 36

What is the role of Protein C in hemostasis?

Back 36

It DEGRADES factors Va and VIIIa (Protein C is an ANTI-COAGULANT)

Front 37

What is the role of Protein S in hemostasis?

Back 37

Protein S is a cofactor for Protein C and is necessary for its functioning. Both Protein C and S need Vitamin K for post-translational modification

Front 38

What is thrombomodulin? What is its role in hemostasis?

Back 38

Thrombomodulin is a protein that is expressed on the surface of healthy endothelium which binds thrombin and shifts thrombin’s enzymatic activity so that thrombin is now activated to convert Protein C to its active form. (thrombomodulin is a co-factor)
Thrombomodulin is down-regulated on injured/inflamed endothelium.

Front 39

What regulates the activity of Protein C?

Back 39

Activated Protein C inhibitor (PAI-3)

Front 40

What is Factor V Leiden?

Back 40

It is a mutated form of Factor V which is resistant to cleavage by Protein C (constitutively active Factor V!)

Front 41

What is ATIII? How does it work? What is its relationship to Heparin?

Back 41

ATIII (antithrombin III) serves to clear excess thrombin. However, it is usually unable to accommodate the active site of thrombin and therefore cannot inhibit it. A binding site on ATIII for heparin exists that induces a conformational change and allows the bait region of this protease inhibitor (ATIII) to become available to the thrombin.
The inhibitory domain of ATIII is actually not very specific for which protease it inhibits (ex: factor Xa) however, heparin increases the affinity for thrombin.
Specificity of ATIII while bound to FULL-LENGTH heparin: thrombin inhibitor!

Front 42

How does heparin work?

Back 42

Heparin has the binding site for ATIII which induces a conformational change in ATIII thereby allowing it to better accommodate thrombin. Heparin ALSO has another site for binding thrombin. This allows heparin to tether ATIII and thrombin together which accelerates the rate @ which the active site thrombin can interact with the inhibitory domain of ATIII

Front 43

How is low molecular weight heparin different from heparin?

Back 43

Low MW heparin is an abbreviated form of heparin (haha I don't know how else to say it. Sorry). It can activate ATIII but it lacks the tether for thrombin so the rate of inhibition between ATIII and thrombin is diminished significantly. This allows other proteases equal opportunity to access the ATIII.
This BROADENS the specificity of ATIII: Non-specific protease inhibitor

Front 44

1. Baby does not receive Vit K shot which factors are decreased?

Back 44

1. 2, 7, 9, 10

Front 45

2. Boy has Hemophilia A. Which clotting test is prolonged?

Back 45

2. Hemophilia A produces a defect in factor 8. PTT is prolonged, but PT is normal since it bypasses factor 8

Front 46

3. Girl has Von Willenbrand’s Disease. When she beings to clot which factor can build up?

Back 46

3. vWF is a part of the factor 8 complex. Factor 9 has the potential to build up since it will not be converted to factor 10. This is another example where the PT may be normal.

Front 47

4. Old man overdoses on Coumadin. What do you give to help reverse it and how do you monitor his progress?

Back 47

4. Coumadin competively inhibits the production of Vit. K factors so you give large doses of Vit. K. Monitor with PT

Front 48

5. Which pathway is activated when the vessel is damaged?

Back 48

5. Endothelial damage releases TF. Extrinsic pathway is activated.

Front 49

to draw out the cascade

Back 49

1. Count down in order
2. 3, 4, and 6 don't exist
3. 10 is special it is the only one out of order
4. 5 and 8 are co factors they go above the line
5. 7 is lucky it goes in your pocket (below the line)
6. 2 is prothrombin, 1 is fibrinogen

Front 50

coag cascade bonus points

Back 50

1. The top row is “in a line” so it is the “intrinsic” pathway
2. Then pathway through Factor 7 starts from the outside so it is the “extrinsic”
3. The intrinsic pathway is longer so it is measured by PTT, the extrinsic pathway is shorter so it is measured by the PT
4. The extrinsic pathway looks like a gun and guns are used in war so you monitor Warfarin (Coumadin) using the PT (extrinsic pathway function)
5. The gun of the extrinsic pathway is shot using the your “trigger finger” [TF] so the extrinsic pathway is activated by the TF of the body or tissue factor
6. 10 is special so all the factors surrounding 10 (9, 2, 7 and 10 itself) are a little special too—all these factors are Vitamin K dependent (ie require Vit. K to be made)

Front 51

Excess Clotting

Back 51

Factor V Leiden = Unresponsive to Protein C/S regulation = excess clotting?
ATIII Deficiency = Excess clotting (all heterozygous b/c homo- incompatible w/ life)

Front 52

Excess Bleeding

Back 52

Deficiency in Factor IX = Hemophilia B = excess bleeding (affects males)
Deficiency in Factor VIII = Hemophilia A = excess bleeding (affects males)
Deficiency in Factor V = Parahemophilia = excess bleeding
On H&P there will be soft tissue/joint bleeding, prior diagnosis of congential disorder, Meds (esp. Warfarin, Dietary history (Vit K deficit), PT/PTT abnormality
Don’t forget about Factor XIII, esp. if PT/PTT normal but history abnormal

Front 53

- ATIII

Back 53

a serine protease inhibitor and therefore inhibits Factors II, IX, X, XI, XII. Heparin is a co-factor needed for ATIII activity. It works by tethering ATIII to its relative factor. LMWH is a medicinal co-factor that may be used but it works in a different way than Heparin. It does not tether the factor with the ATIII, it binds to ATIII and activates it so that ATIII can bind it necessary clotting factor. Since there is no tether, the rate of the reaction is slower than with Heparin. Pentasaccharide is a sugar that modifies ATIII so it binds to Xa instead of IIa.

Front 54

- TFPI
(Tissue Factor Inhibitor)

Back 54

binds factor Xa to form TFPI-Xa. This complex than binds TF-VIIa complex to form TFPI-Xa-TF-VIIa and coagulation stops. Note that for this to work, some Xa must first be made. This is a type of “brake” on the coagulation cascade.

Front 55

- Protein C & Protein S

Back 55

when there is lots of thrombin around, it will bind to thrombomodulin on the endothelial cells. The thrombomodulin changes the activity of thrombin so that it now works on Protein C instead of Fibrinogen. Activated Protein C binds Protein S then inhibits Factors V & VIII.

Front 56

1. Vascular Wall Integrity

Back 56

crucial for maintaining a clot-free environment as well as to prevent excess bleeding. A CLOT WILL NOT OCCUR UNLESS THE VASCULAR INTEGRITY HAS BEEN COMPROMISED AND COLLAGEN HAS BEEN EXPOSED!!!

Ehlers-Danlos Syndrome, Marfans Syndrome, Sticklers Syndrome = Excess Bleeding due to a genetically inherited collagen structural defect. On H&P there will be hyperextensible joints, lens dislocation (vision problems), and valvular heart disease. Can do a template bleeding time although it is rarely done.

Front 57

the prototype disease for excess clotting

Back 57

Atherosclerosis

Front 58

What are the 4 things that platelets can do?

Back 58

Adhere to collagen, adhere to one another, release granules, produce procoagulant factor 3/PF3 (switching membrane leaflets)

Front 59

ADP

Back 59

is a pro-coagulant/platelet agonist and healthy endothelial cells make ADPase to prevent ADP from inducing a pro-coag. state 2) Aspirin inhibits production of PGs by both platelets (TXA2 & PGH2 = pro-coag) and endothelial cells (PGI2 = anti-coag). However, the inhibition is irreversible and the endothelium recovers faster than the platelets so the net effect is an anti-coagulant effect

Front 60

VWD

Back 60

a deficiency or abnormality in VWF that leads to excess bleeding. Affects females!

Front 61

is there a disease of excess clotting at the collagen-platelets adhesion stage?

Back 61

There is no disease of excess clotting at the collagen-platelets adhesion stage

Front 62

3. Platelet-Platelet Aggregation

Back 62

Platelets will bind to one another only at the site of damage. This occurs b/c the platelets are “activated” at the site of injury and produce unique receptors (Glycoprotein 2B, 3A) which allow for cross-linking by VWF and fibrinogen.

Front 63

NSAID use

Back 63

a common cause of dysfunctional platelet-platelet aggregation leading to excess bleeding. NSAIDs mess with the expression of Glycoprotein 2B & 3A.

Front 64

MUCOCUTANEOUS BLEEDING

Back 64

(bleeding involving the skin and mucous membranes)
The hallmark of a bleeding disorder in 1-3

Front 65

is there an excessive clotting disorder of the third component of the hemostatic system?

Back 65

no

Front 66

4. Cross-Linking Fibrin
(The Coagulation Pathways)

Back 66

This process begins and is highly localized b/c of the “flipping” of the platelet membrane leaflets putting a negative charge to the outside. It ends with fibrin cross-linking.

Front 67

Intrinsic Pathway

Back 67

T E N E T – Twelve, eleven, nine, eight, ten

Front 68

Extrinsic Pathway

Back 68

TF & Factor VII

Front 69

Common Pathway

Back 69

Factor X (“X marks the spot”), V, II, XIII

Front 70

Factors using Vit. K

Back 70

Factors II, VII, IX, X, protein C, protein S. Warfarin blocks Epoxide Reductase in the pathway for regenerating Vit. K. It also block Quinone Reductase in the pathway.

Front 71

PTT

Back 71

measures the intrinsic pathway b/c it is the longer acronym and the intrinsic pathway is longer than the extrinsic.

Front 72

PT

Back 72

measures the extrinsic pathway b/c it is the shorter acronym…

Front 73

What do you need to start the extrinsic clotting pathway?

Back 73

TF, Ca+2, PL

Front 74

- Thrombin

Back 74

pulls fibrinopeptides A/B off of fibrin allowing the D&E monomers to bind to one another. Factor XIII is activated by Thrombin and cross-links D domains to one another to stabilize or solidify the fibrin clot.

Front 75

t-PA

Back 75

responsible for converting Plasminogen to plasmin. Plasmin can then degrade fibrin to degradation products (Fibrin Degradation Products and D-Dimer). Plasminogen is literally “built into” fibrin, like the “dynamite of the dam”…all you need do is light it.

Front 76

the brakes of the fibrinolytic system

Back 76

PAI-1 & Alpha2-Antiplasmin

Front 77

the brakes of the clotting system

Back 77

(TFPI, ATIII, & Protein C/S),

Front 78

hollow organs

Back 78

All hollow organs contain local t-PA so that they do not get clogged by clotting and debris. Can use Amicar to control this bleeding.

Front 79

Deficiencies of any of these inhibitors (PAI & Alpha2-Antiplasmin) leads to:

Back 79

bleeding

Front 80

Excess PAI

Back 80

(Inc. TGs, Inc. BMI,
Inc. insulin, Inc. SBP)
can lead to excess PAI
--> leads to increase clotting