3. Thrombosis
• A thrombosis is a pathological clot that forms within the lumen of a blood
vessel or the heart.
• Thromboses may form on the arterial or venous sides of the circulation.
• Deep Vein Thrombosis
– May embolize to form a pulmonary embolism.
• Arterial Thrombosis
– May cause ischemia or necrosis of the affected tissues.
– Myocardial infarction and cerebral infarctions (ischemic stroke) result
from arterial thrombosis.
• We will focus on venous thrombosis
4. Normal Vein Function
• Veins move blood against gravity by use of a series of valves and compression
of the vein by surrounding muscles, especially in the legs.
• There are superficial and deep veins that tend to run in parallel and are connected
by perforating veins. Deep are of much larger capacity.
5. Deep Vein Thrombosis
• Thrombus typically forms at venous valves.
• Legs may be swollen, painful, warm, and erythematous. But often the
signs are much more subtle, or case may be asymptomatic.
6. Pulmonary
Embolism
• Part of thrombus breaks off
(usually from leg, pelvic, or
inferior vena cava), travels
through the right heart, and
lodges in pulmonary artery.
• Direct obstruction of
pulmonary circulation and
vaso-spasm cause
decreased pulmonary blood
flow.
• Associated with pain,
decreased oxygen delivery,
and in severe cases vascular
collapse and death.
• Calf DVT are much less
likely to embolize.
7. Post-Thrombotic (Phlebitic) Syndrome
• Venous incompetence (Varicose veins);
• Recurrent thrombosis and pulmonary
embolism.
• This complicates 25-75% of DVT.
8. Virchow’s Triad
Risk Factors For Thrombosis
• Altered Blood Flow/Venous stasis
– Immobilization
– Obesity
– Heart disease
• Vessel wall damage
– Accidental trauma
– Surgical trauma
– Prior history of DVT
– Advanced Age
• Increase In Blood Coagulability
– Increase in tissue factor
– Presence of activated factors
– Decrease in coagulation inhibitors
10. Physiologic Anticoagulants
• Several physiologic anticoagulant
systems exist.
• All are dependent upon an intact
endothelium.
• Where endothelial cell lining of vessels
is intact (and healthy) anticoagulant
systems prevent blood from clotting.
11. Endothelial Cell-Dependent
Anticoagulant Processes
• Heparan Sulfate: AT III
• Thrombomodulin: Protein C: Protein S
• ADPase (CD39)
• Tissue Factor Pathway Inhibitor
• Nitric Oxide
12. Heparan:Antithrombin III
Deficiency first described in 1965.
– (Egeberg O. Inherited antithrombin III deficiency causing
thrombophilia. Thromb Diath Haemorrh 13:516-30, 1965)
AT III neutralizes the active enzymes in the coagulation
system.
Dominant Inheritance.
13. Protein C/Protein S System
• Constituents;
– Protein C
– Protein S
– Thrombomodulin
• Activated Protein C (With
cofactor Protein S)
inactivates Va and VIIIa, the
cofactors of the cascade
– (Probable role in augmenting
fibrinolysis.)
• Dominant Inheritance.
• Homozygous individuals
have purpura fulminans.
14. Factor V:Leiden/
Activated Protein C Resistance
• Reduced neutralization of
Factor Va by Activated Protein
C.
• Genetically a balanced
Polymorphism.
• Found predominantly in
European populations (~3-7%),
with ~1% in Indian
subcontinent and Arabs.
• Heterozygotes (in isolation);
~3-4-fold increase risk in
thrombosis.
• Homozygotes; ~ 50 fold
increase in thrombotic risk.
15. Prothrombin Gene Mutation:
(Prothrombin G20210A)
• Genetic polymorphism affects the terminal 3' nucleotide of the 3'
untranslated region (UTR) region of the prothrombin mRNA and
causes elevated levels of prothrombin in the plasma.
• Heterozygous: Prothrombin levels that are increased by
approximately 30%.
• Homozygous: : Prothrombin levels that are increased by
approximately 30%.
• Increased prothrombin levels are associated with increased
thrombin generation and correlate with an increased risk of
venous thromboembolic disease.
16. Population Genetics Of Factor V:Leiden
Rees DC. Brit. J. Haemat. 95:579, 1996.
Country Allele Freq Country Allele
(%) Freq(%)
Greece 7.0 India 1.2
Sweden 5.9 China 0
Germany 3.6 Indonesia 0
U.K. 3.4 Japan 0
Spain 2.0 New Guinea 0
Basques 0.0 Aboriginal Australia 0
France 2.0 Sub-Saharan Africa 0
Greenland 0.0 Vancouver Island 0
Indians
Saudi Arabia 1.0 Peruvian Indians 0
17. Polymorphism, Not Mutation
• Factor V:Leiden and prothrombin G20210A are common among
healthy whites but are extremely rare among Asians and
Africans.
• Founder effects have been demonstrated for both mutations,
suggesting that they occurred after the separation of non-
Africans from Africans and after the divergence of whites and
Asians.
– Zivelin et al. Blood 89:397, 1997.
– Zivelin et al. Blood 92:92:1119, 1998.
• Genetics suggest a balanced polymorphism, not new mutations
(i.e. sickle cell vs. hemophilia).
• Factor V:Leiden: Reduced blood loss observed in peripartum
period, improved embryonic implantation rates, protection from
sepsis.
20. Vitamin Supplementation Reduces
Blood Homocysteine Levels
den Heijer et al. Arterioscler Thromb Vasc Biol. 18:356, 1998.
• Homocysteine (tHcy) levels decreased with folic acid or
combinationvitamin therapy.
• Multivitamin Tablets
– 5 mg folic acid,
– 0.4 mg hydroxycobalamin
– 50 mg pyridoxine.
• Dietary supplementation with ~0.4 mg folate daily, since
1996, mainly to prevent neural tube defects.
21. Clinical and Diagnostic Laboratory Criteria for
Antiphospholipid Syndrome (aPL)
• Clinical criteria (one or more)
– Vascular thrombosis
• Arterial, venous, or small vessel thrombosis.
– Pregnancy morbidity
• Unexplained fetal death (>10 week gestation)
• Premature birth of morphologically normal neonates at or before the
34th week of gestation, because of severe preeclampsia or eclampsia,
or severe placental insufficiency.
• Three of more unexplained consecutive spontaneous abortions before
the 10th week of gestation.
• Laboratory criteria
– Anticardiolipin IgG or IgM at moderate to high levels (>20 U) on 2 or
more occasions separated by at least 6 weeks
– Lupus anticoagulant, Twice or more separated by at least 6 weeks.
22. Pathophysiology of Thrombosis and
Antiphospholipid Syndrome
• “Several hypotheses have been proposed to explain
the molecular basis of the prothrombotic state
associated with these antibodies.”
• Antibodies to Beta 2 Glycoprotein 1 (apolipoprotein
H) are functional component?
• However, the clinical significance of any one (or
more) of these pathways remains unclear.
– Ortel. ASH Education Program, 2005
23. Molecular/Biochemical Risk Factors Of
Thromboembolic Disease
• Common
– G1691A mutation in the factor V gene (factor V Leiden)
– G20210A mutation in the prothrombin (factor II) gene
– Homocysteinemia
• Rare
– Antithrombin III deficiency
– Protein C deficiency
– Protein S deficiency
• Very rare
– Dysfibrinogenemia
– Homozygous homocystinuria
– Alterations in fibrinolysis.
• Probably inherited
– Increased levels of factors VIII, IX, XI, or fibrinogen.
24. Synergy of “Risk” Factors For Thrombosis
• Most patients with a hereditary or other underlying
risk for thrombosis do not experience a thrombosis.
• Thrombosis usually develops when there are multiple
risk factors at the same time.
• Therefore need to consider a series of inherited and
acquired risk factors.
Risk Ratio of Thrombosis
Estrogen Containing Contraceptives ~3-4-fold risk
Factor V:Leiden ~3-4-fold risk
Estrogen Containing Contraceptives Plus ~40-Fold risk
Factor V:Leiden
25. Hypercoagulable Work-up
• Why work-up?
– Mostly for decision on duration (life-long) anticoagulation
– Avoidance of oral contraceptives
– Family knowledge
• BIG Debate in Hematology: To test or not to
test?
– Some recommend life-long anticoagulation after initial episode of
idiopathic thrombosis, regardless of molecular/biochemical risks.
– Therefore, is it necessary to test?
– More recent studies suggest presence of thrombophilia may warrant
longer duration of therapy.
26. Risk of Recurrence Dependent on Risk at Time of
Intial Venous Thromboembolism.
Baglin et al. The Lancet. 362: 523-526, 2003.
Unprovoked
Non-surgical triggers
Post-operative
• Post-operative thrombosis have very low recurrence rate. (Removal of risk)
• Non-surgical triggers (Reduced risk)
• Unprovoked: No reduction in risk factors, presumably hereditary.
27. Risk of Recurrence Dependent on Underlying
Thrombophilia.
Baglin et al. The Lancet. 362: 523-526, 2003.
• Presence of thrombophilia does predict risk of recurrence of thrombosis.
• Supports hypercoagulable testing for patients with an “unprovoked” initial
thrombosis.
28. Consider Thrombophilia Testing in VTE
Patients With the Following:
(Cushman, ASH Education Book, 2005)
• Idiopathic first event
• Secondary, non-cancer-related first event and age
< 50, including thrombosis on contraceptives or
postmenopausal hormones
• Recurrent idiopathic or secondary, non-cancer,
events
• Thrombosis at an unusual site
29. Hypercoagulable Work-Up
(By Gerald A. Soff M.D.)
• Thrombophilia Genetic polymorphism
– Factor V:Leiden, Prothrombin G20210A Mutation
– MTHFR (Not worth doing)
• Protein C
• Protein S
• Antithrombin III
• Homocysteine
• Lupus Anticoagulant/Anticardiolipin Antibody
• Except for DNA analysis, do not work-up during acute event,
pregnancy, oral contraceptives, acute medical/surgical illness.
30. Acute Management of Venous
Thromboembolic Disease:
Heparin or Low Molecular Weight Heparin.
• Cofactor for Antithrombin III, neutralizes the activated
enzymes. (LMWH is specific of FXa).
• Heparin dosed to prolong aPTT by approximately two-fold
• Low Molecular Weight Heparin dosed based on body weight.
• Need to treat for at least 5 days and until warfarin is stably
therapeutic. (In non-cancer patients.)
32. Management of Venous Thromboembolic
Disease:
Chronic Oral Vitamin K Antagonists
• Warfarin (coumadin)
– An oral vitamin K antagonist.
– Blocking vitamin K metabolism results in reduced production of
functional zymogens.
– Does not adequately treat acute thrombosis, but reduced risk of
recurrence.
– Dose by INR (Internationalized Normal Ratio), a derivative of the
prothrombin time.
– Target INR: 2.0-3.0.
– Usually treat 6 to 12 months for first episode.
33. How Long To Treat DVT?
• Short-term treatment to help resolve initial VTE.
• Long-term treatment to reduce risk of recurrent VTE.
• Recurrent DVT or PE during anticoagulant treatment:
– Recurrent DVT/PE: 8.8%, (95% CI: 5.0-14.1%)
– Case-fatality rate of only 0.4% (95% CI : 0.2-0.6%).
• Recurrences more likely during the initial 3 weeks of treatment.
– Cancer (odds ratio 2.7),
– Chronic cardiovascular disease (OR 2.3),
– Chronic respiratory disease (OR 1.9)
– Other clinically significant medical disease (OR 1.8).
– Bounameaux & Perrier. ASH Education Book, 2008.
34. How Long To Treat DVT?
• The PROLONG study: Persistently elevated D-Dimer after 3
months of Vit. K antagonist helps identify high risk patients.
– Palareti et al., NEJM 2006; 355:1780
• The DACUS study: Utility of Repeat Ultrasound
– First, idiopathic or provoked, VTE
– Excluded: active cancer, APLS, ATIII, PC, PS, homozygote
FVL/PGM, or compoud heterozygote FVL/PGM
– Residual vein thrombosis (RVT)= >40% of lumen obstructed
by clot.
– Patients without residual thrombus at 3 months, may be safely
discontinued from anticoagulation.
– Siragusa et al., Blood 2008; 112:511
35. Utility of Repeat Ultrasound
(DACUS)
Events per 100 person-years
Initial Event Residual Residual No Residual
Thrombosis, Thrombosis, Thrombosis
Continued Discontinued
Anticoagulation Anticoagulation
Provoked VTE 10.4 9.9 0
Idiopathic VTE 10.0 16.9 1.9
Siragusa et al., Blood 2008; 112:511
36. How Long To Treat DVT?
Indication 8th ACCP Guideline
First episode of VTE secondary 3 months
to a transient risk factor
First episode of idiopathic At least 3 months.
(unprovoked) VTE At 3 months, if favorable
risk-benefit ratio, consider
long-term treatment.
Other (recurrent, active cancer, Long term (Grade 1A).
etc.)
37. Bleeding With Anticoagulants
• Heparin:
– Major bleeding: 0.8% per day
– Fatality rate: 0.05% per day
• Oral anticoagulants:
– Major bleeding: 0.4% per month.
– Bounameaux & Perrier. ASH Education Book, 2008
38. Compression Hose Reduces Development of
Post-Thrombotic Syndrome
Prandoni et al. Ann. Intern. Med. 141:249-245, 2004.
• Anticoagulation was continued
for those with
underlying/persistent risks.
• Hose used for two years, and
reevaluation done at 5 years.
• Control: 40% PTS
• Hose: 21% PTS
• (OR 52%)
39. Thrombolysis In Pulmonary
Embolism
• For massive Pulmonary Embolism:
– Shock
– Right heart strain
– Thrombolytics indicated for reduction in short-term
mortality.
• For submassive PE:
– Improved rate of resolution with thrombolytics, but benefit
does not persist after one month.
40. Event-Free Survival In Acute Submassive
Pulmonary Embolism: tPA Plus Heparin Vs.
Heparin: More Rapid Resolution Within 30 Days
Konstantinides S et al. N Engl J Med 2002;347:1143-1150
41. CLOT Study
Lee et al. NEJM 349:146-53, 2003
• Comparison of Low-Molecular-Weight Heparin versus Oral
Anticoagulant Therapy for the Prevention of Recurrent Venous
Thromboembolism in Patients with Cancer (CLOT)
• Compared LMWH, (Dalteparin) with warfarin (vitamin K
antagonist).
• All got LMWH (Dalteparin 200 IU/kg, SQ, daily for 5-7 days,
then randomized to:
– 6 months of Warfarin (INR target 2.5) or
– 6 months of LMWH:
• 200 IU/kg, SQ, daily for 1 month, then 150 IU/kg for 5
months.
42. Dalteparin Resulted in Approximately 50%
Reduction in Thrombosis Recurrences
Lee, A. Y.Y. et al. N Engl J Med
2003;349:146-153
43. Low Molecular Weight Heparin in
Obese or Mildly Renal Impairment
• The literature is not clear on dosing in obese (i.e.
over >120 Kg), or those with mild renal
impairment.
• One should monitor and adjust therapy, in these
patients with anti-Xa assays.
• Anti-Xa:Treatment Dose: 0.7-1.1 units/mL
• Anti-Xa: Prophylactic Dose: 0.2-0.3 units/mL.
44. Inferior Vena Cava Filters
• Mechanical device inserted into the IVC to “catch” emboli, and
prevent life-threatening pulmonary emboli.
• Short-term protection from Pulmonary Embolism,
• Long-term increased risk of thrombosis.
• New generation of removable filters.
45. “An once of prevention is worth a
pound of cure.” Benjamin Franklin
• Many medical and surgical patients are at very
high risk for developing a thrombosis.
• Pulmonary embolism remains a major cause of
deaths in hospitalized patients.
• Prophylaxis with anticoagulants and pneumatic
compression devices is highly effective in
reducing the risk of thrombosis.
49. Fibrinolytic Pathway
Plasminogen; – PAI-1, PAI-2; Plasminogen Activator
Inhibitors
– Activated to Plasmin (a serine
proteinase) – α2-Antiplasmin.
– Plasmin proteolyzes fibrin and fibrinogen
Plasminogen Activators;
– t-PA (Tissue-Plasminogen Activator)
– u-PA (Urokinase-Plasminogen Activator)
– Released by endothelial cells.
Serpins
50. Ethnic Distribution of Factor V Leiden In
U.S.A.
(Ridker PM et al, JAMA 277:1305, 1997)
Racial Group Incidence Of
Factor V:Leiden
Whites 5.27%
Hispanic Americans 2.21%
African Americans 1.23%
Asian Americans 0.45%
Native Americans 1.25%
51. 57 Year Old Chinese-American Woman
• Diagnosed with early stage breast cancer.
– Second primary (Past left mastectomy)
• Planned for bilateral mastectomy with flap reconstruction.
• Hematology consult for clearance for the flap reconstruction.
• No past history of thrombosis.
• No other significant co-morbidities.
• Physical exam: negative, except for prior left sided mastectomy
without reconstruction.
• What else do you need to know?
52. Family History
• Twin brother in China, at age 27, developed
unprovoked leg DVT. While being
transferred to hospital, by 4 hour taxi ride,
developed acute dyspnea, complained of
“choking” and died!
53. Patient Normal
PT 9.6” 9.4-12.8”
PTT 27.6” 24-35.7”
Lupus Anticoagulant, DRVVT 0.9 <1.2
Lupus Anticoagulant, SCT 1.06 <1.2
Anticardiolipin Antibodies, IgG, IgM, IgA Negative
AT III 99% 70-111%
Protein C Antigen 48% 60-150%
Protein C Functional 56% 83-144%
Protein C Chromogenic 52% 74-164%
Protein S Functional 119% 70-145%
Factor VII 166% 63-125%
Homocysteine 9.0 5.0-12.0
mcM/L mcM/L
