Blood Coagulation and Thrombophilia Cliff Takemoto M.D. Pediatric Hematology The Johns Hopkins University
Disclosure Information Cliff Takemoto MD NONE
Objectives Develop a framework to understand coagulation Know how to approach coagulopathies
What is in a clot? Platelets www.junebughunter.net Fibrin (coagulation proteins) www.uphs.upenn.edu VENOUS ARTERIAL Slow flow Fast flow RED-(rbc’s) WHITE (plts)
How we clot Cut in the endothelium Exposes collagen for platelet binding sites Exposes tissue factor for activating coagulation TF vWF Thrombin collagen fibrinogen collagen TF Activation TF TF collagen fibrinogen vWF vWF And fibrin TF TF TF deposition collagen vWF Platelet Activation Platelet granule secretion Activate fibrinogen receptor Provides site for prothrombinase complex
This is how a clot is made Tissue factor platelets fibrin Falati et al., Nature Medicine 2002 with permission from Nature Publishing Group
how a clot is made in vivo Thrombin activation INITIATED by TISSUE FACTOR (microparticles?) TWO pathways to PLATLET ACTIVATION: TF (thrombin) Collagen (vWF)
Coagulation Cascades … the often-asked question: “Why is coagulation so complicated?” resolves itself into the question: “Why are there so many stages?” R.G. Macfarlane, Nature 1964 John Hagemen Rosenthal syndrome Stephen Christmas proconvertin Antti-hemophilc factor Rufus Stuart proaccelerin prothrombin fibrinogen
Coagulation Cascades Some concepts to remember… •Highly regulated complexes of serine proteases and co-factors •All paths lead to thrombin activation thrombin fibrin •Goal is to make a fibrin clot •They are not just a number— •they have a personality too!!! www.uphs.upenn.edu
Serine Proteases Co-Factors FIX FVIII FX FV procoagulant FVII TF FII TM anticoagulant PC PS
Clot formation--physiology CONTACT FACTORS Know the functions and mechanism of activation of factor___ in coagulation (prekallikrein,HMWK, XII,XI) IXa extrinsic intrinsic VIIa tenase tenase VIIIa “Prothrombinase” TF Ca ++ , PL Xa SERINE PROTEASE Va COFACTOR Ca ++ , Fibrinogen PL II IIa Fibrin prothrombin thrombin polymers
Clot formation--physiology CONTACT FACTORS PTT PT (prekallikrein,HMWK, XII,XI) IXa extrinsic intrinsic VIIa tenase tenase VIIIa “Prothrombinase” TF Ca ++ , PL Xa Va Know the consequences Ca ++ , of deficiency of PL factor___ on II IIa the laboratory assessment of hemostasis fibrinogen Fibrin clot
Clot formation--physiology CONTACT FACTORS (prekallikrein,HMWK, XII,XI) INITIATION IXa VIIa VIIIa “Prothrombinase” TF Xa Va AMPLIFICATION PROPAGATION II IIa fibrinogen Fibrin clot
Clot formation--physiology initiation IXa VIIa X VIIIa TF propagation Xa Va II IIa fibrinogen Fibrin clot
Activation of thrombin: 3 complexes enzyme complexes : protease cofactor Prothrombinase Xa Va Intrinsic tenase IXa VIIIa Extrinsic tenase VIIa TF Also need Calcium and a phosholipid surface
A few words about contact activation… •Regulate Inflammation •HK, PK, FXII deficiency do not bleed •FXI deficiency associated with bleeding C1 inh Protease Prekallikrein (PK) Inibitor FXII C1 esterase inhibitor FXI Cofactor High Molecular-Weight Kininogen (HK)
Thrombin has both pro- and anti-coagulant functions Thrombin IIa Fibrinogen Protein C/S FV, FVIII, FXI bound to Thrombomodulin FXIII TAFI (fibrinolysis inhibitor) Platelet Activation anticoagulant procoagulant
Fibrinogen Structure Know basic structure of fibrinogen and its gene control Fibrin (insoluble) Fibrinogen (soluble) Fibrinogen Genes 6 polypeptide chains 3 genes: Gorkun O. et al., Blood 1997; 89:4407-44. With permission from the American Society of Hematology
Fibrin Clot formation and fibrinolysis fibrinopeptides Thrombin (IIa) A B fibrinogen D E D D E D D E D D E D D E D D E D D E D D E D D E D D E D D E D FXIII D-dimer plasmin
Plasminogen regulation Activators t-PA, u-PA Inhibitors PAI-1, PAI-2 2 antiplasmin 2 macroglobulin TAFI
Endogenous Anticoagulants: Turning off the clot Protein C VIIIa, Va (the cofactors) Protein S Antithrombin IIa, Xa (serine proteases) TFPI VIIa/TF
How to stop the clot TFPI IXa VIIIa VIIa Xa Va Protein C II IIa AT III Protein S IIa thrombomodulin
Heparin—physical characteristics It binds to Antithrombin heparin pentasaccharide binding Activation loop to antithrombin binds to reactive Site in serine protease
Heparin-- physical characteristics Pentasacchride Antithrombin From the Wallstreet jounal binding sequence
Heparin binds and activates Antithrombin Coagulation Factors IIa Suicide inhibitor ATIII Xa Heparin accelerates this reaction >1000fold IIa ATIII Xa Pentasacchride sequence of heparin binds antithrombin
Antithrombin Deficiency • Prevalence 1/5000 IIa • Risk of thrombosis Xa XIa 15-20X IXa • Acquired forms- AT III nephrotic syndrome, heparin liver disease • Lab- Antithrombin activity IIi Xi IXi XIi
Protein C and Protein S Vitamin K dependent VIIIa Protein C-serine protease cofactors Protein S-cofactor Va Activated by thrombin/TM C APC IIa C4b binding protein S S Thrombomodulin
Protein C and S deficiency • Protein C- 1/250-500 • Protein S- 1/1000 T TM • Increase risk 5-10X C4bBP • Acquired causes: Both: Vit. K deficiency S C APC Protein S: estrogens, pregnancy S • Homozygous protein C presents with neonatal purpura S VIIIa VIIIi fulminans Va Vi • Lab- Protein C and S activity
Thromboembolic events with other prothrombotic risk factors
Factor V Leiden 306 506 679 • Prevalence 5% (0-15%) • Autosomal dominant Factor Va • Prevents inactivation of FVa • Thrombosis risk: • FVL +/- = 5X APC • FVL+/+ = 50X • FVL +/- and OCPs = 30X Factor Vi
PTT (APC) What is APC resistance? PTT 75sec normal: = 2.5 30sec 39 sec FVL: = 1.3 30 sec Arg 506 Arg 679 Arg 306 FVa R506Q is the FV leiden mutation
Characteristics of Clotting Factors Invivo T 1/2 Factor Synthesis Function vitK Fibrinogen (I) 2-4 days liver - Prothrombin (II) 3 days liver SP + V 36 hrs liver/(mega) CoF - VII 3-6 hrs liver SP + VIII 8-12 hrs liver/EC CoF - IX 22 hrs liver SP + X 40 hrs liver SP + XI 80 hrs liver SP - XII 50-70 hrs liver SP - 10 days liver/M XIII TG - VWF 12 hrs EC/(mega) mega—megakaryocyte; M —macrophage; EC—endothelial cell; SP—serine protease; CoF—Cofactor;TG--transglutaminase Coleman Hemostasis and Thrombosis 3 rd Edition
Characteristics of Clotting Factors Factor Incidence Inheritance Fibrinogen (I) 1:1 million afibrinogen-recessive hypofibrinogen-dominant Prothrombin (II) 1:2 million recessive V 1:1 million recessive VII 1:300,000 recessive VIII 1:5,000 x-linked IX 1:30,000 x-linked X 1:1 million recessive XI 1:1 million recessive 1:12 (het) Ashekenazi Jewish XII 1:50 (het) recessive XIII 1:1 million recessive VWF 1:100 Type 1 dominant 1:1 million Type 3 recessive Bolton-Maggs et. al., Haemophilia 2004
Approach to abnormal laboratory screens Elevated aPTT Elevated PT Elevated Thrombin Time Elevated aPTT and PT
Elevated aPTT 1:1 ratio Mixing study control + patient plasma correction no correction Bleeding No Bleeding Heparin Circulating Inhibitor FVIII Contact factors FIX --FXII FXI --PK Phospholipid dependent Non-specific --HMWK Lupus Anticoagulant --DRVVT --phospholipid neutralization --platelet neutralization
Elevated aPTT and PT Thrombin Time Fibrinogen activity Low Prolonged Normal Factor Deficiencies Aquired Inherited Heparin Common Pathway Liver disease FGN ag low/absent FDP (DIC) --FV, FX DIC --hypofibrinogenemia Fibrinogen Combined Pathway --afibrinogenemia --Intrinsic/Extrinsic --vitamin K deficiency FGN ag normal --dysfibrinogenemia Thrombin Time--prolonged Low fibrinogen Thrombin Time--prolonged heparin Reptilase Time--normal dysfibrinogenemia Reptilase Time--prolonged
Case 23 year old male with hemoptysis for 3 weeks Seen at Eastern Shore ER and spiral CT shows large PE Transport Team calls you—asks for management advice and recommendation for bloodwork before treatment?
Case Antithrombin, protein C/S, APC, prothrombin 20210, Homocysteine, etc—all normal. One test you were not able to get was the antiphospholipid antibodies. He is already on heparin. When can you do the test? Does it matter?
Case RVVT: 74 (27-45) 1:1 mix 56.2 (27-45) 4:1 mix 65.3 (27-45) aPTT 30 (24-34) PT 10.9 (10.4-12.0) RVVT:confirm 1.8 (1-1.4) ratio DRVVT was tested on coumadin and prolonged. The “confirm ratio” was high, suggesting an antiphospholipid antibody
Recommend
More recommend
