Tabuk University Faculty of Applied Medical Sciences Department Of Medical Lab. Technology 3 rd Year – Level 5 – AY

Thrombotic disorders 2 By/ Dr. Walid ZAMMITI; Phd M.Sc; MLT

Objectives Define terms used in thrombotic disorders. Identify the most common causes for thrombosis. Classify thrombosis into arterial and venous; and the differences between them. Classify thrombotic disorders into hereditary and acquired. Understand the mechanism of thrombosis in specific hereditary & acquired conditions. Learn the diagnostic tests used to identify genetic predisposition to thrombosis. 3

Disease processes Abnormal clotting 4 Abnormal bleeding Bleeding disorders : caused by Platelets, vascular, coagulation factors Thrombotic disorders

Thrombosis Thrombus: singular, Thrombi : Plural solid masses plugs Thrombi are solid masses or plugs formed in the circulation from blood constituents. ischaemia Platelets and fibrin form the basic structure. Their clinical significance results from ischaemia from local vascular obstruction or distant embolization. Thrombi are involved in the pathogenesis of myocardial infarction, cerebrovascular disease, peripheral arterial disease and deep vein occlusion. 5

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Thrombosis may be arterial, causing ischemia, or venous leading to stasis. Thrombosis, both arterial and venous, is more common as age increases and is frequently associated with risk factors. thrombophilia The term thrombophilia is used to describe the inherited or acquired disorders of the haemostatic mechanism that predispose to thrombosis. 7

Arterial thrombosis Atherosclerosis تصلب الشرايين of the arterial wall, plaque rupture and endothelial injury expose blood to subendothelial collagen and tissue factor. This initiates the formation of a platelet plugs on which platelets adhere and aggregate. 8

Venous thrombosis three It is suggested that there are three components that are important in thrombus formation: 1. Slowing down of blood flow; 2.Hypercoagulability of the blood; and 3.Vessel wall damage. Increased systemic coagulability and stasis are most important, vessel wall damage being less important than in arterial thrombosis 9

Thrombotic disorders Hereditary Hereditary -Factor V Leiden gene mutation (activated protein C resistance) -Antithrombin deficiency -Protein C deficiency -Protein S deficiency -Prothrombin allele G20210A -Hyperhomocyst(e)inaemia -Defects of fibrinogen Acquired Acquired – Post surgery – Post delivery – Long distance travel – Immobilization – Malignancy – Inflammation – Blood disorders – Oestrogen therapy – The antiphospholipid syndrome – Factor IX concentrates 10

Activated Protein C (APC) Resistance (Factor V Leiden mutation) Genetic alterations of the factor V molecule at APC binding sites impair, or resist APC’s ability to degrade or inactivate factor Va. Site of mutation is replacement of arginine at position 506 with glutamine (Arg506Gln) in the factor V gene. venous It is the most common inherited cause of increased risk of venous thrombosis. It doesn’t increase risk of arterial thrombosis Diagnosed by PCR : Polymerase Chain Reaction. 11

Antithrombin Also known as Antithrombin III Antithrombin forms "complexes" with all the serine protease coagulation factors except factor VII, this "kills" the enzyme. 12 Prothrombin Thrombin ATIII inhibits thrombin to prevent thrombus formation Antithrombin III Fibrinogen Fibrin “Thrombus”

Antithrombin deficiency There are recurrent venous thromboses usually starting in early adult life. Arterial thrombi occur occasionally. 13

Protein C & S 14

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Protein C and Protein C Deficiency Protein C is a vitamin K dependent glycoprotein produced in the liver In the activation of protein C, thrombin binds to thrombomodulin, a structural protein on the endothelial cell surface This complex then converts protein C to activated protein C (APC), which degrades factors Va and VIIIa, limiting thrombin production For protein C to bind, cleave and degrade factors Va and VIIIa, protein S must be available Protein C deficiency, whether inherited or acquired, may cause thrombosis when levels drop to 50% or below Protein C deficiency occurs with surgery, trauma, pregnancy, liver or renal failure or DIC. 16

Protein S, Protein S Deficiency cofactor Protein S is an essential cofactor in the protein C pathway Protein S exists in a free and bound state About 30% of unbound protein S, called free PS, is the functionally active form of protein S Inherited PS deficiency is an autosomal dominant disorder, causing thrombosis when levels drop to 50% or lower 17

Causes of Acquired Protein S Deficiency Decreased PS Functional activity may be due to : 1.vitamin K deficiency 2.liver disease 3.Due to increased PS consumption which occurs in acute thrombosis, DIC, MPD, sickle cell disease 18

Prothrombin gene mutation increased Prothrombin allele G20210A is a variant (prevalence 2- 3% in the population) that leads to increased plasma prothrombin levels and increases thrombotic risk by at least twofold. 19

Acquired risk factors of thrombosis 20

Post surgery: - Post surgery: elderly, obese & those with family history. Venous stasis and Immobilization : - Venous stasis and Immobilization : probably responsible for the high incidence of postoperative venous thrombosis. -Malignancy : -Malignancy : carcinoma of the ovary, brain and pancreas have a particularly increased risk of venous thrombosis but there is an increased risk with all cancers. -Inflammation : -Inflammation : down regulates anticoagulant pathways, particularly proteinC. Blood disorders : - Blood disorders :In polycythaemia vera and essential thrombocythaemia; there are Increased viscosity, thrombocytosis, altered platelet membrane receptors and responses. 21

Antiphospolipid syndrome Def: occurrence of thrombosis or miscarriage in association with antiphspholipid antibodies. * Antiphospholipid antibodies may be: Lupus anticoagulant (LA); causing prolonged APTT not corrected by mixing with normal plasma. Anticardiolipin antibodies (ACA). 22

Antiphospholipid Syndrome : Diagnosis Clinical association of (APA): -Arterial or venous thrombosis -Pregnancy loss -Thrombocytopenia -CNS stroke Laboratory Criteria -IgG or IgM anticardiolipin antibody-medium or high titer. -Detected in an ELISA assay 23

Oestrogen therapy Oestrogen therapy, particularly high-dose therapy, is associated with Increased plasma levels of factors II, VII, VIII, IX and X and, Depressed levels of antithrombin and tissue plasminogen activator in the vessel wall. 24

Investigation of thrombophilia Screening tests: Screening tests: -Blood count and erythrocyte sedimentation rate (ESR) -Blood film examination - Prothrombin time (PT) and APTT : (a shortened APPT is often seen in thrombotic states and may indicate the presence of activated clotting factors. A prolonged APTT test, not corrected by the addition of normal plasma, suggests a 'lupus anticoagulant‘ or an acquired inhibitor to a coagulation factor.) -Anticardiolipin and anti-β 2 -GPI antibodies - Thrombin time and reptilase time: (prolongation suggests an abnormal fibrinogen) 25

-Fibrinogen assay. - Activated protein C (APC) resistance test and DNA analysis for factor V Leiden. -Antithrombin-immunological and functional assays. - Protein C and protein S-immunological and functional assays. - Prothrombin gene analysis for the G20210A variant. - Plasma homocysteine estimation - Test for CD59 and CD55 expression (PNH) in red cells. (if paroxysmalnocturnal haemoglobinuria is suspected.) 26

Anticoagulant drugs Anticoagulant drugs are used widely in the treatment of venous thromboembolic disease. Their value in the treatment of arterial thrombosis is less well established. Heparin: laboratory controlled using APTT mainly. Oral anticoagulants : e.g : Warfarin, laboratory controlled using PT & INR (International Normalized Ratio). 27

THANK you 28