Venous Thromboemobolism (anticoagulants/thrombolitics) Flashcards
What is the pathological formation of a clot, which may cause occlusion w/in blood vessels of the heart?
Thrombosis
What forms as a result of endothelial injury because of arterial wall pathology like atherosclerosis and usually consists of platelets?
Arterial thrombus
What can arterial occlusion lead to?
MI
Stroke
Peripheral ischemia
What tends to forrm as a result of blood stasis allowing the build up of fibrin and platelets and consists more of fibrin?
Venous occlusions
What can venous occlusions lead to?
DVT
PE
What occludes blood vessels and adheres to vessel walls?
Thrombus
What occludes blood vessels and is an intravascular clot that floats with the blood?
Emboli
What encompasses both deep venous thrombosis (DVT) and pulmonary embolism (PE)?
Venous thromboemoblism
What do the majority of patients with a proximal DVT have?
PE and vice versa
What is a thrombus composed of cellular material (RBCs, WBCs, platelets) bound together by fibrin strands?
Deep Vein Thrombosis
What type of DVT has typical location of DVTs is in the veins of the calf (peroneal, anterior and posterior tibial veins). Thrombi arising from these veins are small and rarely cause significant emboli?
Distal DVT
What type of DVT is characterized by about 20% propagate or extend above the knee to the larger veins such as the popliteal and pelvic veins?
Proximal DVT
What is a thrombus or foreign substance arising from systemic circulation and lodging in pulmonary artery or one of its branches causing complete or partial obstruction of blood flow?
Pulmonary embolism
Thrombi usually derive from where?
Larger veins above the knees
Where do 95% of PEs derive from and what fraction of patients die within 30 minutes?
2/3 of patients die within 30 minutes
95% of PE’s derived from deep vein thrombi
What is the process of intact endothelium protecting against coagulation?
Normal Endothelial cells make prostacycline (PGI2) → activates cAMP in platelets → inhibits Ca2+ → inhibits platelet aggregation.
During clot formation the fibrinolytic pathway is locally activated and plasminogen is processed to plasmin. Plasmin dissolves the fibrin network as wounds heals.
What is the pathophysiology for clot formation?
Vascular injury exposes the subendothelium and platelets adhere becoming activated
Resting → Adhesion → Activation → Aggregation→ Clot → Fibrinolysis
Fibrin cross-links and stabilizes the clot.
What defense mechanism dissolves the fibrin network as injury heals?
Fibrinolysis-plasmin
What is the blood coagulation intrinsic and extrinsic pathway?
Extrinsic: TISSUE INJURY expresses TISSUE FACTOR
TISSUE FACTOR complexes with and converts factor VII to VIIa.
VIIa converts factor IX to IXa
Which in turn converts factor X to Xa.
Factor Xa CONVERTS PROTHROMBIN (FACTOR II) TO THROMBIN
THROMBIN removes small peptides from FIBRINOGEN CONVERTING IT TO FIBRIN monomer which POLYMERIZES TO GIVE THE FIRBIN CLOT.
What is virchow’s triad?
Venous stasis
Venous endothelial injury
Hypercoagulability
What results from various conditions (surgery, trauma, MI, CHF, varicose veins, etc) and leads to formation of thrombi as a result of high concentrations of clotting factors?
Venous stasis
What is mechanical or chemical trauma that as a result of collagen exposure activates coagulation cascade?
Venous endothelial injury
What is Activation of coagulation system in excess of the fibrinolytic system. Several inherited or genetic conditions (activated protein C resistance, protein C & S deficiency, anti-phospholipid ab’s, lupus anticoagulant, antithrombin III deficiency, malignancy)?
Hypercoagulability
What are the risk factors for VTE?
Age PRIOR HISTORY OF VTE (DVT/PE) Major surgery/Trauma of lower extremity, pelvis, hip, abdomen Immobility (bedridden) or paralysis Malignancy Pregnancy Estrogen use Obesity Inflammatory bowel disease Varicose Veins Chronic venous insufficiency Chronic lung disease Heart disease: CHF, Afib, Myeloproliferative disorders Antiphospholipid ab’s (lupus anticoagulant, anticardiolipin ab) Indwelling central venous catheters Nephrotic syndrome Hypercoagulable state Inherited Risk Factors
What is the gold standard, invasive, procedure that has adverse effects of allergic rxn, neprhotoxicity, pain, and is the only test available to detect proximal and distal?
Venography
What is a non-invasive measure of blood flow following occlusion that is only sensitive for proximal DVT?
Impedance plethysomography (IPG)
What is a non-invasive, test that measures rate of blood flow from the reflection of sound waves off RBCs?
Doppler U/S
What combines doppler with real-time B-mode U/S to give better sensitivity and specificity of detecting proximal DVTs?
Duplex U/S
What involved A fibrin-derived fragments that are released into circulation when cross-linked fibrin is broken down by the fibrinolytic system?
Hint- high sensitivity but low specificity, useful to rule out but not to rule in if elevated
D-Dimer Test
What should you do if non-invasive tests are negative but you are clinically suspicious of a DVT?
If non-invasive tests are negative but clinically suspicious of DVT, perform serial testing on days 5-7 and again on days 10-14.
What should you do in you suspect a PE and non-invasive tests are negative?
For suspected PE, if non-invasive tests are negative, perform ventilation/perfusion radionuclide scan (V/Q scan)
Detects ventilation/perfusion mismatch
Reported as normal, low, intermediate/indeterminate, or high probability
May need pulmonary angiography if low or intermediate probability and moderate clinical suspicion.
What are the objectives for the treatment of DVT?
Prevent development of PE
Prevent postphlebitic syndrome
Reduce mortality
Minimize adverse events and cost
What does the treatment of DVT involve?
General Measures Elevation of affected extremity Localized heat/antiembolic exercises (flexion/extension) Reduced activity/bedrest Analgesics for pain Oxygen for pulmonary embolism Pharmacologic treatment
What medications can be used for DVT?
Platelet Aggregation inhibitors
Anticoagulants
Fibrinolytics (Thrombolytics)- clot busters.
What are the platelet aggregation inhibitors?
Aspirin Dipyridamole Clopidogrel (Plavix®) Glycoprotein IIb/IIIa inhibitors- option for substitution or adding for coronary clotting as well. --Abciximab- specific link to PCI --Tirofiban --Eptifbatide
Aspirin-MOA
Blocks the synthesis of thromboxane A2 from arachidonic acid by inhibiting the enzyme cyclooxygenase. (Irreversible acetylation)
Salicylic acid is a reversible inhibitor of prostacyclin formation
Aspirin- Indications
Prevention and treatment of MI and ischemic strokes, and TIAs.
Analgesic
Anti-inflammatory
Anti-pyretic
Aspirin- contraindications
Children under age 12- due to reyes syn Breast feeding Hemophilia PUD Known hypersensitivity rxns
Aspirin- ADRs
Bronchospasms
GI hemorrhage
Dipyridamole (Persantine®)- MOA
ER dipyridamole in the combination product with aspirin (Aggrenox®)
MOA: causes inhibition of phosphodiesterase enzyme that hydrolyses cAMP. Increase cAMP levels result in decreased thromboxane A2 synthesis and thus platelet aggregation.
Indications:
Dipyridamole (Persantine®)- Indications
Aggrenox® to prevent thrombosis.
Licensed indication for prosthetic mechanical valves, in combo with warfarin
Alternative to exercise in thallium myocardial perfusion imaging.
Dipyridamole (Persantine®)- ADRs
Headache- typically self limiting
GI Bleed
Hypotension
Can Dipyridamole (Persantine®) be used as a monotherapy?
No
Dipyridamole (Persantine®)- contraindications
Contraindications
Caution in patients w/ hypotension
Caution in patients w/serious CAD
Combination w/aspirin was not much more effective than aspirin alone in controlled trials.
Ticlopidine (Ticlid®)- MOA
Blocks ADP-induced platelet-fibrinogen and platelet-platelet binding.
Ticlopidine (Ticlid®)- pharmacokinetics
ROA: Oral administration
Better absorption when administered w/food
Highly protein bound
Ticlopidine (Ticlid®)- Indications
Prevention of repeat stroke or TIA
Coronary Artery Stinting
Ticlopidine (Ticlid®)- contraindications
Patients w/severe liver dysfunction
Patients w/blood disorders such as thrombocytopenia, neutropenia
PUD
Internal bleeding
Ticlopidine (Ticlid®)- drug/drug interactions
Cimetidine
Digoxin
Theophylline
Red clover (herb)
Ticlopidine (Ticlid®)- ADRs
Bleeding
N/V/D
Thrombocytopenia, NEUTROPENIA, pancytopenia—monitor CBC
Nephrotic syndrome, dark colored urine
Clopidogrel- MOA
inhibits activation of the glycoprotein IIb\IIIa receptor on the surface of platelets, which is required for aggregation to occur.
Clopidogrel- Indications
Secondary prevention of cardiovascular and cerebrovascular events.
In patients allergic to aspirin