Anticoagulation Flashcards
Anticoagulation recommended…
in addition to antiplatelet therapy to improve vessel patency and prevent re-occlusion
Unfractionated Heparin (UFH)
- Anti-Xa and anti-IIa activity
- Risk of heparin induced thrombocytopenia (HIT):
- Drop in platelet count AND increased thrombosis
- Caused by formation of antibodies that activate platelets
- If suspecte –> Calculate 4T Score (What are the 4 T’s?)
- Screening tests available if HIT suspected: Enzyme-linked immunosorbent assay (ELISA)- quick, high false positive rate; Serotonin release assay (SRA)- gold standard for diagnosis, often a “send-out” lab
Is unfractionated heparin the only anticoagulant that can cause HIT?
no, LMWH can also cause HIT, but there is a lower risk
Can a patient with a history of HIT be re- challenged with unfractionated heparin or LMWH?
no, pts should not be rechallenged with either
Unfractionated Heparin (UFH) half life
- Quick onset and short half life
- Administered as a continuous infusion
- Dosing of UFH is based on the activated partial thromboplastin time (aPTT) or activated clotting time (ACT)
Enoxaparin
- Low molecular weight heparin (LMWH)
- Anti-Xa and anti-IIa activity: Higher ratio of anti-Xa/anti-IIa than UFH
- Eliminated by kidneys: Accumulates in renal impairment
Do we routinely check anti-Xa levels for patients on enoxaparin?
no, usually not necessary and difficult to interpret the results; consider in certain cases, - very high or low body weight, renal impairment, development/worsening clot
Bivalirudin
- Direct thrombin inhibitor
- Not used together with GPIIb/IIIa inhibitors (except ”bail
out”) - Conflicting results vs unfractionated heparin: Many studies used GPIIb/IIIa inhibitors with heparin - Difficult to determine if differences were due to
bivalirudin vs heparin; May not be as effective for MACE and stent thrombosis - HEAT-PPCI trial; May have lower bleeding risk - BRIGHT trial and MATRIX trial
Fondaparinox
- Factor Xa inhibitor
- Not commonly used: Can use in patients with a history of HIT
- Do not use alone for PCI: High rates of thrombosis; Not drug of choice if planning PCI; If already giving fondaparinux and patient needs PCI, need to give unfractionated heparin or bivalirudin also
- Contraindicated for CrCl < 30mL/min
Unfractionated heparin use in UA/NSTEMI and STEMI
UA/NSTEMI: ischemia guided strategy - yes (48 hrs); early invasive strategy - yes (until PCI)
STEMI: fibrinolytic - yes (48 hrs); PCI - yes (until PCI)
Bivalirudin use in UA/NSTEMI and STEMI
US/NSTEMI: ischemia guided strategy - no; early invasive strategy - yes (until PCI)
STEMI: fibrinolytic - no, consider using for HIT; PCI - yes (until PCI, preferred in high bleeding risk)
Enoxaparin use in UA/NSTEMI and STEMI
UA/NSTEMI: ischemia guided strategy - yes (duration of hospital stay up to 8 days); early invasive strategy - yes (until PCI)
STEMI: fibrinolytic - yes (duration of hospital stay up to 8 days); PCI - no
Fondaparinux use in UA/NSTEMI and STEMI
UA/NSTEMI: ischemia guided strategy - yes (duration of hospital stay up to 8 days); early invasive strategy - not ideal, do not use alone for PCI
STEMI: fibrinolytic - yes (duration of hospital stay up to 8 days); PCI - no