Anticoagulation

Question 1

Anticoagulation recommended…

Answer 1

in addition to antiplatelet therapy to improve vessel patency and prevent re-occlusion

Question 2

Unfractionated Heparin (UFH)

Answer 2

• 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

Question 3

Is unfractionated heparin the only anticoagulant that can cause HIT?

Answer 3

no, LMWH can also cause HIT, but there is a lower risk

Question 4

Can a patient with a history of HIT be re- challenged with unfractionated heparin or LMWH?

Answer 4

no, pts should not be rechallenged with either

Question 5

Unfractionated Heparin (UFH) half life

Answer 5

• 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)

Question 6

Enoxaparin

Answer 6

• 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

Question 7

Do we routinely check anti-Xa levels for patients on enoxaparin?

Answer 7

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

Question 8

Bivalirudin

Answer 8

• 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

Question 9

Fondaparinox

Answer 9

• 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

Question 10

Unfractionated heparin use in UA/NSTEMI and STEMI

Answer 10

UA/NSTEMI: ischemia guided strategy - yes (48 hrs); early invasive strategy - yes (until PCI)
STEMI: fibrinolytic - yes (48 hrs); PCI - yes (until PCI)

Question 11

Bivalirudin use in UA/NSTEMI and STEMI

Answer 11

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)

Question 12

Enoxaparin use in UA/NSTEMI and STEMI

Answer 12

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

Question 13

Fondaparinux use in UA/NSTEMI and STEMI

Answer 13

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