Warfarin/INR

Indications to continue longterm Warfarin

• Valvular Afib / Prosthetic heart valves
• eGFR<30
• Severe liver disease (Child-Pugh class C)
• Antiphospholipid syndrome
• Compliance/cost

Contraindications

• Pregnancy (Consider LMWH)
• Allergy
• Active bleeding

Complications

• Bleed
• Skin necrosis (typically in the setting of protein C deficiency)
• Cholesterol embolization ("blue toe syndrome")
• Teratogenicity
• Vascular calcification
• Allergic reactions

Unexplained poor INR control, r/o

• Adherence
• Vitamin K deficiency
  • Suspect in poor nutrition
    • INR sensitive to small amounts of vitamin K
  • Consider supplement Vitamin K low-dose 100 to 200 mcg daily

Target

• INR 2-3 (most of the time)
• INR 2.5-3.5
  • Mechanical mitral valve
  • Older mechanical heart valves including caged-ball and caged-disk valve
  • Aortic or mitral mechanical valve with Afib

Adjustment

• Rule out transient cause (medication, diet, alcohol, infection)
• If under, increase by 10% and repeat in 1 week
  • If INR <1.5 consider extra dose (20% of weekly) with increase
• If above, decrease by 10% and repeat in 1 week
  • If INR >4 consider hold 1-2 dose with decrease
  • If INR >9 hold and consider vitamin K 2-5mg orally
  • VKA-associated major bleeding
    • 4-factor prothrombin complex concentrate
    • Vitamin K 5-10 mg by slow IV injection
• If at target, repeat in 1 week, then 2 weeks, then 4 weeks (consider 6-12 weeks if very stable)

When to consider Warfarin over DOAC

• Valvular Afib
• CrCl<30
• Weight >120kg
• Gastrectomy, gastric bypass
• Liver failure
• Breasfeeding

Switch to DOAC when INR <2 except for

• Rivaroxaban INR <3
• Edoxaban ≤2.5