37yo male complains of left leg painful swelling. Ultrasound
confirms popliteal DVT. There was no antecedent trauma, surgery, hospitalizations,
or trips. Family history is negative and thrombophilia workup is negative. After
three months of warfarin therapy, what is the next step?
- Continue Warfarin for 1 year
- Stop Warfarin
- Countinue Warfarin indefinitely
- Stop Warfarin and start aspirin
- Further diagnostic testing
After an
idiopathic thrombotic event, the 10-year risk of recurrence is about 30 percent. The risk of major bleeding while on warfarin therapy is
approximately 2 percent per year when warfarin is well managed. Therefore, it can be helpful to to further risk stratify patients which can be done with D-Dimer testing or lower extremity doppler ultrasound.
The Prolong Trial assessed using D-Dimer testing to determine the duration of anticoagulation. This was a prospective trial
that evaluated 600 people with
idiopathic DVT after 3 months of therapy with warfarin. Their D-Dimer was
checked one month after stopping warfarin and if it was abnormal the patients
were randomized to further anticoagulation or no therapy. The risk of venous
thrombosis if you had a positive D-Dimer and you were left off of warfarin
therapy was approximately 10 percent per year. A negative D-Dimer predicted a risk of
recurrence of about 3 percent per year
The DACUS trial looked at 250 patients who had on warfarin for at least 3
months and then assessed residual thrombus by ultrasound. If there was residual
thrombus, then they randomized patients either to resume warfarin or to stop
warfarin; if there was no residual thrombus then they simply stopped warfarin
therapy. Patient's without evidence of thrombosis had a low risk of DVT recurrence suggesting continued warfarin therapy was unnecessary in this group past the three month window.
Prolong Trial:
DACUS Trial:
