Duration of anticoagulation therapy

NOTES ON MAINTENANCE TREATMENT OF VTE

Following initial heparinisation or fondaparinux in patients with VTE, maintenance of anticoagulation with oral anticoagulants is recommended. Following discharge, those on warfarin should be followed up within a week with a repeat INR.

If the INR remains within therapeutic range, the same dose is maintained and the next follow-up will be 2 weeks later. If the INR still remains within therapeutic range, then monthly follow-up with INR is advised. More frequent visits are required if therapeutic INR is not achieved.

Patients on rivaroxaban do not need initial heparinisation or laboratory monitoring. Patients are seen within 1 to 2 weeks of treatment to monitor response and to assess drug tolerability. Thereafter monthly follow-up is advised.

Duration of anticoagulation

The aim of anticoagulant therapy is to prevent extension of the thrombus and recurrence of the disease; however, the optimal duration is still not known. Anticoagulant therapy should be continued until the reduction of recurrent VTE no longer outweighs the increase risk of bleeding.

Risk factors for VTE recurrence

The risk of recurrence after stopping therapy is primarily determined by two factors:

(1) whether the acute episode of VTE has been effectively treated and

(2) the patient's intrinsic risk of having a new episode of VTE (Table).

Risk factors for recurrence
  • Unprovoked (idiopathic) VTE
  • Previous VTE
  • Male gender
  • Active cancer
  • Antiphospholipid syndrome
  • Proximal versus distal DVT
  • Post-thrombotic syndrome

The most important factors that influence the risk of recurrence after stopping anticoagulant therapy are the presence of a reversible provoking risk factor, unprovoked (idiopathic) VTE and the presence of active cancer.

Among patients with VTE provoked by a reversible risk factor, the risk of recurrence is much lower if the provoking factor was recent surgery compared with a nonsurgical trigger (e.g. estrogen therapy, pregnancy, long-haul flight).

Risk factors for increased bleeding

The risk factors for increased bleeding in patients on anticoagulation are listed below (Table)

Risk factors for increased bleeding
  • Uncontrolled hypertension
  • Age >75 years
  • Renal impairment
  • Anaemia
  • Recent major bleeding

The recommended duration of anticoagulation hence depends on the risk of recurrence and the risk of bleeding (Table)

Table: Duration of anticoagulation (Grade B Recommendation)

First VTE

Recommended Duration of AC

Provoked by a transient surgical risk factor

3 months

Provoked by a transient nonsurgical risk factor

3 months

Unprovoked VTE

Offer indefinite anticoagulation after taking into account:

  • Patient's preference
  • Low bleeding risk
  • Good anticoagulant monitoring is achievable

Unprovoked VTE and one or more bleeding risk

3 months

Unprovoked VTE in association with active cancer and the anti-phospholipid syndrome

Anticoagulation is continued as long as the risk factor remains

Completion of anticoagulation

There is no strong evidence to recommend routine D-dimer testing or US examination upon completion of anticoagulation in order to determine VTE recurrence and the decision to prolong therapy, unless guided by clinical symptoms. A high D-dimer does not typically predict recurrence while a normal D-dimer does not exclude recurrence. Ultrasound examination is operator-dependent and an old thrombus with partial recanalization may falsely suggest a recurrrence.