Prognosis

DVT rarely affects the overall prognosis of the patient; the presence or absence of an underlying malignancy, and the presence or absence of underlying medical comorbidities, such as liver disease or chronic kidney disease, remain the major prognostic determinants among patients with DVT. People with cancer have reduced survival rates compared with people without cancer, and cancer patients who sustain DVT have a shorter life expectancy than cancer patients without venous thromboembolism (VTE; although this appears to be related to an association with more severe malignancy and VTE, rather than to the DVT itself). If a patient dies due to DVT, this is usually caused by concomitant pulmonary embolus or major haemorrhage as a complication of the anticoagulation therapy.

In one systematic review, during the initial 3 months of anticoagulation, the rate of recurrent fatal VTE was 0.4% with a case-fatality rate of 11.3%. The rate of fatal major bleeding events was 0.2% with a case-fatality rate of 11.3%. After anticoagulation, the rate of fatal recurrent VTE was 0.3 per 100 patient-years with a case-fatality rate of 3.6%.[140]

In community cohort studies, the incidence of acute recurrent DVT within 60 days is as high as 25% to 30%. The reasons for this acute recurrence are not known, but subtherapeutic anticoagulant therapy or patient non-adherence to therapy may contribute.[141][142]

In patients with acute DVT or pulmonary embolism enrolled in prospective cohort studies, only 5% of patients develop recurrent VTE during the initial 6 months of anticoagulation; however, 30% of patients develop recurrent VTE between 6 months and 5 years after the initial event, if off anticoagulation.[143][144]

Compared with patients with no thrombophilic defects, the rate of recurrence during warfarin therapy is not increased in the presence of one or more defects.[145]

The incidence of major life-threatening haemorrhage owing to anticoagulant treatment is low, with the precise risk varying by anticoagulant agent and patient characteristics.

Recurrence

A significant factor that determines the risk of recurrence is whether a DVT is provoked or unprovoked.

  • A provoked DVT is a DVT associated with a major transient risk factor that was present in the 3 months prior to the DVT.[12] 

  • An unprovoked DVT is a DVT in a patient who had no pre-existing, major, transient, provoking risk factor in the prior 3 months.[12] 

  • Major provoking risk factors include: major surgery; trauma; significant immobility (bedbound, unable to walk unaided, or likely to spend a substantial proportion of the day in bed or in a chair); pregnancy or puerperium; use of oral contraceptive/hormone replacement therapy).[12]

The principal means of preventing recurrence (secondary prevention) is the extended duration (beyond 3 months) of anticoagulation. Bear in mind that not all patients will need continued anticoagulation beyond 3 months. However, other considerations may be required (e.g., VTE prophylaxis at periods of higher risk). See Secondary prevention under Prevention for more information. 

Seek advice from haematology for any patient who has a recurrent VTE despite adequate anticoagulation treatment. Recurrent VTE is unusual among patients receiving therapeutic-dose anticoagulant therapy, except in those with active cancer (7% to 9% on-therapy recurrence with low molecular weight heparin).[13][137][138]

  • Check adherence to anticoagulation treatment.[12] 

  • Address other sources of hypercoagulability (e.g., underlying malignancy).[12] 

  • Consider other reasons for reduced efficacy of anticoagulation (e.g., rivaroxaban not being taken with food).[139] 

In the absence of any of the above issues, options include:[12] 

  • Increasing the dose of anticoagulant

  • Changing to a different anticoagulant with a different mode of action.

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