Hereditary thrombophilia rarely influences the indicated duration of anticoagulation. Genetic mutations causing antithrombin, protein C and protein S deficiencies, when associated with a family history of thrombosis, result in increased risk of recurrence, and indefinite anticoagulation is usually indicated in patients with these deficiencies; however, these mutations are rare.20 More common abnormalities such as factor V Leiden and prothrombin gene mutations do not affect anticoagulation duration.21 Thus, hereditary thrombophilia testing in patients without significant family history should be limited to younger patients (less than 45 years of age) with significant unprovoked thrombosis and must be accompanied by suitable counselling. It should be noted that acute thrombosis and anticoagulant medication may interfere with the results of these tests.
Long-term follow up of VTE
On cessation of anticoagulation for DVT, a repeat ultrasound is recommended to assess residual venous obstruction as not all thrombi will completely resolve. Residual clot burden has minimal effect on decisions regarding duration of anticoagulation, although these results serve as a useful baseline. If the patient develops new symptoms, a negative d-dimer test result and unchanged ultrasound findings may be used to exclude recurrent DVT.
Women with a history of VTE should avoid oestrogen-containing contraceptives and oral menopausal hormone therapy (MHT) after discontinuing anticoagulation. Progestin-only contraceptives are generally safe. There is no evidence that using the levonorgestrel intrauterine device increases the risk of VTE. There is also no evidence that transdermal MHT increases VTE recurrence, and it can therefore be considered as a safe replacement for oral MHT.22
Patients receiving anticoagulation indefinitely should be reassessed on a regular basis to ensure they are still deriving benefit from their treatment. Finally, all patients should be monitored for the development of chronic complications of VTE. One in three patients suffers from post-thrombotic syndrome after a lower-limb DVT. The syndrome is characterised clinically by swelling, discomfort, hyperpigmentation and lipodermatosclerosis in the affected limb. Treatment options are, unfortunately, limited. An elastic compression stocking may reduce the swelling and pain but is not tolerated by all patients.23,24
If a patient who has suffered a PE complains of exertional dyspnoea in the ensuing two years, chronic thromboembolic pulmonary hypertension should be considered. A VQ scan to assess residual clot burden and an echocardiogram to assess right heart pressures should be carried out in these patients. If the results are abnormal, the patient should be referred for assessment by a specialist.25
VTEs are challenging diagnoses commonly encountered in the primary care setting. The THANZ guideline is a valuable resource for physicians looking for a pragmatic, evidence-based framework to inform their decision-making. Timely diagnosis and optimal management minimise both unnecessary therapy for minor events, and morbidity and mortality in more significant events. MT