Two weeks’ anticoagulation may be enough to treat low-risk isolated symptomatic deep vein thrombi (IDDVT), despite current guidelines recommending six to 12 weeks’ therapy, Australian and New Zealand haematologists say.

A prospective study of 241 low-risk IDDVT patients on enoxaprin (1 mg/kg BD or 1.5 mg/kg once daily) or rivaroxaban (15 mg BD) between 2010 and 2018 showed just two weeks’ therapy could help resolve symptoms and prevent thrombus extension on complete whole leg compression ultrasound (CUS), without any major bleeding events.

During the study, 69% percent of patients treated within 72 hours of diagnosis achieved complete pain, swelling and erythema resolution within two weeks, though 30% progressed to six-week therapy and 1% had extension into the popliteal vein on two week CUS, the authors wrote in Thrombosis Research.

Symptom resolution persisted in most patients, with only two in the two-week treatment group having recurrent symptomatic IDDVT at three-month follow-up and two having recurrent venous thromboembolism. At six months, 4.4% had post-thrombotic syndrome, they found.

Twenty five patients developed bleeding while on treatment, 22, in the first two weeks, however, five cases were clinically relevant non-major bleeding and the rest were minor bleeds, they reported.

Although optimal IDDVT treatment “remains uncertain”, “our findings suggest it’s safe/efficacious to stop therapeutic anticoagulation at two weeks in low-risk IDDVT patients with resolution of symptoms/no extension on ultrasound,” they wrote.

This could drastically reduce anticoagulant therapy duration for ambulatory, low-risk IDDVT patients, they suggested, dropping treatment down from the six to 12 weeks recommended by current Australian guidelines.

“The standard of care for DVT diagnosis in Australia and New Zealand is whole leg CUS. Consequently, calf vein thrombi (distal DVT) are routinely diagnosed, accounting for 50% of patients diagnosed with symptomatic DVT,” the authors wrote.

“When left untreated, the proportion of distal DVT that propagate to proximal veins, increasing the risk of PE, is unknown but likely low (0.9–6%). Therefore the management of IDDVT is uncertain.”

Given the low risk of extension, 2019 guidelines suggested IDDVT do not always require anticoagulation. However, they advised patients should be treated with anticoagulants for six weeks where their IDDVT is “caused by a major provoking factor that is no longer present” or three months if they have a significant symptom burden, risk factors for extension (e.g. thrombosis > 5 cm in length, > 7 mm maximum diameter, involving multiple veins), unprovoked DVT, a history of active cancer or previous VTE or current hospital admission.

“If the patient is asymptomatic and does not initially receive anticoagulation, it is suggested to repeat the CUS after 1–2 weeks to detect possible proximal extension,” they noted.

“We suggest that may be safe and efficacious to stop therapeutic anticoagulation at two weeks in patients with low-risk IDDVT who have resolution of symptoms and no extension on ultrasound, with very low rates of recurrent VTE and no proximal DVT/PE recurrence. This could replace six to twelve weeks of anticoagulation for ambulatory, low-risk IDDVT patients,” the authors concluded.