Preventing de Novo Portal Vein Thrombosis With Antithrombin-III in Patients With Cirrhosis: A Randomized, Double-blinded, Placebo - Controlled Trial (PiVoT-AC Trial)

PVT is a common complication in patients with cirrhosis, affecting 10% to 25% of patients. PVT is a potentially life-threatening occurrence, complicating transplant candidacy and reducing five-year survival. In addition to the mortality risk posed by PVT, microthrombi within the liver have been linked to decompensation due to the phenomenon of parenchymal extinction. Because of the developing understanding of a baseline hypercoagulable state in many cirrhosis patients, recent studies have demonstrated the benefit of prophylactic anticoagulation with enoxaparin in patients with cirrhosis to prevent PVT. In addition to the benefit in reducing PVT, prophylactic anticoagulation was also found to reduce liver decompensation and improve overall survival.

Risk factors for PVT are well described. The strongest independent risk factor for PVT is portal vein velocity. For each 1 cm/s decrease in portal vein velocity, PVT risk increases 16%. Portal vein velocity <15cm/sec is the best-established cutoff for predicting the development of de novo PVT over the ensuing twelve months.

In addition, patients with cirrhosis and venous thromboembolism (PVT, deep vein thrombosis, pulmonary embolus) have abnormally low levels of AT-III. A recent report by the NPB-06 study group suggest that administering intravenous AT-III at dosage of 1500 units/day for five consecutive days in patients with cirrhosis and AT-III <70% serum level is a safe and effective treatment for PVT with promising short-term partial and complete resolution of PVT. Despite this, the role of AT repletion in preventing PVT remains unknown.