PREVENT: PREVENTION OF RECURRENT VENOUS THROMBOEMBOLISM

深静脉血栓形成和肺栓塞患者的标准治疗通常包括使用全剂量华法林抗凝3至6个月。 然而，在停止抗凝治疗后的几年内，接受该方案的患者发生血栓复发、再住院和死亡的几率很高。 对于疾病复发风险平均的患者，以及由于存在遗传性抗凝缺陷（如凝血因子V Leiden突变）而风险升高的患者，情况也是如此。 不幸的是，目前没有临床方案已被证明有足够的好处，以支持长期预防。 特别是，当长期使用时，全剂量华法林与出血风险显著增加相关。 相比之下，虽然靶向低剂量华法林（INR 1.5-2.0）对于长期治疗是安全的，但这种方法在预防复发性静脉血栓栓塞性疾病方面的疗效尚未得到验证。预防复发性静脉血栓栓塞（PREVENT）试验将评价低剂量华法林长期治疗在静脉血栓栓塞（VTE）二级预防中的疗效。 有记录的特发性静脉血栓形成史并已完成标准抗凝治疗疗程的患者将入组一项随机、双盲、安慰剂对照试验，比较常规护理加靶向低剂量华法林与常规护理加安慰剂，为期长达4年。 试验终点将包括总患者人群中的复发性VTE、大出血事件和全因死亡率，以及单独在莱顿因子V患者中的死亡率。 PREVENT试验的潜在临床影响是广泛的，因为阳性结果将强烈支持在停止标准门诊抗凝治疗后有复发风险的静脉血栓形成患者中进行慢性低强度抗凝治疗。

Standard therapy for patients with deep venous thrombosis and pulmonary embolism typically includes anticoagulation for a 3 to 6 month period with full dose warfarin. However, patients following this regimen experience high rates of recurrent thrombosis, re-hospitalization, and mortality in the years immediately following cessation of anticoagulation. This is true for patients at average risk of disease recurrence, and for patients at elevated risk due to the presence of inherited defects of anticoagulation such as factor V Leiden mutation. Unfortunately, no clinical regimen currently available has proven to have sufficient benefit to support long term prophylaxis. In particular, full dose warfarin is associated with substantially increased risks of hemorrhage when used on a long term basis. In contrast, while targeted low dose warfarin (INR 1.5-2.0) is safe for long term therapy, the efficacy of this approach in the prevention of recurrent venous thromboembolic disease has remained untested. The Prevention of Recurrent Venous Thromboembolism (PREVENT) trial will evaluate the efficacy of prolonged treatment with low dose warfarin in the secondary prevention of venous thromboembolism (VTE). Patients with a history of documented idiopathic venous thrombosis who have completed a standard course of anticoagulation therapy will be enrolled in a randomized, double-blind, placebo-controlled trial comparing usual care plus targeted low-dose warfarin to usual care plus placebo for a period of up to four years. Trial endpoints will include recurrent VTE, major bleeding episodes, and all cause mortality in the total patient population and separately in those patients with factor V Leiden. The potential clinical impact of the PREVENT trial is broad since a positive finding would strongly support chronic low-intensity anticoagulation among patients with venous thrombosis who are at risk for recurrence following cessation of standard outpatient anticoagulation.