Antithrombotic Treatment and Outcomes of Splanchnic Vein Thrombosis in an International Prospective Registry: Results of 2-Year Follow-up

Background: Little information is available on the long-term clinical outcome of patients with splanchnic vein thrombosis (SVT). We aimed to assess incidence rates of bleeding, recurrence, and mortality in a large prospective cohort of SVT patients after a 2-year follow-up.

Methods: Consecutive SVT patients were enrolled in a multicenter international registry, from 2008 to 2012. Information was gathered on baseline characteristics, risk factors and therapeutic strategies. Clinical outcomes (major bleeding; vascular events, defined as venous or arterial thrombosis, and mortality) during follow-up were collected and reviewed by a Central Adjudication Committee. Major bleeding was defined using the ISTH definition plus the need for hospitalization. The primary analysis was performed up to the first adjudicated major bleeding or thrombotic event.

Results: 604 patients from 31 centers were enrolled in this study, 21 (3.5%) were lost to follow-up. Median follow-up duration was 2 years (IQR 1-2). Median age was 54 years (range 16-85); 62.6% were males. Most common risk factors were liver cirrhosis in 27.8% of patients and solid cancer in 22.3%. Portal vein was the most common site of thrombosis. 139 patients were not anticoagulated; 175 received parenteral anticoagulants only (median duration 5.8 months, IQR 3-12) and 290 were started on vitamin K antagonists (median duration 24 months, IQR 7-24).

According to the primary analysis, 103 events occurred during follow-up: 35 major bleeding events (3.8/100 patient-years [pt-y]; 95%CI, 2.7-5.2), 2 of which were fatal bleeding, and 68 thrombotic events (7.3/100 pt-y; 95%CI 5.8-9.3), 9 of which were vascular deaths. All-cause mortality occurred in 106 patients (10.3/100 pt-y; 95% CI 8.5-12.5).

The incidence of major bleeding events was 4.0/100 pt-y in patients on anticoagulant drugs and 3.4/100 pt-y in patients not receiving anticoagulants. The incidence of vascular events was 5.6/100 pt-y and 9.7/100 pt-y, respectively.

Major bleeding and vascular event rates were highest in cirrhotic patients (10.0/100 pt-y and 11.3/100 pt-y, respectively), and lowest in the subgroup of non-malignant non-cirrhotic patients (1.8/100 pt-y and 5.6/100 pt-y, respectively).

Conclusions: SVT patients have a non-negligible long-term risk of both bleeding and thrombotic events, but this risk varies according to the pathogenesis of SVT. Anticoagulant treatment is associated with a reduced incidence of thrombotic events without apparently resulting in an increased risk of bleeding.

Funding: The study was funded by a grant from Pfizer Canada to ISTH