PB0987 - Hereditary Antithrombin Deficiency Pilot Project Registry from the American Thrombosis and Hemostasis Network (ATHN)

Background: Patients with hereditary antithrombin deficiency (HAD) are at high risk of developing venous thromboembolism (VTE).

Aims: The purpose of ATHN 12: HAD Pilot Project is to collect data on participants with HAD across the United States to develop guidelines for screening, anticoagulation therapy, and indications for using antithrombin (AT) concentrate to optimize patient care.

Methods: The prospective HAD Registry was designed in 2020 to identify 100 participants with HAD followed at ATHN-affiliated thrombosis centers. We collected demographics, type of AT deficiency, thrombotic events and risk factors, use of anticoagulation therapy, and AT concentrate.

Results: Ninety-four participants were enrolled; mean age 37 years (2-87); 61 (65%) females; 81% White; 48 (51%) had type 1 HAD. Fifty-seven (61%) had VTE most commonly lower extremity deep vein thrombosis [61 (55%)] and pulmonary embolisms [30 (27%)]. Twenty-nine (51%) had recurrent VTEs. Eight (9%) had arterial thrombosis and a recurrent event in 1 (13%) (Table 1). Of the 57 participants with VTE, 20 (44.4%) had no other risk factors for VTE. Anticoagulation therapies prescribed were direct Xa inhibitors in 46%, heparin in 28% and warfarin in 25% (Table 2). There were 135 pregnancies in 46 women. Low molecular weight heparin (LMWH) was administered in 33% of the pregnancies and AT concentrate in 25 (19%) pregnancies before delivery. Fifteen women received AT concentrate 24 hours post-delivery. Thirty-seven women (27%) restarted anticoagulation post-delivery. There were 55 (41%) pregnancy complications (Table 2). Seventy-nine participants (84%) underwent 239 surgeries or procedures most commonly gastrointestinal and vascular, respectively (Table 2). Overall, 33 (35%) participants received AT concentrate without adverse events

Conclusion(s): VTE was the main clinical manifestation, and oral factor Xa inhibitors the most common anticoagulation prescribed. LMWH was administered in one-third of the pregnancies and AT concentrate in one-fifth of the pregnancies before delivery without adverse events