Hereditary antithrombin deficiency pilot project registry from the American Thrombosis and Hemostasis Network

Patients with hereditary antithrombin deficiency (HAD) have an increased risk of venous thromboembolism (VTE). The American Thrombosis and Hemostasis Network (ATHN) 12: HAD Pilot Project established a registry to collect data on patients with HAD. To inform current practice and serve as a platform to design a multicenter global registry for patients with HAD. The HAD registry was designed in 2020 to identify 100 patients with HAD receiving care at ATHN-affiliated centers. Demographics, type of HAD, thrombotic events, risk factors, anticoagulants, and antithrombin (AT) concentrate administration were recorded. Ninety-four patients were included; 65% were females; 51% had type 1 HAD. Mean age at diagnosis was 26 years (SD, 18 years); 61% had VTE: 55% deep vein thrombosis and 27% pulmonary embolisms. Eight patients had arterial thrombosis. Recurrent thrombosis occurred in 58.6% of patients (44.8%) despite anticoagulation. The main risk factor for thrombosis in females was estrogen. Direct oral anticoagulants were prescribed in 30%, heparin in 34%, and warfarin in 32%. There were 139 pregnancies. Low-molecular-weight heparin was administered in 33% and AT concentrate in 19% and 11% prior to and after delivery, respectively. Twelve patients developed thrombosis in pregnancy. Seventy-nine patients underwent 239 surgeries or procedures, mainly gastrointestinal and vascular. Overall, 35% of participants received AT concentrate without adverse events. In ATHN 12, VTE was the predominant manifestation, frequently recurrent. There was a trend toward using direct oral anticoagulants. Low-molecular-weight heparin was administered in one-third of pregnancies and AT concentrate in one-fifth without adverse events. These data should encourage prospective studies to optimize the management of these patients.