OP0276 PATTERNS OF RECURRENT THROMBOTIC EVENTS IN PATIENTS WITH ANTIPHOSPHOLIPID SYNDROME
Authors: B. Geertsema-Hoeve, N. Keijzer, R. Urbanus, T. Noordermeer, P. M. J. Welsing, C. Wong, M. Limper
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Antiphospholipid syndrome (APS) is a rare autoimmune disorder characterized by the development of arterial and/or venous thrombotic events, as well as obstetric complications, in the presence of antiphospholipid antibodies (aPL). Generally, APS is associated with a higher risk of venous thromboembolism (i.e. deep vein thrombosis (DVT) and pulmonary embolisms) than arterial thrombosis. However, arterial events can still occur, and the risk may vary among individuals. Arterial thrombosis may manifest as strokes, transient ischemic attacks (TIAs), or other arterial events. Additionally, there are non-criteria manifestation in APS, such as livedo reticularis, Libman-Sacks endocarditis and thrombocytopenia. Recurrent thrombosis is frequently observed despite treatment. However, information regarding the patterns of recurrent thrombotic events is limited, and there is a lack of consensus in guidelines, particularly for the treatment of (recurrent) arterial thrombotic events. One of the open questions is whether a subgroup of APS-patients could be treated with platelet-aggregation inhibitors like clopidogrel, instead of treatment with vitamin K antagonists (VKA) with a potentially higher risk of bleeding complications. <h3>Objectives:</h3> The objective of this study is to discern patterns of recurrent thrombotic events and identify predictive factors associated with specific recurrent thrombotic patterns <h3>Methods:</h3> We conducted a retrospective analysis of data from the UMC Utrecht APS cohort, including patients diagnosed with APS based on the international Sydney classification criteria. The study encompassed only patients with recurrent thrombotic events. Binary logistic regression analysis was used to examine the association between the type of initial event (venous thromboembolism or arterial thrombosis), antibody profile, and the subsequent recurrence type of thrombosis. <h3>Results:</h3> The total APS cohort consists of 300 patients. Among them, there were 73 patients with recurrent thrombotic events. The initial thrombotic event was arterial in 21 (28.8%) patients, and venous in 52 (71.2%) patients. The median duration of follow-up was 24 years (IQR 16-31.5). During that time, the median number of thrombotic events, including the initial event, was 3 (IQR 2-3). Seventeen patients (23.3%) experienced only arterial events and four patients (5.5%) switched from an initial arterial thrombosis to at least one VTE; thirty-two patients (43.8%) only experienced venous events whereas 20 patients (27.4%) switched from an initial VTE to at least one ATE (Figure 1). In patients with an arterial thrombotic event, the non-criteria manifestations livedo reticularis, Libman-Sacks endocarditis and epilepsy significantly occurred more frequently compared to the patients with venous events. A triple positive antibody profile was associated with a higher risk of having the same type of recurrent events, compared with a single positive antibody profile (OR 7.46, 95% CI 1.77-31.44). A higher number of events was associated with a higher chance of switching events (OR 2.20, 95% CI 1.36-3.57). Cardiovascular risk factors or type of anticoagulation were not associated with a higher chance of switching events (Table 1). In the switch group, the mortality rate was higher, with 9 out of 24 (37.5%) deaths, compared to 7 out of 49 patients (14.3%) in the no switch group (p=0.024). The deceased group comprised a subset of more severely ill patients who experienced earlier mortality. <h3>Conclusion:</h3> Patients who undergo an initial arterial event display an elevated susceptibility to subsequent recurrent arterial events, whereas a higher incidence of event switching is observed among those experiencing a primary venous event. Patients with a triple positive antibody profile are less likely to switch from type of thrombotic event. This might be a preliminary step towards conducting further research on best treatment choices in APS patients with recurrent thrombotic events and to tailor treatment in these patients accordingly. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>