Background

Antiphospholipid syndrome (APS) is an autoimmune prothrombotic disorder that is frequently associated with systemic lupus erythematosus (SLE). Cardiac surgery in patients with APS presents unique challenges because activated clotting time (ACT) monitoring can be unreliable, frequently yielding falsely prolonged results due to the presence of lupus anticoagulant. Although heparin concentration-based monitoring is more accurate, devices such as the Hemostasis Management System Plus have been discontinued, creating a gap in practical anticoagulation management.

Case presentation

We report two female patients with APS and severe aortic regurgitation (AR) who underwent aortic valve replacement (AVR) under cardiopulmonary bypass (CPB).

Case 1: A 58-year-old woman with long-standing SLE and APS underwent preoperative ACT simulation using her serum mixed with a 60 U/mL heparin solution to estimate the ACT corresponding to a heparin concentration of 3.0 U/mL. The resulting ACT range (567–708 s) guided intraoperative anticoagulation. AVR with a mechanical valve and left atrial appendage amputation (LAAA) was performed. Protamine was administered at half the calculated dose. Postoperative bleeding was transient and well controlled.

Case 2: A 62-year-old woman with recent APS, deep vein thrombosis, and infective endocarditis underwent ACT simulation. The simulated ACT ranged from 325 to 413 s, and an intraoperative ACT target of > 450 s was established. AVR and LAAA were performed uneventfully with half dose protamine. No thrombotic or bleeding complications occurred.

Discussion

These cases highlight the limitations of conventional ACT monitoring in patients with APS and demonstrate the utility of individualized preoperative ACT simulation as a practical alternative. This approach allowed safe anticoagulation management without requiring advanced equipment. Reduced protamine dosing likely minimized the risk of rebound hypercoagulability, a concern in APS. Notably, despite identical heparin concentrations, ACT responses varied among the patients, underscoring the need for personalized strategies.

Conclusion

Preoperative ACT simulation using patient serum offers a practical, accessible, and individualized method for guiding anticoagulation therapy in patients with APS undergoing cardiac surgery. This technique may enhance perioperative safety in resource-limited settings, and warrants further validation in larger cohorts.