Low-Dose Apixaban Added to Standard Heparin Lock Versus Heparin Lock Alone to Prevent Tunneled Hemodialysis Catheters Dysfunction (APICATH-HD)

Inclusion Criteria: * Age ≥18 years with end-stage kidney disease (CKD stage 5) receiving maintenance hemodialysis or initiating hemodialysis. * Recently placed tunneled, double-lumen central venous hemodialysis catheter (tunneled CVC) in place for ≥8 days, with a post-placement radiograph confirming adequate tip position. * Permitted catheter insertion sites: right internal jugular, left internal jugular, right femoral, or left femoral vein. * Adequate initial catheter function, defined as ability to achieve the prescribed extracorporeal blood flow (suggested ≥300 mL/min) for ≥8 days after catheter placement. * Conventional in-center hemodialysis schedule (2-3 sessions/week) at the study unit, with expected ability to complete follow-up for up to 24 months. * Written informed consent provided. * Willingness to receive only the protocol-assigned antithrombotic prophylaxis and to avoid non-study systemic anticoagulants or antiplatelet agents during the study period. Exclusion Criteria: * Non-tunneled hemodialysis catheter, subclavian catheter, or intracaval catheter placement not consistent with the protocol (e.g., catheter located in the SVC/IVC without a subcutaneous tunnel, or catheter location/site not permitted by the study). * Tunneled catheter placed \<8 days before randomization or radiographically confirmed catheter tip malposition at screening. * Active bleeding; active peptic ulcer disease; or clinically significant gastrointestinal bleeding within the past 30 days; uncorrectable INR \>1.5; platelet count \<100,000/µL. * High bleeding risk (HAS-BLED score \>3) or major bleeding that is active or recent. * Known coagulopathy; history of heparin-induced thrombocytopenia (HIT); or allergy/hypersensitivity to heparin, citrate, or rt-PA (alteplase). * Severe hepatic impairment (e.g., Child-Pugh class C), clinically significant liver dysfunction that contraindicates DOAC therapy, or ongoing hemodialysis with regional citrate anticoagulation that cannot be modified per protocol. * Active catheter exit-site infection or bloodstream infection/bacteremia at the time of randomization. * Concomitant use of other systemic anticoagulants (e.g., warfarin, low-molecular-weight heparin, other DOACs) or high-intensity antiplatelet therapy (e.g., dual antiplatelet therapy). * Pregnancy or breastfeeding. * Women of childbearing potential who are unwilling to use a highly effective contraception method during the study and for 48 hours after the last dose of study medication. * Life expectancy \<6 months, current palliative/hospice care, or planned kidney transplant within ≤3 months. * Concurrent participation in another clinical trial that could interfere with the study interventions or outcomes. * Venography demonstrating significant venous stenosis involving the superior vena cava (SVC) or inferior vena cava (IVC).