LAUSR

OBJECTIVE While current guidelines recommend single antiplatelet therapy (SAPT) for patients undergoing revascularization for chronic limb-threatening ischemia (CLTI), antithrombotic management varies by patient and provider. Our aim was to examine the impact of different post-operative antithrombotic regimens on 3-year clinical outcomes after infrapopliteal bypass for CLTI. METHODS We identified patients undergoing infrapopliteal bypass for CLTI in the Vascular Quality Initiative registry from 2003-2017 with linkage to Medicare claims for long-term outcomes. We divided patients into 3 cohorts based on discharge antithrombotic regimen: SAPT (aspirin or clopidogrel), dual antiplatelet therapy (DAPT; aspirin and clopidogrel), and anticoagulation(AC)+any antiplatelet(AP) agent. To reduce selection bias, we restricted the analysis cohorts to patients treated by providers who discharge >50% of patients on each antithrombotic regimen. Our primary outcome was 3-year major adverse limb events (MALE; major amputation or reintervention). Secondary outcomes included 3-year major amputation, reintervention, and mortality. We used Kaplan Meier and Cox regression analyses to assess these outcomes by antithrombotic regimen, adjusting for demographic, comorbid, clinical, and operative differences between treatment groups with clustering at the center level. RESULTS Among 1812 patients (median follow-up >2years), 693 (38%) were discharged on SAPT, 544 (30%) on DAPT, and 575 (32%) on AC+AP. At 3 years, MALE rates were 75% with DAPT, 74% with AC+AP, and 68% with SAPT. In adjusted analyses with SAPT as the reference group, there were no differences in 3-year MALE with DAPT (adjusted HR[aHR] 1.0, 95%CI 0.85-1.3, p=.71) or with AC+AP (aHR 1.1, 0.96-1.3, p=.14). Across treatment groups, there were also no differences in the individual endpoints of 3-year major amputation (DAPT: aHR 0.98, 0.72-1.3; AC+AP: aHR 1.3, 0.96-1.7), reintervention (DAPT: aHR 1.0, 0.84-1.3; AC+AP: aHR 1.1, 0.96-1.3) or mortality (DAPT: aHR 1.1, 0.88-1.4; AC+AP: aHR 0.95, 0.74-1.2). In a sensitivity analysis evaluating patients treated by providers who discharge >60%, >70%, or >80% of patients on these regimens, the association between antithrombotic regimen and MALE was unchanged. CONCLUSIONS Compared with SAPT, DAPT or anticoagulation therapy were not associated with improved outcomes among Medicare beneficiaries who underwent infrapopliteal bypass for CLTI at VQI-participating centers. These findings support current guidelines recommending SAPT after lower extremity bypass and suggest that routine use of DAPT or anticoagulation therapy may not provide a clinical benefit in this high-risk, elderly population. However, further evaluation of the risks and benefits of various antithrombotic regimens in relevant subgroups is warranted.