Effect of postoperative antithrombotic therapy on lower extremity outcomes after infrapopliteal bypass for chronic limb-threatening ischemia

Abstract

Objective: Although the current guidelines have recommended single antiplatelet therapy (SAPT) for patients undergoing revascularization for chronic limb-threatening ischemia (CLTI), antithrombotic management has varied by patient and provider. Our aim was to examine the effects of different postoperative antithrombotic regimens on 3-year clinical outcomes after infrapopliteal bypass for CLTI.

Methods: We identified patients who had undergone infrapopliteal bypass for CLTI in the Vascular Quality Initiative (VQI) registry from 2003 to 2017 with linkage to Medicare claims for long-term outcomes. We divided the patients into three cohorts according to the discharge antithrombotic regimen: SAPT (aspirin or clopidogrel), dual antiplatelet therapy (DAPT; aspirin and clopidogrel), or anticoagulation (AC) plus any antiplatelet (AP) agent. To reduce selection bias, we restricted the analysis cohorts to patients treated by providers who discharged >50% of patients with each antithrombotic regimen. Our primary outcome was 3-year major adverse limb events (MALE; major amputation or reintervention). The secondary outcomes included 3-year major amputation, reintervention, and mortality. We used Kaplan-Meier and Cox regression analyses to assess these outcomes stratified by antithrombotic regimen and adjusted for demographic, comorbid, clinical, and operative differences between the treatment groups with clustering at the center level.

Results: Among 1812 patients (median follow-up, >2 years), 693 (38%) were discharged with SAPT, 544 (30%) with DAPT, and 575 (32%) with AC+AP. At 3 years, the MALE rates were 75% with DAPT, 74% with AC+AP, and 68% with SAPT. In adjusted analyses with SAPT as the reference group, no differences were found in 3-year MALE with DAPT (adjusted hazard ratio [aHR], 1.0; 95% confidence interval [CI], 0.85-1.3; P = .71) or AC+AP (aHR, 1.1; 95% CI, 0.96-1.3; P = .14). Across the treatment groups, we also found no differences in the individual end points of 3-year major amputation (DAPT: aHR, 0.98; 95% CI, 0.72-1.3; AC+AP: aHR, 1.3; 95% CI, 0.96-1.7), reintervention (DAPT: aHR, 1.0; 95% CI, 0.84-1.3; AC+AP: aHR, 1.1; 95% CI, 0.96-1.3), or mortality (DAPT: aHR, 1.1; 95% CI, 0.88-1.4; AC+AP: aHR, 0.95; 95% CI, 0.74-1.2). In a sensitivity analysis evaluating patients treated by providers who discharged >60%, >70%, or >80% of patients with these regimens, the association between antithrombotic regimen and MALE was unchanged.

Conclusions: Compared with SAPT, DAPT and anticoagulation therapy were not associated with improved outcomes among Medicare beneficiaries who had undergone infrapopliteal bypass for CLTI at VQI participating centers. These findings support current guidelines recommending SAPT after lower extremity bypass and suggest that the routine use of DAPT or anticoagulation therapy might not provide 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.

Keywords: Anticoagulation; Antiplatelet therapy; Antithrombotic therapy; Chronic limb-threatening ischemia; Infrapopliteal bypass.