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Objective: Therapeutic anticoagulation is used for prolongation of infrainguinal bypass patency, but evidence for the efficacy of this practice is conflicting. The objective of our study is to determine the effects of anticoagulation on bypass graft primary patency.
Methods: Clinical and comorbid data on patients receiving infrainguinal bypass grafts to a below-knee target with at least one year of follow-up performed from 2003 to 2015 were obtained from the Society for Vascular Surgery Vascular Quality Initiative. Inverse propensity of treatment-weighted Cox regression was used to assess the effect of anticoagulation on patency in the total cohort while adjusting for clinical, operative, and comorbid differences between treatment groups. Subgroup analyses of distal targets and conduit type were performed; conduit types included single-segment vein, prosthetic graft, and a composite non-single-segment-vein group (NSSV) defined as all prosthetic, spliced vein, and composite grafts.
Results: We identified 7612 bypass grafts with intact one-year follow-up information from 2003-2015. The mean age was 67.5±11.2; 30.5% (n=2320) were female, and 28.6% (n=2165) were discharged on therapeutic anticoagulation. The anticoagulated group had a higher rate of tibial/ankle/pedal targets (52.1%, n=1127 vs 47.6%, n=2269; p<0.001), a greater usage of NSSV conduits (44.3%, n=951 vs. 26.5%, n=1426; p<0.001), and were more likely to have had a previous ipsilateral bypass (27.2%, n=589 vs. 14.7%, n=794; p<0.001) or stent (25.4%, n=550 vs. 20.9%, n=1130; p<0.001). Estimated unadjusted primary patency was 70.8% at one year, and lower for anticoagulated bypasses (66.9% vs. 72.4%, p<0.001). Propensity-weighted analysis of primary patency showed no significant impact of anticoagulation on the overall cohort or in any subgroups but demonstrated a trend toward improvement of primary patency in those with a NSSV conduit to a below-knee popliteal target (Table).
Conclusions: Patients receiving anticoagulation for an infrainguinal bypass to a below-knee target tend to have a higher rate of distal targets, non-single-segment-vein conduit usage, and previous ipsilateral intervention. This study does not demonstrate any significant impact of therapeutic anticoagulation on primary patency for infrainguinal bypass grafts but does suggest a trend toward benefit in patients with a prosthetic or spliced vein bypass to the below knee popliteal artery.

	HR	95% CI	P
Total Cohort	0.98	[0.87, 1.11]	0.80
Subgroup: Single-segment vein conduit	1.05	[0.89, 1.24]	0.58
Subgroup: Prosthetic conduit	0.85	[0.70, 1.02]	0.10
Subgroup: Prosthetic + Below-Knee Popliteal Target	0.90	[0.69, 1.18]	0.46
Subgroup: NSSV conduit	0.88	[0.74, 1.05]	0.15
Subgroup: NSSV + Below-Knee Popliteal Target	0.78	[0.60, 1.01]	0.06
Subgroup: NSSV + Tibial/Ankle/Pedal Target	0.97	[0.76, 1.24]	0.81