Direct and Indirect Effects of Race and Socioeconomic Deprivation on Outcomes Following Lower Extremity Bypass

Chloé A Powell, Jeremy Albright, Jacob Culver, Nicholas H Osborne, Matthew A Corriere, Devraj Sukul, Hitinder Gurm, Peter K Henke

The goal of this study is to evaluate the potential pathway through which race and socioeconomic status, as measured by the social deprivation index (SDI), affect outcomes following lower extremity bypass chronic limb threatening ischemia (CLTI), a marker for delayed presentation. Racial and socioeconomic disparities persist in outcomes after lower extremity bypass; however, limited studies have evaluated the role of disease severity as a mediator to potentially explain these outcomes using clinical registry data. We captured patients who underwent lower extremity bypass using a statewide quality registry from 2015-2021. We used mediation analysis to assess the direct effects of race and high values of SDI (5th quintile) on our outcome measures: 30-day major adverse cardiac event (MACE) defined by new myocardial infarction (MI), transient ischemic attack (TIA)/stroke, or death, and 30-day and 1-year surgical site infection (SSI), amputation and bypass graft occlusion. 7,077 patients underwent a lower extremity bypass procedure. Black patients had a higher prevalence of CLTI (80.63% vs. 66.37%, P<0.001). In mediation analysis, there were significant indirect effects where Black patients were more likely to present with CLTI and thus had increased odds of 30-day amputation (OR 1.11, 95% CI 1.068-1.153), 1-year amputation (OR 1.083, 95% CI 1.045-1.123) and SSI (OR 1.052, 95% CI 1.016-1.089). There were significant indirect effects where patients in the 5th quintile for SDI were more likely to present with CLTI and thus had increased odds of 30-day amputation (OR 1.065, 95% CI 1.034-1.098) and SSI (OR 1.026, 95% CI 1.006-1.046), and 1-year amputation (OR 1.068, 95% CI 1.036-1.101) and SSI (OR 1.026, 95% CI 1.006-1.046). Black patients and socioeconomically disadvantaged patients tended to present with more advanced disease, CLTI, which in mediation analysis was associated with increased odds of amputation and other complications following lower extremity bypass compared with White patients and those that were not socioeconomically disadvantaged.