Abstract 18280: Five-Year Major Amputation Risk in Patients Undergoing Lower Extremity Bypass Taking into Account All-Cause Mortality Risk and Age Groups

Abstract

Background: Selecting good lower extremity bypass (LEB) surgery candidates for chronic limb threatening ischemia (CLTI) is important to optimize risk-benefit ratios for amputation and death. As mortality risks may be different across age groups, we aimed to examine whether amputation risks across age groups differ by their differential competing risk of death. Methods: Individuals with CLTI undergoing infrapopliteal LEB from 2014 to 2019 in the Medicare linked Vascular Quality Initiative registry were included. The cumulative incidence Function (CIF) for 5-year mortality and major amputation in age groups <65 and ≥65 years, was calculated by Aalen-Johansen, taking mortality into account, and compared against the CIF derived from a traditional Kaplan-Meier, not accounting for competing death. The major amputation risk by age groups was estimated using a Fine and Gray competing risk model (sHR) accounting for competing death and traditional Cox regression (HR) not accounting for competing death. Results: A total of 2,105 patients were included (22% aged <65 years; 70% male, 7% Hispanic, and 18% black). Amputation rates in < 65 vs. ≥65 years were 35.2% and 19.2%; for mortality 34.4% and 44.6%, respectively. In those <65 years, death without amputation was over-estimated by a relative difference of 42%; and major amputation by 16%. Death without amputation in the ≥65 years group was over-estimated by 18%; amputation risk was over-estimated by 23%. When not accounting for competing death risk, adjusted amputation risk for <65 vs ≥65 years was HR 1.17 95%CI 0.90 -1.50 vs. sHR = 1.26 95%CI 0.97-1.62 in the competing risk model. (Table) Conclusions: Younger individuals with CLTI have the highest amputation vs. mortality risk; for those older than 65 years it is the other way around. Collapsing estimates across age groups, while not incorporating competing death risk overestimates amputation risk and can mislead the interpretation of therapeutic benefits of CLTI interventions.