Retrospective cohort examines pre-amputation vascular workup phenotypes in chronic limb-threatening ischemia patients

Background. Guidelines recommend vascular specialist evaluation and revascularization consideration before major amputation in chronic limb-threatening ischemia (CLTI). Whether patients consistently receive pre-amputation vascular workup is poorly characterized nationally. Methods. We conducted a retrospective cohort study of Medicare fee-for-service beneficiaries 66 years with CLTI undergoing incident major lower-extremity amputation (2021-2022) with 12 months continuous enrollment. Using claims in the 180 days preceding hospitalization for amputation, we classified patients into mutually exclusive pathway phenotypes: (A) no specialist, no imaging, no revascularization attempt; (B) specialist only, no revascularization attempt; (C) imaging, no revascularization attempt; or (D) revascularization attempted. Mixed-effects multinomial regression with hospital random intercepts identified predictors of phenotype membership. Post-amputation outcomes were compared across phenotypes. Results. Among 10,666 patients (mean age 76.6 years; 35% female; 70% White, 21% Black), phenotype distribution was: A, 9.4%; B, 7.1%; C, 50.7%; D, 32.7%. Thus, 16.6% had no vascular imaging before amputation. Dementia (OR 2.0; 95% CI, 1.61-2.52), paralysis (OR 4.1; 2.62-6.34), and dual eligibility (OR 1.2; 1.01-1.42) were independently associated with phenotype A. Higher comorbidity burden was inversely associated with A (OR 0.49 for >6 vs 0-3 Elixhauser comorbidities). Phenotype A patients had lower 1-year mortality (40% vs 51% for D), fewer readmissions (90-day OR 0.54; 0.47-0.64), and lower costs (adjusted 50% lower at 180 days). Results were robust to acuity adjustment, exclusion of early deaths, and propensity-score matching (n=824 pairs). Phenotype A prevalence varied widely across hospital referral regions, ranging from 3% (Boston, Atlanta) to 16% (Little Rock) among regions with >100 patients. Conclusions. One in six CLTI amputees had no vascular imaging before amputation. Patients without evaluation were characterized by cognitive impairment, functional limitation, lower healthcare engagement, and socioeconomic disadvantage rather than extreme medical complexity. Hospital-level variation suggests system-level interventions could address these gaps.