Outcomes in chronic limb-threatening ischemia (CLTI) depend on timely revascularization and sustained continuity of specialty care. Although community-level socioeconomic disadvantage is associated with worse outcomes, the impact of individual-level socioeconomic vulnerability on longitudinal outcomes and healthcare utilization after CLTI revascularization remains unclear. We analyzed 333,173 Medicare beneficiaries who underwent CLTI revascularization between 2016 and 2023. Socioeconomic vulnerability was defined by Dual Enrollment (DE) in Medicaid. Outcomes were assessed using Kaplan–Meier analyses and multivariable Cox proportional hazards models. The primary clinical outcome was major amputation. A composite endpoint of major amputation or death was analyzed to contextualize overall disease burden. The study period was stratified into pre-COVID (01/2016–03/2020), COVID (03/2020–12/2021), and post-COVID (12/2021–12/2023) phases. Healthcare utilization was compared between DE and Medicare-Only patients. Among the included patients, 26.2% were DE. DE patients were younger, more frequently female, and had a higher comorbidity burden. The crude cumulative incidence of the primary outcome was higher in DE patients (80.1% vs 79.7%; unadjusted HR 1.07, 95% CI 1.06–1.08), but this difference was not significant after adjustment (adjusted HR 1.00, 95% CI 0.99–1.01). DE patients had higher rates of major amputation (17.8% vs 12.7%; adjusted HR 1.10, 95% CI 1.07–1.12), with no adjusted differences in repeat revascularization or all-cause mortality. During COVID, DE patients had a higher adjusted risk of the primary outcome (HR 1.05, 95% CI 1.02–1.08), whereas risks were similar pre- and postpandemic. DE identifies CLTI patients at increased risk of limb loss despite similar adjusted survival, highlighting individual-level barriers to care continuity and the need for targeted strategies to reduce preventable amputations.
Key Learning Points
What is already known
• Socioeconomic disadvantage is associated with worse outcomes in chronic limb-threatening ischemia, including higher risks of amputation and mortality.
• Previous studies have largely relied on community-level socioeconomic measures, which may not fully capture individual patient vulnerability.
• Disruptions in care continuity, such as those observed during the COVID-19 pandemic, disproportionately affect vulnerable populations.
What this study adds
• Dual enrollment in Medicare and Medicaid , an individual-level marker of socioeconomic vulnerability, is independently associated with a higher risk of major amputation after CLTI revascularization, despite similar adjusted survival.
• Socioeconomic vulnerability primarily impacts limb preservation rather than mortality , suggesting barriers in longitudinal care rather than intrinsic disease severity.
• Dual-enrolled patients experience fragmented care pathways , with fewer outpatient vascular visits and greater reliance on emergency and inpatient care, highlighting actionable targets for intervention.
Chronic limb-threatening ischemia (CLTI) represents the most advanced stage of peripheral arterial disease and is associated with substantial risks of limb loss, mortality, and healthcare utilization. Optimal management of CLTI extends beyond the technical success of revascularization and relies on timely diagnosis, coordinated multidisciplinary care, and sustained longitudinal follow-up to preserve limb function and improve survival. Despite advances in endovascular techniques, outcomes after CLTI revascularization remain highly variable, suggesting that nonclinical factors play a critical role in shaping patient trajectories.
Socioeconomic disparities have consistently been identified as major determinants of outcomes in CLTI. Previous national analyses have demonstrated that patients residing in socioeconomically distressed communities experience higher rates of major amputation, mortality, and reduced access to vascular specialty care, with these disparities further amplified during the COVID-19 pandemic. Community-level measures such as the Distressed Communities Index (DCI) have been instrumental in quantifying the structural and geographic dimensions of disadvantage, capturing variations in regional resources, healthcare infrastructure, and population-level deprivation. However, while these measures effectively characterize where patients live, they do not fully reflect how individual patients interact with the healthcare system.
Community-level socioeconomic indices are limited in their ability to capture patient-level financial hardship, insurance instability, and barriers to navigating complex care pathways. Individuals residing in the same geographic area may face markedly different challenges in accessing timely specialty care, maintaining continuity after revascularization, and adhering to follow-up surveillance. As a result, geographic measures alone may obscure important mechanisms of inequity that operate at the level of the individual patient rather than the community.
Dual enrollment (DE) in Medicare and Medicaid represents a distinct, individual-level marker of socioeconomic vulnerability within the US healthcare system. , It is not a direct measure of poverty but an administrative designation encompassing financial hardship, disability, and medical complexity. Dual-enrolled patients often face fragmented coverage and increased reliance on acute care services, and this designation may capture dimensions of vulnerability not fully accounted for by traditional clinical risk adjustment or geographic measures.
Accordingly, this study sought to evaluate the association between DE status and clinical outcomes following endovascular revascularization for CLTI, with a focus on limb-related events, mortality, and patterns of healthcare utilization before and after intervention. ,, By examining DE as an individual-level proxy for socioeconomic vulnerability, and by assessing outcomes across pre-COVID, COVID, and post-COVID periods, this analysis aims to elucidate patient-level mechanisms of inequity that extend beyond community distress. , Understanding these mechanisms is essential to inform targeted, patient-centered strategies to improve continuity of care and reduce preventable limb loss among socioeconomically vulnerable populations. These concepts are summarized in the Central Illustration .
Individual-level socioeconomic vulnerability and outcomes after endovascular revascularization for chronic limb-threatening ischemia.
Material and Methods
Study design and population
This is a nationwide retrospective cohort study encompassing all 50 states and US territories, including Medicare beneficiaries who underwent revascularization between January 1, 2016 and December 31, 2023. Dual eligibility status served as the primary exposure variable and was defined as enrollment in both Medicare and Medicaid in the month of the index procedure. Patients were categorized into 2 groups: Medicare-Only beneficiaries and DE beneficiaries.
Data sources
Data were extracted from Medicare administrative claims, including the Medicare Fee-for-Service Inpatient File, Outpatient File, and Carrier File. Additional demographic and clinical information was obtained from the Master Beneficiary Summary File and Chronic Condition Data Warehouse. To assess institutional and regional characteristics, data from the American Hospital Association Annual Survey and the DCI were incorporated. Distressed communities were defined as ZIP-code areas scoring in the ≥80th percentile on the national DCI, a composite measure of educational attainment, employment, income, and housing stability. The DCI serves as a proxy for community-level disadvantage, while dual enrollment reflects individual-level socioeconomic vulnerability. Patients were identified through administrative claims codes, including ICD-10-CM codes for a diagnosis of CLTI and ICD-10-PCS and CPT codes to identify endovascular revascularization procedures ( Appendix Table 1 – 6 ).
Inclusion and exclusion criteria
Patients were eligible for inclusion if they had complete Medicare claims data for at least 12 months before the index revascularization procedure and underwent endovascular revascularization for CLTI at an eligible facility, which included hospital-based inpatient and outpatient settings, ambulatory surgery centers, and office-based laboratories. Patients were excluded if they had previous major amputation during the 12-month look-back period, lacked essential sociodemographic data such as ethnicity, geographic location, or socioeconomic indicators, or were treated at centers performing fewer than 2 procedures over the study period. A detailed breakdown of the exclusion criteria and patient flow is provided in the Appendix Figure 1 .
Outcomes
The primary outcome was a composite of major amputation or all-cause mortality following revascularization, reflecting the most severe clinical consequences of CLTI. Major amputation was defined as any above-ankle amputation, including below-knee amputation and above-knee amputation, identified using the procedure codes listed in Appendix Table 7 – 9 .
Secondary outcomes included individual rates of major amputation, any repeat revascularization, all-cause mortality, and healthcare utilization metrics, including vascular specialist visits, imaging studies, emergency department visits, and hospital readmissions.
Statistical analysis
Baseline characteristics of the study population were summarized using means (standard deviations) for continuous variables and frequencies (percentages) for categorical variables. Standardized mean differences (SMDs) were used to evaluate the balance of baseline characteristics between Medicare-Only and DE groups, with an SMD >10% considered indicative of imbalance. The cumulative incidence of outcomes was assessed using Kaplan–Meier methods for time-to-event data that included death, and the Cumulative Incidence Function for nondeath outcomes to account for the competing risk of death. Multivariable Cox proportional hazards models were constructed to adjust for potential confounders, including sociodemographic characteristics such as age, sex, ethnicity, geographic region, and SES, clinical characteristics such as comorbidities including diabetes, chronic kidney disease, and congestive heart failure, procedural factors such as type and location of revascularization, and regional and facility-level factors, including institutional volume and teaching status. Cox models using the Fine–Gray approach for competing risks were used to estimate subdistribution hazard ratios (HR) for nondeath outcomes. Subgroup analyses were conducted to assess the interaction between DE status and periods of care: pre-COVID (January 1, 2016–March 31, 2020), during COVID (April 1, 2020–December 31, 2021), and post-COVID (January 1, 2022–December 31, 2023). All analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC), with a two-tailed significance level of p < 0.05.
Ethical considerations
This study was approved by the Institutional Review Board (IRB) of Beth Israel Deaconess Medical Center. A waiver of informed consent was granted for this retrospective analysis of de-identified data. The study adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for cohort studies.
Results
Study population
Between January 1, 2016 and December 31, 2023, a total of 333,173 Medicare beneficiaries underwent endovascular revascularization for CLTI across eligible facilities. The mean age of patients was 74.39 years (SD 10.42) (SMD = −48.4%), with 42.84% of patients identified as female (SMD 21.5%). The racial composition was predominantly White (76.25%, SMD −63.5%), followed by Black (13.46%), Asian (3.87%), and other ethnicities (6.42%). Cardiovascular comorbidities were prevalent, including hypertension (95.37%, SMD 7.5%), hyperlipidemia (90.11%, SMD −1.0%), and diabetes mellitus (69.57%, SMD 28.2%).
Patients were categorized into 2 groups based on dual Enrollment status: Medicare-Only beneficiaries (N = 245 716, 73.8%) and DE beneficiaries (N = 87 457, 26.2%).
Compared to Medicare-Only beneficiaries, DE patients were younger (mean age 70.56 ± 11.83 years vs 75.75 ± 9.51 years, SMD = −48.4) and more likely to be of Black (25.6% vs 12.2%, SMD = 34.7) or another ethnicity (15.96% vs 4.26%, SMD = 39.6). They were also more likely to reside in distressed communities (30.03% vs 16.5%, SMD = 32.5%) and to have comorbidities such as chronic kidney disease (77.54% vs 69.74%, SMD = 17.8%) and congestive heart failure (63.11% vs 54.18%, SMD = 18.2%). Baseline characteristics of the study cohort are summarized in Table 1 .
Table 1
Baseline characteristics of patients who underwent endovascular CLTI revascularization, stratified by Dual Enrollment status.
| Subject Characteristic | Medicare Only (N = 245 716) | Dual Enrollment (N = 87 457) | SMD: Dual Enrollment vs. Medicare Only (%) |
|---|---|---|---|
| Age, mean (SD) | 75.75 (9.51) | 70.56 (11.83) | -48.4 |
| Age, median (IQR) | 76 (69- 83) | 70 (63- 79) | — |
| Female, % | 101 274 (41.22%) | 45 370 (51.88%) | 21.5 |
| Ethnicity | |||
| White, % | 203 593 (82.86%) | 47 937 (54.81%) | -63.5 |
| Black, % | 29 984 (12.20%) | 22 392 (25.60%) | 34.7 |
| Asian, % | 1 669 (0.68%) | 3 171 (3.63%) | 20.4 |
| Other, % | 10 470 (4.26%) | 13 957 (15.96%) | 39.6 |
| Distressed Community | 40 497 (16.48%) | 26 260 (30.03%) | 32.5 |
| Rural Locations | 9 279 (3.78%) | 3 108 (3.55%) | -1.2 |
| Region | |||
| Northeast, % | 41 014 (16.69%) | 13 093 (14.97%) | -4.7 |
| Midwest, % | 35 452 (14.43%) | 10 828 (12.38%) | -6.0 |
| South, % | 133 243 (54.23%) | 41 836 (47.84%) | -12.8 |
| West, % | 36 007 (14.65%) | 21 700 (24.81%) | 25.7 |
| Medical Comorbidities | |||
| Acute Myocardial Infarction, % | 37 238 (15.15%) | 13 829 (15.81%) | 1.8 |
| Alzheimer’s Disease, % | 12 424 (5.06%) | 8 308 (9.50%) | 17.2 |
| Alzheimer’s Disease, Related Disorders, or Senile Dementia, % | 50 587 (20.59%) | 26 721 (30.55%) | 23.0 |
| Anemia, % | 181 917 (74.04%) | 70 305 (80.39%) | 15.2 |
| Arthritis (RA/OA), % | 164 187 (66.82%) | 59 332 (67.84%) | 2.2 |
| Atrial Fibrillation, % | 73 997 (30.11%) | 19 995 (22.86%) | -16.5 |
| Cancer, % | 49 897 (20.31%) | 12 463 (14.25%) | -16.1 |
| Chronic Kidney Disease, % | 171 364 (69.74%) | 67 817 (77.54%) | 17.8 |
| Heart Failure, % | 133 128 (54.18%) | 55 193 (63.11%) | 18.2 |
| COPD/Bronchiectasis, % | 110 076 (44.80%) | 45 646 (52.19%) | 14.8 |
| Depression, % | 97 529 (39.69%) | 48 884 (55.89%) | 32.9 |
| Diabetes, % | 167 637 (68.22%) | 70 350 (80.44%) | 28.2 |
| Hip/Pelvic Fracture, % | 16 980 (6.91%) | 5 493 (6.28%) | -2.5 |
| Hyperlipidemia, % | 223 002 (90.76%) | 79 120 (90.47%) | -1.0 |
| Hypertension, % | 234 459 (95.42%) | 84 717 (96.87%) | 7.5 |
| Ischemic Heart Disease, % | 191 439 (77.91%) | 69 594 (79.58%) | 4.1 |
| Osteoporosis, % | 49 782 (20.26%) | 19 025 (21.75%) | 3.7 |
| Stroke/TIA, % | 66 592 (27.10%) | 28 294 (32.35%) | 11.5 |
| Liver Disease, Cirrhosis and Other Liver Conditions, % | 37 992 (15.46%) | 18 378 (21.01%) | 14.4 |
| Obesity, % | 93 822 (38.18%) | 38 398 (43.91%) | 11.7 |
| Alcohol Dependency, % | 20 628 (8.40%) | 10 640 (12.17%) | 12.4 |
| Tobacco Dependency, % | 81 209 (33.05%) | 37 882 (43.32%) | 21.2 |
| Procedural Characteristics | |||
| Atherectomy, % | 98 071 (39.91%) | 37 648 (43.05%) | 6.4 |
| Balloon only, % | 158 630 (64.56%) | 58 962 (67.42%) | 6.0 |
| Stent, % | 87 086 (35.44%) | 28 495 (32.58%) | -6.0 |
| Revascularization Modality Category | |||
| Balloon with atherectomy, % | 61 911 (25.20%) | 25 052 (28.64%) | 7.8 |
| Balloon without atherectomy, % | 96 719 (39.36%) | 33 910 (38.77%) | -1.2 |
| Stent with atherectomy, % | 36 160 (14.72%) | 12 596 (14.40%) | -0.9 |
| Stent without atherectomy, % | 50 926 (20.73%) | 15 899 (18.18%) | -6.4 |
| Peripheral Artery Disease Severity | |||
| Rest pain, % | 88 197 (35.89%) | 30 608 (35.00%) | -1.9 |
| Ulceration, % | 103 293 (42.04%) | 33 614 (38.43%) | -7.4 |
| Gangrene, % | 54 226 (22.07%) | 23 235 (26.57%) | 10.5 |
| Arterial Segment of Intervention Categories | |||
| Iliac alone, % | 27 469 (11.18%) | 8 967 (10.25%) | -3.0 |
| Fempop alone, % | 86 932 (35.38%) | 28 146 (32.18%) | -6.8 |
| Tibial alone, % | 47 298 (19.25%) | 17 485 (19.99%) | 1.9 |
| Iliac and fempop, % | 16 240 (6.61%) | 5 427 (6.21%) | -1.6 |
| Iliac and tibial, % | 901 (0.37%) | 324 (0.37%) | 0.1 |
| Fempop and tibial, % | 62 041 (25.25%) | 25 003 (28.59%) | 7.5 |
| All levels, % | 4 835 (1.97%) | 2 105 (2.41%) | 3.0 |
| Place of Service | |||
| Hospital-based inpatient, % | 86 427 (35.17%) | 30 709 (35.11%) | -0.1 |
| Hospital-based outpatient, % | 83 722 (34.07%) | 24 457 (27.96%) | -13.2 |
| ASC/OBL, % | 75 567 (30.75%) | 32 291 (36.92%) | 13.1 |
| Hospital Characteristics (Excluding ASCs/OBLs) | |||
| Teaching Hospital, % | 113 927 (66.97%) | 37 043 (67.16%) | 0.4 |
| Bed Size | |||
| 6 to 49, % | 1 347 (0.79%) | 544 (0.99%) | 2.1 |
| 50 to 99, % | 7 796 (4.58%) | 2 155 (3.91%) | -3.4 |
| 100 to 299, % | 62 712 (36.86%) | 19 611 (35.55%) | -2.7 |
| 300 to 499, % | 49594 (29.15%) | 16 570 (30.04%) | 1.9 |
| ≥ 500, % | 48 674 (28.61%) | 16279 (29.51%) | 2.0 |
| Endovascular revascularization volume, annual, mean (SD) (All Centers) | 140.73 (144.30) | 154.85 (170.44) | 8.9 |
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