Carotid Endarterectomy and Carotid Artery Stenting in the US Medicare Population, 1999-2014

Abstract

Importance: Carotid endarterectomy and carotid artery stenting are the leading approaches to revascularization for carotid stenosis, yet contemporary data on trends in rates and outcomes are limited.

Objective: To describe US national trends in performance and outcomes of carotid endarterectomy and stenting among Medicare beneficiaries from 1999 to 2014.

Design, setting, and participants: Serial cross-sectional analysis of Medicare fee-for-service beneficiaries aged 65 years or older from 1999 to 2014 using the Medicare Inpatient and Denominator files. Spatial mixed models adjusted for age, sex, and race were fit to calculate county-specific risk-standardized revascularization rates. Mixed models were fit to assess trends in outcomes after adjustment for demographics, comorbidities, and symptomatic status.

Exposures: Carotid endarterectomy and carotid artery stenting.

Main outcomes and measures: Revascularization rates per 100 000 beneficiary-years of fee-for-service enrollment, in-hospital mortality, 30-day stroke or death, 30-day stroke, myocardial infarction, or death, 30-day all-cause mortality, and 1-year stroke.

Results: During the study, 937 111 unique patients underwent carotid endarterectomy (mean age, 75.8 years; 43% women) and 231 077 underwent carotid artery stenting (mean age, 75.4 years; 49% women). There were 81 306 patients who underwent endarterectomy in 1999 and 36 325 in 2014; national rates per 100 000 beneficiary-years decreased from 298 in 1999-2000 to 128 in 2013-2014 (P < .001). The number of patients who underwent stenting ranged from 10 416 in 1999 to 22 865 in 2006 (an increase per 100 000 beneficiary-years from 40 in 1999-2000 to 75 in 2005-2006; P < .001); by 2014, there were 10 208 patients who underwent stenting and the rate decreased to 38 per 100 000 beneficiary-years (P < .001). Outcomes improved over time despite increases in vascular risk factors (eg, hypertension prevalence increased from 67% to 81% among patients who underwent endarterectomy and from 61% to 70% among patients who underwent stenting) and the proportion of symptomatic patients (all P < .001). There were adjusted annual decreases in 30-day ischemic stroke or death of 2.90% (95% CI, 2.63% to 3.18%) among patients who underwent endarterectomy and 1.13% (95% CI, 0.71% to 1.54%) among patients who underwent stenting; an absolute decrease from 1999 to 2014 was observed for endarterectomy (1.4%; 95% CI, 1.2% to 1.5%) but not stenting (-0.1%; 95% CI, -0.5% to 0.4%). Rates for 1-year ischemic stroke decreased after endarterectomy (absolute decrease, 3.5% [95% CI, 3.2% to 3.7%]; adjusted annual decrease, 2.17% [95% CI, 2.00% to 2.34%]) and stenting (absolute decrease, 1.6% [95% CI, 1.2% to 2.1%]; adjusted annual decrease, 1.86% [95% CI, 1.45%-2.26%]). Additional improvements were noted for in-hospital mortality, 30-day stroke, myocardial infarction, or death, and 30-day all-cause mortality as well as within demographic subgroups.

Conclusions and relevance: Among fee-for-service Medicare beneficiaries, the performance of carotid endarterectomy declined from 1999 to 2014, whereas the performance of carotid artery stenting increased until 2006 and then declined from 2007 to 2014. Outcomes improved despite increases in vascular risk factors.

Figure 1.. National Carotid Revascularization Rates Among Fee-for-Service Medicare Beneficiaries per 100 000 Beneficiary-Years From 1999 to 2014

Annual procedure rates were calculated by dividing the number of unique patients undergoing the specified carotid revascularization procedure in each year by the corresponding number of beneficiary-years of fee-for-service Medicare enrollment for all beneficiaries in that year within subgroups for age, sex, and race. The shaded area represents the 95% CI. The lines were smoothed using the LOESS method (local regression).

Figure 2.. County-Level Risk-Standardized Carotid Revascularization Rates Among Fee-for-Service Medicare Beneficiaries for 1999-2000 and 2013-2014

A spatial mixed model with a Poisson link function and adjustment for age, sex, and race was fit for each period to calculate and map annualized county-specific risk-standardized rates for carotid endarterectomy and carotid artery stenting. The US counties are shaded from green (lowest rate) to red (highest rate) according to the carotid revascularization rate per 100 000 beneficiary-years. The scales are specific to the procedure and period, and they reflect 6 equal quantiles based on the data. The carotid endarterectomy rates ranged from 77 to 735 per 100 000 beneficiary-years for 1999-2000 and from 41 to 351 per 100 000 beneficiary-years for 2013-2014. The carotid artery stenting rates ranged from 11 to 263 per 100 000 beneficiary-years in 1999-2000 and from 15 to 209 per 100 000 beneficiary-years for 2013-2014. Areas shaded white indicate insufficient data that precluded rate calculations (not calculable). Data from Puerto Rico were used to estimate the national county-level carotid revascularization rates, but they are not included in the maps. For Puerto Rico, the median risk-standardized annual procedure rate for carotid endarterectomy was 195 (interquartile range [IQR], 170-240) per 100 000 beneficiary-years in 1999-2000 and 121 (IQR, 110-132) per 100 000 beneficiary-years in 2013-2014 vs 38 (IQR, 33-49) per 100 000 beneficiary-years in 1999-2000 and 42 (IQR, 40-46) per 100 000 beneficiary-years in 2013-2014 for carotid artery stenting.

Figure 3.. Adjusted Annual Percentage Reduction in Carotid Endarterectomy and Carotid Artery Stenting Outcomes Among Fee-for-Service Medicare Beneficiaries Overall and by Patient Demographic Subgroups From 1999 to 2014

Mixed models with hospital-specific random intercepts, an interval time variable, and adjustment for demographic characteristics, comorbid conditions, and symptomatic status were used to calculate adjusted odds ratios (for in-hospital mortality and 30-day all-cause mortality) and hazard ratios (for 30-day ischemic stroke or death, 30-day ischemic stroke, myocardial infarction, or death, and 1-year ischemic stroke) representing annual change in outcomes after carotid endarterectomy and carotid artery stenting. The time variable was transformed to reflect the percentage annual reduction in outcome by subtracting the odds ratio or hazard ratio from the null value of 1.0; a positive number indicates a decline in the adverse outcome. The forest plots summarize these annual percentage reductions and corresponding 95% CIs for the overall carotid endarterectomy and stenting procedure populations and for subgroups defined by sex, race, and age (the data marker and 95% CI values appear in eTable 5 in the Supplement).