Effect of hospital-level variation in the use of carotid artery stenting versus carotid endarterectomy on perioperative stroke and death in asymptomatic patients

Abstract

Objective: Perioperative stroke and death (PSD) are more common after carotid artery stenting (CAS) than after carotid endarterectomy (CEA) in symptomatic patients, but whether this is also true in asymptomatic patients is unclear. Furthermore, use of both CEA and CAS varies geographically, suggesting possible variation in outcomes. We compared odds of PSD after CAS and CEA in asymptomatic patients to determine the impact of this variation.

Methods: We identified CAS and CEA procedures and hospitals where they were performed from 2005 to 2009 California hospital discharge data. Preoperative symptom status and medical comorbidities were determined using administrative codes. We compared PSD rates after CAS and CEA using logistic regression and propensity score matching. We quantified hospital-level variation in the relative utilization of CAS by calculating hospital-specific probabilities of CAS use among propensity score-matched patients. We then calculated a weighted average for each hospital and used this as a predictor of PSD.

Results: We identified 6053 CAS and 36,524 CEA procedures that were used to treat asymptomatic patients in 278 hospitals. Perioperative stroke and death occurred in 250 CAS and 660 CEA patients, yielding unadjusted PSD rates of 4.1% and 1.8%, respectively (P < .001). Compared with CAS patients, CEA patients were more likely to be older than 70 years (66% vs 62%; P < .001) but less likely to have three or more Elixhauser comorbidities (37% vs 39%; P < .001). Multivariate models demonstrated that CAS was associated with increased odds of PSD (odds ratio [OR], 1.865; 95% confidence interval [CI], 1.373-2.534; P < .001). Estimation of average treatment effects based on propensity scores also demonstrated 1.9% increased probability of PSD with CAS (P < .001). The average probability of receiving CAS across all hospitals and strata was 13.8%, but the interquartile range was 0.9% to 21.5%, suggesting significant hospital-level variation. In univariate analysis, patients treated at hospitals with higher CAS utilization had higher odds of PSD compared with patients in hospitals that performed CAS less (OR, 2.141; 95% CI, 1.328-3.454; P = .002). Multivariate analysis did not demonstrate this effect but again demonstrated higher odds of PSD after CAS (OR, 1.963; 95% CI, 1.393-2.765; P < .001).

Conclusions: Carotid endarterectomy has lower odds of PSD compared with CAS in asymptomatic patients. Increased utilization of CAS at the hospital level is associated with increased odds of PSD among asymptomatic patients, but this effect appears to be related to generally worse outcomes after CAS compared with CEA.

Figure 1

Selection of hospital discharge records for analysis.

Figure 2

Annual asymptomatic carotid revascularization procedures in California.

Figure 3

Histogram of weighted average hospital-level probability of performing CAS versus CEA across all propensity score matched strata (“relative CAS utilization”).