Regarding “Stroke and death after carotid endarterectomy and carotid artery stenting with and without high risk criteria”

Abstract

In a recent article by Giles et al,1Giles K.A. Hamdan A.D. Pomposelli F.B. Wyers M.C. Schermerhorn M.L. Stroke and death after carotid endarterectomy and carotid artery stenting with and without high risk criteria.J Vasc Surg. 2010; 52: 1497-1504Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar the authors report higher risks of stroke, death, and a composite end point of stroke or death among patients undergoing carotid artery stenting (CAS) compared with carotid endarterectomy (CEA). We are concerned that the results of the study likely reflect substantial unmeasured confounding rather than a true difference in outcomes between the cohorts. Limitations of the administrative data source regarding clinical indication are apparent when considered in the context of the existing Medicare national coverage decision for patients undergoing CAS with embolic protection, defined as follows:1patients who are at high risk for CEA and have symptomatic carotid artery stenosis ≥70%;2patients who are at high risk for CEA and have symptomatic carotid artery stenosis between 50% and 70%, in accordance with the category B investigational device exemption; and3patients who are at high risk for CEA and have asymptomatic carotid artery stenosis ≥80%, in accordance with the category B investigational device exemption. High-risk features were defined as congestive heart failure New York Heart Association functional class III/IV, left ventricular ejection fraction <30%, unstable angina, contralateral carotid occlusion, recent myocardial infarction, previous CEA with recurrent stenosis, prior radiation treatment to the neck, and other conditions that were used to determine patients at high risk for CEA in prior CAS trials. Given these criteria, one would expect event rates with CAS to be higher than event rates with CEA because, by definition, the eligible population for CAS is at higher risk. The similarities between patients who underwent CAS and patients who underwent CEA calls into question the validity of the data, not the relative effectiveness of the interventions. In contrast, the categorization of high-risk vs non–high-risk patients did not affect the observed mortality rate in the overall CAS group (1.5% in both groups). The mortality rate was marginally higher among patients with asymptomatic CAS deemed non–high-risk compared with high-risk (0.9% vs 0.7%). These findings again call into question the categorization of high risk in the CAS group, a definition in this study that depended on inpatient diagnosis and billing codes that, to our knowledge, are poorly validated. Finally, data from several randomized trials provide important information. In Carotid Revascularization Endarterectomy vs Stent Trial (CREST),2Brott T.G. Hobson 2nd, R.W. Howard G. Roubin G.S. Clark W.M. Brooks W. et al.Stenting versus endarterectomy for treatment of carotid-artery stenosis.N Engl J Med. 2010; 363: 11-23Crossref PubMed Scopus (2091) Google Scholar for example, the composite end point was not different between the CAS and CEA groups; however, minor stroke rates were higher for patients undergoing CAS and myocardial infarction rates were higher for patients undergoing CEA. None of the available data have identified a mortality difference. In fact, the current Medicare coverage rule for patients who are undergoing CAS and are enrolled in clinical trials (two of the three approved indications) likely introduces ascertainment bias among patients who undergo routine mandated stroke evaluations by independent neurologists. We appreciate the limitations noted by the authors, but we have serious concerns that the adjusted comparisons suffer from unmeasured confounding. The presentation of observed outcomes is helpful for clinicians and patients, but appropriate interpretation for health care policy makers requires judicious consideration of these issues. Stroke and death after carotid endarterectomy and carotid artery stenting with and without high risk criteriaJournal of Vascular SurgeryVol. 52Issue 6PreviewCenters for Medicare and Medicaid Services (CMS) reimbursement criteria for carotid artery stenting (CAS) require that patients be high surgical risk or enrolled in a clinical trial. This may bias comparisons of CAS and carotid endarterectomy (CEA). We evaluate mortality and stroke following CAS and CEA stratified by medical high risk criteria. Full-Text PDF Open ArchiveReplyJournal of Vascular SurgeryVol. 54Issue 1PreviewAlthough we agree that the database used for this study has limitations related to the identification of comorbidities, we do not believe that this should negate the findings. In fact, this analysis was undertaken because we believed that prior analyses of carotid stenting (CAS) vs endarterectomy (CEA) using this database suffered from potential confounding related to high-risk status. The definitions of International Classification of Disease (9th revision) coding to identify high risk, as we have noted, do overestimate some of the criteria. Full-Text PDF Open Archive