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Background
Stroke is the fourth leading cause of mortality in the United States, accounting for over 130,000 deaths each year. More than 85% of all strokes are ischemic in origin, with approximately 20% of those attributable to stenosis of the carotid artery. Interventions aimed at primary or secondary stroke prevention in patients with carotid stenosis have evolved over time. Throughout the 1990s, several randomized clinical trials among symptomatic patients (defined as transient or permanent focal neurological deficits) found that carotid endarterectomy (CEA) was superior to, at the time, best medical management. This benefit was most significant in patients with greater than 70% stenosis. Similar results were noted among asymptomatic patients. In a sample of 444 men from the VA medical system, Hobson et al. noted a significant reduction in adverse events in the surgery arm of the trial as compared to the medical management arm. Larger and more inclusive studies have reiterated these findings. However, CEA is an invasive surgical procedure, and carries the associated risks of such.
Toward the later 1990s, carotid artery stenting (CAS) emerged as a less invasive procedure for revascularization. Despite this advantage, it was unclear whether CAS conferred therapeutic benefit equal to that of CEA with respect to stroke prevention. Several clinical trials have attempted to address this question, with somewhat conflicting results. In studies among symptomatic patients, both the EVA-3 S and SPACE trials failed to show non-inferiority of CAS over CEA in reducing the number of endpoint events. Other studies involving both symptomatic and asymptomatic patients found that CAS was either not inferior to or not significantly better than CEA. However, in contrast to SPACE and the early phase of EVA-3 S, CAS was performed with embolic protection in the majority of subjects in both of these studies.
With respect to procedural risk, in 2010, the International Carotid Stenting Study (ICSS) reported that the risk of stroke, death, or myocardial infarction (MI) was significantly higher in the group assigned to stenting. It should be noted that follow-up was for 120 days and embolic protection was not mandated in the study. A later meta-analysis of EVA-3 S, SPACE, and ICSS data found that estimated risk with CAS was twice that of CEA in patients greater than age 70. Similarly, the risk for stroke, MI, or death with CAS significantly increased with age. There was no age-associated increase noted for CEA. There is also evidence from the CREST trial that women may be at higher risk with CAS as compared to CEA.
It now seems clear that the relative benefits of an intervention must be assessed within the context of the individual patient in which it is to be implemented. Patients under the age of 70 or who were excluded from CEA due to high surgical risk were found to have superior outcomes with CAS over CEA or medical management. However, CEA appears to provide the greater benefit to older patients with symptomatic disease. While evidence-based referral of one intervention over the other is presently ambiguous, CAS should be offered as an alternative to surgery for qualified candidates. The number of those qualified, however, is currently limited by a restriction on CAS reimbursement by the Centers for Medicare and Medicaid Services (CMS), an important primary payer of the procedure. At present, stenting (with embolic protection) is reimbursed by the CMS only for those patients excluded from CEA due to high surgical risk and who have ≥ 70% symptomatic stenosis, or who have symptomatic stenosis ≥ 50% or asymptomatic stenosis ≥ 80% and who are enrolled in an FDA-approved clinical trial.
In an effort to describe CEA and CAS utilization over time, this study examined the respective prevalence of these interventions in the Nationwide Inpatient Sample (NIS) annually from 1998 to 2008. The NIS is a nationally-representative database of US hospital discharges, and provides comprehensive information across a range of data variables. It was the aim of this study to report on current CEA and CAS utilization trends with respect to several specific patient demographic factors that may influence intervention, and how these factors may have changed over time. The guiding hypothesis of the study was that CAS use has increased over the study period, and that this increase parallels a decline in the rates of CEA.
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