Indications, outcomes, and provider volumes for carotid endarterectomy

Context.-While trials have demonstrated that carotid endarterectomy is superior to best medical therapy, most recently among asymptomatic patients, uses and outcomes of the procedure in more representative settings have not been established. Objectives.-To profile the use and outcomes of carotid endarterectomy in a representative sample of Ohio's Medicare beneficiaries and to examine the relationships between provider-specific procedural volumes and patient outcomes. Design.-Retrospective cohort using Medicare Provider Analysis and Review files supplemented by detailed reviews of medical records on a random sample of patients. Setting.-Ohio hospitals performing carotid endarterectomy. Patients.-A random sample of 678 charts of the 4120 non-health maintenance organization Medicare beneficiaries who underwent carotid endarterectomy between July 1, 1993, and June 30, 1994. Main Outcome Measures.-Nonfatal stroke or death within 30 days of surgery. Results.-The reviewed patients were similar to all eligible patients in sociodemographic characteristics and 30-day mortality rates. Among the 678 patients, indications for surgery were asymptomatic carotid stenosis in 167 (24.6%), transient ischemic attack in 294 (43.4%), completed stroke in 62 (9.1%), and nonspecific symptoms in 155 (22.9%), Thirty-two patients (4.7%) died or suffered nonfatal strokes by 30 days postoperatively. In univariate analyses, rates varied by hospital volume (P=.004) but not surgeons' volume (P=.47), although power to detect this difference was limited. Patients at higher- and lower-volume hospitals had similar indications and distributions of comorbidities. In analyses controlling for indications, comorbid conditions, and surgeon's volume, being operated on in a higher-volume hospital conferred a 71% reduction in risk for 30-day stroke or death (odds ratio, 0.29; 95% confidence interval, 0.12-0.69; P=.006). Conclusions.-Almost half (47.5%) of the carotid endarterectomies among Ohio's Medicare population are performed on persons who are asymptomatic or who have nonspecific symptoms. These results highlight the importance of identifying patients and providers having the most favorable outcome profiles. The higher rate of adverse outcomes observed in lower-volume hospitals deserves further investigation, as it does not appear to be due to differences in patient selection.