Outcomes/Effectiveness Research

Rates of inappropriate carotid endarterectomy surgery decreased after publication of the results from clinical trials

Carotid endarterectomy (CEA) is surgery to prevent stroke by removing atherosclerotic plaque that is blocking the carotid artery in the neck. Few major procedures have engendered more controversy and undergone more rigorous evaluation than CEA. In the 1980s, one-third of CEAs among Medicare beneficiaries were done for inappropriate reasons. Based on these concerns, several large international randomized controlled trials (RCTs) were done to clarify the indications for and efficacy of CEA. These RCTs showed that CEA reduced the risk of stroke and death compared to medication alone among carefully selected patients and surgeons. The New York Carotid Artery Surgery (NYCAS) study was undertaken to assess if rates of inappropriate surgery dropped since the publication of these RCTs.

The NYCAS study analyzed data on all 9,588 CEAs performed on elderly patients from January 1998 through June 1999 in New York State. The investigators convened a panel of national experts to develop a detailed list of 1,557 indications for CEA to assess the appropriateness of surgery. They also identified deaths and strokes within 30 days of surgery.

The investigators found that the rate of inappropriate surgery dropped substantially from 32 percent in 1981 prior to the RCTs to 8.6 percent in 1998/1999 after publication of the clinical trials. As such, these results can be interpreted as the success of evidence-based medicine. The most common reasons for inappropriate CEAs were high rate of coexisting illnesses (comorbidity) in asymptomatic patients (62.2 percent), operating after a major stroke (14.2 percent), or for minimal stenosis (10.5 percent).

However, the investigators also found that the reasons for surgery have changed over the past 15 years. Nearly three-fourths of patients (72.3 percent) underwent CEA for asymptomatic stenosis, 18.6 percent for TIA, and 9.1 percent for stroke. What started as a procedure largely to prevent stroke among patients with recent strokes or transient ischemic attacks, three-quarters of the time is now done for patients without any symptoms from their carotid blockages—a group known to have less to gain from surgery.

Among asymptomatic patients, those with high comorbid illness burden had over twice the risk of death or stroke compared to those without high comorbidity (7.13 vs. 2.69 percent) and twice the acceptable risk recommended by national guidelines. The shift toward use of CEA for many asymptomatic patients is of concern because the net benefit from surgery for these patients is low and is reduced even further for asymptomatic patients with a number of coexisting illnesses, explain the researchers.

The study was supported in part by the Agency for Healthcare Research and Quality (HS09754).

See "Has evidence changed practice? Appropriateness of carotid endarterectomy after the clinical trials," by Ethan A. Halm, M.D., M.P.H., Stanley Tuhrim, M.D., Jason J. Wang, Ph.D., and others, in the January 16, 2007, Neurology 68, pp. 187-194.

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