Other findings

Endarterectomy rates fell from 3.2 per 1,000 person-years in 2003 to 2.6 per 1,000 person-years in 2006, while stenting rates rose about a tenth of a percent, from 0.3 in 2005 to 0.4 in 2006.

Previously the estimated rate of carotid stenting, in 2003 and 2004 before Medicare coverage began, was 0.3 per 1,000, the report said.

"The similarly low rate of carotid stenting we observed is likely related to the fact that the CMS national coverage decision for carotid stenting was limited to patients at high surgical risk," the authors wrote.

Unsurprisingly, prior diagnosis of diseased arteries and having previous procedures increased the likelihood of getting treatment, the study found. More than two-thirds of those getting endarterectomy had a prior diagnosis of coronary artery disease, while 37 percent had peripheral vascular disease. About half had cerebrovascular disease. For stenting, two-thirds had a prior diagnosis of coronary artery disease; nearly half had a prior diagnosis of peripheral vascular disease, and 61 percent had cerebrovascualr disease. They were also likely to have had a previous endarterectomy.

Also unsurprising, the reports said, stenting was linked with higher morality rates.

For carotid endarterectomies, 1 percent died within a month, and 7 percent within 1 year, for the most recent year, 2005. But for stenting, 2 percent died within a month and almost one out of ten died within a year. The higher mortality for stenting is likely because patients getting stents are sicker; as noted, Medicare only covers the procedure for high-risk patients.

"The differences likely reflect the differential selection of high-risk patients into the carotid stenting cohort, consistent with the CMS national coverage decision," the report said.

Of note, the mortality rates for both procedures were higher than those reported in the clinical studies that led to regulatory approval of the procedures, the report said. While mortality rates for the endarterectomy in 2005 declined almost 50 to 100 percent from some reported death rates in the mid-1990s, they were substantially higher than those in the regulatory-granting studies of 0.5 to 0.8 percent, according to the report.

But this was also not entirely surprising, the report said.

"Because this analysis was limited to elderly Medicare beneficiaries, the differences between the mortality rates we observed and those reported in clinical trials are not unexpected," concluded the report.


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