Progress in understanding the role of carotid endarterectomy.
The North American Symptomatic Carotid Endarterectomy Trial (NASCET) was initiated because of genuine uncertainty about the appropriateness of the increasing popularity of this procedure. Evidence of this uncertainty was the geographic disparity in its application. In the United States it was performed 27 and 8 times as often on a population based calculation as in the United Kingdom and Canada respectively. As well, the numbers performed annually in the United States fluctuated widely. In 1980 approximately 70,000 were performed and the numbers for 1985 and 1988 were 107,000 and 68,000 respectively. A study initiated by the American Medicare to define the application of endarterectomy, agreed upon by a panel of experts in the field, tested its use against an "appropriateness index". It concluded that one-third of those who received the procedure were appropriate, one-third were not appropriate and one-third were of uncertain appropriateness. All of this uncertainty existed despite the fact that a voluminous literature describing scores of thousands of case reports had accumulated, two negative randomized trials of small size had been conducted and one million patients had been submitted to the procedure between 1954 when it was introduced and 1985.