Now that the Trials are Finished and Quantitated, What Fraction of Carotid Endarterectomies Reflects Mere Entrepreneurism?

abstracts & commentary

Sources: Barnett HJM, et al. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. N Engl J Med 1998;339:1415-1425; Tu JV, et al. The fall and rise of carotid endarterectomy in the United States and Canada. N Engl J Med 1998;339:1441-1447; Chassin MR. Appropriate use of carotid endarterectomy. Editorial. N Engl J Med 1998;339:1468-1471.

During the past 20 years, carotid endarterectomy has been a popular, but largely unregulated, surgical procedure in the United States and less enthusiastically in Canada and Europe. The operation’s incidence in the United States reached a peak of 107,000 during 1985. Then, after the initiation of carefully conducted clinical trials, the incidence first fell to 80,000 and then to 60,000 between 1986 and 1991. Subsequently, a steady operative climb has occurred to reach 120,000 operations in 1996.

All well controlled trials have focused on patients known to have experienced within the previous 180 days either non-crippling stroke(s) or TIAs ipsilateral to the potential carotid stenosis. Outcomes of these proceedings were measured at least at two and five years after onset. Kaplan-Meier curves of outcomes indicated a perioperative risk of 2-6% of associated severe stroke and/or death within 30 days following surgical treatment. From that point forward, symptoms related to ipsilateral carotid artery endarterectomy showed significant reductions in stroke or death compared to non-operated controls after the first two to three postoperative years. After this time, new strokes in both operated and non-operated patients occurred at an annual rate. (See Table).

    Table
    Surgical Risk Reduction for Carotid Endarterectomies
    Stenosis Symptomatic Study Groups Risk Reduction Point (P =) % Surgical Complication
    > 70% North American (NASCET) 16.5 @ 2 yr. < 0.001
    5.8
    > 60% European (ECST) 11.6 @ 3 yr. < 0.001
    4.8
    50-69% NASCET 10.1 @ 5 yr. < 0.005
    6.7
    < 50% NASCET 0.8 @ 5 yr. < 0.97
    6.7
    > 60% ACAS (Asymptomatic)  6.3 @ 5 yr. < 0.08
    2.3

    (Surgical complications = strokes or deaths in 30 post-op days. Table adapted from Chassin MR. N Engl J Med 1998;339:1468-1471.)
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Commentary

Tu and associates evaluate the above surveys that favored endarterectomy in patients who preoperatively had recently experienced either non-severe strokes or TIAs ipsilateral to the carotid artery narrowed more than 60%. However, they question the force behind the increasing gap that distinguishes the Canadian annual incidence of 40,000 or less endarterectomies since 1983 compared to the current lofty numbers in the United States. The age rate of endarterectomy in California (CA) and New York (NY) differed sharply from Ontario (ONT). Incidence of endarterectomy per 100,000 in patients 65 years and older was as follows: CA: 1989 = 163, 1995 = 277; NY: 1989 = 85, 1995 = 239; ONT: 1989 = 26, 1995 = 86.

The costs and cost effectiveness of these large jumps in operative selection deserves better justification than simply the appearance of internal carotid artery stenosis more than 6% with or without corollary symptoms.

Neurology Alert editor asks the following, logical questions: Why do we have no outcome statistics justifying this huge surgical effort in the United States compared to Canada? How many of these operations were performed on asymptomatic patients? What was the recorded success rate of the surgeons and how many neurologists participated in the choice and the eventual results? Regrettably, no such answers exist. Only one study (ACAS) has analyzed outcome in patients with asymptomatic stenosis. Its results indicate that despite only a 2.3% perioperative risk, the procedure rescued only one severe stroke and no deaths among the subscribers. Without such data, and in the presence of all the clinical trials on symptomatic patients, one can’t help but wonder why the insurance companies don’t demand such cost/benefit facts.

Three additional questions arise: 1) Without knowledge of five-year outcomes associated with asymptomatic carotid stenosis, how can one estimate the future benefit of carotid endarterectomy in these large numbers of preoperatively asymptomatic patients? Certainly, surgical skill, hospital practice, and public health sources should require such data. 2) What were the perioperative 30-day complications in these patients?

3) Given that Canada and the United States have adult populations with relatively similar health, why do Canadian surgeons perform only one-third the number of endarterectomies performed in the United States? We recognize that it is impolite to ask, but who besides the surgeons’ are benefitting from this huge operative venture?