How Much Follow-up After Carotid Endarterectomy?
ABSTRACT & COMMENTARY
Source: Frericks H, et al. Carotid recurrent stenosis and risk of ipsilateral stroke. Stroke 1998;29:244-250.
Physicians order follow-up carotid ultrasound examinations on their patients after carotid endarterectomy because they assume both that a considerable number will develop restenosis and that restenosis increases the risk of an ipsilateral stroke. There is little consensus on the best follow-up schedule because the reported rates of restenosis and stroke risks vary widely. In order to determine the most cost-effective follow-up schedule, Frericks et al systematically reviewed the literature on carotid artery restenosis and ipsilateral stroke using standard meta-analytical techniques. They found 29 articles in English published in 1985 or later that met inclusion criteria. The articles reviewed reported on the long-term follow-up of 100 or more patients treated by carotid endarterectomy with direct or patch closure, defined restenosis as a 50% stenosis of the operated artery, followed up patients with noninvasive diagnostic tests, and used systematic follow-up not just of symptomatic patients.
Although the data showed enormous heterogenicity, the authors were able to plot the cumulative incidence of restenosis against average follow-up time. The risk of recurrent stenosis was 10% in the first year, 3% in the second year, and 2% in the third year. Thereafter, the long-term risk of restenosis was about 1% per annum. Of the five variables that could be examined-year of publication, mean age of patients, percentage men, percentage asymptomatic patients, and percentage patch closure-only two, mean age and percentage patch closure, were statistically significant (P < 0.001). Increasing mean age was associated with a higher risk of ipsilateral stroke, and increasing percentage patch closure with a lower risk.
Only 10 articles provided ipsilateral stroke rates for patients with and without restenosis. There were very few ipsilateral strokes; therefore, the relative risk of stroke in patients with recurrent stenosis compared with patients without recurrent stenosis within each study showed extreme heterogenicity, and the odds ratios ranged from 10:1 to 1:10. Therefore, no scientific conclusion could be made from these data about relative risk.
The authors did conclude that carotid ultrasound examinations can be done in the first few years after endarterectomy but that testing for restenosis should not be done after four years.
COMMENTARY
At the very least, this review has pointed out the need for better follow-up studies in patients with carotid endarterectomy. Until such studies are available for analysis, no uniform timetable for post-operative carotid ultrasound examinations can be recommended. The authors have pointed out, too, that variations in the timing of testing lead to different restenosis rates because of the high incidence during the first year of intimal hyperplasia, a "benign" lesion that may regress and also may not carry the same risk of obstruction and thromboembolism as atherosclerotic lesions.
Although the risk of ipsilateral stroke in patients has not been established, it may reasonably be assumed to be moderately increased. Since it may be important to detect restenosis in order to select out patients for reoperation or intensive medical therapy, the authors' recommendation that ultrasound examinations be done at one and two years post-operatively seems appropriate. The low restenosis rate beyond two years following carotid surgery makes repeated ultrasound examinations not cost-effective. Whether physicians will dispense with these follow-up studies on this basis remains to be seen. -jjc
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