Degree of Stenosis Not Only Factor to Consider in Carotid Surgery

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Age, sex, and the time delay to surgery, in addition to the degree of stenosis, all affect the risk of stroke in patients receiving carotid endarterectomy (CEA) for symptomatic disease, according to a review of randomized trials published online July 28, 2011, ahead of print in Stroke.

The paper is also being published in the Cochrane Database of Systematic Reviews 2011, Issue 4.

Kittipan Rerkasem, MD, PhD, of Chiang Mai University (Chiang Mai, Thailand), and Peter M. Rothwell, MD, PhD, of the University of Oxford (Oxford, United Kingdom), performed a pooled analysis of 6,092 patients from 3 randomized trials comparing CEA and best medical therapy alone in patients with symptomatic carotid atherosclerosis. The trials were:

• NASCET (North American Symptomatic Carotid Endarterectomy Trial)
• ECST (European Carotid Surgery Trial)
• VACSP (Veterans Affairs trial)

The overall 30-day rate of stroke or death across all the trials was 7.1%, with a 30-day mortality rate of 1.1%. When stratified by degree of stenosis, surgery increased the risk of ipsilateral ischemic stroke in patients with low levels of carotid stenosis, but this effect lessened as the degree of stenosis increased, until patients with 70% to 99% stenosis but not near occlusion benefited greatly (table 1).

Table 1. CEA and Effect on Risk of Ipsilateral Ischemic Stroke

In subgroup analyses based on pooled data from ECST and NASCET, sex (P = 0.003), age (P = 0.03), and time between the last symptomatic event and surgery (P = 0.009) all modified the effectiveness of CEA. For instance, the number of patients with 50% to 99% stenosis who needed to undergo CEA to prevent 1 ipsilateral stroke within 5 years was 9 for men vs. 36 for women. In addition, the number needed to treat was 5 for patients older than 75 years vs. 18 for patients younger than age 65, and 5 for patients randomized within 2 weeks of their last ischemic event vs. 125 for patients randomized more than 12 weeks from their last event.

The overall results are generalizable only to “surgically fit patients operated on by surgeons with low complication rates,” meaning less than 7% risk of stroke and death, the authors write.

“Benefit from endarterectomy depends not only on the degree of carotid stenosis, but also on several other factors, including the delay to surgery after the presenting event,” they conclude. “In particular, in patients with only 50% to 69% stenosis, there was no evidence of benefit in women and little evidence of benefit if surgery was delayed by more than 2 weeks after the presenting event.”

Paper Reinforces Practice

According to K. Craig Kent, MD, of the University of Wisconsin School of Medicine and Public Health (Madison, WI), the analysis reinforces what is already known in standard practice. “What the authors essentially said was that if you have less than 50% stenosis in a symptomatic patient, then it either hurt the patient or provided no benefit to treat them,” he told TCTMD in a telephone interview. “Then they said if you take a 50% to 69% stenosis, there’s some benefit, but it’s not an incredibly great benefit. I think we know that. That’s the way we practice.”

And in terms of combining factors such as female sex and a 50% to 69% stenosis, which according to the report lower the effectiveness of CEA, “we’re savvy enough as clinicians to understand these things are additive,” Dr. Kent said.

Two-Week Rule Should Not Exclude Patients

Nevertheless, he cautioned that over interpreting the findings would lead to an overly rigid approach, particularly with regard to the length of time from an ischemic event to surgery, which, the paper advises, should not be longer than 2 weeks. “So if you see someone that’s female and has a 60% stenosis and had a TIA 2 months ago, doing an endarterectomy on that patient would still be considered the standard of care,” Dr. Kent said. “They’re arguing that if it’s not a 70% stenosis, and it was a long time ago and in a female, maybe you don’t need to treat that person.”

Christopher K. Zarins, MD, of the Stanford University School of Medicine (Stanford, CA), also took issue with that concept. “When someone has a TIA and a greater-than-50%-stenosis lesion, you try and get that done as quickly as you can,” he said in a telephone interview with TCTMD. “But if someone comes in 3 weeks after a TIA and has a 70% stenosis, would I say, ‘Oh, you’re past 2 weeks, so you’ll get no benefits and I’m not going to fix you?’ That’s not right.”

Dr. Zarins explained that it is not uncommon for a patient to come in 3 or 4 weeks after an event. “And you do a study and you find a 70% stenosis. You go through the risk-benefit and you recommend treatment,” he said. “And that’s correct and the literature strongly supports that.”

Near Occlusions Cause Concern

Both Drs. Kent and Zarins expressed confusion over the researchers’ use of the term ‘near occlusion,’ which was not adequately defined in the paper. “What’s the difference between a 99% occlusion and a near occlusion?” Dr. Zarins asked. “Is a near occlusion 99.5%? If they had said you shouldn’t operate on occlusions, I would agree with that, but near occlusions that are 99% with a TIA, you should operate on those. As a clinician, that would be a source of confusion about how to apply that finding to clinical practice because it’s not clear what that is.”

Dr. Kent called that part of the paper “somewhat disquieting.”

“I hope they’re not saying that if you have a high grade stenosis but a normal artery beyond, you shouldn’t treat it, because I have never seen any data from NASCET or elsewhere to suggest that those patients shouldn’t be treated,” he said.

‘Shades of Gray’

Overall, the paper performs a service in pointing out “shades of gray,” in the clinical decision making process to perform CEA, Dr. Kent said. “It’s probably worthwhile reminding all of us we ought to consider all these factors, and that it’s not just black and white that everybody greater than 50% with a TIA should have surgery,” he said. “It’s just a matter of how far you should push it. If you start taking some of that to an absolute degree, I think that would be a mistake.”

For instance, “an aggressive carotid surgeon might assimilate all these data and say that a woman who has a 60% stenosis and had a TIA 2 months ago should have endarterectomy,” Dr. Kent said. “[The authors] would assimilate the data and say that individual doesn’t need endarterectomy.”

Dr. Zarins, meanwhile, maintained that “the fundamental idea that symptomatic patients greater than 50% benefit from endarterectomy is supported here. This paper does not refute that.”

Source:

Rerkasem K, Rothwell PM. A systematic review of randomized controlled trials of carotid endarterectomy for symptomatic carotid stenosis. Stroke. 2011;Epub ahead of print.

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