Anatomy’s role is elusive in carotid stenting risk



CHICAGO – Pinning down the anatomic characteristics that increase the risk of stroke with carotid artery stenting continues to be a challenge, as demonstrated by a database study and literature review presented at a symposium on vascular surgery sponsored by Northwestern University.

"I am absolutely convinced that certain anatomic and plaque characteristics increase the risk of a stroke for patients with carotid artery stenting," Dr. Melina R. Kibbe said in presenting her study. "The studies are not consistent in the literature, but there is a pattern."

Dr. Melina Kibbe

She presented a prospective database review that evaluated no less than a dozen anatomic variables in 381 carotid arteries stented at the university from 2001 to 2010. The mostly male (75%), asymptomatic (70%), and moderate- to high-risk cohort had an average age of 70.5 years.

Within 30 days of carotid stenting, there were six strokes and eight transient ischemic attacks (TIAs), for an overall neurologic event rate of 3.7%, she said. Three patients had a heart attack, and two died.

The risk of perioperative stroke or TIA was significantly increased only in patients with a higher degree of internal carotid artery (ICA) stenosis (87% stenosis vs. 81% stenosis; P = .03).

It also trended higher, but fell short of significance, in those with greater arch calcification (P = .06).

Surprisingly, no statistical association was found between neurologic events and arch type (P = .16), despite the clinical belief that increasing arch type can be associated with more difficulty accessing the target lesion, said Dr. Kibbe, professor of vascular surgery and surgical research at Northwestern University, Chicago.

Other variables with trends that failed to reach statistical significance included internal to common carotid artery angulation, tortuous carotid artery, ipsilateral external carotid artery (ECA) stenosis, plaque calcification, and lesion length.

Turning to the literature for more answers, Dr. Kibbe and her colleagues performed a review of eight carotid stenting studies between 1993 and 2013. These studies included SAPPHIRE, which demonstrated an association between type II and III arches and increased stroke risk. Two other studies implicated type II, type III, and bovine arches, while three other studies, including a systematic review that incorporated the EVA-3S study (Stroke 2011;42:380-8), found no association between arch type and stroke.

Still, Dr. Kibbe said she’s convinced no two patients are alike when it comes to arterial anatomy and called for data from pivotal trials like CREST to be reanalyzed for stroke, based on arch type and plaque characteristics.

"Even better, I’d like to see a prospective, randomized study that excludes patients for carotid artery stenting based on their anatomy; for example, excluding all type III arches," she said. "My own personal bias is that patients with type III arches should not have carotid stenting. We don’t need to push the envelope."

Interestingly, no study in the review has shown ICA stenosis to be a risk factor for stroke or TIA, although lesions with a higher degree of stenosis would be expected to contribute to perioperative stroke risk.

Arch calcification, ECA stenosis, and plaque calcification also failed to register as risk factors, despite their potential to increase the risk of embolization with wire or catheter manipulation, Dr. Kibbe observed.

Two studies found that lesions longer than 1 cm or 1.5 cm were predictive of stroke, while one study (Catheter Cardiovasc. Interv. 2012;80:321-8) linked stroke with ICA tortuosity, defined as a distal ICA angle of more than 60 degrees.

Conventional thinking would suggest that right-sided carotid stenting would also confer a greater stroke risk because selecting the right ICA requires crossing the orifice of the left ICA, but only the SAPPHIRE trial reported more strokes with right-sided lesions, she said.

Finally, Dr. Kibbe highlighted an anatomic scoring system for carotid artery stenting developed by an international panel of seven vascular surgeons and five interventional radiologists (Stroke 2009;40:1698-703). Based on expert consensus, the greatest risk factor is type III arch, followed in descending order of risk by arch atheroma, diseased common carotid artery, ECA disease, angulated distal ICA, bovine arch, and pinhole stenosis. The resulting color-coded, traffic-light scoring system looks rather busy, but is relatively easy to use and provides guidance on carotid stenting suitability for the novice physician, she said.

Dr. Kibbe reported having no financial disclosures.

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