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Complex aortic arch configurations and internal carotid artery (ICA) tortuosity were bad news for carotid artery stenting, but not endarterectomy, according to an MRI substudy of the International Carotid Stenting Study (ICSS).

New ischemic brain lesions on diffusion-weighted MRI after treatment were found in 51% of cases after stenting and 16% of cases after surgery (OR 6.0, 95% CI 2.9-12.4), the paper in the May 2017 issue of Stroke showed.

With carotid artery stenting, Leo Bonati, MD, of University Hospital Basel in Switzerland, and colleagues found age-independent predictors for new brain lesions to be aortic arch configuration type 2 or 3 (OR 2.8, 95% CI 1.1-7.1) and an ICA angle of 60 or higher (OR 4.1, 95% CI 1.7-10.1).

Those whose largest ICA angle was at least 60 had a 12-fold higher risk of strokes during stenting over their peers with smaller ICA angles (OR 11.8, 95% CI 4.1-34.1).

Complex vascular anatomy was not a factor for strokes during surgery. However, aortic arch configuration types 2 and 3 did trend numerically to a higher risk for cerebral ischemia (OR 3.5, 95% CI 0.7-17.1).

Bonati's group suggested that these configurations are associated with increased atherosclerotic burden or represent markers of general vascular risk. Aortic arch type 2 was defined in the study as having at least 1 supra-aortic artery originating between the outer and inner curvature; aortic arch type 3 was for cases where there was at least 1 supra-aortic artery originated below the level of the inner curvature.

"Older age has consistently been shown a risk factor for procedural stroke in carotid artery stenting, but not in carotid endarterectomy," they wrote. "It has been speculated whether the association might be mediated by vascular anatomy."

"Elongation of the aortic arch and supraaortic arteries was found to be more prevalent in elderly patients, possibly leading to more difficulties during the carotid artery stenting procedure," they concluded. "Notably in our analysis, the associations between ICA angulation and aortic arch configuration with cerebral ischemia in the stenting group remained significant after correction for age. Hence, vascular anatomy should be taken into account when selecting the appropriate treatment option for an individual patient, independent of the patient's age."

The ICSS trial randomized 1,700 patients with symptomatic internal carotid artery stenosis to stenting or surgery. Top-line results put stenting recipients at a disadvantage for adverse events.

For this ICSS substudy, the authors included the 184 patients who got magnetic resonance (n=126) or CT angiography (n=58) at baseline on top of brain MRIs before and after treatment.

Bonati and colleagues posed several reasons why it would make sense that complex vascular anatomy has an association with procedural stroke.

"A complex configuration of the aortic arch and the supraaortic arteries increases the technical difficulty of the stent procedure," they wrote. "Repeated attempts to advance the catheter and guidewire may cause endothelial microtrauma or dislodge atherosclerotic plaque and ultimately cause cerebral emboli."

"The protocol of ICSS did not contain detailed precautions against these complications, such as advice on catheter and guidewire handling, limiting guidewire maneuver time between flushing, syringe aspiration and cleansing, concentration of heparin in saline flush, use of constant infusion via infusion ports to stopcocks, etc.," the authors noted.

"We are therefore unable to verify that all possible precautions against thromboembolism were taken," they wrote. "This limitation must be borne in mind when interpreting the results of our study."

Another limitation is the exclusion of patients with extremely unfavorable anatomy for stenting.

"The fact that the ICSS protocol excluded patients with a stenosis that was thought to be unsuitable for stenting because of proximal tortuous anatomy is likely to have limited the number of patients with very unfavorable anatomy," according to Bonati's group. "The full impact of vascular anatomy on carotid artery stenting risk may therefore have been underestimated in this study."

ICSS was funded by several European government and industry grants.

Bonati disclosed serving on scientific advisory boards for Bayer.

2017-04-13T16:00:00-0400

Excerpt from:
Complex Vascular Anatomy Problematic for Carotid Artery Stenting - MedPage Today