Microembolization Linked with Cognitive Decline After Carotid Revascularization

Download this article's Factoid in PDF (& PPT for Gold Subscribers)

Cerebral microemboli, a relatively frequent byproduct of carotid revascularization, are associated with memory loss 30 days following the procedure, according to a small study published online August 10, 2012, ahead of print in the Journal of Vascular Surgery.

Researchers led by Wei Zhou, MD, of Stanford University (Stanford, CA), looked at 51 patients who underwent either carotid artery stenting (CAS; n = 16) or carotid endarterectomy (CEA; n = 35) in the Veterans Administration Palo Alto Health Care System from 2004 to 2011. The CEA and CAS cohorts showed similar baseline characteristics, although the CAS patients were at higher surgical risk. All CAS patients received distal embolic protection with an Emboshield filter device (Abbott Vascular, Santa Clara, CA).

On MRI via diffusion-weighted imaging (DWI), postoperative ipsilateral microembolic lesions were found in both groups but were more common with CAS (50% vs. 9%; P = 0.0019). Contralateral microemboli, meanwhile, were only found in CAS patients (19% vs. 0; P = 0.0269). At 1 month, evidence of memory decline on the Rey Auditory Verbal Learning Test (RAVLT) was found in 21 patients (41%; 8 CAS patients and 13 CEA patients), with no statistical difference in memory change between the 2 cohorts.

Microemboli Predict Memory Loss

On regression analysis, there was a trend (P = 0.0525) for increased memory decline in patients with micoemboli. Patients with procedure-related microemboli had a decrease in mean RAVLT score from 32.7 preoperatively to 29.7 postoperatively, whereas those without microemboli had a slight increase in mean RAVLT score from 33.3 to 34.2. Using a different linear regression model, postprocedural DWI microemboli were the only significant predictor of decline on RAVLT score (P = 0.0162).

Dr. Zhou and colleagues note that previous research has shown a prevalence of procedure-related microemboli of 20% to 70% in CAS patients and 10% to 20% in CEA patients, but that the clinical relevance and long-term cognitive effects of such lesions are largely unknown.

The new study, the authors say, adds “critical information to our limited knowledge on carotid revascularization-associated microembolization” by showing that while “microembolization is not significantly associated with overall cognitive change, it is an independent predictor of memory decline after carotid revascularization procedures.”

Moreover, they add, “although the CEA and CAS cohorts did not differ significantly in baseline cognitive function or memory change, the CAS cohort had a significantly higher incidence of microembolic lesions.”

CAS Implication Unfair

In a telephone interview with TCTMD, William A. Gray, MD, of Columbia University Medical Center (New York, NY), noted that a drawback of the study is a lack of volumetric assessment of DWI abnormalities. This is relevant, he said, since “there are some data starting to emerge showing that although there may be more numerical hits with carotid stenting, the volume of brain affected is about the same. That is, for each hit you take from endarterectomy, it tends to be a little bigger, even though there are fewer of them.”

He added that the study is too small and the populations too unmatched to draw any definitive conclusions. Dr. Gray also cited a slightly disingenuous line of argument in the study, noting an emphasis on the finding that microemboli, which were increased with CAS, were an independent predictor of memory loss, despite the fact that there was no difference in memory loss between the 2 procedures.

The author “is implicating CAS, even though his own study didn’t show it,” Dr. Gray said. “I have a problem with the tone and tenor of what’s being said here.”

Longer-term Problems the Real Issue

While it is true that more DWI abnormalities have been shown with CAS than CEA, “we don’t really know what they mean clinically,” Dr. Gray said. “In fact, most of the data are difficult to decipher. If there was going to be a significant difference, we’d have known about it by now. That doesn’t seem to be the case. It’s not like getting on a pump for bypass where there’s a huge insult to the brain.”

In addition, the study may not even be addressing the right issue. “The measure of an acute cognitive decline around these procedures is not really the question that’s being raised around microemboli. It’s really about long-term vascular dementia,” Dr. Gray said. “I don’t think anybody’s saying here that there’s more dementia in these patients, because it’s really too acute. People often have short-term issues around procedures [simply] because they had a procedure.”

That is not to say, though, that clinicians are not concerned about microemboli. “Anybody who’s being honest would say, ‘I’d like my patients to have fewer microemboli even if I don’t think they mean anything,’” Dr. Gray noted. “There are some data to suggest that flow reversal minimizes microemboli better than filter protection, so there are efforts underway to [reduce them].”

 

---

Source:
Zhou W, Hitchner E, Gillis K, et al. Prospective neurocognitive evaluation of patients undergoing carotid interventions. J Vasc Surg. 2012;Epub ahead of print.

 

 

Related Stories:

• Carotid Stenting, Surgery Equivalent in Patients with Contralateral Occlusion
• Carotid Stenting Shows Steady Improvement in Patients at High Surgical Risk
• Early Carotid Stenting Outcomes Linked to Operator, Hospital Volume