Proximal Occlusion Device Offers Better Cerebral Protection in Carotid Stenting

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Due to its ability to reduce microembolization, proximal occlusion may provide more effective cerebral protection than distal filter devices in patients with high-risk plaque undergoing carotid artery stenting (CAS), according to a study appearing in the October 11, 2011, issue of the Journal of the American College of Cardiology.

Researchers led by Piero Montorsi, MD, of the University of Milan (Milan, Italy), looked at 53 patients with lipid-rich carotid stenosis deemed at high risk for embolic complications undergoing CAS at their institution from February 2009 to March 2010. Patients were randomized to distal protection (FilterWire EZ; Boston Scientific, Santa Clara, CA) or proximal protection (MO.MA system; Invatec, Brescia, Italy.)

Unlike conventional distal filter devices—which maintain antegrade flow and catch debris downstream for retrieval—proximal protection consists of 2 balloons that are inflated in the common carotid and external carotid artery to suspend both antegrade blood flow from the common carotid and retrograde blood flow from the external carotid artery. The balloons essentially act like endovascular surgical clamps to protect the brain during the procedure. To complete the procedure safely, the suspended blood is then aspirated along with any particles.

Technical success with CAS was achieved in all patients. On transcranial Doppler imaging, proximal protection lowered the percentage of patients with any detectable microembolic signals during 3 out of 6 phases comprising the procedures (table 1).

Table 1. Patients with Detectable Microembolic Signals During CAS

Proximal protection also lowered the total mean number of microembolic signals during CAS (16 vs. 93; P < 0.0001), as well as the mean number during 4 of the 6 phases compared with distal protection (P < 0.0001 for each):

• Lesion wiring: 2 vs. 18
• Stent crossing: 0 vs. 23
• Stent deployment: 0 vs. 30
• Stent dilation: 0 vs. 16

Mean number of microembolic signals were equivalent during predilation (0 with proximal protection vs. 7 with distal protection; P = 0.268) and higher with proximal protection during device retrieval/deflation (8.5 vs. 2; P = 0.0036).

On multivariable analysis, proximal protection was the only significant independent predictor of microembolic signals, achieving an estimated 81.7% reduction in total mean signals compared with distal protection (95% CI -88.6% to -70.7%; P < 0.0001).

Cerebral diffusion weighted MRI was performed in 66% of the cohort and showed 45 new lesions in 11 patients (31.4%) 48 hours after CAS, with no further lesions detected at 1 month in either group. The lesions were spread between 9 filter group patients (42.8%) and 2 proximal protection patients (14.3%; P = 0.14). Most of the new lesions (78%) occurred in the target vessel territory, and they were silent in all but 1 case. Almost all (91.1%) had a diameter of 10 mm or less.

“Microembolization was significantly reduced by MO.MA compared with FilterWire EZ during CAS of high-risk, lipid-rich lesions, suggesting that [proximal endovascular occlusion] may provide better brain protection,” Dr. Montorsi and colleagues conclude.

Surrogate Signals

The researchers caution that microembolic signals were used as a surrogate marker for microemboli and that “the clinical impact of cerebral microembolization during CAS is not established. However, cerebral microemboli have been involved in cognitive decline after heart surgery, carotid endarterectomy, and CAS. . . . If this holds true, [microembolic signal] reduction during CAS should be pursued to improve clinical outcome.”

In an e-mail communication with TCTMD, Dr. Montorsi noted that due to the accumulating data on the efficacy and safety of proximal protection in CAS, the study results were “somewhat expected,” although a randomized trial in high-risk patients had not been performed previously.

He pointed out that there is, in fact, a reported relationship between the number of microembolic signals and the rate of clinical complications. “The higher the number, the higher the rate of clinically detectable cerebral complications,” Dr. Montorsi said. “I do believe [microembolic signals] may play a role in cognition deterioration over time.”

‘First Option’ Urged

Overall, “the concept of [proximal embolic occlusion] is clear and simple,” Dr. Montorsi added, noting that in Europe, the rate of proximal protection use in clinical practice is about 10% to 13%. “I do think [it] should become the first option in any patients undergoing CAS,” he continued. “The learning curve is steep and the rate of intolerant patients, when appropriately investigated before CAS, is low.”

Dr. Montorsi stressed that appropriate imaging tests—CT angiography is used at his institution—must be performed in all CAS patients. “Data on the aortic arch, supra-aortic vessel course, bifurcations, distal [internal carotid artery], and intracranial circulation/collaterals are easily obtained,” he said.

Following the current results, Dr. Montorsi emphasized that “a randomized trial of CAS with [proximal embolic occlusion] by truly expert investigators vs. carotid endarterectomy is the next step.”

Study Details

Patients were well matched in terms of baseline and lesion characteristics, with the exception of a higher percentage diameter stenosis (89 ± 6% vs. 86 ± 5%; P = 0.027) and an increased rate of ulcerated plaque (35% vs. 7.4%; P = 0.019) in proximal protection patients compared with distal filter patients.

The carotid Wallstent (Boston Scientific) was used in all patients for CAS procedures. Proximal protection was well tolerated in all but 1 patient, who developed transient aphasia and right sensory deficit during debris aspiration that immediately resolved after common carotid artery balloon deflation.

 

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Source:
Montorsi P, Caputi L, Galli S, et al. Microembolization during carotid artery stenting in patients with high-risk, lipid-rich plaque: A randomized trial of proximal versus distal cerebral protection. J Am Coll Cardiol. 2011.58:1656-1663.

 

Disclosures:

• Dr. Montorsi reports no relevant conflicts of interest.
  

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