Registry Finds No Stark Differences Between Proximal, Distal Embolic Protection in CAS

Fewer than 1 in 15 US patients undergoing elective CAS are treated using proximal rather than distal embolic protection, according to a registry study published in the April 2015 issue of JACC: Cardiovascular Interventions. However, both types of embolic protection devices carry similarly low rates of in-hospital and 30-day outcomes. 

Using data from the CARE (Carotid Artery Revascularization and Endarterectomy) Registry, Jay Giri, MD, MPH, of the Perelman School of Medicine at the University of Pennsylvania (Philadelphia, PA), and colleagues examined 10,246 patients who had elective CAS between January 2009 and March 2013.

Only 590 of those cases (5.8%) involved proximal embolic protection, 63.4% using the Gore Flow Reversal System (WL Gore and Associates) and 36.4% using the MO.MA Ultra Proximal Cerebral Protection Device (Medtronic), while the others involved distal filter embolic protection. Thirty-day follow-up data were available for 75.1% of the original cohort.

There were numerous baseline differences between the 2 groups. For example, patients treated with proximal devices were more likely to be male and to have higher BMI, dyslipidemia, symptomatic lesions, A-fib/flutter, and history of TIA. They were less likely than those treated with distal devices to have contralateral carotid artery occlusion.

Crude rates of in-hospital and 30-day death and stroke did not differ by device type. Results were consistent after propensity matching patients in a 1:4 ratio using 40 variables (table 1).

 

Both proximal and distal embolic protection result in “similarly low rates of in-hospital stroke/death,” the researchers conclude, cautioning that the study “may be underpowered to detect potentially meaningful differences in outcomes between the devices.”

They predict that a cohort of more than 34,000 patients would be required to ascertain in-hospital differences and more than 6,000 would be needed to assess 30-day differences. As such, ‘[a]n adequately powered randomized trial comparing clinical outcomes between these devices is unlikely to be feasible,” they conclude.

Complex Reasons Behind Lack of Adoption

Based on available evidence, selection of embolic protection devices should depend on anatomic factors as well as operator comfort and experience, Dr. Giri told TCTMD in an email.

Operators in the US have not adopted proximal devices for a number of reasons including familiarity, he said, noting that distal filter devices have been on the market “much longer than proximal detection devices. There are several unique cognitive and technical issues that operators must become comfortable with in order to properly use a proximal protection device. Many physicians may prefer to just stick with what they know.”

Dr. Giri also observed that there has been no “definitive comparative effectiveness study demonstrating superiority of proximal protection devices. Thus, there is not as much of a push for operators to learn how to use the new devices.” Finally, he added, “due mostly to reimbursement restrictions from Medicare and other insurers, carotid stenting accounts for less than 20% of all carotid revascularizations and this is not showing significant growth. Hence, there are relatively few truly high-volume operators in the US that can develop true expertise with different devices.”

William A. Gray, MD, of Columbia University Medical Center (New York, NY), agreed that it is hard “to make any meaningful conclusions” about differences in stroke and death in the current study, given the low event rates and small number of patients receiving proximal protection.

“In spite of this, these data trend in favor of [proximal embolic protection devices], and these trends seem to be borne out in other clinical data sets as well,” he noted in an email interview with TCTMD, adding that surrogate markers such as asymptomatic abnormalities on magnetic resonance diffusion-weighted imaging (MR-DWI) “fairly strongly and routinely favor” proximal devices.

According to Dr. Gray, the “dominant reason” US operators have largely shied away from proximal protection in CAS is reimbursement.

“So much of the utilization of equipment in the US is driven by access, [which in this case] is only enabled by reimbursement coverage by CMS. [This] was largely made possible by individual registries run by individual manufacturers (covered by CMS),” he explained noting that registries focusing on proximal devices “were scarce relative to” those focusing on distal devices.

An Eye Toward Comparative Effectiveness

Looking to the future, Dr. Gray highlighted several technologies. “There are mesh-covered stents meant to reduce stent-related sources of emboli and early data from MR-DWI [studies suggest] they are doing just that. Double filtration methods are in early [proof-of-concept studies], and direct carotid access with proximal protection mode has completed a trial with the lowest rate of stroke ever reported for CAS. The combination of these next-generation [embolic protection devices] and stents together are likely to result in the safest CAS yet [with outcomes] as good or better than [carotid endarterectomy (CEA)].”

Dr. Giri noted that, “[f]rom a technical perspective, it will be interesting to see how the new transcarotid artery stenting technique performs in comparative effectiveness analyses against CEA and traditional transfemoral carotid stenting.”

However, he stressed, the most pressing issue is the “appropriate management strategy for asymptomatic carotid artery stenosis patients.” While such cases represent the majority of carotid revascularizations performed in the United States, “with dramatically improved medical therapies over the past 2 decades, it is unclear whether we are truly providing long-term benefit to these patients with aggressive interventional management, be it CEA or carotid stenting.

“All participating specialties in this field—neurology, vascular surgery, and interventional cardiology—have a responsibility to produce modern comparative effectiveness evidence that justifies the correct therapeutic choices in this important patient group,” Dr. Giri concluded.

 

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Source:
Giri J, Parikh SA, Kennedy KF, et al. Proximal versus distal embolic protection for carotid artery stenting: a National Cardiovascular Data Registry Analysis. J Am Coll Cardiol Intv. 2015;8:609-615.

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