Small Study Suggests Filter Protection More Effective Than Flow Reversal in Carotid Stenting

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In patients undergoing carotid artery stenting (CAS) via femoral access, filter protection may be more efficacious in reducing the incidence, number, and size of new ischemic brain lesions than flow reversal, or proximal protection, according to a small pilot study published online October 1, 2013, ahead of print in Circulation: Cardiovascular Interventions.

Investigators led by Daniel Giansante Abud, MD, PhD, of the University of São Paulo (São Paulo, Brazil) randomized 40 consecutive patients with internal carotid artery stenosis of at least 50% to CAS with either the GORE flow-reversal system (n = 21; WL Gore and Associates, Flagstaff, AZ) or the filter wire EZ (n = 19; Boston Scientific, Natick, MA) from March 2011 to July 2012.

MRI and neurological assessment were performed between 6 and 24 hours after CAS and neurological assessment was repeated at 3 months. Baseline characteristics, including age, comorbid diseases and carotid stenosis grade, did not differ significantly between the 2 groups.

Reduction in New Lesions with Filter

Overall, use of filter protection during CAS resulted in a greater reduction in the incidence (OR 4.85; 95% CI 1.08-21.76), number, and size of new ischemic brain lesions than use of flow reversal. Patients who had flow reversal tended to have higher rates of ipsilateral lesions and more ipsilateral lesions than bilateral lesions (table 1).

Table 1. Primary Endpoints

There were no incidents of the secondary endpoint of major adverse cardiac and cerebrovascular events (MACCE) in either group in-hospital or at 3-month follow-up. While there was no difference in definitive ischemic brain lesions at 3 months between the groups, FLAIR-MRI demonstrated that filter protection resulted in a reduction in the number (0.40 vs. 0; P = 0.05) and size (1.34 mm vs. 0 mm; P = 0.05) of definitive ischemic brain lesions

All procedures were performed by the same operator, in the same angiography suite, using the same MRI, stent, and dosages of heparin, aspirin, and clopidogrel. Mean procedure time was greater in the flow-reversal group compared with the filter group (22.41 min vs. 16.78 min; P < 0.001), while mean protection time was shorter (4.49 min vs. 5.32 min; P = 0.02). However, regardless of protection type, all procedures were performed within 34 minutes. There were no clinical, technical, or device-related complications during any procedure.

Simple Profile of Filter Elicits Better Outcomes

Dr. Abud and colleagues say the differences in procedure and protection times “probably could not justify differences in the primary endpoints obtained but did prove that [the] filter protection device is simpler to use than [the] flow-reversal system.”

Additionally, they suggest that the poorer results obtained in the flow-reversal group may stem from the larger diameter (9.5 Fr) of the flow reversal’s balloon sheath and its higher rigidity compared with the guiding catheter (7.0 Fr) used in the filter group. “The larger size and the high rigidity of the GORE balloon sheath possibly increased shear stress in the artery walls during carotid catheterization, promoting the release of microemboli from plaques,” they write.

Compared with other studies in the literature, their filter protection findings “were among the best CAS results reported and were even similar to some standard carotid endarterectomy results,” Dr. Abu and colleagues write. They attribute this to operator experience with CAS, the use of general anesthesia, which likely minimized risk of movement accidents, and the filter protection device profile.

Future CAS trials should compare different protection techniques using the same embolic protection device in each arm, as well as testing the Filterwire device against other embolic protection devices, the authors conclude.

Patient Selection Key to Success

“The bottom line is we should stop arguing about which [embolic protection device] is better and start thinking about what is the best for each individual patient,” countered L. Nelson Hopkins, MD, of University at Buffalo Neurosurgery (Buffalo, NY), in a telephone interview with TCTMD. “There are situations where we know that filters don’t do as well and where proximal embolic protection has very good results, [specifically] recently symptomatic patients with unstable plaque.”

Dr. Hopkins said the suggestion by the study authors that the flow reversal device is more likely than a filter to result in release of microemboli is simply untrue.

“It doesn’t take a rocket scientist to figure out that crossing a recently ruptured plaque with a filter, no matter how small it is, is going to increase the risk,” he said.  For example, “someone who is recently symptomatic probably has an ugly recent rupture with high plaque burden and we can see some of that with Doppler and other noninvasive studies. That is an instance where we want to use proximal embolic protection.”

Additionally, if there is significant tortuosity in the region of the lesion, “[it’s] best not to ram a filter through there,” Dr. Hopkins explained. “If you don’t have a good ‘landing zone’ for your filter, you want to think about proximal protection then, too. These are very complementary devices and we should focus on using them accordingly in the appropriate patient populations.”

Dr. Hopkins reported that in a US Food and Drug Administration-sponsored trial, the Gore proximal protection device showed “extraordinarily good results,” adding that there is a learning curve for using it that may explain the results of the Brazilian investigators.

 

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Source:
de Castro-Afonso LH, Abud LG, Rolo JG, et al. Flow reversal versus filter protection: A pilot carotid artery stenting randomized trial. Circ Cardiovasc Interv. 2013;Epub ahead of print.

 

 

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