Clinical Research

Technical Limitations of Carotid FilterEmbolic Protection Devices

Mark K. Eskandari,1,2 Samer F. Najjar,1 Jon S. Matsumura,1 Melina R. Kibbe,1

and Mark D. Morasch,1 Chicago, Illinois

Improved carotid artery stenting (CAS) results are credited to the development of embolic protec-tion devices (EPDs). Reported are outcomes and technical failures of two classes of EPDs: distalballoon occlusion and distal filtration. We present a retrospective review of 206 CAS proceduresfrom April 2001-September 2005. Filters (AccuNet, Angioguard, Filterwire, or Emboshield) wereused in 98 cases (48%), distal balloon occlusion (PercuSurge) in 94 (46%), and no protection in14. Data include demographics and procedural records. Mean age was 70 years (76% men, 24%women). At 30 days, there were no deaths, no myocardial infarctions, two major ipsilateralstrokes (1%), two minor posterior strokes (1%), four transient ischemic attacks (2%), and onemajor access site complication (0.5%). Major neurologic events were equally divided betweenballoon occlusion and filters. Mean balloon occlusion time was 12 min, with only two patients(2%) manifesting reversible neurologic intolerance during flow arrest. In the last 100 cases, filterdevices were preferentially used due to preserved antegrade flow. However, 11 cases (11%) ne-cessitated intraoperative switching to balloon occlusion because of either extreme tortuosity orsevere stenosis of the target lesion precluding passage of the filter element. CAS-specific equip-ment has improved procedural results. Despite theoretic advantages of filter EPDs, up to 10% oflesions are either too narrow or tortuous to allow safe passage of the filter element. Switching toa distal balloon occlusion system, which is well tolerated, may be preferred to unprotectedpredilation. Practitioners of CAS should be versed in both.

INTRODUCTION

Design, development, and usage of mechanical em-

bolic protection devices (EPDs) appear to have had

a significant impact on the success of percutaneous

carotid artery and stenting (CAS).1-4 The in-

herent functionality of each particular device has

Presented at the Thirty-Fourth Annual Symposium of the Societyfor Clinical Vascular Surgery, Las Vegas, NV, March 8-11, 2006.

1Division of Vascular Surgery, Northwestern Memorial Hospital,Feinberg School of Medicine, Northwestern University, Chicago, IL.

2Department of Radiology, Northwestern Memorial Hospital,Feinberg School of Medicine, Northwestern University, Chicago, IL.

Correspondence to: Mark K. Eskandari, MD, Division of VascularSurgery, Northwestern Memorial Hospital, Feinberg School of Medicine,Northwestern University, 201 East Huron Street, Suite 10-105, Chicago,IL 60611, USA, E-mail: meskanda@nmh.org

Ann Vasc Surg 2007; 21: 403-407DOI: 10.1016/j.avsg.2006.07.005� Annals of Vascular Surgery Inc.Published online: March 27, 2007

resulted in a division into three broad categories:

(1) distal balloon occlusion, (2) distal filtration,

and (3) proximal balloon occlusion.5-7 While

many devices are being scrutinized through clinical

trials and registries, only three are indicated specifi-

cally for use during CAS, all of which are filter

systems: AccuNet (Guidant, Santa Clara, CA),

Emboshield (Abbott Vascular Devices, Redwood

City, CA), and Spider (ev3, Plymouth, MN). The

purported advantage of a distal filter device is the

preservation of antegrade cerebral flow throughout

the procedure while providing capture of released

embolic particulate debris. Unfortunately, filter sys-

tems tend to be bulkier and more rigid than other

classes of EPDs. Conversely, distal balloon occlusion

systems are low-profile, flexible systems capable of

negotiating rather tortuous or severely stenotic

anatomy. Theoretically, these systems provide

complete capture of released particulate debris;

however, a period of ipsilateral intracerebral flow

403

404 Eskandari et al. Annals of Vascular Surgery

arrest is required to achieve this.8,9 Technical fail-

ures of these two classes of EPDsddistal balloon

occlusion and distal filtrationdare reviewed along

with suggested procedural alternatives.

METHODS

Patients

From April 2001 to September 2005, 206 consecu-

tive cervical carotid stent procedures were per-

formed at Northwestern Memorial Hospital and

the Jesse Brown VA Medical Center (Chicago, IL).

Overall neurologic complications (minor and major

stroke) and non-neurologic complications (myocar-

dial infarction, death, and access-site complications)

were reviewed. Minor stroke was defined as any

new neurologic deficit persisting beyond 24 hr with-

out increasing the National Institutes of Health

(NIH) stroke scale by more than three points. Major

stroke was any new neurologic event persisting for

more than 30 days and/or increasing the NIH stroke

scale more than three points. All treated patients

had either symptomatic (�50% diameter stenosis)

or asymptomatic (�80% diameter stenosis) carotid

bifurcation disease. Patients were excluded if they

had a major neurologic deficit, illness impeding

informed consent, or peripheral vascular disease pre-

cluding femoral artery access. All patients were re-

viewed under institutional review boardeapproved

protocols at the listed institutions.

Operative Procedure

CAS was performed in an operating room with ded-

icated endovascular capabilities as previously de-

scribed.10 Briefly, preoperatively, the patients’

diagnostic studies included carotid duplex ultraso-

nography with magnetic resonance angiography of

the neck and cerebral circulation or a carotid/cere-

bral angiogram. All patients were loaded with clopi-

dogrel (Plavix, Sanofi Aventis, Somerset, NJ) at least

24 hr prior to stenting and given clopidogrel 75 mg

daily, including the morning of the procedure. In ad-

dition, each patient was given aspirin 325 mg on the

morning of the procedure.

Percutaneous access was obtained through a com-

mon femoral artery puncture. A J-wire (0.035 inches)

and then a short 6F sheath were used to secure access.

A markerpigtail catheter (5F, 110 cm long)wasplaced

in the ascending arch under fluoroscopy. A left ante-

rior oblique aortogram at an angle of 30� was ob-

tained. Selection of the common carotid artery was

achieved using a Vitek Catheter (Cook, Bloomington,

IN) or a Davis (DAV) catheter (Cook). Systemic

heparin (100 units/kg IV) was given to obtain an acti-

vated clotting time of 250-300 sec. A Storq wire (300

cm long; Cordis, Miami Lakes, FL) was used to cannu-

late the common carotid artery and then ‘‘buried’’ dis-

tally in the external carotid artery. With the Storqwire

in place, the 6F sheath was replaced with a 100-cm-

long 6F or 7F Shuttle Sheath (Cook). The distal tip of

the shuttle sheath was placed 2-4 cm proximal to

the target lesion. Angiograms were performed of the

intracranial and extracranial arteries with at least

two different views, anteroposterior (AP) and lateral.

The lesion was then crossed with either a 0.014-

inch wire-based filter or a balloon occlusion embolic

protection system. Preference was given to the filter

systems as they became available. Adjunctive mea-

sures to facilitate use of a filter system in tortuous

anatomy included turning the patient’s head, pull-

ing back on the shuttle sheath, or use of a 0.014-

inch buddywire to straighten any angulation of

the artery. For extremely narrowed target lesions,

slow and gentle forward pressure of the filter ele-

ment with the shuttle sheath in close proximity to

the carotid bifurcation was attempted. Inability to

cross the target lesion with the filter element due

to the severity of stenosis or tortuosity of the vessel

led to intraoperative switching to the balloon occlu-

sion system. The EPD was deployed in the distal ex-

tracranial internal carotid artery, and appropriate

deployment and positioning were documented by

angiography by the observance of either flow arrest

with the balloon occlusion device or good vessel

wall apposition of the basket struts when using filter

systems. The stenosis was then predilated with

a low-profile monorail 4 � 20 mm balloon. Intrave-

nous atropine (0.5-1 mg) was administered immedi-

ately prior to predilation for de novo lesions. Stent

size was based on the diameter of the trailing end

of the stenotic segment. A self-expanding nitinol

stent was deployed over the wire and then postdi-

lated using a 5� 20 mm balloon. The protection de-

vice was then retrieved. Surprisingly, macroscopic

debris was rarely encountered regardless of the

method of cerebral protection used. Completion an-

giograms of the intracranial and extracranial vessels

were done, employing AP and lateral views.

Postoperatively, the patients were sent to the re-

covery room. If the patient remained hemodynami-

cally stable, he or she was then sent to the regular

ward. On postoperative day 1, the patients under-

went carotid duplex ultrasonography as a baseline

study. Surveillance carotid duplex ultrasound was

performed at 3, 6, 9, 12, 18, and 24 months and

then annually. Daily clopidogrel (75 mg) and aspirin

(325 mg) were prescribed for at least 1 month and

preferably indefinitely.

Vol. 21, No. 4, 2007 Technical limitations of carotid filter EPDs 405

EPD

Some form of EPD was attempted in all but 14 cases.

Among the remaining 192 procedures, either a distal

balloon occlusion systemdPercuSurge Guardwire

(Medtronic Vascular, Santa Rosa, CA)dor one of

the following distal filter systems was utilized:

AccuNet, Angioguard (Cordis), Filterwire (Boston

Scientific, Maple Grove, MN), and Emboshield

(Figs. 1 and 2).

Statistical Analysis

All statistical analyses were performed with SPSS

software (SPSS, Chicago, IL). Data are expressed as

mean ± standard error of the mean. All probability

values were two-tailed, and values of P < 0.05

were considered statistically significant.

RESULTS

Patient Characteristics

A total of 206 CAS procedures were performed in

193 patients. The mean age of this patient group

was 70 years, with the majority being men (76%).

Asymptomatic lesions comprised 72% of all cases,

whereas preprocedural neurologic symptoms were

documented in 28%.

Procedural Data

An EPD was used in 192 of the 206 cases. The first 10

cases were performed without an EPD due to lack of

an available device. Four additional cases were also

done without an EPD due to either intolerance to

Fig. 1. Pie chart showing the breakdown of actual usage

of the EPDs.

flow arrest manifested by reversible neurologic

symptoms (n ¼ 2) or severe stenosis (n ¼ 2). A total

of 94 cases (46%) were actually performed using the

PercuSurge Guardwire system and 98 cases (48%)

with one of the following filter devices: AccuNet

(n ¼ 72), Angioguard (n ¼ 11), Filterwire (n ¼12), and Emboshield (n ¼ 3). In the last 100 proce-

dures, preference was given to a filter system; how-

ever, in 11 cases (11%), intraprocedural switching

to PercuSurge was necessary due to either extreme

vessel tortuosity or severe stenosis precluding safe

passage of the filter element (Figs. 3 and 4). Mean

balloon occlusion time for the PercuSurge was

12.3 ± 0.93 min (maximum 30 min, minimum 6

min). No attempts were made to predilate a target

lesion prior to delivery of an EPD.

30-Day Outcomes

Among this entire cohort of patients at 30 days there

were no deaths or myocardial infarctions. Neuro-

logic complications included two major ipsilateral

strokes (1%), two minor posterior strokes (1%),

and four transient ischemic attacks (2%). One major

access complication required surgical exploration

and repair of the femoral arterial puncture. The ma-

jor strokes were equally divided between distal bal-

loon occlusion and distal filtration systems. There

were no strokes in the 14 patients where an EPD

was not used or in the 11 cases in which the filter

system was abandoned for balloon occlusion.

DISCUSSION

Acceptance of CAS as a viable alternative to carotid

endarterectomy (CEA) has been due to several trials

Fig. 2. Bar graph of the number of procedures performed

per year with the corresponding actual use or not of an

EPD.

406 Eskandari et al. Annals of Vascular Surgery

demonstrating favorable outcomes in high-risk pa-

tients.1,3,11 Certainly, improvements in technical

expertise have played a role in achieving good re-

sults; however, the design and development of

equipment dedicated specifically to CAS cannot be

overlooked. This includes low-profile balloon and

stent delivery systems, tapered self-expanding niti-

nol stents, and EPDs. The early original description

of an EPD by Theron et al.12 more than a decade

ago was rather crude and cumbersome, yet it ush-

ered in a novel percutaneous device that now has

far-reaching applications.13 Due to the functional

components of these devices, they are now gener-

ally categorized in one of three classes: (1) distal bal-

loon occlusion, (2) distal filtration, and (3) proximal

balloon occlusion (with or without flow reversal).7

Each has its own inherent weaknesses. The focus

of this report is on some of the difficulties of the

Fig. 3. Carotid angiogram through a sheath in the

common carotid artery showing an extremely tortuous

internal carotid artery (ICA) lesion crossed with the Percu-

Surge Guardwire system.

only class of EPD approved for CAS, namely distal

filter systems.

One of the primary unanswered questions is

what size and amount of released particulate debris

is clinically safe.14,15 Many would argue the number

should be zero. This, of course, causes a quagmire in

determining the appropriate pore size for filter de-

vices that protect the patient while preserving ante-

grade flow to the brain during the procedure.

Additional recognized problems with the currently

approved filter devices include the risk of failed

particle capture emanating from incomplete wall

apposition of the filter element and the risk of embo-

lization while crossing the target lesion. As a class,

filter systems tend to be bulkier and more rigid

than other EPDs, preventing safe passage through

tortuous or severely stenotic target lesions. Options

other than proceeding without an EPD or predi-

lating a lesion should be considered in these

Fig. 4. Carotid angiogram through a sheath in the com-

mon carotid artery showing a severe stenosis of the inter-

nal carotid artery (ICA).

Vol. 21, No. 4, 2007 Technical limitations of carotid filter EPDs 407

circumstances. As we have shown, the use of a distal

balloon occlusion systemdPercuSurge Guardwiredis well tolerated and results in comparable clinical

outcomes. While this is not a prospective random-

ized study appropriately powered to detect a differ-

ence between devices, this report does substantiate

the utility of an alternative class of EPD in cases of dif-

ficult carotid anatomy. Others have reported similar

clinical outcomes.16,17 Obvious advantages include

crossing the target lesion with an exceedingly low-

profile (0.036-inch), flexible system and capability

to capture all released particles contained within

the stagnant column of blood below the occlusion

balloon.

In summary, CAS is a safe alternative to CEA in

experienced hands. As in the case of CEA, meticu-

lous technique with the appropriate equipment is

required in order to obtain excellent outcomes. In

the case of CAS, this means availability of low-

profile balloon and stent delivery systems as well

as various classes of EPDs. The use of an EPD for

CAS is now strongly recommended; however, up

to 10% of cases cannot be managed safely with cur-

rent filter systems. Practitioners of CAS should not

be encouraged to proceed without protection or re-

sort to predilation to deliver a filter element when

the option of using a distal balloon occlusion system

remains viable.

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