The Albany Vascular Group Experience
Embolic protection during carotid artery stenting using the GORE Flow Reversal System.
The intent of carotid endarterectomy (CEA) or carotid artery stenting (CAS) is to improve the ipsilateral stroke-free survival rate. During the past decade, CAS with distal cerebral embolic protection devices (EPDs) has undergone intense scrutiny and, for the time being, survived with US Food and Drug Administration (FDA) and CMS approval of CAS for high-surgical-risk symptomatic patients with carotid stenosis > 70%. At the same time, the results of CAS have clearly improved, albeit difficult to assess whether the improvement is secondary to increasing operator experience, improving technology, or a combination of both.
Distal filters are the most extensively studied and most frequently used EPDs and have several advantages in that they limit distal cerebral embolization, have a relatively low crossing profile, and preserve cerebral flow during CAS. They also have several limitations in that they need to traverse the carotid lesion before establishing cerebral protection, require a considerable length of relatively straight internal carotid artery (ICA) beyond the carotid lesion (safe landing zone), can cause significant ICA vasospasm, allow microemboli < 200 to 250 µm (depending on the EPD) to escape, and have the potential to occlude during the procedure. 1-6 The other form of EPD includes a distal ICA occlusion balloon, which also requires the need to cross the carotid lesion before establishing cerebral protection, and although the balloons do not require significant length for the landing zone, they do lead to complete ICA occlusion, which can lead to cerebral ischemia and intolerance to the ICA occlusion balloon.3 Based on these limitations, it is obvious that innovation of disruptive technology, which adds to our armamentarium the ability to provide embolic protection during CAS, will continue to carve out its niche in the treatment of carotid stenosis, stroke prevention, and possibly stroke treatment.
Earlier this year, based on the results of the multicenter EMPiRE (Embolic Protection With Reverse Flow) study, which evaluated the safety and efficacy of high-surgical-risk patients with carotid stenosis undergoing CAS, the FDA granted approval to the GORE Flow Reversal System (W. L. Gore & Associates, Flagstaff, AZ). The GORE Flow Reversal System for CAS is a disruptive technology, unique from all other FDA-approved EPDs in that it allows proximal common carotid artery (CCA) occlusion and establishes cerebral flow reversal via an ex vivo arteriovenous shunt before traversing the carotid lesion. By providing the ability to establish cerebral flow reversal before coming in contact with the carotid lesion, the GORE Flow Reversal System overcomes some of the theoretic limitations of currently available EPDs in that cerebral protection is obtained before ever traversing the carotid artery lesion. Although the brain’s ability to tolerate microembolization without any clinical manifestation of transient ischemic attack (TIA) or stroke remains a mystery, surrogate markers of transcranial Doppler (TCD) high-intensity transient signals (HITS) and diffusion-weighted imaging (DWI) lesions indicate the potential for ischemic damage beneath the level of TIA and stroke during CAS. Data from TCD monitoring during CAS with flow reversal indicate a reduction in embolic signals when compared to distal EPDs.1,2 A small study evaluating the presence of new DWI lesions after CAS using flow reversal in comparison to angiography was comparable.3
THE ALBANY VASCULAR GROUP EXPERIENCE
From 2006 to 2008, The Albany Vascular Group was one of the 29 participating sites in the United States that enrolled a total of 245 subjects into the EMPiRE study using GORE Flow Reversal for cerebral protection during CAS (a prospective multicenter, single-arm trial). The EMPiRE trial evaluated symptomatic patients with ≥ 50% carotid artery stenosis or asymptomatic patients with ≥ 80% carotid artery stenosis. All 49 CAS procedures with GORE Flow Reversal performed at the Albany Vascular Group were performed under local anesthesia and conscious sedation. Antiplatelet therapy included aspirin (325 mg/daily) and clopidogrel (75 mg/twice daily), which was started at least > 48 hours before the procedure and was continued for at least 30 days after the procedure. During the CAS procedure, patients received intravenous anticoagulation (heparin or bivalirudin) to maintain an activated clotting time of > 250 seconds.
The GORE Flow Reversal System includes a balloon sheath (7 F), a balloon wire, and an external filter (Figure 1). The procedure steps are as follows:
- Obtain femoral artery access (9-F Terumo Pinnacle Sheath [Terumo Interventional Systems, Somerset, NJ]) and femoral venous access (6-F sheath) (Figure 2).
- Balloon sheath access into the CCA
- Balloon wire advanced into the external carotid artery (ECA)
- The femoral arterial and venous sheaths are connected with the external filter to create an arteriovenous shunt.
- The ECA balloon is inflated, and subsequently, the CCA balloon is inflated.
- Flow reversal is established as the direction of blood flow is from the ipsilateral ICA into the balloon sheath, across the ex vivo femoral arteriovenous shunt and the external filter, and back into the femoral vein (Figure 3).
- Once flow reversal is achieved, a 0.014-inch wire is traversed across the ICA lesion, and a self-expanding stent is advanced across the carotid lesion and deployed. Pre- and postdilatation are carried out as needed.
- Throughout the procedure, multiple active aspirations are performed at the level of the femoral arteriovenous shunt after stent placement and angioplasty.
- Once an adequate result is obtained, the ECA balloon is deflated and removed, and subsequently, the CCA balloon is deflated, and the balloon sheath is removed.
During a 2-year period, we enrolled 49 patients into the study and will present our experience and lessons learned with CAS using the GORE Flow Reversal System in this article. The primary endpoint included TIA, stroke, death, and myocardial infarction within 30 days of CAS. The secondary endpoints included technical success of device placement and establishing flow reversal that was tolerated by patients (Table 1). The mean age was 69 years, 67% male, 25% symptomatic, 49% with previous CEA, and 14% of patients were octogenarians. High surgical risk was secondary to medical comorbidity risk factors in 35% of patients and due to anatomical risk factors in 80% (Table 2). Eleven (22.4%) of the 49 patients were considered to be high risk for a routine CAS procedure with the currently available distal EPDs due to significant carotid artery tortuosity, significant calcifications/ulcerations, or a combination of both.
Technical success was achieved in 47 (96%) patients, and in the remaining two (4%) patients, the procedure was discontinued due to hostile thoracic arch anatomy (type III arch with significant calcifications). Two (4%) patients experienced intolerance to flow reversal during the procedure; one patient required intravenous vasopressors to elevate systemic blood pressure, and the other required intermittent discontinuation of flow reversal by deflating the CCA balloon during parts of the procedure that were considered lower risk for embolization. Both patients were treated successfully and without any adverse sequela. None of the six (12%) patients with contralateral ICA occlusion developed intolerance to flow reversal. The median procedure time was 50 minutes (range, 23–126 minutes), and the median flow reversal time was 11 minutes (range, 4–51 minutes). The major adverse event rate, which included death, stroke, TIA, and myocardial infarction, was 4%; one patient suffered a minor stroke, one patient suffered a TIA, and there were no deaths or myocardial infarctions. The octogenarians accounted for 14% of the subjects, and none experienced any major adverse events.
In our experience with CAS, when compared to the distal cerebral EPDs, we have found the GORE Flow Reversal System to have several additional advantages:
- Cerebral protection from embolization is established before crossing the carotid lesion.
- Flow reversal continuously directs micro- and macroemboli away from the brain during the procedure and is associated with less microemboli reaching the brain.1-3
- Flow reversal expands the treatment options for challenging carotid lesions, including tortuous carotid arteries that do not allow for safe crossing and placement of distal EPDs.
- Anchoring a balloon in the CCA provides added stability during CAS.
- Initial data are promising for treating all patients, including octogenarians.
Although we await the publication of the initial data from the EMPiRE trial, which led to FDA approval of the GORE Flow Reversal System, and certainly look forward to longer-term data with this device, our initial experience would suggest that the GORE Flow Reversal System has many advantages as described previously. In our experience, the learning curve varies depending on the expertise of the interventionist and probably ranges between three to five procedures. As an emerging disruptive technology, the GORE Flow Reversal System also has some nuances, such as flow reversal intolerance. Our initial experience would suggest that flow reversal intolerance is not easy to predict on the basis of patency of the contralateral carotid and vertebral arteries and the Circle of Willis. Fortunately, flow reversal intolerance is an infrequent event and most often can be managed by a few simple maneuvers. Intravenous vasopressors can be used transiently for elevating the systemic blood pressure during flow reversal, and flow reversal can be discontinued intermittently by deflating the CCA balloon during parts of the procedure that are considered lower risk for embolization. During catheter, balloon, or stent manipulation across the carotid lesion, the flow reversal can be re-established for a short duration.
Although our experience is only a subset analysis of the EMPiRE trial, it indicates the safety and efficacy of the GORE Flow Reversal System during CAS in high-surgicalrisk patients, and this is validated by the FDA approval of the device. What is exciting about this disruptive technology is that it might have the potential for expanding the role of CAS to a broader patient population that might otherwise have been considered high risk for carotid stenting, including treatment of embolic stroke; of course, this must be validated by additional investigations.
Manish Mehta, MD, MPH, is Associate Professor of Surgery
with The Institute for Vascular Health and Disease, The
Vascular Group, PLLC in Albany, New York. He has disclosed
that he is a paid consultant to and receives grant/research
funding from W. L. Gore & Associates. Dr. Mehta may be
reached at (518) 262-5640; email@example.com.
Dr. Mehta's coauthors are from The Institute for Vascular Health and Disease, The Vascular Group, PLLC in Albany, New York. Dr. Mehta's coauthors have disclosed that they are paid consultants to and receive grant/research funding from W. L. Gore & Associates.
- Garami ZF, Bismuth J, Charlton-Ouw K, et al. Feasibility of simultaneous pre- and postfilter transcranial Doppler monitoring during carotid artery stenting. J Vasc Surg. 2009;49:345-350.
- Parodi JC, Schonholz C, Parodi FE, et al. Initial 200 cases of carotid artery stenting using a reversal-of-flow cerebral protection device. J Cardiovasc Surg. 2007;48:117-124.
- Asakura F, Kawaguchi K, Sakaida H, et al. Diffusion-weighted MR imaging in carotid angioplasty and stenting with protection by the reversed carotid arterial flow. Am J Neuroradiol. 2006;27:753-758.
- Atkins MD, Bush RL. Embolic protection devices for carotid artery stenting: have they made a significant difference in outcomes? Semin Vasc Surg. 2007;20:244-251.
- Bosiers M, Deloose K, Verbist J, et al. The impact of embolic protection device and stent design on the outcome of CAS. Perspect Vasc Surg Endovasc Ther. 2008;20:272-279.
- Schlüter M, Tübler T, Steffens JC, et al. Focal ischemia of the brain after neuroprotected carotid artery stenting. J Am Coll Cardiol. 2003;42:1007-1013.