Advantages and Disadvantages of Distal Protection Filter Devices

Approximately 20 years ago, Jacque Theron suggested that embolic protection with balloon occlusion during carotid angioplasty could reduce procedure-related strokes.1 This was documented in his report, with a >50% reduction in strokes when using distal balloon occlusion. Henry et al2 described similar results using the PercuSurge balloon (Medtronic, Inc., Santa Rosa, CA) for distal protection. Clinical evidence suggested that not all patients tolerate the temporary interruption of blood flow caused by occlusion balloons and retrograde flow devices, as well as the possibility of the latter to cause carotid artery spasm during proximal occlusion. MüllerHülsbeck et al3 described the GuardWire (Medtronic) plus balloon occlusion in a comparative study with filters as having a 14% missed particle embolic event rate in their in vitro bench top model. Nonetheless, there are now four systems with proximal balloon occlusion and reversal of flow and three systems with distal balloon occlusion. The most recent entry into distal protection is a .014-inch wire integrated with an expandable three-dimensional mesh of polyethylene terephthalate fibers (PET). This FiberNet distal protection device (Lumen Biomedical, Inc., Plymouth, MN) has both occluding and filter functions and in early studies has captured particles as small as 40 μm. At the present time, both distal and proximal balloon technology is limited to those patients with a functionally complete circle of Willis who will tolerate complete occlusion. There is also a question of emboli to the contralateral carotid and particle retention at the balloon junction with the arterial wall. Proximal balloons are also encumbered by their large profiles. In spite of these criticisms, the occlusion flow reversal systems have the ability to capture particles smaller than 100 μm, and that in itself makes this category of emboli protection viable. Certainly, flow reversal systems have gained momentum and ideally should be integrated into dual-device development to include both a distal filter and a flow reversal system. The notion of a filter-based protective device, rather than occlusion balloons, was described in 1987 when we invented a filter integrated with a 5-mm angioplasty balloon used during carotid angioplasty procedures.4 When stents replaced balloons for managing carotid stenosis, several additional filter designs were introduced. Initially, the AngioGuard filter (Cordis Corporation, a Johnson & Johnson company, Miami, FL) was used as a system with the Precise stent (Cordis Corporation) for the landmark SAPPHIRE trial. This was followed by the Boston Scientific Embolic Protection Inc. (EPI) filter (Boston Scientific Corporation, Natick, MA) in the BEACH and CABERNET trials, the Accunet filter now distributed by Abbott Vascular (Abbott Park, IL) in the ARCHeR trial, and the Spider device (ev3, Inc., Plymouth, MN) for the CREATE trials. There are eight filter-designed distal protection devices in either clinical practice or developmental stages. Distal protection filters have decreased the procedure-related stroke risk by 50% in several registries, including the multicenter World Registry that included 44 US and European sites.5 Distal protection filter devices have their own significant inherent problems that, although rare, include dissection, filter detachment, and clot formation. Variation in profile, trackability, torqueability, and suboptimal capture efficiency also exist.