CDU Contributing Editor
ORLANDO, Florida – Percutaneous treatment of coronary artery disease has historically been one of the most dynamic disciplines in medicine and one of the most rapidly changing segments of the medical device market. Technological advances continue to drive changes in the preferred approach to treatment of patients in this segment. The 50th annual scientific sessions of the American College of Cardiology (ACC, Bethesda, Maryland), held here in mid-March, provided ample evidence that the pace of innovation has not slowed. Coronary stents, now used in up to 80% of patients treated for coronary occlusions by transcatheter techniques in many centers, have in some respects become a mature technology. The refinement of the mechanical aspects of stent design has reached a stage at which only minor improvements in performance appear possible. However, based on the most recent studies comparing stents to surgery, the technology has now reached a point at which patient outcomes with stenting are equivalent to those achievable with coronary artery bypass graft surgery.
For example, the results of the Stent or Surgery (SoS) Trial, reported at the ACC sessions by Rodney Stables, MD, of Liverpool, United Kingdom, indicate that long-term outcomes are now probably equivalent for the two modalities. Short-term results, including procedural mortality, are also at least as good for stents, and in actual practice in many centers are likely to be better because of the less invasive nature of stenting. A new dimension has recently been added with the introduction of brachytherapy to treat in-stent restenosis, perhaps followed in the future by drug coatings for stents, conferring a significant improvement in performance that may possibly give percutaneous treatment both a short-and long-term advantage over surgery in many patients. The FDA approved two radiation therapy devices for the treatment of in-stent restenosis in November 2000, and the use of brachytherapy for the treatment of in-stent restenosis is now being adopted rapidly for that application, especially in Europe. While results of trials using beta radiation to treat de novo lesions have been disappointing, brachytherapy still is expected to play a valuable role in interventional cardiology for the large number of patients with in-stent restenosis. Rapamycin, an immune suppressant, is the most promising drug coating at present, but stent suppliers are evaluating many other compounds.
A number of other advances were discussed at the ACC sessions that promise to further enhance patient outcomes in percutaneous therapy, including embolization protection devices, devices for thrombus removal prior to angioplasty and stenting to minimize the impact of thrombotic debris on downstream vessels, and devices such as the Cutting Balloon and improved atherectomy catheters to allow interventional treatment of lesions that previously would have required surgery or would not otherwise be amenable to repair. Technologies such as photoangioplasty are also under development that may provide even lower restenosis rates or prove to be valuable adjuncts to existing methods.
Another development in transcatheter therapy involves the way in which treatment is being delivered. Until recently, interventional therapy was typically not available universally, even in developed countries, particularly in smaller hospitals in outlying areas. Patients with an acute coronary syndrome who were within reach of one of the approximately 600 cardiac catheterization laboratories in the U.S. that offer interventional therapy could expect to have access to less-invasive treatment if their condition warranted it. However, those patients in outlying areas, often presenting at community hospitals for treatment, would in many cases only have the option to undergo thrombolytic therapy, followed by transport to a tertiary center if that treatment did not succeed in restoring patency. Now, a new trend is emerging, starting in Europe, in which networks of treatment centers are being established, such as one in the Netherlands, which make it possible for all patients to undergo primary angioplasty or stenting.
Advances in stents outpace surgery
Recent trends in procedure volumes clearly indicate that percutaneous intervention is becoming the dominant mode of treatment of obstructive coronary artery disease. As shown in Table 1, PTCA and stent procedures have grown much more rapidly than CABG procedures recently, and the trend is expected to continue for at least the next few years in spite of new developments in less invasive surgery. Stenting can now be performed successfully on patients with multi-vessel disease, as demonstrated in the SoS trial, and newer devices are allowing cardiologists to address even more complex cases. The SoS trial, which involved 988 patients recruited in 53 countries in Europe and Canada and an average follow-up of two years, showed that stents reduced unplanned revascularization from 33% to 17%, a key factor in allowing interventional techniques to compete with surgery. Although mortality was somewhat higher in the percutaneous coronary intervention (PCI) group at 4.1% vs. 1.2% for surgery, the trial was not powered to detect mortality differences, and the investigators believe that the difference is due to an unusually high number of cancer-related deaths in the PCI group.
|No. Patients Undergoing |
|Growth||No. Patients with Coronary |
Artery Bypass Procedures
|Note: PTCA data is based on National Center for Health Statistics (NCHS) figures for total inpatients with a procedure, as well as NCHS data for 1994-1996 for ambulatory procedures extrapolated to 1997-2000. Figures for 2000 are extrapolated. 1995-1999 data for number of patients with CABG is latest available from NCHS; 2000 figure is estimated.|
Source: National Center for Health Statistics
Indeed, others discussing the role of stents vs. surgery at the ACC sessions, such as Mark Connolly, MD, of Lenox Hill Hospital (New York), note that short-term mortality for patients treated with surgery, if data from many studies are considered, is around 3% vs. 0.5% to 1% for PCI. And in the SoS trial, the combined rate of death or myocardial infarction at two years was the same for both groups at 9.5%. Other trials, such as ERACI II, have shown a considerable advantage for PCI in terms of major adverse cardiac events.
Surgery still will have a place in coronary artery disease treatment, according to Connolly, particularly as less invasive surgical techniques improve. At Lenox Hill, minimally invasive surgery now comprises 100% of coronary bypass cases and long-term outcomes are equivalent to conventional CABG. Essentially all regions of the heart can be accessed, and operative mortality is lower at 1.2% vs. 9.8% for conventional surgery. Thus, for patients who cannot be treated with percutaneous intervention, including diabetics with complex lesions and many patients with ostial, bifurcated or left main coronary artery lesions, improved surgical techniques offer lower risk and improved outcome and are particularly attractive because adverse cognitive effects are minimized.
Cost is another factor to be taken into account when considering surgery vs. percutaneous intervention, assuming safety and efficacy are equivalent. The most recent data on cost, discussed by Connolly, indicates that, when assessed over an eight-year period, costs are about the same for PCI vs. surgery. Initially, based on a retrospective analysis, costs for PTCA are considerably lower (about $21,100 for PCI vs. $32,300 for surgery). However, due to the need for more re-interventions with PCI, the total cost increases more with time to $69,400 for PTCA vs. $72,500 with surgery. Those figures neglect the effect of stent use, which increases costs up front, but decreases long-term costs because of fewer repeat interventions. If stents are included in the analysis, the findings are not reversed, and in the future, as drug coatings and brachytherapy drive further reductions in repeat procedures, the picture will increasingly favor percutaneous techniques.
Coated stents are the hottest topic in coronary intervention at the moment, based on initial results from pilot studies conducted in Brazil and the Netherlands. Table 2 describes coated stent technologies under development for the prevention of restenosis.
Table 2. Coated Stent Technologies
|Abbott Laboratories (Abbott Park, Illinois)||Coronary stent coated using Biocompatibles' PC Technology containing anti-proliferative agent||In trials at Mayo Clinic. Preclinical data indicate 43% reduction in neointimal formation and no significant inflammation.|
|Biocompatibles (Farnham, Surrey, United Kingdom)||BiodivYsio stent coated with Batimastat; partnership with British Biotech for drug technology||Clinical trials planned for mid-2001, with commercial launch targeted within 24 months|
|Chonnam National University Hospital (Kwang Ju, South Korea)||ReoPro-coated stent||Animal (porcine artery) studies demonstrate inhibition of neointimal cell proliferation and restenosis|
|Cook (Bloomington, Indiana)||Hydrocarbon polymer coating loaded with VEGF. Acts to stimulate endothelial cell growth to cover stent and improve biocompatibility.||In vitro studies of sterilized stents demonstrate eluted VEGF can stimulate cell growth|
|Paclitaxel-coated Logic stent||In clinical trials in Europe and Asia; approval to begin clinical trials in the U.S. received March 12, 2001.|
|Cordis (Miami Lakes, Florida)||Sirolimus/Rapamycin coating. Acts as cytostatic agent to inhibit cell proliferation and neointima formation post-stenting.||Enrollment of 220 patients in RAVEL trial in Europe completed December 2000. SIRIUS trial with 1,100 patients at 50 sites in U.S. started March 2001.|
|Carmeda (heparin) coating for Bx Velocity stent||Introduced in November 2000 in the U.S. and Europe|
|Guidant (Indianapolis, Indiana)||Pharma-Link Actinomycin-D coated stent with timed-release coating||Clinical trials planned for 2Q01|
|Medtronic/AVE (Santa Rosa, California)||Hepamed (heparin)-coated BeStent||Evaluated in 74 patients vs. PTCA; restenosis rate (per protocol) of 6.3% vs. 24.2% for PTCA at six months.|
|Shiga Medical Center (Moriyama, Japan)||Igaki-Tamai PLLA self-expanding biodegradable stent||Evaluated in 50 patients with complex lesions; 14% repeat intervention at 12 months. Planning to develop drug-eluting version.|
|Precision Cutting Systems (Kalken, Belgium)||Elut drug delivery stent. Laser-cut holes in metal framework serve as controllable reservoirs for drugs loaded in polymer matrix.||In vitro studies using methylprednisolone in polymer matrix demonstrate higher local drug concentration in Elut vs. controls, and significant prolongation of drug release.|
|Quanam Medical/Boston Scientific (Santa Clara, California)||Polymer-coated stent using paclitaxel derivative as active agent||No restenosis at two-year follow-up in pilot studies; clinical experience includes more than 200 patients. Now in pivotal trials in Europe.|
|Boston Scientific (Natick, Massachusetts)||Paclitaxel-coated stent employing technology licensed from Angiotech Pharmaceuticals (Vancouver, British Columbia)||60 patients enrolled in Phase I trial in Germany|
Source: Cardiovascular Device Update
As discussed by Patrick Serruys, MD, of the Thoraxcenter (Rotterdam, The Netherlands), initial attempts to use anti-restenosis coatings on stents failed because the coatings cracked upon stent expansion. However, using coatings from companies such as Surmodics (Eden Prairie, Minnesota), those problems have been solved, and drug release and the site of delivery can now be controlled with good precision. In the group of patients treated with Bx Velocity stents from Cordis (Miami Lakes, Florida) coated with Sirolimus (Rapamune/Rapamycin) in Rotterdam and Sao Paolo no restenosis has been observed at one-year follow-up in the 15 patients treated in Sao Paolo, and in another 18 patients treated in Rotterdam. Coatings to prevent intimal hyperplasia offer an even greater advantage as the size of the vessel to be treated becomes smaller in diameter. A given amount of neointimal growth results in a much higher degree of restenosis in a 2 mm vessel than in a larger one.
Cordis, the clear leader in coated stent technology at the moment, is investing on multiple fronts to remain ahead of the competition. In addition to funding randomized trials of its Sirolimus-coated stent in Europe and the U.S., Cordis is already beginning to address reimbursement issues for its coated stent, with the goal of avoiding the three-year delay in reimbursement authorization that created financial hardship for many hospitals during the adoption of the Palmaz-Schatz stent. Cordis also has obtained an exclusive license to Rapamune for use in coating of stents from the developer of the drug, Wyeth/American Home Products (Madison, New Jersey). The drug is unique in that it is a cytostatic, not a cytotoxic, compound, which allows endothelial cells to cover the stent but prevents neointimal cells from proliferating to block the lumen. Cordis invested six years in the development of the Sirolimus stent coating.
Cordis previously developed a version of the Bx Velocity coated with heparin (Hepacoat), which is indicated for use in improving coronary luminal diameter in the treatment of abrupt or threatened vessel closure. The heparin coating addresses the issue of thrombogenicity of the stent material in the first few weeks following implantation, before the struts become covered by endothelial cells. Medtronic AVE (Santa Rosa, California) also has developed a heparin-coated stent, based on its BeStent platform.
Paclitaxel is another drug that is being evaluated for use as a stent coating. Paclitaxel, a chemotherapy agent, also inhibits cell growth, although due to its cytotoxic nature it may allow less endothelial cell coverage of the stent. Indeed, as discussed by Frederick Welt, MD, of the West Roxbury VA Medical Center (West Roxbury, Massachusetts), studies with Paclitaxel-coated stents have demonstrated that thrombosis can be an issue. However, both Boston Scientific (BSX; Natick, Massachusetts) and Cook (Bloomington, Indiana) are moving ahead with trials of paclitaxel-coated stents, including a device developed by recent BSX acquisition Quanam Medical (Santa Clara, California) that, until enrollment in the trial was halted suddenly last month, hasd looked promising in pilot studies. Given the effectiveness of new anti-coagulation agents, thrombosis is not likely to prove to be an insurmountable hurdle in the development of drug-coated stents.
Other promising drugs for use in anti-restenosis coatings on stents include Actinomycin D and Batimastat. A stent coated with Actinomycin D, a drug developed by Merck & Co. (Whitehouse Station, New Jersey), is being developed by Guidant (Indianapolis, Indiana), while Biocompatibles (Farnham, United Kingdom) is developing stents coated with Batimastat. Biocompatibles has an extensive development program under way for drug-coated stents, with 11 different compounds under study targeting all four aspects of the restenosis cycle (injury, proliferation, migration, and healing). The company is partnering with British Biotech (Oxford, United Kingdom) in its drug-coated stent development programs. A key aspect of prevention of in-stent restenosis is to inhibit the formation of the extracellular matrix produced by smooth muscle cells. Extracellular matrix comprises about 80% of the volume of neointimal tissue, with the remainder composed of cells. However, it is also important to avoid complete inhibition of cell growth in the stented region, since coverage of the bare metal stent with host cells is key in preventing thrombogenic interactions. Consequently, successful pharmaceutical compounds will need to address multiple requirements. Stent geometry and the properties of the coating are also important factors to ensure that the drug is delivered in the most effective fashion and that it is targeted to all the tissues involved in restenosis.
Brachytherapy trial results raise questions
Brachytherapy is another approach to minimize restenosis, and is already approved by the FDA for treatment of in-stent restenosis. Table 3 describes vascular brachytherapy systems designed to help prevent restenosis. Two systems are now on the market worldwide: the Beta-Cath beta brachytherapy system from Novoste (Norcross, Georgia), and the CheckMate System using gamma radiation from Cordis.
|Company||Device||Technology Employed||Current Status|
|Cordis (Miami Lakes, Florida)||Checkmate Gamma Radiation System||Gamma radiation system using radioactive source ribbon and autoloader for delivery.||Positive results in GAMMA and WRIST trials; FDA-cleared in November 2000.|
|Guidant (Indianapolis, Indiana)||Galileo Intravascular Radiotherapy System||Galileo automated afterloader and catheter for gamma radiation delivery. Touch screen control.||Galileo under study for peripheral vascular use (PARIS trial); available in certain countries outside U.S.|
|Boston Scientific (Natick, Massachusetts)||Intracoronary Beta Irradiation System||Automated afterloader with Monorail centering balloon catheter||Development discontinued at Boston Scientific and outsourced to third party.|
|Radiance Medical Systems (Irvine, California)||RDX||Beta radiation source incorporated into balloon; provides direct wall apposition, self-centering, and lower source activity for equivalent dose.||BRITE II and BRITE SVG trials under way.|
|Novoste (Norcross, Georgia)||Beta-Cath||Beta irradiation using manual delivery of source catheter.||Cleared by the FDA in November 2000.|
|Note: Clinical trials for another device, the AngioRad system from the Vascular Therapies division of U.S. Surgical (Norwalk, Connecticut), have been halted but may be restarted at a later date. Medtronic (Minneapolis, Minnesota) is developing a soft X-ray system, and Interventional Technologies (San Diego, California), acquired recently by Boston Scientific, is developing the Irradiator catheter for delivery of liquid radioactive agents.|
Sources: Company interviews, Cardiovascular Device Update
The advantage that Beta-Cath has is that minimal radiation shielding is required, vs. a portable lead shield needed with CheckMate. Regulatory and licensure issues related to radiation use are also less onerous for beta radiation, and treatment time is shorter (3 to 5 minutes vs. 15 to 30 minutes for gamma systems). However, placement of the radiation source relative to the ballooned segment of the vessel must be more precise with beta, while gamma radiation has more forgiving characteristics in terms of catheter positioning. Overall, given equivalent efficacy and cost, an evaluation of the ease of use of both types of systems would appear to favor beta brachytherapy. That conclusion is borne out by cumulative procedure data for the two marketed systems: more than 5,000 procedures have now been performed with the Beta-Cath worldwide, vs. approximately 1,000 in the U.S. with the CheckMate system. Both systems have been in use, either for clinical trials or for patient treatment, for about the same period of time. A comparison of efficacy data from clinical trials shows that gamma brachytherapy has generally produced larger reductions in restenosis, with a reduction from 45% to 17% in the WRIST trial using gamma radiation, and target vessel revascularization rates of 10% vs. 48% in controls, as compared to 28.8% restenosis in patients treated with the Beta-Cath vs. 45.2% in the placebo group, and target vessel revascularization rates of 16% vs. 24.1%. However, as a general rule, one cannot directly compare percent restenosis rates from separate trials because the patients enrolled in different studies are not necessarily equivalent from a clinical perspective.
For de novo lesions, however – that is, for prevention of restenosis when a stent is first placed – recent clinical trial results reveal significant issues, at least for the Beta-Cath. As discussed by Richard Kuntz, MD, of Brigham and Women's Hospital (Boston, Massachusetts), principal investigator for the Beta-Cath trial, at an ACC press briefing, beta brachytherapy actually was deleterious when used in de novo lesions, with a restenosis rate of 44.9% vs. 35.3% in the placebo group. The higher restenosis rate was due entirely to recurrence of tissue growth outside the stented area, or outside the region receiving the intended radiation dose, since a beneficial effect of beta radiation was observed if only the lesion segment was analyzed. According to the Beta-Cath investigators, edge effects that result from the rapid fall-off of radiation dose with distance from the end of a beta source catheter are probably to blame for the poor results in de novo lesions. The investigators believe that radiation dosages below those needed to inhibit proliferation can cause enhanced proliferation in injured tissues. The trial was begun before the importance of edge effects was appreciated. Kuntz said he believes the edge effect problem can be solved by use of direct stenting procedures, where the stent is placed without pre-dilatation, and radiation is delivered subsequently. That approach should allow more precise alignment of the beta source with the injured regions of the vessel, since in the trial, radiation was delivered first, and pre-dilatation and stenting were performed afterwards, leading to considerable opportunity for positioning error.
At least one study presented at the ACC sessions cast doubt on the role of edge effects in beta brachytherapy. Christoph Naber, MD, of University Clinic (Essen, Germany), reported on a study of vascular brachytherapy using beta radiation in in-stent restenosis patients in Germany that showed patients with no geographic miss had a higher percentage late loss vs. those with geographic miss. Clearly, additional trials will be needed to resolve the issues regarding efficacy of beta brachytherapy in de novo lesions. On the other hand, studies with gamma brachytherapy have shown that the technique is quite insensitive to source positioning, compared to beta, and tends to mask any differences between various stents in terms of their tendency to induce restenosis. The key question of whether gamma brachytherapy is beneficial in reducing restenosis in de novo lesions may soon be addressed, according to Dr. Ron Waksmann of the Washington Hospital Center (Washington), who is planning to begin a trial of the technology for de novo lesions. Waksmann already has obtained very encouraging results with gamma brachytherapy in peripheral vessels such as the superficial femoral artery in the PARIS trial. The restenosis rate at one year was only 10% in 30 patients evaluated, better than SFA results with any other interventional technique, according to Waksmann.
Other technologies continue to be explored for their potential to further reduce restenosis after interventional procedures. Photoangioplasty is one alternative that has been investigated for a number of years, using the light-activated compound Antrin from PharmaCyclics (Sunnyvale, California) as an anti-restenosis agent. Antrin is of particular interest because it is activated by red light, which is easily transmitted by blood and tissue, and the drug tends to localize in plaque and binds well to key target cells such as macrophages and smooth muscle cells. The advantage of photoactivation is that the drug can be activated using an optical fiber catheter in only the regions that require treatment, i.e., at the site of tissue injury. PharmaCyclics has initiated clinical trials with Antrin photoangioplasty for peripheral vessels as well as for use in conjunction with coronary stenting. Other approaches to inhibit restenosis include a soft X-ray device under development by Cook; the URx sonotherapy catheter from PharmaSonics (Sunnyvale, California); and a radioactive balloon catheter from Radiance Medical (Irvine, California). The treatment of coronary restenosis represents a major market opportunity worldwide, as shown in Table 4. By one estimate, the market could be as large as $2.8 billion worldwide.
|Patient Type||Annual Procedures||Restenosis Rate*||Restenosis Procedures||Potential Market**|
|Stented||1.2 million||20%-30%||435,000||$1.1 billion|
|Saphenous vein grafts||900,000||25%||180,000||$450 million|
|Peripheral vessels||1 million||20%-50%||350,000||$875 million|
|Total||1.125 million||$2.8 billion|
|* Within five years of original procedure. ** Assumes $2,500 per procedure. Novoste charges $2,750 per catheter and $3,000 per month to lease the Beta-Cath equipment.|
Sources: Abbott Laboratories/Prudential Vector Healthcare
Technologies drive percutaneous treatment
The continued improvement in outcomes for interventional therapy is a major factor driving expanded use of techniques such as angioplasty and stenting. Also, a variety of adjunctive technologies continue to evolve, including atherectomy, thrombectomy catheters and novel approaches such as the Cutting Balloon from Interventional Technologies (San Diego, California), acquired recently by Boston Scientific, allowing treatment of patients who in the past would have been sent to surgery or would have not had good treatment options. Recent experience with the latest versions of the Cutting Balloon has been quite promising, and some newer technologies such as ultrasound-assisted thrombolysis also may open up new patient subsets for interventional therapy.
As discussed by Antonio Colombo, MD, of Centro Cuore Columbus (Milan, Italy), at the ACC conference, the Cutting Balloon is proving particularly effective for treatment of in-stent restenosis, while a new nickel-titanium-coated 8 Fr version of the Directional Coronary Atherectomy (DCA) catheter from Guidant offers considerably improved efficiency as compared to previous 10 Fr devices. The 8 Fr DCA catheter can cut through calcium and is often used by Colombo for left main, ostial and proximal LAD lesions. Overall, Colombo usess the DCA device in about 15% of patients, and the Cutting Balloon in 20% of patients.
Other clinicians discussing the use of such devices at the ACC sessions generally use atherectomy on a lower percentage of their patients, ranging from 5% to 10%. At present, U.S. physicians do not have access to the new 8 Fr DCA catheter, and consequently most find DCA to be too inefficient for routine use. The Boston Scientific Rotablator is probably used more widely than DCA in the U.S. at present.
Use of the Cutting Balloon is growing rapidly in a number of centers for treatment of in-stent restenosis. More than 125,000 Cutting Balloon catheters have been used worldwide, a large number considering the device was not cleared by the FDA until April 2000. However, the Cutting Balloon has been on the market in Europe and Japan for four to five years. According to Interventional Technologies, the key properties of the device that make it useful in treating in-stent restenosis are the avoidance of pressure trauma and alleviation of hoop stress in the treated vessel. Plaque compression is maximized while vessel wall extension is minimized. Those features are a result of the blades mounted on the balloon, which are five times sharper than surgical blades. A recent study in Japan demonstrated a 28% target lesion revascularization rate for patients with in-stent restenosis at one year, and another study (REDUCE II) is evaluating the device as an alternative to PTCA. Overall, there has been a dramatic increase in interest in use of the Cutting Balloon, according to clinicians.
Another area generating strong interest among interventional cardiologists is the use of embolic protection devices to help avoid adverse events associated with angioplasty and stent procedures. Data from studies such as the SAFER trial with the GuardWire from PercuSurge (Sunnyvale, California) has been positive, with a 50% reduction in major adverse cardiac events observed in patients treated for diseased saphenous vein grafts. The field is evolving rapidly as suppliers develop second-generation products that will be easier to use. A drawback to the PercuSurge device, for example, is that long procedures generally cannot be accommodated because the vessel is occluded during the time when the device's balloon is inflated. Newer devices using filters do not have that drawback, although some researchers are concerned that particles can still pass the filter that may create downstream embolization. The capture efficiency for small particles apparently is better than anticipated, however, because at least some filter devices – such as the filter from Embolic Protection (Campbell, California), also becoming part of Boston Scientific – can capture particles that are smaller than the filter pores.
Protection devices may have a role not only in PTCA and stent procedures, according to experts discussing such devices at the ACC conference, but may also prove useful in improving outcomes for CABG patients. The Embolic Protection FilterWire is already available for coronary and peripheral applications in Europe, and data has been submitted in support of applications in carotid procedures. A Phase II trial for saphenous vein graft applications, with a target to recruit 800 patients, was to begin last month.
Kensey-Nash (Exton, Pennsylvania) is a second company developing a balloon protection device for saphenous vein grafts, the TriActive, which features instant inflation and deflation to minimize the drawbacks of vessel occlusion.
Other companies developing embolic protection devices for use in cardiology and radiology include Scion Cardiovascular (Miami, Florida), MedNova (Horsham, West Sussex, United Kingdom), Cordis/ Angioguard, Guidant, Metamorphic Surgical Devices (Pittsburgh, Pennsylvania), Intratherapeutics (St. Paul, Minnesota), ArteriA (San Francisco, California), and Microvena (White Bear Lake, Minnesota). There may also be a role for thrombus removal devices such as the Possis (Minneapolis, Minnesota) Angiojet in conjunction with protection devices to cut down on the embolic load that the capture device must accommodate.