Directional Atherectomy With the SilverHawk Plaque Excision
Device in the Treatment of a Proximal Subclavian-Vertebral
Artery

Subclavian artery stenoses can, in patients who have undergone previous left internal mammary artery (LIMA) to left anterior descending (LAD) bypass grafting, lead to coronary-subclavian steal syndrome (CSSS).¹ This occurs when a proximal subclavian lesion, leading to retrograde flow through the LIMA to feed the post-stenotic subclavian, causes symptomatic myocardial ischemia. A noticeable blood pressure gradient between the left and right arms is not uncommon. First described in 1977² and assigned a prevalence in the same year of 0.44%,³ CSSS has increased in incidence as the LIMA has gained popularity as the conduit of choice for coronary artery bypass grafting (CABG).⁴ A study published in 2001 put the incidence of CSSS in patients undergoing non-cardiac surgery at 3.4%.⁵ It can occasionally occur concomitantly with cerebral (traditional) subclavian steal syndrome,⁶ wherein cerebrovascular insufficiency ensues secondary to flow reversal in the vertebral artery. Possible interventions include balloon angioplasty with or without stenting,^7–9 carotid-subclavian bypass surgery,¹⁰ relocation of the LIMA graft,¹¹ or directional atherectomy.¹² We describe our experience with a newly approved device, the SilverHawk plaque excision device, which was used to debulk the subclavian-vertebral bifurcation prior to balloon dilatation. This device allowed us to avoid the risk of plaque shift inherent in balloon dilatation without prior debulking.¹³ An inherent limitation of using stents at bifurcations is the potential for jailing the side branch of the bifurcation.¹⁴ An embolic protection device was deployed in the vertebral to reduce the possibility of distal embolization to the posterior circulation of the brain. Case Report. A 55-year-old woman with known coronary artery disease (CAD) was referred to our institution for evaluation of a left subclavian bruit and angina. Physical examination revealed a 20 mmHg difference in blood pressures between the right and left arms (right higher). Her previous medical history was pertinent for coronary artery bypass grafting of 3 vessels, hypertension and dyslipidemia. An angiogram 2 years prior revealed a widely patent left internal mammary artery grafted to the left anterior descending artery and vein grafts to 2 diagonals that were also patent. The status of the subclavian artery was unknown at the time of the diagnostic catheterization. Given her current presentation, the patient underwent a nuclear perfusion scan which demonstrated ischemia in the anterior wall, and a magnetic resonance angiogram (MRA) of the cervical region demonstrated a high-grade proximal subclavian stenosis. Cardiac catheterization was performed which revealed a high-grade left subclavian stenosis at the bifurcation of the vertebral artery proximal to the origin of the left internal mammary artery (Figure 1). This stenosis was deemed to be the culprit lesion responsible for the patient’s symptoms and the anterior ischemia noted on the nuclear perfusion scan. An intervention was therefore performed on this vessel. An 0.014 Filter Wire Ex^™ distal protection device (Boston Scientific, Natick, Massachusetts) was advanced into the left vertebral artery (Figure 2) through a 7 French shuttle sheath. The SilverHawk plaque excision device (Fox Hollow Technologies, Redwood City, California) was then advanced over this wire. The SilverHawk was advanced along the subclavian artery going into the vertebral, and then along the subclavian, going beyond the narrowing of the vertebral (Figure 3). Three cut and excise passes were made in each branch of the bifurcation (Figure 4). Intravascular ultrasound then confirmed that the subclavian artery lumen was 6 mm. A Savvy^® 5mm x 2 cm balloon (Cordis/J&J, Miami, Florida) was inserted and inflated to 8 atm. This percutaneous transluminal angioplasty (PTA) involved the vertebral artery limb of the bifurcation (Figure 5) and was carried out over the 0.014 Filter Wire. Another guidewire was then inserted into the left subclavian, whereupon an OPTA^™ Pro peripheral balloon 6 mm x 2 cm (Cordis/J&J) was deployed and dilated to 4 atm for 20 seconds over a 0.035 inch wire. Visualization of the bifurcation then showed no evidence of dissection or thrombus formation and excellent resolution of the left subclavian stenosis. The balloon was removed and replaced with a 6 French JR 4.0 catheter where a subclavian-into-aorta pullback was performed; no pressure gradient was noted (Figure 6). No embolic debris was found in the Filter Wire after it was removed from the vertebral artery. One month later, the patient continues to have no evidence of ischemia in the left arm or the heart. Follow-up MRA showed no evidence of proximal subclavian stenosis, a widely patent vertebral artery, and no evidence of vascular shunt in the neck. Discussion. Distal embolization and ischemic stroke is not an uncommon complication during percutaneous interventions for brachiocephalic atherosclerosis.15 The concept of distal protection is one that has been borrowed from saphenous vein graft interventions and carotid artery intervention where it became clear that there was significant embolization of debris during percutaneous intervention that could be mitigated by using some form of distal protection device. Although not considered to be a major issue in the treatment of vertebral stenosis when PTA and stenting are used as the revascularization strategy, the potential embolization of debris following atherectomy with a new device was the reason for the use of the distal protection device in this case report. The EX Filter wire distal protection device was used successfully to protect the posterior circulation in the event of distal embolization while using a new atherectomy catheter in treating a subclavian-vertebral stenosis. Although no debris was noted in the filter, its presence allowed for a sense of security while performing cut and excise passes with the SilverHawk device. Bifurcation lesions are a challenging lesion subset frequently requiring either two stents or kissing balloons for optimum angiographic and long-term outcome in the absence of some form of debulking strategy. Plaque removal without distal embolization, plaque shift or compromising either branch of the bifurcation was feasible with the SilverHawk. This serves as a potential advantage of using this device in the management of bifurcation lesions in both the periphery and coronary tree. The long-term clinical outcome and restenosis rates need to be determined by randomized trials or larger patient registries, which are currently in progress.

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