Introduction

Peripheral vascular disease (PVD) or peripheral artery disease (PAD) is a clinical manifestation of systemic atherosclerosis that presents with symptoms ranging from claudication to rest pain, progressive ulceration, extensive tissue loss, or gangrene. PVD affects 200 million people worldwide and is associated with significant morbidity and mortality [1]. Treatment for PAD is dictated by the symptoms and severity of disease. Treatments include medical therapy, endovascular interventions, open surgical bypass procedures, or hybrid procedures [2]. Endovascular therapy with percutaneous transluminal angioplasty (PTA) and adjunctive stenting has recently become a primary treatment for lower extremity PVD [3]. However, there has been concern regarding the long-term patency of endovascular interventions and the increased need for reinterventions. PTA and stent placement, which is based on mechanical plaque disruption and displacement within the arterial wall, has not been able to become default therapy on its own because of inconsistencies from lesion to lesion, lack of significant durability in longer lesions, and reduced vessel compliance in the presence of heavy calcification, which results in suboptimal angioplasty and/or significant differential expansion that potentially may lead to significant dissections. Without exception, placement of intravascular prostheses—bare-metal, covered, or drug-eluting stents—has proven better than PTA alone in the lower extremity. The principal limitation with stenting is the process of in-stent restenosis. Moreover, stent placement is not advisable in certain anatomical locations such as the distal foot arterial system, and flexion points such as the hip and knee joints could provoke stent deformation or fracture, leading to acute arterial occlusion.

Advancements in technology have provided vascular surgeons with more options for endovascular revascularization. Atherectomy refers to the endovascular obliteration of atheromatous plaque by cutting, shearing, drilling, or pulverization by sanding, resulting in luminal gain (debulking) and relieving the need for a scaffold or stent placement to obtain long-lasting patency. The debulking effects of its mechanism of action may theoretically allow for a more uniform angioplasty with minimal vessel barotrauma and improved luminal gain, thereby decreasing the risk of plaque recoil and dissection and allowing effective administration of antiproliferative drug to prevent negative remodeling and neointimal hyperplasia. Atherectomy has emerged as a novel endovascular technology for atheroma removal, with both the benefits of surgical endarterectomy and a minimally invasive modality.

Classification of Atherectomy Devices

Basic Steps of Endovascular Interventions

Endovascular interventions such as atherectomy are performed with patients under local anesthesia and moderate conscious sedation, using fixed imaging in hybrid operating rooms or interventional radiology suites or a C-arm in an office-based laboratory (OBL). All interventions are performed after systemic heparinization (100 units/kg).

Most commonly, interventions are performed through contralateral retrograde femoral artery access, whereas ipsilateral antegrade common femoral and left transbrachial access can be used selectively.

A catheter is then used to steer guidewires up to the aortic bifurcation and over to the common iliac artery. A baseline angiogram is then completed in order to clearly define the extent and severity of the target lesion(s), identify the location of the distal vessel reconstitution, and identify important collaterals.

Before a treatment modality is chosen, a guidewire must be used to traverse the target lesion. This most often can be done intraluminally, but in circumstances such as chronic total occlusions, special techniques such as subintimal crossing can be performed.

Once the target lesion has been traversed and re-entry is confirmed, a decision is then made to use either balloon angioplasty or atherectomy as the primary initial treatment. The contraindications to atherectomy are reviewed on a case-by-case basis; these include subintimal dissection, evidence of perforation of the vessel, size of the vessel outside the instructions for use (IFU) of the particular device, and the patient’s comorbidities and condition.

Post-intervention adjunct balloon angioplasty, drug-coated balloon (DCB) angioplasty, or bailout stenting is performed on case-by-case basis.

Completion angiography is performed to assess the technical success of the intervention and to rule out, diagnose, and treat embolization and its complications.

Antiplatelet therapy is instituted to prevent restenosis. Surveillance of the treated segment is performed; clinical follow-ups use noninvasive arterial studies.

Directional Atherectomy

Directional atherectomy (DA) refers to active removal of plaque in a controlled and directional fashion. The atheromatous plaque is removed by guiding the cutting device on a catheter directly to the plaque. By rotating the catheter, the cutter is placed in the preferred direction to accomplish targeted plaque removal, and the excised plaque is packed into a nosecone.

The SilverHawk™, TurboHawk™, and the latest HawkOne™ directional atherectomy plaque excision systems (Medtronic, Minneapolis, MN, USA) have received approval from the US Food and Drug Administration (FDA). These are side-cutting cutting devices. The catheter is equipped with a rotating blade within a tubular cover that ends at a nose-cone (collection area). The rotating blade is powered by a motor.

Pantheris Lumivascular™ atherectomy device (Avinger Inc., Redwood City, CA, USA), a new directional atherectomy device, received FDA clearance in 2016. The Pantheris over-the-wire catheter is equipped with optical coherence tomography technology to enhance directional atherectomy efficacy and safety by allowing targeted removal of eccentric plaque (characteristic of directional atherectomy and minimizing the risk of trauma to non-diseased vessel wall as the cutter is placed under ultrasound guidance).

Case

Endovascular intervention is being performed in a patient with lifestyle-limiting claudication despite medical therapy. The patient is under local anesthesia and moderate conscious sedation. Contralateral (left) femoral artery retrograde access was obtained.

Omni flush catheter is then used to steer the guidewire up to the aortic bifurcation and over to the right common iliac artery.

A baseline angiogram reveals complete total occlusion (CTO) of the right superior femoral artery (SFA); the right above-the-knee popliteal artery (P1) reconstitutes from collateral arising from right profunda femoris artery (Fig. 27.1a, b).

Systemic heparinization (100 units/kg) is performed. A 7 Fr guide sheath is advanced to the right external iliac artery for support—the size most commonly used for the larger device (HawkOne L). Meanwhile, a 6 Fr sheath is selected for tibial atherectomy and the smaller-diameter popliteal artery (HawkOne M & S).

The CTO is traversed and reentry into the true lumen is confirmed. Patency of the runoff in the right anterior tibial artery, posterior tibial artery, and peroneal artery is confirmed (Fig. 27.1c).

A distal embolic protection device (Spider AFX® 6 mm) is placed in the distal right popliteal artery to prevent embolization (Fig. 27.1f). The Spider AFX® filter device has been FDA-indicated for use with the SilverHawk in calcified lesions, and I routinely use it in all directional atherectomy cases.

A HawkOne L device is used for atherectomy of this right SFA. The hinge of the catheter deflects the rotating blade away from the center of the vessel toward the target plaque. With the torque on the catheter, the cutting blade is directed towards the plaque. The conical cutter engages plaque and spins at 8000–12,000 rpm to perform longitudinal excision of the plaque.

The cutter is advanced gently in one place for the distance of the nosecone. Then it is halted and the plunger is advanced, to pack the excised atheroma into the nosecone. Atheroma is excised longitudinally and is collected and stored in the nosecone, which is located distal to the cutter window.

The same procedure of atherectomy is repeated in at least four planes. To reduce embolization, it is crucial to advance the cutter very slowly and gently.

The device is exteriorized to facilitate emptying of the nosecone before it is full (Fig. 27.2a), in order to avoid inadvertent embolization of the excised plaque.

Post-intervention angiogram is obtained, which reveals adequate luminal gain. I decided to proceed with DCB angioplasty to prevent restenosis.

Completion angiogram reveals no residual stenosis, and no evidence of distal embolization (Fig. 27.1f), so the distal embolic protection device is removed. Inspection of the device shows that an embolic atheroma is present (Fig. 27.2b).

After the procedure, the patient was continued on dual antiplatelet therapy and statin therapy.

Orbital Atherectomy

Orbital atherectomy (OA) consists of high-speed rotational spin of the shaft and the orbital rotation (eccentric) of a specially designed debulking, diamond-coated crown. Atheromatous and calcified plaque is removed by the orbital movement of the crown. The debulking area increases with the increase of the rotational speed of the crown. OA modifies the surface of calcified plaques by preferentially cutting or sanding the atheroma plaque while avoiding the elastic arterial wall. All debris generated is considered to be smaller than a red blood cell, so the embolization risk hypothetically is reduced, though it cannot be excluded.

The only approved OA device is the Diamondback 360^° Peripheral Orbital Atherectomy System (Cardiovascular Systems; St. Paul, MN, USA). It consists of an orbiting eccentric diamond-coated crown, mounted at the end of a shaft, and a saline pump. Three types of crowns are available: A solid micro-crown is recommended for tortuous vessel anatomy, tight bends, and distal below-the-ankle lesions; a solid crown is recommended for calcified lesions and maximum plaque removal in short atherectomy time (additional diamond-coated surface area); the classic crown (the most flexible) is recommended for below-the-knee lesions [7].

Case

In a patient with critical limb ischemia and tissue loss, the baseline angiogram reveals patent inflow and no significant femoropopliteal disease. There is distal stenosis of the posterior tibial artery and multifocal calcified plantar artery stenosis (Fig. 27.3a).

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