Introduction

Balloon angioplasty has given way to stenting as the primary modality of percutaneous coronary intervention (PCI). However, because the amount of atherosclerotic plaque in the artery may influence outcomes, physical removal of the plaque from inside the artery, called atherectomy (athero, “plaque”; ectomy, “cut”), was thought to improve the results of PCI. Although this promise was not fulfilled, two devices developed for this purpose remain in current practice: the high-speed rotational ablation catheter (Rotablator) and the directional atherectomy catheter (DCA).

None of the devices directed at plaque modification and removal can clear thrombus very well. Thus, additional non-balloon devices include thrombus aspiration catheters designed to treat arteries with significant amounts of thrombus complicating PCI and/or acute myocardial infarction (MI).

This chapter will focus on interventional devices that are commonly used as adjunctive therapy to balloon angioplasty and stenting in specific clinical scenarios. Specifically, this chapter will review the indications and techniques involved in performing rotational atherectomy, thrombectomy, and cutting balloon atherectomy and will describe embolic protection devices.

Rotational Atherectomy

The primary purpose of rotational atherectomy (RA) is to remove calcific atherosclerotic plaque (i.e., debulk) from vessels prior to stenting. The physical principle underlying RA is that of differential cutting, that is, the ability to selectively ablate or remove one material (i.e., plaque, calcium, etc.) while sparing and maintaining the integrity of a second material (i.e., normal elastic tissue) based on differences in substrate composition. As data comparing RA to balloon angioplasty demonstrate no consistent benefit of RA with regard to restenosis and/or target vessel revascularization (TVR) in the treatment of either de novo coronary disease or in-stent restenosis, the use of RA has diminished greatly since its introduction in the late 1980s and has decreased even further in today’s era of drug-eluting stent use.

LV, left ventricular; LVEF, left ventricular ejection fraction; PCI, percutaneous coronary intervention.

Equipment

The Rotablator Rotational Atherectomy System (Boston Scientific Corporation, Natick, MA) is the only commercially available RA system (Figs. 6-1 and 6-2). The system consists of a nickel-plated brass elliptical burr (available in sizes of 1.25–2.5 mm in diameter) that is coated on its leading edge with diamonds that are 20 to 30 microns in diameter. The burr is attached to a long, flexible driveshaft that is inserted through a guide catheter (6–10 F; see Table 6-2) over a 0.009-inch stainless steel guidewire (i.e., RotaWire). The RotaWire is available in both extra-support and floppy grades of stiffness. Whereas the floppy RotaWire is used in the majority of cases, the extra-support version may assist in advancing the device to very distal lesions. Finally, the Rotablator driveshaft itself is contained in a 4.3 F Teflon sheath and is connected to a turbine driven by compressed nitrogen gas. A continuous infusion of pressurized emulsifier solution (i.e., Rotaglide) with saline is infused through the drive shaft to aid lubrication and heat dissipation.

Figure 6-1 A, Rotablator Rotational Atherectomy System. B, Diagram of the rotational atherectomy burr.

(Courtesy of Boston Scientific Corp., Natick, MA.)

Figure 6-2 Rotablator advancer unit with removable catheter and burr attachment. (1) Brake defeat knob, (2) Air pressure close, (3) WireClip, (4) Rotablator wire, (5) Burr position control knob, (6) Fiberoptic tachometer, (7) Pressurized saline infusion port with lubricant that can be independently advanced and steered. CPC, catheter protector connection. The guidewire comes with a 0.017-mm (maximum) spring tip (0.43 mm inch diameter), facilitating negotiation of the wire through the vasculature.

(Courtesy of Boston Scientific Corp., Natick, MA.)

^{Table 6-2} Recommended Guide Catheter Sizes for Use With the Coronary Rotablator

^* For a given size of catheter, the inside diameter varies from manufacturer to manufacturer. French sizes assume thin-wall (high-volume flow) catheters with side holes.

Technique and Technical Tips

RA technique is aimed at plaque debulking to facilitate stent delivery while at the same time minimizing slow reflow/no reflow (resulting from large particulates) and avoiding significant arterial wall damage (e.g., perforations).

The initial clinical decision before beginning RA is to determine the optimal burr-to-vessel ratio. While larger burrs (i.e., > 0.85 burr-to-artery ratio) will result in more aggressive debulking, their use may also be associated with a higher complication rate. In general, a good practice is to first use a small diameter burr (1.25–1.5 mm) to create a pilot channel, and then gradually work up to a maximum burr diameter that is no larger than 70% to 80% of the normal arterial luminal reference segment diameter. For the sole purpose of device delivery (e.g., balloons and/or stents), however, RA with smaller burrs is usually sufficient.

Crossing of the lesion can be performed either with the RotaWire or with a standard 0.014-inch guidewire that can subsequently be exchanged for a RotaWire using either a tracking catheter or an over-the-wire balloon system. Although the RotaWire size (0.009-inch) often makes crossing lesions challenging, in cases where exceptionally severe lesions preclude the passage of either a tracking catheter or over-the-wire balloon catheter, direct wiring with the RotaWire may in fact be necessary. The infusion port on the drive shaft is connected to a pressurized bag of saline and lubricant mixture (i.e., Rotaglide—egg yolk/olive oil/EDTA mixture). A combination of verapamil (10 mg/L), nitroglycerin (4 mg/L), and heparin (2000 U/L) can also be added to the saline flush in order to minimize vessel spasm during RA. After loading onto the RotaWire, the burr’s speed is tested (i.e., platforming) prior to introduction into the guide catheter. The burr speed during platforming should range from 160,000 to 180,000 rpm, depending on the burr size (Table 6-3). Following successful platforming, the burr is advanced through the guide catheter and is positioned immediately proximal to the lesion. Advancement of the burr through the guide catheter around the aortic arch often requires the operator tasked with securing the back end of the RotaWire to provide additional back tension to both facilitate burr advancement and limit acquired tension. Although many operators will transiently activate the system inside the guide to further alleviate acquired tension within the system, activating the system in the vessel proximal to the lesion accomplishes the same goal of preventing the burr from “leaping forward” during the initial RA pass. Direct intracoronary administration of vasodilators prior to system activation can be performed at this time to combat coronary spasm potentially instigated by RA.

After the burr is positioned and transiently activated proximal to the lesion, the system is activated and the burr is advanced gently and slowly in a “pecking motion” (i.e., gentle forward and backward motions of the advancer so that the burr effectively “pecks” at the lesion) using the advancer integrated into the drive shaft. Burr decelerations signal obstruction to burr motion and should be minimized (i.e., less than 5000 rpm decelerations), as these deceleration speeds are associated with increased complications. In addition, burr activation runs should not exceed 30 seconds per pass, as prolonged RA sessions may be associated with increased ischemia and precipitation of slow reflow or no reflow. At the end of the initial RA pass, the burr is positioned in its starting position proximal to the lesion before the system is deactivated. The system should not be deactivated while the burr is contained within the lesion. Intracoronary nitroglycerin and/or nitroprusside may be administered at this time to help counteract any potential slow reflow in the distal vessel created by embolization of microparticles. Several burr passes are performed before the burr is removed and decisions are made to pursue more debulking with larger burr sizes.

Of note, in particularly severely narrowed lesions with heavy calcium, the RotaWire may retract proximally during burr advancement. By ensuring coaxial guide catheter alignment and applying gentle forward pressure on the guide catheter, distal wire position can be maintained. Finally, if excessive decelerations (i.e., > 5000 rpm decrease) repeatedly occur during RA, it is recommended to downsize to a smaller burr. Figures 6-3 and 6-4 are case examples demonstrating the use of RA in various clinical settings.

Figure 6-3 Case example using rotational atherectomy in the treatment of fibrocalcific disease. A, Baseline fluoroscopy demonstrating severe calcification (arrow) in the mid LAD. B, Baseline angiography demonstrating a severe, calcific plaque in the mid LAD. C, Post-RA angiography using a 1.5-mm burr. D, Post-PTCA angiography. LAD, left anterior descending; PTCA, percutaneous transluminal coronary angioplasty; RA, rotational atherectomy.

Figure 6-4 Case example using rotational atherectomy in the treatment of ISR. A, Baseline angiography demonstrating severe ISR (arrow) in the mid LAD stent. B, RA performed with a 1.5 mm burr. C, Post-RA angiography. D, Final angiography following PTCA with both a cutting balloon and noncompliant balloon. ISR, in-stent restenosis; LAD, left anterior descending; PTCA, percutaneous transluminal coronary angioplasty; RA, rotational atherectomy.

Finally, a temporary pacing lead is recommended by the manufacturer during the treatment of right coronary or dominant circumflex arteries to resolve electrical aberrations that can occur during RA. In addition, instructing the patient to cough during episodes of RA-induced conduction block or arrhythmia often overcomes the hypotension associated with such electrical disturbances. In some catheterization laboratories, patients are actually instructed to practice coughing prior to RA burr activation in order to prepare them should electrical abnormalities arise during performance of RA.

No Reflow or Slow Reflow After Rotablator Ablation

No reflow or slow reflow is the occurrence of no blood flow (no reflow) or blood flow reduced by one angiographic thrombolysis in myocardial infarction (TIMI) study flow grade (slow reflow) in the treated artery despite the fact that the treated segment is patent. No reflow or slow reflow is believed to occur because of the transient increase in blood viscosity due to the presence of microparticles or vasospasm at the level of the distal microvasculature. No reflow or slow reflow has been observed in 6% to 7% of patients undergoing PTCA (see Fig. 6-2). No reflow and slow reflow can be minimized by the following actions:

No slow or slow reflow generally resolves within a short period of time (< 15 min) with or without the use of nitroglycerin. Intracoronary verapamil (200 mcg) or nitroprusside (50–100 mcg) has been reported to improve no slow or slow reflow.

When performed in a controlled setting by an experienced operator, RA offers a safe and effective means of debulking plaque and preparing lesions for stent implantation. Additional technical tips on performing safe and successful RA are listed in Table 6-4.

^{Table 6-4} Technical Notes and Tips on Performing Rotational Atherectomy

Clinical Outcomes

Although prospective and retrospective studies have demonstrated the safety and efficacy of rotational atherectomy in treating complex coronary lesions with regard to immediate procedural success and postprocedure MLD when compared to either balloon angioplasty or balloon angioplasty followed by stenting, the long-term data supporting the use of RA to reduce restenosis or TVR for treatment of both de novo coronary lesions (including chronic total occlusions) and in-stent restenosis remain less conclusive (Table 6-5).

Mechanical Thrombectomy

The prevalence of visible thrombus in acute coronary syndrome (ACS) is dependent on multiple factors, including clinical state (75%–90% prevalence in patients with unstable angina or non-ST-segment elevation myocardial infarction [NSTEMI]; close to 100% prevalence in patients with ST-segment elevation myocardial infarction [STEMI]), type and duration of anticoagulant and antiplatelet therapy, and anatomic features (e.g., tortuous vessel segment, recent instrumentation, bifurcation, etc.). In addition, the presence of thrombosis is associated with increased rates of death, MI, and need for urgent revascularization.

The most serious complication of intracoronary thrombus is distal embolization resulting in microvascular obstruction often manifesting as slow reflow or no reflow. Despite patent epicardial coronary arteries, microvascular obstruction may contribute to persistent chest pain, ST-segment abnormalities, and compromised TIMI flow. Distal thromboembolization may be induced by forceful coronary injections, passage of intracoronary devices, and the initial balloon angioplasty and/or stenting. In addition, intracoronary thrombus may contribute to underestimation of vessel and stent sizing, increasing the subsequent risk of stent malapposition, in-stent restenosis, or stent thrombosis.

Indications

Mechanical thrombectomy is indicated when thrombus is present in a coronary artery of sufficient diameter to safely accommodate a thrombectomy device. Accurate detection and recognition of intracoronary thrombus, however, is fundamental to the performance of mechanical thrombectomy. Fiberoptic angioscopy is the “gold standard” for detection of intracoronary thrombus, as it is the only modality that can reliably distinguish between red, fibrin-rich and gray/white, platelet-rich thrombus. However, most catheterization laboratories do not have angioscopy. Intracoronary thrombus is thus identified with increasing sensitivity using standard coronary angiography, intravascular ultrasound (IVUS), or optical coherence tomography (OCT).

Angiographically, intracoronary thrombus is recognized as a filling defect surrounded on three sides by contrast visible in multiple projections in the absence of calcification, with or without persistent contrast staining (Fig. 6-5). Other angiographic features of thrombus include reduced contrast density and/or haziness. The overall sensitivity and specificity of detecting thrombus by angiography when compared to angioscopy is reported as 26% and 92%, respectively.

Figure 6-5 Angiographic appearance of intracoronary thrombus. A, Contrast staining noted in distal RCA suggestive of intracoronary thrombus. B, Complete occlusion of flow distal to the intracoronary thrombus. RCA, right coronary artery.

By angiography alone, however, intracoronary thrombus may be difficult to distinguish from irregular filling defects caused by protruding plaques or recently ruptured plaques. In these clinical situations, IVUS may better define angiographically ambiguous lesions and further guide appropriate therapy.

By IVUS and OCT (with higher resolution), coronary thrombus is recognized as a protruding mass of low echogenicity and a globular or layered appearance that may or may not be visibly attached to the vessel wall. Fresh thrombus may in fact be echolucent on IVUS and indistinguishable from fibrofatty plaque or a plaque with a necrotic lipid core. In contrast, organized thrombus is more echogenic and may cast an acoustic shadow similar to that seen in fibrous plaque if the thrombus is rich in collagen.

Mechanical Thrombectomy Systems

Mechanical thrombectomy devices that are currently available are classified into two primary mechanisms: (1) aspiration, and (2) physical disruption with extraction.

Aspiration Thrombectomy

Aspiration thrombectomy devices are dual lumen tubes (Fig. 6-6) that are passed across the target lesion over a standard 0.014-inch guidewire. The smaller lumen houses the guidewire using a rapid exchange monorail system while the larger, aspiration lumen connects the distal aperture(s) to a proximal port that is attached to a large (30–50 mL) lockable syringe.

Figure 6-6 Medtronic Export XT Aspiration Catheter.

(Courtesy of Medtronic, Inc., Minneapolis, MN.)

The most commonly used aspiration thrombectomy catheters used today are the Pronto V3 Extraction Catheter (Vascular Solutions, Inc., Minneapolis, MN), the Export XT Aspiration Catheter (Medtronic, Inc., Minneapolis, MN), and the Extract Catheter (Volcano Therapeutics, Rancho Mirage, CA), all of which are available in 6 F and 7 F sizes.

Technique and Technical Tips

Mechanical aspiration (i.e., suction using the lockable syringe attached to the proximal catheter port) should be performed while crossing the target thrombus in an antegrade fashion and continued during withdrawal of the catheter into the guide catheter and subsequently out of the body. In addition, several passes can be made across the thrombus before removal of the system from the body, as long as blood (and thrombus) is actively collecting into the lockable syringe. Continuous aspiration in this fashion helps to avoid withdrawing thrombus from the distal vessel and then prematurely releasing it proximally. Following removal of the aspiration catheter from the guide catheter, sufficient “back-bleeding” should be performed to ensure that the guide catheter and Y connector are clear of thrombus.

Aspiration thrombectomy catheters are appealing because of their simplicity and ease of use. Virtually no preparation of the catheter is necessary (short of flushing the aspiration lumen with saline), and thus there is no delay in achieving rapid reperfusion during primary PCI. The technique, however, is limited by catheter deliverability (especially in tortuous, small, or calcified vessels), trackability, and pushability. In addition, the maximum thrombus extraction rate is limited to the minimum diameter of the extraction lumen. Although extraction of blood and thrombus may be up to three times more effective using the larger 7 F thrombectomy catheters, these benefits are traded for the increased risk of difficult delivery (i.e., larger profile, stiffer catheter), restriction of use in only larger epicardial vessels, and increased risk of vessel injury (e.g., dissection, perforation, etc.). Figure 6-7 is a case example demonstrating the utility of aspiration thrombectomy.

Figure 6-7 Case example using mechanical thrombectomy. A, Heavy thrombus burden in the left main coronary artery (arrow). B, Embolization of thrombus to the mid LAD occluding distal flow (arrow). C, Aspiration thrombectomy (arrow). D, Restoration of flow to the distal LAD (arrow). LAD, left anterior descending.

Clinical Data

Early trials failed to demonstrate that the adjunctive use of aspiration thrombectomy improved clinical outcomes. However, recently, the TAPAS (Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction Study) trial showed benefit of thrombus aspiration in patients presenting with STEMI. TAPAS was a large (n = 1071 patients), randomized, controlled trial comparing manual thrombus aspiration to conventional PCI in STEMI patients. Adjunctive use of manual thrombus aspiration resulted in more frequent complete ST-segment resolution, lower incidence of suboptimal myocardial blush scores (e.g., 0 or 1), and lower rates of both death and major adverse cardiac events at 30 days. At the 1-year follow-up, STEMI patients treated with adjunctive aspiration thrombectomy demonstrated significantly lower incidences of both cardiac death and nonfatal MI. Based in large part on the results of the TAPAS trial, initial aspiration thrombectomy is now commonly performed during primary PCI in patients presenting with STEMI.

Rheolytic Thrombectomy

The AngioJet Rheolytic Thrombectomy System (MEDRAD, Inc., Warrendale, PA) aspirates thrombus by creating high-pressure water jets directed backward into the aspiration catheter, thereby producing a strong suction (approximately 600 mm Hg) at the space near the catheter tip (i.e., Venturi effect). Thrombotic material is drawn into the catheter shaft where the powerful water jets macerate and extract it. Cross-Stream technology enhances thrombus removal by allowing a small amount of saline to wash into the coronary artery prior to maceration and extraction (Fig. 6-8). The system can be used to aspirate and remove intracoronary thrombus in the setting of acute MI, stent thrombosis, saphenous vein graft thrombosis, and thrombosed peripheral vessels or grafts (Fig. 6-9).

Figure 6-8 AngioJet Rheolytic Thrombectomy System Cross-Stream technology.

(From MEDRAD, Inc.,Warrendale, PA.)

Figure 6-9 Example of AngioJet thrombectomy in a 37-year-old man 8 hours after the onset of chest pain for acute inferior wall myocardial infarction. A, Right coronary artery with thrombus in proximal portion. B, Angioplasty guidewire traversing lesion with large amount of clot in the proximal portion of the artery. C, Right coronary artery after 4 F AngioJet. A temporary pacemaker was also inserted. D, The thrombus was almost completely extracted from the vessel. The final angiogram demonstrates residual distal embolic occlusions but good patency, with TIMI grade 3 flow. TIMI, thrombolysis in myocardial infarction.

The AngioJet system is comprised of three components: driver, pump set, and replaceable catheters. The driver is a pump system that generates approximately 10,000 psi of water pressure and monitors the aspiration and system flow during the procedure to maximize patient safety. The pump set drives saline into the aspiration catheter and helps to maintain a balance between the fluid both leaving and entering the catheter so as to maintain a constant pressure within the artery. The AngioJet catheter is a 135- to 140-cm long, 4 F to 6 F catheter that tapers from the distal 5 cm to the tip. The AngioJet Spiroflex, SpiroflexVG, and XMI catheters are indicated for use in both native coronary arteries and saphenous vein grafts.

Technique and Technical Tips

The AngioJet catheter is first prepped and primed outside of the body while submerged in saline. The prepared catheter is positioned proximal to the target thrombus, the system is activated, and the catheter is slowly advanced through the thrombotic region at a rate of approximately 0.5 mm/sec and then pulled back slowly to the proximal starting position at the same rate. Multiple passes are typically performed until no further improvement by angiography is noted, although total device use should not exceed 10 minutes as prolonged sessions of rheolytic thrombectomy may precipitate the development of hemolytic anemia.

Significant bradyarrhythmias can occur during the performance of rheolytic thrombectomy and are thought to be mediated by hemolysis-induced adenosine release that occurs during the aspiration process. For this reason, placement of a temporary pacing wire is recommended prior to performing rheolytic thrombectomy, especially when thrombectomy is performed in either the right coronary artery or a dominant left circumflex coronary artery.

Although rheolytic thrombectomy effectively removes intracoronary thrombus, performing the procedure is often limited by the time required for setting up and priming the device and placement of a temporary pacing wire (if required). Either of these processes may potentially lead to significant delays in establishing rapid vessel reperfusion, which may subsequently negatively impact long-term prognosis.

Clinical Data

Clinical trials investigating the safety and efficacy of adjunctive rheolytic thrombectomy during primary PCI for STEMI have been largely favorable, though not definitive. One single-center study of 100 patients with STEMI randomized to primary PCI with or without pretreatment with rheolytic thrombectomy using the AngioJet system demonstrated that pretreatment with the AngioJet system resulted in improved ST-segment resolution, smaller infarct size, and no increase in adverse events. These findings, however, were not confirmed in the larger AIMI (AngioJet Rheolytic Thrombectomy in Patients Undergoing Primary Angioplasty for Acute Myocardial Infarction) trial. The ongoing JETSTENT (AngioJet Thrombectomy and Stenting for the Treatment of Acute Myocardial Infarction) trial has been designed to address the potential limitations of the AIMI trial. Although current evidence does not support the routine use of the AngioJet system in primary PCI, it can be argued that, with regard to the efficacy of adjunctive use of rheolytic thrombectomy in primary PCI, the door is not yet shut.

Cutting Balloons

The Flextome Cutting Balloon (Boston Scientific Corporation, Natick, MA) is a special balloon catheter that was designed to reduce trauma to the vessel wall and on plaque by making small incisions into the plaque. Doing so theoretically may limit the splitting and tearing of the plaque and vessel wall as commonly occurs during standard balloon angioplasty. The Flextome Cutting Balloon has three or four 0.1- to 0.4-mm thick stainless steel blades (i.e., atherotomes) that are fixed to the surface of the balloon (Fig. 6-10). The blades are safety embedded within the folds of the undeployed balloon to allow for safe delivery to the lesion site. Upon balloon inflation, the blades are purported to make microscopic incisions in the plaque and do not cut through the plaque completely. The force of inflation is concentrated on the incising element, thereby allowing for predictable cutting of the coronary plaque.

Figure 6-10 A, Flextome Cutting Balloon in its inflated state. Microtomes (arrows) can be seen extending outward from the balloon. (Courtesy of Boston Scientific Corp., Natick, MA.) B, Flextome Cutting Balloon (above) in the deflated state and (below) in the inflated state. The microtomes can be seen extending outward from the balloon.

Embolic Protection Devices

Approximately one half of saphenous vein grafts (SVGs) either occlude or develop severe occlusive disease within 10 years of coronary artery bypass graft surgery. In the vast majority of such cases, PCI of either the graft or the native coronary artery is pursued because of the inherent risks associated with repeat surgery. SVG interventions, however, are laden with an array of technical challenges, most notably of which is an increased risk of the no-reflow phenomenon due to distal embolization of atherosclerotic debris. Although administration of vasodilators (i.e., nitroglycerin and/or nitroprusside) assists in restoring distal flow in these situations, there is little to no evidence to suggest that restoration of flow by this mechanism actually improves long-term clinical outcomes. It therefore stands to reason that either preventing or minimizing distal embolization can improve both procedural and clinical outcomes in patients undergoing SVG interventions.

Embolic Protection Systems

A number of embolic protection systems have been developed throughout the years, each employing one of two primary mechanisms to capturing embolic material: balloon occlusion (either proximal to distal to the lesion) to trap particles which are subsequently aspirated, or deployment of a filter device distal to the lesion to trap antegrade traveling particulate matter. Table 6-6 outlines the major advantages and disadvantages of each system type (i.e., balloon occlusion vs. filter).

^{Table 6-6} Advantages and Disadvantages of Embolic Protection Device Systems

	Filter	Balloon Occlusion
Perfusion	Permits antegrade blood flow	Prevents antegrade blood flow during use precipitating ischemia if no collateral flow is present
Emboli	Traps emboli > filter pore size (e.g., 100 μm)	All emboli and debris remain stagnant, allowing for aspiration prior to restoration of antegrade blood flow
Vasoactive substances & cytokines	Freely flows through filter	Limited ability to reach the distal bed due to lack of antegrade blood flow
Technical considerations in crossing lesions	Bulky; risk of distal embolization prior to device deployment	Lower profile; ability to be deployed prior to crossing the lesion, minimizing distal embolization
Retrieval considerations	Full of debris; may be difficult to collapse and fully retrieve filter; may become ensnared in proximal stent	Slow balloon deflation may prolong ischemic time
Embolization during device placement	Possible	Possible (unlikely with proximal balloon occlusion devices, however)
Visualization of distal vessel	Adequate	Compromised during balloon inflation

Balloon Occlusion

The best known EPD utilizing proximal balloon occlusion is the Proxis Embolic Protection System (St. Jude Medical, Inc., St. Paul, MN). The device is housed in a 3.6 F infusion catheter that is advanced through a 7 F guide catheter over a standard guidewire and is positioned proximal to the lesion. The balloon is inflated, which occludes antegrade flow, creating a stagnant column of blood that is aspirated after the intervention before coronary blood flow is restored upon balloon deflation (Fig. 6-11). The Proxis system is designed for use in vessels 3.0 to 5.0 mm in diameter. Use in larger diameter vessels is not recommended, as the occlusion balloon may not allow for complete vessel occlusion. Similarly, use of the device in smaller diameter vessels is not recommended because of the risk of vessel trauma during inflation of the occlusion balloon.

Figure 6-11 Proxis Embolic Protection System.

(Courtesy of St. Jude Medical, Inc., St. Paul, MN.)

The main benefit of the Proxis system is its ability to protect against distal embolization even before the lesion is crossed with a guidewire. Although it can be used in any SVG where there is an adequate “landing zone” proximal to the lesion, its use is especially beneficial in settings where the absence of an adequate “distal landing zone” precludes the use of a distal filter device. The primary downside in using the Proxis system is that antegrade flow down the vessel is temporarily occluded, predisposing to myocardial ischemia and limiting the ability to achieve adequate contrast opacification of the distal vessel.

In contrast to the Proxis system, which utilizes proximal balloon occlusion to disrupt antegrade blood flow, the GuardWire Temporary Occlusion and Aspiration System (Medtronic, Inc., Minneapolis, MN) balloon occludes the vessel several centimeters distal to the lesion. The debris that is released during PCI is suspended in a stagnant column of blood that is subsequently aspirated prior to deflation of the balloon occluder. Similar to the filter-based EPDs, a sufficient distal “landing zone” must be present to deploy the device. Like the Proxis system, however, the GuardWire system is limited both by the need to disrupt antegrade flow, thereby predisposing to myocardial ischemia, and minimizing contrast opacification of the distal vascular bed.

Clinical Data

The PROXIMAL (Proximal Protection During Saphenous Vein Graft Intervention Using the Proxis Embolic Protection System) trial compared efficacy of the Proxis system to distal EPDs in preventing clinical events during SVG interventions. The primary end point was a composite of death, MI, emergent coronary artery bypass graft (CABG), and TVR (i.e., Major Adverse Cardiac Event) at 30 days. The study demonstrated that for MACE, the Proxis system was statistically equivalent to distal EPDs (7.1% vs. 11.7%; P = 0.10 for superiority; P = 0.001 for noninferiority).

The SAFER (Saphenous Vein Graft Angioplasty Free of Emboli Randomized) trial compared the GuardWire system to conventional SVG PCI without the use of distal embolic protection. The primary end point studied was a composite of death, MI, emergency CABG, or TVR (i.e., MACE) at 30 days. Use of the GuardWire system resulted in a significant reduction in the primary end point (9.6% vs. 16.5%; P = 0.004), equating to a 42% relative risk reduction in MACE.

Distal Embolic Protection

The Filterwire EZ Embolic Protection System (Boston Scientific Corporation, Natick, MA) is comprised of a uniform, 110-micron-pore basket filter fixed to a guidewire that, when released, expands up to 5.5 mm (Fig. 6-12). Prior to deployment, the entire Filterwire EZ system is advanced across the lesion, positioned in the distal vessel, and subsequently deployed. At the conclusion of the procedure, the filter is collapsed into a proprietary retrieval catheter, trapping the particulate matter, and is removed from the body. The primary advantage of the Filterwire EZ system over the balloon occlusion-based systems is that it allows for antegrade blood flow throughout the procedure while still capturing larger embolic particles. Although the Filterwire EZ system may theoretically not capture small particulate matter because of limitations in filter pore size, studies comparing it to balloon occlusion systems have demonstrated similar debris size distribution and equivalent clinical outcomes. The primary limitation of the Filterwire EZ system is the need for an adequate distal “landing zone” to safely deploy the device (25–30 mm from the distal edge of the lesion).

Figure 6-12 Boston Scientific Filterwire EZ Embolic Protection System. A, The filter is deployed distal to the lesion. B, Embolic material is captured during intervention.

(Courtesy of Boston Scientific Corp., Natick, MA.)

The SpiderFX Embolic Protection Device (ev3, Inc., Plymouth, MN) is another distal protection device that can be employed during SVG interventions (Fig. 6-13). The device comes in a variety of filter sizes (ranging from 3.0 to 7.0 mm), is heparin coated, and offers the advantage of delivery over any standard 0.014-inch interventional guidewire (unlike the Filterwire EZ, which is integrated onto the guidewire itself). The filter is delivered via a 3.2 F catheter employing a rapid exchange (SpideRX) system and, following intervention, is retrieved using a separate 4.2 F or 4.9 F SpideRX retrieval catheter.

Figure 6-13 A, The SpiderFX Embolic Protection Device. (Courtesy of ev3, Inc., Plymouth, MN.) B, Other Distal protection devices. (1) The guard wire, PercuSurge balloon occlusion, and export catheter. (2) AngioGuard in the undeployed state. (3) AngioGuard in the deployed state acting as an umbrella-type filter. (4) An Emboshield filter device.

Clinical Data

The FIRE (Filterwire EX Randomized Evaluation) trial compared the Filterwire EX EPD to the GuardWire system during SVG PCI. The primary end point was a composite of death, MI, and TVR. At 30 days, the primary end point was reached in 9.9% of patients treated with the Filterwire EX EPD versus in 11.6% of patients treated with the GuardWire system (P = 0.53 for superiority; P = 0.0008 for noninferiority). At the 6-month follow-up, however, MACE rates had increased (driven largely by both recurrent MI and TVR) to 19.3% in the Filterwire EX EPD group and 21.9% in the GuardWire system group, indicating the complex disease pattern often present in patients undergoing SVG PCI.

The SPIDER (Saphenous Vein Graft Protection in a Distal Embolic Protection Randomized) trial (not published) compared the SpiderFX EPD to a control group treated with either the Filterwire EZ EPD or GuardWire system during SVG PCI. The primary end point was a composite of death, MI, TVR, or urgent CABG (i.e., MACE). At 30 days, the primary end point was reached in 9.1% of patients treated with the SpiderFX EPD versus 8.4% in the control group (P = 0.59 for superiority; P = 0.012 for noninferiority).

Summary

As the complexity of coronary disease (i.e., heavily calcified lesions, bifurcation lesions, saphenous vein grafts, etc.) increases, the traditional “predilation and stenting” approach used in less complex lesions often cannot be realistically employed. In these situations, alternative interventional devices as an adjunct to traditional stenting often results in improved clinical and angiographic outcomes. Familiarity with these devices their indications, limitations, and overall efficacy is a necessity for effective and safe PCI in contemporary interventional cardiology practice.