Non-Balloon Coronary Interventional Techniques and Devices: Rotational Atherectomy, Thrombectomy, Cutting Balloons, and Embolic Protection Devices

6 Non-Balloon Coronary Interventional Techniques and Devices Rotational Atherectomy, Thrombectomy, Cutting Balloons, and Embolic Protection Devices



Michael S. Kim, Andrew J. Klein, Morton J. Kern



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.



Indications and Contraindications


While RA has been successfully utilized in a variety of clinical scenarios, in the contemporary practice of interventional cardiology, RA is most commonly used to facilitate stent delivery, particularly in lesions that are not easily dilatable because of the proliferation of fibrocalcific plaque. Heavily calcified lesions pose a particular technical challenge during PCI for two primary reasons:



1. The treatment of fibrocalcific plaques with balloon angioplasty often results in incomplete lesion dilation, which subsequently increases the risk of restenosis or acute/subacute stent thrombosis. Aggressive attempts to dilate resistant lesions with either high-pressure inflations or the use of noncompliant balloons carries the risk of vessel wall injury (i.e., dissection or perforation).


2. Non-dilatable lesions often inhibit the passage of balloons and stents, thereby limiting options for definitive revascularization. In these clinical situations, initial plaque debulking with RA may improve initial procedural success by improving arterial compliance, thereby facilitating more uniform and symmetric stent deployment while potentially allowing for increases in postprocedure minimal lumen diameter. Finally, while treating bulky lesions at or near a large branch vessel, preemptive use of RA may help minimize plaque shifting (i.e., the “snow-plowing” phenomenon) and alleviate the need for subsequent side branch intervention.


Although RA may assist in the delivery and deployment of interventional equipment (i.e., balloons and stents), there are specific clinical situations where its use should either be used with great caution or avoided altogether (Table 6-1).


Table 6-1 Indications and Contraindications to Rotational Atherectomy











Indicated High-Risk Contraindicated


• Single-vessel atherosclerotic coronary artery disease with a calcified plaque that can be passed with a guidewire


• Low-risk, multivessel coronary artery disease


• De novo lesion < 25 mm in length

• Severe, diffuse multivessel coronary artery disease


• Unprotected left main PCI


• Patients with compromised LV function (LVEF < 30%)


• De novo lesion > 25 mm in length


• Severely angulated (> 45 degrees) lesions


• Last remaining conduit with compromised LV function


• Angiographic evidence of thrombus

• Occlusions where a guidewire cannot be passed


• Saphenous vein graft PCI


• Angiographic evidence of significant dissection Type C or greater at the treatment site


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.


image

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


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


image

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



































Rotablator Burr Size (mm) Recommended Guide Catheter Internal Diameter (inch) Guide Size (French [F])*
1.25 0.053 6–8
1.50 0.063 6–8
1.75 0.073 6–8
2.00 0.083 7–9
2.15 0.089 7–9
2.25 0.093 7–9
2.50 0.102 9–10

* 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.



Table 6-3 Recommended Rotablator Advancer Turbine Speed

image

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.


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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.


image

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:



1. Advancing the burr slowly


2. Using a stepped burr approach (smaller, then larger) in long or calcified lesions


3. Using a “pecking” motion at the plaque to avoid blocking the arterial lumen


4. Maintaining maximum blood flow by repeated flushing with saline (bolus of 10–30 mL)


5. Using guide catheters with side holes


6. Maintaining the left ventricular filling pressures (and mean arterial pressure) by increasing the patient’s volume status appropriately


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







• A nitrogen compressed-gas cylinder with pressure regulator capable of delivering a minimum 140 L/min at 90–100 psi is required.


• The compressed-gas cylinder valve must be open to supply compressed gas to the console. The regulator should be adjusted so that the pressure does not exceed 100 psi.


• Angulated lesions and branch ostial lesions have a higher incidence of dissection and/or perforation. Downsize initial burrs and stepwise increase burr size to achieve the final result.


• RA can be performed on chronic total occlusions only if the guidewire is confirmed to be in true lumen distally.

Related posts:

  1. Aorto-Ostial and Branch Ostial Lesions and Unprotected Left Main Percutaneous Coronary Interventions
  2. Percutaneous Mitral Commissurotomy and Balloon Aortic Valvuloplasty
  3. High-Risk Percutaneous Coronary Interventions
  4. Peripheral Vascular Intervention

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Jun 5, 2016 | Posted by in CARDIAC SURGERY | Comments Off on Non-Balloon Coronary Interventional Techniques and Devices: Rotational Atherectomy, Thrombectomy, Cutting Balloons, and Embolic Protection Devices

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