Coronary Atherectomy and Transradial Access Part I of III: Laser Atherectomy

Question: You have shown cases in the past using atherectomy. Do you think one is better than the other, and is there a preference from a radial approach?

Answer:  Fortunately, we have access to all 3 forms of coronary atherectomy in our lab (laser, rotational, and orbital atherectomy). In addition, all 3 devices can be utilized from a radial approach. I choose my particular device based on the clinical scenario and angiographic characteristics. Starting in this issue, we will present a series of cases illustrating the clinical applications of each device followed by a brief discussion. In Part I, I will discuss laser atherectomy, which will be followed by rotational and orbital atherectomy in upcoming issues. 

Case 1 (Underdeployed stent)

This is a 79-year-old male with a history of hypertension, hyperlipidemia, and polycythemia. He underwent percutaneous coronary intervention (PCI) of the mid left anterior descending coronary artery (LAD) 1 week prior, with placement of a 3.0 x 13 mm Integrity bare-metal stent (Medtronic) x 2. He presented with acute onset of chest pain and ST elevation in the precordial leads. The patient was compliant with his medications. Initial angiography demonstrated occlusion of the stent with significant waste in the mid portion (Figure 1A-B). Initial dilation with a 2.5 mm and then 3.0 mm non-compliant balloon resulted in failure to expand the stent. A 0.9 mm excimer laser coronary atherectomy (ELCA) catheter (Spectranetics) was advanced into the underdeployed segment, but was unable to pass through the lesion. Laser was performed for 1 minute with a puff of contrast (Figure 1C). It was then possible to expand the stent with a 3.0 mm NC Emerge (Boston Scientific) at high pressure, with subsequent post dilation with a 4.0 mm NC Emerge after intravascular ultrasound (IVUS). Final angiography demonstrated adequate stent expansion and TIMI-3 flow. 

Case 2 (Acute myocardial infarction)

A 73-year-old male with no previous cardiac history presented to an outside hospital with intermittent chest pain for about 3 hours prior to presentation. He was found to have ST elevation in the inferior leads and was transferred emergently for revascularization. A radial approach was used and a Judkins right (JR)-4 guide was used to engage the right coronary artery (RCA) (culprit). Three passes were made with the laser, restoring TIMI-3 flow and visualization of the culprit lesion. A 3.5 x 22 mm Integrity stent was placed without embolization or no reflow.

Case 3 (Chronic total occlusion)

A 69-year-old male with history of coronary artery disease status post coronary artery bypass graft surgery (CAD s/p CABG) in May 2015 in Puerto Rico [left internal mammary artery to the LAD (LIMA-LAD), saphenous vein graft to the obtuse marginal (SVG-OM), SVG-RCA] developed angina and underwent a left heart catheterization at another institution, demonstrating an occluded SVG-RCA. After a failed antegrade attempt at crossing the native RCA chronic total occlusion (CTO), he was referred for revascularization. A 6/7 Slender sheath (Terumo) was placed in the right radial along with a 7 French (Fr) Extra Backup (EBU) 3.5 guide (Medtronic). A 7 Fr Amplatz left-right (ALR) 1.2 guide catheter was used to engage the RCA from the femoral approach. The native RCA was 100% occluded in the mid portion, with calcification noted. After an initial antegrade attempt resulted in subintimal wire passage, a CrossBoss catheter (Boston Scientific) was attempted, but could not advance past the CTO. From a retrograde approach, a Sion wire (Asahi Intecc) and Corsair microcatheter (Asahi Intecc) were able to cross. A Confianza Pro 12 (Abbott Vascular) was used to penetrate the distal cap and was then switched to a Pilot 200 (Abbott Vascular). GuideLiner (Vascular Solutions) catheter reverse CART (controlled antegrade and retrograde tracking) was performed with a 3.0 x 15 mm balloon proximal to the CTO. On the externalized RG3 wire (Asahi Intecc), a 1.5 mm Emerge balloon was unable to pass in order to predilate. A 0.9 mm laser was advanced and atherectomy was performed for 3 minutes, but the lesion was still unable to be crossed with the laser. At this point, a 1.5 mm Euphora balloon (Medtronic) was able to cross after modifying the plaque, followed by serial balloon inflations. An AngioSculpt balloon (Spectranetics) was used prior to IVUS and stent placement. 

Case 4 (Vein graft)

A 57-year-old male with a history of CAD s/p CABG, peripheral arterial disease, cerebrovascular accident, and hypertension presented with a non ST-elevation myocardial infarction. He had a known occlusion of the SVG-right posterior descending artery (RPDA) and SVG-OM3. He was found to have high-grade stenosis of the SVG-OM2. From a right radial approach, an Amplatz left (AL) 1 guide was used to engage the SVG. A 5.0 SpiderFX embolic protection filter (Medtronic) was advanced. An attempt to perform primary stenting with a 4.5 x 12 mm Ultra stent (Abbott Vascular) resulted in failure to deliver and the guide backing out. A 1.4 mm ELCA catheter was used to make 3 passes with an increased rate. The stent was delivered without difficulty and the procedure was completed. Final angiography demonstrated TIMI-3 flow without embolization. 

Discussion

It has been over 30 years since laser atherectomy was first introduced as an alternative to overcoming the low success and high complications associated with non-ideal-balloon angioplasty lesions. Early success in the clinical series was countered by concerns regarding laser-induced complications, in particular, dissection and perforation. Device refinements included using a lower wavelength, pulsed wave energy, technique (the use of saline flush), and changes to the catheter design, resulting in better outcomes. A full discussion of laser is beyond the scope of this article, but we will briefly discuss the concept. 

“Laser” is an acronym for light amplification by stimulated emission of radiation. The basic principle is delivery of a monochromatic light to a small area, resulting in vaporizing and debulking plaque. In brief, laser atherectomy works by three unique mechanisms of action: photochemical (breaking mechanical bonds), photothermal (producing thermal energy) and photomechanical (producing kinetic energy). The rapid expansion and implosion of the vapor bubble caused by use of the laser results in acoustic-mechanical disruption of the plaque in front of the catheter tip, with shallow penetration.^1,2 The quick, brief delivery of energy avoids the generation of significant thermal effect (a limitation of the older, continuous-wave lasers utilizing energy in the infrared spectrum). 

The current laser catheter (ELCA, or excimer laser coronary atherectomy) is available in a number of sizes (0.9 mm, 1.4 mm, 1.7 mm, and 2.0 mm); however, the 0.9 mm and occasionally the 1.4 mm catheter can be utilized for the majority of cases. In an ideal situation, it is possible to achieve approximately a 60% luminal gain greater than the catheter (i.e., a 0.9 mm should generate approximately a 1.5 mm lumen); however, this claim arises from work in a gel model. Plaque tends to be heterogenous, with different ablative properties. Therefore, much like any atherectomy, it is not a standalone therapy. Typically, use of ELCA does permit the operator to achieve some degree of plaque modification that allows for better lumen expansion with balloon inflation and less vessel trauma beyond the lesion of interest. The result is easier stent delivery, increased luminal gain, and avoidance of issues such as no reflow or distal embolization.^1-3 

ELCA catheters have two settings controlled by the operator: fluency and rate. Fluency is essentially the size of the vapor bubble. Rate refers to the rate of the bubble’s expansion and contraction. Increasing these 2 settings will cause greater plaque disruption and lumen increase, but also increases the risk of complications (vessel dissection, perforation, etc.). 

ELCA’s current clinical indications can be found in Table 1. Real-world scenarios for typical use are described in Table 2.^4-8 The device setup is very simple and it only requires a single operator. It is a rapid-exchange catheter with a pedal for starting and stopping the laser. The 0.9 mm has a 10-second “on” time with a 5 second “off” (the idea is to allow for coronary perfusion to resume, as the operator should flush with saline during energy delivery). The 1.4 mm and larger sizes have a 5-second “on” with a 10-second “off”. We advise use of the laser over a workhorse wire, not a coated wire. Prolonged lasing could result in disruption of the wire coating and the coating sticking to the catheter. That being said, it is not uncommon to laser over a Pilot 200 wire in a CTO where a microcatheter cannot be delivered to exchange the wire. 

Laser atherectomy has several advantages over other available atherectomy devices (Table 3):

• It does not require a proprietary wire, permitting the operator to perform atherectomy over any wire that crosses.
• The operator can have a second wire down, so in a bifurcation, one can maintain simultaneous vessel access while performing atherectomy.
• Low ejection fraction is not a relative contraindication, as the risk of no reflow is not the same as with the use of rotational and orbital atherectomy. 
• Thrombus is not a contraindication. In fact, the device does an excellent job of ablating thrombus and we use it routinely in acute coronary syndrome (ACS) cases (laser works well to disrupt fresh and even organized thrombus). 
• ELCA does not require the temporary pacemaker placement often required with other devices in certain clinical scenarios. 
• ELCA works well for in-stent restenosis; we will typically use a 1.4 mm catheter.
• For underdeployed stents, a “puff” of contrast can be given in order to disrupt the plaque under the struts. This is off-label and increases the risk of dissection or perforation, but can be an effective technique.

Although laser is indicated in calcified lesions, we still think that rotational and orbital atherectomy work better in heavily calcified lesions (270˚ arc). Ideal use of the excimer laser includes a guide without side holes, to allow for saline delivery. Size the catheter to two-thirds of the vessel size (again, in the coronaries, a 0.9 mm catheter is used to modify plaque in the majority of cases). Use slow advancement, at approximately 0.5-1 mm/second. Even if the laser does not cross the lesion, prolonged lasing at the lesion can result in enough plaque modification to allow delivery of a low-profile balloon or microcatheter. 

All devices we have described here can be utilized from a radial approach; however, the laser requires good guide support so one can “push” against the lesion and ablate plaque in more resistant lesions. Because guide support can be less aggressive from a radial approach than from a femoral approach, we tend to laser first in order to prep the vessel and facilitate stent delivery. 

In Part II, we will discuss rotational atherectomy and some key concepts regarding its use. 

Disclosure: Dr. Zaheed Tai reports the following: Terumo (speaker, proctor for transradial course), Spectranetics (proctor for laser course, speaker, advisory board member), and Boston Scientific (speaker, CTO proctor).

Dr. Zaheed Tai can be contacted at zaheedtai@gmail.com.

References

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