Utility of Laser Atherectomy in Complex Revascularization of Coronary Chronic Total Occlusion

Case Report

A 55-year-old male with past medical history of hypertension and hyperlipidemia sustained an out-of-hospital cardiac arrest. He was successfully resuscitated by emergency medical services and brought in to an outside hospital for further evaluation. An echocardiogram showed a left ventricular ejection fraction of 30-35% without any significant valvular abnormalities. Emergent coronary angiography at the outside facility demonstrated severe obstructive proximal left anterior descending artery (LAD) disease that was successfully revascularized with a drug-eluting stent. He was also noted to have chronic total occlusions (CTOs) of proximal ramus intermedius (RI) and proximal left circumflex (LCx) arteries. Revascularization of his RI CTO was unsuccessful at the outside hospital and he was subsequently referred to our center for revascularization.

Right radial artery access and micropuncture access to the right femoral artery was obtained with placement of 6 French (F) and 8F sheaths, respectively. A 6F Judkins right (JR) 4 guide was used to engage the right coronary system and an 8F XB 3.5 guide (Cordis, A Cardinal Health company) was used to engage the left coronary system for simultaneous dual contrast injection. The RI branch was chronically occluded at the proximal segment with reconstitution at the mid to distal bifurcation point via left-to-left collaterals from the distal LAD (Figure 1A).

A Fighter wire (Boston Scientific) with a Turnpike LP microcatheter (Teleflex) was advanced antegrade into the proximal cap of the occluded RI artery. Wire escalation was employed with a Pilot 200 (Abbott Vascular) and then a Confianza Pro 12 (Asahi Intecc) guidewire, which was successful in entering the true lumen in the distal RI. The Confianza guidewire was exchanged for a Wiggle (Abbott Vascular) guidewire for increased support (Figure 1B). We encountered difficulty passing a small-profile balloon catheter and thus laser atherectomy was performed with a 0.9 mm excimer laser coronary atherectomy (ELCA) catheter (Philips) with multiple runs at settings of 40 mJ/mm²/40 Hz and 60 mJ/mm²/60 Hz (Figure 1C). Pre-dilatation was performed with a Trek 2.5 mm x 20 mm balloon (Abbott Vascular). A Xience 2.5 mm x 38 mm drug-eluting stent (Abbott Vascular) was deployed in the mid-CTO segment, followed by a Xience 2.5 mm x 18 mm drug-eluting stent in overlapping fashion in the proximal RI branch. Intravascular ultrasound (IVUS) (Opticross HD, Bostic Scientific) imaging was performed of the stented segment. It revealed adequate stent expansion and apposition of the distal segment, with mild underexpansion of the proximal to mid segment. The entire stented segment was post-dilated using a NC Trek 2.75 mm x 20 mm non-compliant balloon (Abbott Vascular) with good expansion. The final angiogram revealed an excellent angiographic result with TIMI-3 flow through the entire RI branch (Figure 1D).

After eight weeks, the patient returned for a staged revascularization of the LCx CTO. Access was obtained in the right radial artery and a second access was obtained in the right common femoral artery. A 6F JR4 guide catheter was used to selectively engage the right coronary artery via right radial access and an 8F EBU 3.5 guide catheter (Medtronic) was used to selectively engage the left main coronary artery via the right femoral artery access. Dual simultaneous injection confirmed a proximal LCx CTO with filling of the mid to distal vessel via retrograde collaterals from the distal right coronary artery (RCA) (Figure 2A).

A Fighter wire with a Turnpike LP support microcatheter was advanced antegrade into the proximal LCx CTO cap. Antegrade wire escalation was employed using Fielder XT, Pilot 200, and Miracle Bros (Asahi Intecc) wires, which were unsuccessful in crossing the occlusion. It had an ambiguous proximal cap (Figure 2B). A retrograde crossing strategy via the distal RCA collateral was initiated using a Turnpike LP 150cm microcatheter with a Sion wire (Asahi Intecc) to enter the retrograde collateral from the distal RCA into the distal LCx after maneuvering through multiple collaterals (Figure 2C). Retrograde wire escalation with a Pilot 200 wire was successful in crossing the distal CTO cap into the antegrade left coronary guide (Figure 2D). A Trapper Exchange balloon (Boston Scientific) was used to trap the Turnpike LP catheter, and the retrograde Pilot 200 wire was exchanged for a R350 guidewire (Teleflex) and externalized.

Laser atherectomy was performed using a 0.9 mm ELCA catheter at settings of 40 mJ/mm²/40 Hz, which led to improvement in antegrade flow (Figure 3A). A Trek 2.5 mm x 20 mm balloon was used to pre-dilate the entire lesion with good expansion. A Xience 3.0 mm x 38 mm drug-eluting stent was deployed and post-dilated with a non-compliant NC Trek 3.25 mm x 20 mm balloon with good expansion. OCT imaging (Dragonfly Optis, Abbott Vascular) of the stented segment was performed and revealed mild underexpansion of the proximal segment of the stent (Figure 3B). The entire stented segment was further optimized using the NC Trek 3.25 mm x 20 mm non-compliant balloon at high inflation pressures with good expansion. The final angiogram revealed good stent expansion with no edge dissection and TIMI-3 flow through the entire LCx artery (Figure 3C).

Discussion

CTO revascularization has been shown to improve angina-related quality of life, provide survival benefit, improve left ventricular function and exercise tolerance, and reduce mortality and need for coronary artery bypass surgery.^1-9 Advancements in the CTO toolbox and techniques, algorithms for approach, classification of lesion type, and operator experience have greatly increased revascularization success. Successful CTO crossing is dependent upon careful planning, assessment and understanding of lesion complexity, and strategic use of the hybrid CTO algorithm. We describe two CTOs in the same patient with both antegrade and retrograde recanalization, which were successfully prepped with laser atherectomy after low-profile balloons failed to cross the lesions. A J-CTO score of 2 was calculated for the RI branch on the basis of calcification and the previous failed attempt. The LCx artery had a J-CTO score of 3 for ambiguous cap, presence of calcification, and long lesion length (≥20 mm). For the RI CTO, entry into the true lumen with an antegrade wire escalation strategy was successful. However, for the LCx CTO, the J-CTO score suggested a lower success of antegrade recanalization with a greater than 30-minute time to guidewire crossing.¹⁰ Based on the hybrid CTO algorithm, the failed antegrade strategy was switched early to a retrograde approach, with wire escalation through the distal cap, and wire externalization in order to improve the odds of successful crossing in a timely manner and avoid contrast and prolonged radiation risks.¹¹

Due to presence of calcification in CTOs, failure of balloon delivery is not uncommon, and atherectomy was performed to debulk the lesion using excimer laser coronary atherectomy (ELCA). Current indications for ELCA include failed prior PCI, in-stent restenosis, CTOs, occluded saphenous vein grafts, ostial and long (≥20 mm) lesions, and presence of moderate calcification.¹² In the literature, laser atherectomy has been described as a third-line strategy in balloon-uncrossable CTOs after use of low-profile balloons, ruptured balloon in the vessel, and where advancement through a CTO with a microcatheter, wire “cutting”, wire puncture, and anchor balloon strategies have failed.¹³

Excimer laser uses a mixture of pulsed gas and halogen to create short wavelength, high energy ultraviolet (UV) light and leads to plaque modification by three mechanisms: photochemical, photothermal, and photomechanical energy. The UV light breaks carbon-carbon bonds and vibration of bonds heats the intracellular water temperature, creating cell rupture and vapor bubbles. These vapor bubbles atherectomize by causing fragmentation to <10 µm, small enough to be absorbed by the reticulo-endothelial system. The threshold energy, called ‘fluence’, is the energy required to create vapor bubbles by UV light and ranges between 30-80 mJ/mm². The pulse repetition rate is the number of pulses emitted during a one-second period. Both parameters are set by the operator for optimal results. Saline is infused to clear contrast and cool the catheter, as performing laser atherectomy with blood and contrast media can create microbubbles and high temperatures, leading to dissections with energy delivery.¹⁴

An ELCA catheter can be advanced over any standard .014-inch guidewire, giving it an advantage over other atherectomy devices, and is available in 0.9, 1.4, 1.7 and 2.0 mm sizes.  The 0.9 mm X80 catheter (Philips) is preferred for CTOs as it is able to deliver the highest fluence of 80 mJ/mm² and highest pulse repetition rate of 80 Hz. It permits energy delivery for 10 seconds with five seconds of rest. Slow advancement of the catheter (0.5 mm/second) is preferred for optimal results with adequate energy penetration and plaque modification.¹⁵

ELCA is increasingly utilized in CTOs with balloon failure despite successful distal wire crossing and holds a success rate of 86-91%. In a four-year retrospective analysis¹⁶, ELCA alone achieved a successful balloon crossing in 91% and was successful in an additional 8.6% in combination with rotational atherectomy. One patient died from coronary perforation directly related to ELCA.¹⁶ The ULTRAMAN registry (indications and outcomes of excimer laser coronary atherectomy: efficacy and safety for thrombotic lesions), enrolling 328 patients at six centers in Naniwa, Japan, of which 5.5 % had CTOs, achieved a high success rate of 92.5%.¹⁷ Bader et al reported a 93.8% success rate for ELCA in 32 CTO lesions.¹⁸ In the Excimer Laser Coronary Angioplasty Registry, 172 CTOs treated with laser atherectomy had a final procedural success of 90%, defined as residual stenosis of <50% and no major complications (bypass surgery, myocardial infarction, or death).¹⁹ These studies have helped establish use of ECLA as a safe option for balloon-uncrossable CTOs and optimization of CTO PCI.

Conclusion

We describe a case of complex proximal RI and LCX CTOs in the same patient with a high J-CTO score. Use of hybrid algorithm led to successful crossing and revascularization with the utilization of laser atherectomy and imaging guidance. ELCA was used to facilitate balloon and stent delivery with image-guided optimization. ELCA in balloon-uncrossable CTO lesions has been shown to have high success rates with low complications and is an essential tool in the CTO revascularization toolbox. 

Disclosures: Dr. Memon and Dr. Kalra report no conflicts of interest regarding the content herein. Dr. Janzer and Dr. George both report consulting for Abbott, Boston Scientific, Medtronic, and Philips.

The authors can be contacted via Jon C. George, MD, at jcgeorgemd@gmail.com.

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