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Introduction

Excimer laser coronary atherectomy (ELCA) has been applied in the treatment of arterial atheroma for over 20 years. Early results when compared with conventional percutaneous coronary intervention (PCI) techniques were disappointing resulting in limited uptake of the technology . Advances in laser catheters and PCI technique has led to a resurgence of interest, reflected in recent literature . Contemporary challenges in PCI include an ability to deal with calcified lesions and chronic total occlusions (CTO). Both are an approved indication for the use of ELCA.

Optical coherence tomography (OCT) is a recently developed intra-vascular imaging modality. It uses near-infrared light to provide high resolution (12–15 μm) images of the coronary vessel lumen and wall. It can clearly identify and differentiate intravascular thrombus, and provides a wealth of information on the effects of intervention on the coronary intima and media .

The aim of this article is to describe the coronary OCT appearance after ELCA, using case examples, to aid in PCI decision making. Each indication for ELCA is described, followed by a case description and analysis of the OCT images.

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Indication 1: In-Stent Restenosis (ISR)

Despite significant advances in drug eluting stents (DES), target lesion revascularization (TLR) remains a limitation of PCI, with angiographic ISR of up to 10% in patients with DES .

ELCA is a safe and effective technique in the treatment of ISR. Lesions treated with ELCA, compared to balloon angioplasty (POBA), had a greater cross sectional area and luminal gain (on IVUS), with more intimal hyperplasia ablation . However, these favorable angiographic criteria were not followed with a reduction in TLR at 6 months.

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Indication 1: In-Stent Restenosis (ISR)

Despite significant advances in drug eluting stents (DES), target lesion revascularization (TLR) remains a limitation of PCI, with angiographic ISR of up to 10% in patients with DES .

ELCA is a safe and effective technique in the treatment of ISR. Lesions treated with ELCA, compared to balloon angioplasty (POBA), had a greater cross sectional area and luminal gain (on IVUS), with more intimal hyperplasia ablation . However, these favorable angiographic criteria were not followed with a reduction in TLR at 6 months.

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Case 1

A 57-year-old with previous multi-vessel PCI (using a 3.0x24mm sirolimus eluting stent) 3 years previously underwent angiography, identifying a severe fibrotic re-stenotic lesion in the proximal LAD ( Fig. 1 Ai). Due to the dense fibrotic restenosis, laser atherectomy was undertaken. This approach was adopted to maximize luminal gain in this large prognostic vessel.

Severe concentric fibrotic In-stent restenosis in the proximal LAD DES on angiography (panel Ai) and the corresponding OCT (panel A). Post ELCA, a cleft/dissection plane is evident (panel B), extending to the true intimal layer (panel B-zoom). This was subsequently treated with sequential non-compliant and paclitaxel eluting balloon inflations with an excellent final angiographic result (panel Ci).

A 1.4 mm concentric ELCA catheter using an energy of 60 mJ/mm ² at a pulse repetition rate (PRF) of 40 Hz, delivered approximately 8000 pulses over 20 runs. The OCT appearance post ELCA ( Fig. 1 B) demonstrates a reduction in neo-intimal material, and creating a cleft/dissection plane having, extending to the media ( Fig. 1 B (zoom)). Stent expansion was achieved with sequential non-compliant (NC) and Paclitaxel eluting balloon inflations ( Fig. 1 C).

ELCA proved effective in debulking the lesion, an effect that is not a consequence of thermal injury , as in-vivo models have demonstrated acceptable temperature changes within stented porcine arteries. Neither does ELCA distort stainless steel stent architecture, when 1000 pulses of energy are applied . The process of Laser tissue ablation disrupted the neo-intima, creating tissue planes to facilitate balloon expansion, allowing full stent apposition with a drug eluting balloon.

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Indication 2: Coronary Calcification and Uncrossable lesions

With an ageing population, the frequency with which complex, calcific coronary disease is encountered during PCI is increasing. The presence of a CTO or calcific/non-compliant stenoses can make intervention challenging, often requiring adjuvant techniques. Within heavily calcified arteries, rotational atherectomy is considered the most effective plaque modification therapy. This requires a specific 0.009 in. guide wire (Rotawire ^Tm ). However, a proportion of lesions cannot be crossed with either Rotawire ^Tm directly or using a micro-catheter exchange system. In these circumstances, an ELCA catheter can be advanced over a standard 0.014” guide wire to create a sufficient channel to permit subsequent Rotawire ^Tm passage. Our group has recently published our experience of ELCA in 58 patients where the lesion was non-crossable or non-expandable . The delivery of one or more trains of laser energy, even if the lesion is not transversed, will often induce sufficient plaque modification to allow passage of a micro-catheter or Rotawire ^Tm . This combination of ELCA and rotational atherectomy, termed “RASER”, is an effective solution in previously untreatable lesions .

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Case 2 ( Fig. 2 )

A 70 year old with angina was referred for intervention to his right coronary CTO.

Panel A demonstrates a severe calcific lesion in the proximal RCA. This proved uncrossable. ELCA was undertaken, and the OCT taken post-ELCA is shown in panels a-c, with the position in the RCA indicated on panel B. A variegated fibro-thrombotic lesion in seen in the proximal artery with the appearance of white thrombus on the inferior border (a). Extensive media calcification is evident, but little involving the intima directly (shown with *in panel b & c) Multiple dissection planes are evident distally, within the diseased intimal layer, not extending into the calcific media (panel b & c), and not apparent angiographically (panel B). The lesion was now easily crossable with an NC balloon. After pre-dilatation, the case was completed with 2 DES, with the final angiographic appearance shown in panel C.

The proximal lesion ( Fig. 2 A) proved un-crossable – and ELCA was undertaken. An X80 0.9 mm catheter, at an energy of 80 mJ/mm ² with a PRF of 80Hz, was used to deliver 7900 pulses over 12 trains.

OCT taken post-ELCA demonstrates a variegated fibro-thrombotic lesion in the proximal artery – with white thrombus apparent on the inferior border ( Fig. 2 a). Extensive media calcification is evident, but little involving the intima directly. Multiple dissection planes are observed distally, within the diseased intimal layer, not extending into the calcific media ( Fig. 2 b and zoom), and not apparent angiographically ( Fig. 2 B). The lesion was now easily crossable with an NC balloon, and the case was completed with 2 DES. Rotational atherectomy was not required as predicted by the OCT images.

When a lesion proves to be uncrossable, ELCA is an effective strategy to facilitate PCI. Here, ELCA debulked the atheroma, increasing vessel compliance allowing large calibre balloon inflation and stent delivery with minimal further preparation. OCT supports this – illustrating the focused tissue ablation resulting from ELCA ( Fig. 2 b and c).

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Indication 3: Saphenous Vein Graft Intervention

Atheromatous degeneration of saphenous vein grafts (SVGs) is characterized by multi-focal, diffuse, degenerative lesions that often contains significant athero-thrombotic material This is prone to distal embolization and subsequent no-reflow. Hence, distal protection devices (DPD) are advocated when attempting SVG-PCI .

ELCA has been proposed as an alternative to a DPD, as particulate matter released during tissue ablation is below the diameter of a capillary. Where a lesion is too severe for DPD passage, ELCA can traverse the lesion, avoiding distal embolization, facilitating DPD delivery and subsequent PCI.

ELCA in SVG-PCI has been studied in a number of registries. Data from the original laser registry showed that distal embolization occurred in only 18/546 (3.3%) of SVG stenoses treated . Prospective data from the CORAL multi-centre registry compared 98 patients who underwent SVG-ELCA, where DPD delivery was not possible, with the SAFER (Saphenous Vein Graft Angioplasty Free of Emboli) control group. They demonstrated that ELCA was safe and feasible but failed to demonstrate an advantage over standard treatment In contrast, in retrospective cohort of 119 patients who presented with acute myocardial infarction (AMI) and underwent ELCA SVG revascularization, the peri-procedural MI (CK-MB release) rate was dramatically lower than that seen in the SAFER group (2.4% vs. 8.4%, P = .02) . There are no randomized control trails of ELCA versus DPD to date.