Excimer Laser Coronary Angioplasty

Laser coronary angioplasty is a minimally invasive advanced technique that utilizes laser energy (light ampli-fication by stimulated emission of radiation) to remove blockages in the coronary arteries that supply the heart. Considered a ‘niche procedure’, it is typically employed when traditional angioplasty is not feasible, particularly in cases of complex or calcified plaques or in recurring blockages within previously stented arteries. The proce-dure has shown promising results.¹

The procedure involves inserting a catheter with a laser tip into the blocked artery and directing pulses of light to vaporize plaque buildup, thereby improving blood flow. This treatment is indicated when traditional angioplasty is not feasible. Any new approach must be evaluated for both its immediate success and long-term clinical outcomes. For a wider application in clinical practice, the simplicity and safety of the procedure, along with an acceptable learning curve, are important considerations. Modern laser angioplasty should be considered through the prism of its simplicity, safety, immediate success, natural history of the treated lesion, and long-term clinical outcomes.

Excimer laser technology (derived from ‘excited dimer’), along with a variety of athero-ablative approaches such as rotational atherectomy, orbital atherectomy, cutting balloon atherectomy, and intracoronary lithotripsy, is used to modify the characteristics of the lesions and facilitate stent delivery when needed.²

Excimer laser coronary angioplasty (ELCA) utilizes a pulsed ultraviolet laser to clear blockages in arteries, allowing an improved blood flow. These lasers generate a high-energy, single-wavelength light beam by passing a high-voltage electrical discharge through a mixture of xenon gas and diluted hydrogen chloride solution. The resultant excited dimers (excimers) release photons at an ultraviolet wavelength, which deliver high-energy laser beam to the target tissue.³ Upon contact, the laser beam induces changes through photochemical, photother-mal, and photokinetic/photomechanical mechanisms. The resultant breakdown products are cleared by the reticuloendothelial system, preventing distal emboli-zation.³ ECLA has been shown to be a safe and effective minimally invasive adjunct to conventional percutaneous coronary intervention (PCI). The procedure is performed under general anaesthesia and has demonstrated improved clinical outcomes in carefully selected patients with arteries that are undilatable by conventional balloons.

Laser coronary angioplasty was introduced in 1985 by Grundfest and colleagues as laser ablation of human atherosclerotic plaque.⁴ However, its adoption faced significant obstacles, including the high cost of laser systems, disappointing clinical results, and complications associated with the continuous waveform argon and Nd: YAG lasers used at that time.⁵ These limitations dampened the initial enthusiasm.

The introduction of excimer lasers, designed for more precise tissue ablation, marked a new chapter in the management of balloon-untreatable coronary lesions. Excimer lasers generate pulsed ultraviolet laser energy with shallow tissue penetration. Precise ablation of plaque was possible with the pulsatile nature of laser without causing thermal injury to the artery.⁴ Their shorter wavelength further limits the depth of penetration. In an initial cohort of 3000 consecutive patients who underwent laser coronary angioplasty at Cedar Sinai Medical Centre, Los Angeles, the procedure demonstrated clinical benefit.⁶ Improved catheter design and enhanced safety protocols have contributed to the reemergence of interest in this technology. However, ECLA is not advocated for poorly visualized or heavily calcified lesions, nor in vessels with a diameter smaller than the smallest available catheter size.⁷

The equipment for ELCA consists of a laser generator and catheters of varying sizes for energy delivery.⁸ The arrangement of fiberoptic fibers may be either concentric around the guidewire lumen or eccentrically localized, with the former being more commonly used. The proximal end of the catheter connects to the laser unit. During the procedure, a PCI guidewire is advanced beyond the target lesion, followed by catheter advancement till the tip makes direct contact with the lesion. The requisite fluency is then increased in a stepwise manner. This process is preceded by a saline flush to create a clear interface for optimal energy transmission.⁹ The catheter is advanced slowly within the vessel, allowing sufficient time for plaque tissue to absorb the light energy, resulting in vapourization and debulking.¹⁰

ELCA has emerged as a safe and effective procedure, particularly in the management of calcified and complex coronary artery lesions.¹⁰ In a retrospective analysis of the data from the NCDR/CATH PCI Registry of United States covering a ten-year period from 2009 to 2019, Sintek and colleagues reported the use of ELCA in 19,688 cases (0.3%) out of 6,043,596 coronary interventions.¹¹ They observed a gradual increase in its utilization over time. The primary safety endpoint occurred in 4.2% of lesions, which was higher compared to 3% in cases where ELCA was not used.

Presently, the use of excimer laser has been reported to be successful in the following scenarios:

1. Severe calcified coronary lesions, for plaque modification and improved procedural success.

2. In-stent restenosis.

3. Complex coronary lesions, including osteal and long segment, as well as cases where balloon crossing is expected to be difficult.

4. Saphenous vein graft lesions.

5. Acute coronary syndromes, for thrombus vapouriza­tion.

In a recent mini-narrative review, Oltunji and colleagues stated that careful patient selection is critical for procedural success. They highlighted the dynamic role of ELCA as a tool with better procedural outcomes, including in patients with acute coronary syndromes. The review reported improved reperfusion, higher success rates in complex lesions, and the potential for long-term clinical benefits.¹²

Laser angioplasty has been shown to be highly precise and effective. It can be performed more quickly with shorter recovery times that allow patient to return to an active life sooner. Coronary laser angioplasty may also reduce the need for coronary artery bypass graft (CABG) surgery. While generally considered safe, the risk of complications increases especially in the presence of chronic total occlusion. Potential complications include perforation and dissection. These observations underscore the importance of careful patient selection, assessment of the size of the lesion, and meticulous planning and execution.¹¹

Laser angioplasty adds to the cost of coronary intervention. The procedure has been shown to be useful in certain subset of patients, and more research is needed to evaluate its cost-effectiveness. Comparative randomized controlled trials are required to assess its clinical and economic value relative to other treatment modalities. In addition, large-scale clinical studies involving broader populations are necessary to confirm the generalizability of the findings from smaller studies. Such investigations will throw light on its true cost-effectiveness and determine whether widespread adoption is justified.

With the current aggressive approach to coronary revascularization and the growing interest in expanding the patients’ cohorts eligible for percutaneous approach, modern laser angioplasty offers an important strategy for improving immediate angiographic outcomes. The continued adoption of this technology will depend not only on its internal merits and demerits, but also on the science and utility of other competing technologies that address the challenges faced by interventional cardiologists. It is likely that, for the foreseeable future, a range of such technologies will remain available, allowing clinicians to select the most appropriate option for each patient.

Conflicts of Interest

Nil