Resurrecting “Laser-us”

Despite advancements in stent technology, procedural success in complex lesion morphologies is often dependent upon pre-stent lesion preparation. Lesion subtypes such as bifurcation, thrombotic, chronic total occlusion, and friable saphenous vein graft (SVG) lesions continue to pose procedural challenges and risks. Excimer laser coronary atherectomy (ELCA, Spectranetics Corporation, Colorado Springs, Colorado) has demonstrated efficacy in these situations. The catheter emits excited dimer (excimer) laser of 308 nm ultraviolet wavelength, thereby creating a cavitation bubble which vaporizes the debris into erythrocyte-sized microparticles. This is achieved through photomechanical, photothermal, and photochemical effects.

While ELCA remains a valuable tool in peripheral vascular procedures,¹ it is utilized in only a minority of modern percutaneous coronary interventions (PCIs), as previous experience had demonstrated alarming rates of coronary dissections and perforations. This unfortunate phenomenon was likely due to the then unrecognized interactions of the laser energy with the ambient circulatory milieu. Both erythrocytes, more specifically hemoglobin, and contrast media are efficient absorbents of the 308 nm ultraviolet energy. In that setting, rapid expansion and implosion of cavitation bubbles result, leading to accelerated pressure pulses; this process not infrequently produces vascular wall trauma and potentially perforation.

However, the current standard practice of constant and steady infusion of saline, which remains inert in the presence of laser energy, during ablative runs virtually eliminates this risk.² When caution and meticulous efforts to assure a blood- and contrast-free ablative environment are exercised, ELCA can be a valuable asset in the interventionalist’s device armamentarium. Food and Drug Administration (FDA)-approved indications for ELCA include: long lesions, moderately calcified lesions, chronic total occlusions traversed by guidewire, balloon-resistant lesions, ostial lesions, SVG lesions, and in-stent restenosis. Furthermore, based upon the CARMEL Registry,³ which demonstrated promising ELCA results in acute myocardial infarction (AMI), the FDA removed prior contraindications of acute myocardial infarction, acute thrombosis, and depressed left ventricular ejection fraction.

For cases of heavy or friable thrombotic or atherosclerotic burdens such as in AMI or SVG, respectively, techniques for debris and plaque extraction are frequently employed prior to stent deployment. These include aspiration devices, either manual or mechanical, with or without distal protection. However, rarely these bulky devices, which are designed to prevent distal embolization, can themselves cause this complication. Additionally, balloon occlusive protective devices can lead to transient ischemia, while filter devices may allow passage of smaller embolic debris. The ELCA catheter, with its low profile and forward ablative action, however, is not generally associated with these shortcomings (Figure 1). Moreover, the excimer laser energy has been demonstrated to inhibit platelet aggregation in acute coronary syndromes.⁴

A recent large randomized bifurcation PCI trial failed to demonstrate clinical benefit of complex versus simple stenting strategies.⁵ With improved technique, it is possible that ELCA pretreatment may, through atheroablation, help to decrease the risk of plaque shift in these patients. This strategy can be of particular benefit in distal left main or ostial left anterior descending or circumflex stenoses (Figure 2). The device has also been utilized in cases of balloon catheter advancement failure in chronic total occlusions. While clearly a “niche” device with applications limited to specific clinical and anatomic subgroups, ELCA, when performed with caution, remains a potentially valuable adjuctive tool for PCI. Thus, like Lazarus, the all-but-forgotten Laser may yet be resurrected back to life in conventional PCI practice.

References

1. Garnic JD, Hurwitz AS. Endovascular excimer laser atherectomy techniques to treat complex peripheral vascular disease: An orderly process. Techniques Vasc Interv Radiol 2005;8:150–159.

2. Tcheng JE. Saline infusion in excimer laser coronary angioplasty. Seminars Interv Cardiol 1996;1:135–141.

3. Dahm JB, Ebersole D, Das T, et al. Excimer laser angioplasty in acute myocardial infarction (the CARMEL multicenter trial). Am J Cardiol 2004;93:694–701.

4. Topaz O, Minisi AJ, Bernardo NL, et al. Alterations of platelet aggregation kinetics with ultraviolet laser emission: the “stunned platelet” phenomenon. Thromb Haemost 2001;86:1087–1093.

5. Jensen JS, Galloe A, Lassen JF, et al. Safety in simple versus complex stenting of coronary artery bifurcation lesions. The Nordic bifurcation study 14-month follow-up results. Eurointervention 2008;4:229–233.

6. Kern MJ, Ouellette D, Frianeza T. A new technique to anchor stents for exact placement in ostial stenoses: The stent tail wire or Szabo technique. Cathet Cardiovasc Interv 2006;68:901–906.

From Saint Joseph’s Heart and Vascular Institute, Saint Joseph’s Hospital of Atlanta, Atlanta, Georgia The authors have reported no conflicts of interest regarding the content herein. Address Correspondence to Dr. Chen at jchen@sjha.org