Improved results of coronary excimer laser angioplasty by the use of advanced transmission devices

Excimer laser angioplasty is an alternative method for the treatment of obstructive coronary lesions. Initial clinical results demonstrated the safety and feasibility of the procedure. However, efficacy was limited by low catheter flexibility and unreliable energy transmission. Advanced transmission devices were used in 80 interventions in 79 patients. The catheter diameter is 1.3, 1.5 or 1.8 mm, the catheters consist of 20, 30 or 35 quartz fibres (100 m) respectively. The mean energy density was 55 ±18 mJ mm^–2, mean loss of energy transmission was 20%. The pulse width was 60 ns and 115 ns in 40 interventions each. The target vessel was the LAD in 53, the LCX in 6 and the RCA in 21 interventions.Failure of laser angioplasty occurred in 10 patients due to failed guidewire placement (N=6), failed catheter placement (N=3) or impossibility to cross the lesion with the catheter (N=1). Stand-alone laser angioplasty was performed in 43/70 procedures. Additional balloon angioplasty was necessary due to an unsatisfactory result (N=10) or due to complications (N=17) in 27 patients. Vessel occlusion occurred in 18 patients (25%) and could be successfully resolved by balloon dilatation (N=16) or additional laser angioplasty (N=1) in 17 patients. Two early occlusions were found at the 24-h control angiography. The incidence of myocardial infarction and in-hospital death (N=1) was 1.4%.Conclusion: The use of an advanced energy delivery system with trusted energy transmission and higher energy density increased the primary success rate of stand-alone excimer laser angioplasty. However, further improvement of catheter flexibility and reduction of dead space at the catheter tip is necessary to optimize ablation efficacy.     

Coronary laser angioplasty

Percutaneous coronary angioplasty has become an accepted method of non-surgical myocardial revascularization. The constant problem of restenosis has stimulated the research of new techniques able to completely eliminate the atherosclerotic plaque. Excimer laser energy has demonstrated in vitro and in vivo capability of plaque dissolution with minimal damage to surrounding tissue.In seven patients with critical coronary stenoses, before surgical anastomoses, a mono- or multifibre catheter (0.6–1.6 mm) was introduced via the coronary arteriotomy coupled with a specifically designed Xe-Cl pulsed laser (308 nm) at the time of cardio-pulmonary by-pass. Eleven stenoses were treated: three successfully and five with perforation. Technical progress is needed to eliminate this serious complication.     

Vascular contractile function following experimental excimer laser angioplasty

The aim of this study was to determine the vasomotor response to in vivo excimer laser irradiation with regard to laser-induced tissue effects. Transfemoral excimer laser angioplasty was performed in the right carotid artery of 11 New Zealand white rabbits. In four additional rabbits (sham group), the procedure was performed without the application of laser energy. Angiography documented vessel dissection in five laser-treated animals. Perforation occurred in one animal. Rings of the treated artery and controls of the contralateral artery were investigated in a contraction chamber. The passive stress-strain relation (PSS) and the maximum contraction force (MCF) after stimulation with noradrenaline, serotonin and potassium chloride were determined. The treated vessels had a higher PSS than the control (p=0.05). The MCF was lower in the treated vessels (p<0.05). The contraction force of the sham-operated vessels was higher, although statistically not significant, compared to the laser-irradiated segments. In a subset analysis, performed to compare vessels with moderate and severe trauma, MCF was significantly reduced in vessels with severe laser-induced injury. Experimental in vivo excimer laser angioplasty in this model resulted in heterogeneous structural changes, including dissections and perforation. Post-mortem assessment of vasomotor response showed no significant difference between laser-treated and sham-operated animals. However, the contractile function of the target vessel seems to be reduced following extensive laser-induced vessel injury.     

Platelet accumulation and fibrin deposition following peripheral laser angioplasty in rabbits

The platelet response and fibrin deposition following the delivery of an argon-ion laser beam to the rabbit ear artery has been evaluated kinetically using a minimally invasive technique utilizing⁵¹Cr-labelled platelets and¹²⁵I-labelled human fibrinogen. After laser irradiation there was an immediate increase in platelet-associated radioactivity which was followed by a series of transient increases and decreases suggesting that micro-embolization was occurring. When fibrin deposition was studied, there was a lag time of six minutes before rapid deposition of fibrin. However, once the increase in radioactivity was established the series of transient increases and decreases previously observed with⁵¹Cr-labelled platelets was not observed using¹²⁵I-labelled human fibrinogen. Histological examination of the arteries confirmed platelet accumulation and fibrin deposition. Our findings confirm that platelet accumulation with probable microembolization and fibrin deposition occurs following laser angioplasty.     

Percutaneous transluminal excimer laser angioplasty in total peripheral artery occlusion in man

Laser angioplasty and laser-assisted angioplasty have become a clinical reality. Producing sharply defined borders of the ablated area with minimal adjacent thermal damage, excimer lasers offer several proven and some potential advantages over conventional systems. To evaluate the feasibility of excimer laser angioplasty, we have treated one patient using 308-nm radiation via a bare fiber in direct contact with the total occlusion of a right femoral artery. The lesion was successfully recanalized, thus allowing easy passage of the balloon catheter and subsequent dilatation. This percutaneous laser recanalization of an occluded peripheral artery is one of the first to be done in man using excimer laser radiation, thus demonstrating that the technique is feasible and the system is potentially useful.     

Application of excimer laser coronary angioplasty (ELCA) in bifurcation lesions

. Excimer laser coronary angioplasty (ELCA) offers a unique approach to the treatment of bifurcation lesions that continues to present a challenge in percutaneous coronary intervention. Debulking plaque prior to stenting or balloon angioplasty has demonstrated significant improvement in the treatment of bifurcation lesions. Clot dissipation properties of excimer laser combined with its ability to debulk, makes this device unique when applied to thrombus-laden bifurcation lesions. ELCA is the only debulking technique that allows retention of two guide wires with resultant protection of the bifurcation vessels during the debulking procedure. We herein describe three patients with unstable angina who underwent a debulking procedure with ELCA involving application of single and double wire techniques. These three cases illustrate two different techniques used for debulking bifurcation lesions. Both single and double wire techniques are described. ELCA can be used safely and effectively in high-risk patients with bifurcation lesions, even in the presence of thrombus.     

Preliminary results of intraoperative excimer laser angioplasty: phase 1: an adjunct to coronary artery bypass surgery.

The excimer laser underwent phase I clinical trials at three centers to determine its safety for intraoperative coronary laser angioplasty as an adjunct to coronary artery bypass grafting. A 308-nm Xenon-Chloride, pulsed-wave excimer laser was used to perform angioplasty in 30 patients undergoing coronary artery bypass surgery. Forty vessels (30 patients) were treated, in which the extent of occlusion ranged from 30% to 100%, with complete occlusion in 40% of all vessels. Improvement in vessel luminal caliber was achieved in 33 (79%) vessels, with perforations occurring in 4 (12%) vessels, 2 of which required surgical repair. The lumens of the remaining 8 (19%) vessels were not enlarged, and 2 (5%) of these vessels were perforated. Luminal enlargement was most often achieved in totalled occluded vessels in which 16/17 (94%) were recanalized. No patients died within 30 days postoperatively. Five patients demonstrated biochemical and electrocardiographic evidence of myocardial injury 48 hr postoperatively, and one patient died of cardiac arrest 139 days postoperatively. On the basis of these results, we believe that excimer laser angioplasty can be performed safely to improve coronary luminal patency, even in totally occluded vessels, in an operative setting. The long-term value of this procedure remains to be elucidated.     

Application of excimer laser angioplasty in acute myocardial infarction

BACKGROUND AND OBJECTIVE: Patients presenting with acute myocardial infarction who fail to respond to standard therapy with thrombolytics or have contraindications for their use oftentimes need revascularization with a mechanical device for removal of an occlusive coronary thrombus and its underlying atherosclerotic plaque. As both thrombi and plaques absorb laser energy in the ultraviolet wavelength (308 nm), we studied the feasibility and safety of excimer laser angioplasty in selective patients with complicated acute myocardial infarction. STUDY DESIGN/MATERIALS AND METHODS: Fifty patients with acute myocardial infarction complicated by continuous chest pain and/or ischemia who had a total of 54 obstructive lesions were treated with percutaneous excimer coronary laser angioplasty (ELCA). A Q-wave myocardial infarction was documented in 56% and a non-Q-wave myocardial infarction in 44%. The baseline left ventricular ejection fraction was reduced at 43 +/- 13% and six patients (12%) presented to the cardiac catheterization laboratory in cardiogenic shock. Twenty-nine patients failed to respond to thrombolytic therapy and 16 had contraindications for thrombolytics and IIb/IIIa receptor antagonists. Following laser debulking, all patients received adjunct balloon dilation and then stents were deployed in 83% of the target lesions. Quantitative coronary arteriography (QCA) was performed at an independent core laboratory. RESULTS: Ninety-eight percent laser success and 100% procedural success were achieved. By QCA the minimal luminal diameter increased from baseline of 0.7 +/- 0.5 to 1.3 +/- 0.5 mm post-lasing and then to 2.0 +/- 0.6 with balloon dilation to a final of 3.0 +/- 0.5 mm. Pre-laser percent stenosis diameter of 77 +/- 17% was reduced to 51 +/- 22% post-laser to 3.0 +/- 17% post-balloon and to a final of 15 +/- 25%. An 83% laser-induced reduction of thrombus burden area was achieved as well as an increase in TIMI flow from baseline of 1.7 +/- 1.1 to 2.8 +/- 0.4 by laser to a 2.9 +/- 0.4 final. There were no deaths, emergency bypass surgery, cerebral vascular accident, neurologic injury, or major perforation. In one case, a laser-induced major dissection was successfully treated by stenting. All 50 patients survived the procedure, improved clinically, and were discharged. CONCLUSION: Application of excimer laser coronary angioplasty is feasible and safe in selected patients with acute myocardial infarction who either fail to respond to thrombolytics or have contraindications to these agents. Intracoronary thrombus at the target lesion can be successfully dissolved with this wavelength laser energy without adverse effect on the procedure results.     

French experience in intra-operative XeCl excimer laser coronary artery endarterectomy

We present the results of 15 XeCl laser coronary artery endarterectomies performed in 13 patients during CABG surgery. The results are very encouraging but they show that the development of new and more efficient laser catheter delivery systems with a better proportion of optical active surface at the distal tip of the multifibre catheters is necessary to reduce the longterm and mid-term rates of restenosis.     

Excimer laser coronary angioplasty: Initial experience in Amsterdam

This paper reports on the initial clinical experience with 308 nm XeCl-excimer laser coronary angioplasty (ELCA) in the Academic Medical Center in Amsterdam and on calculations of light fluence rate distributions resulting from laser beams incident on tissue.Monte Carlo numerical computations were used to compute the light fluence rate distributions of a finite 308 nm excimer laser beam with various diameters incident on a liquid-tissue interface. It was found that light scattering is an important component in the resulting light distribution in aortic tissue. The calculations predict that there will be hardly any broadening of the beam outside the laser beam area. Therefore, the distributions from different fibres in multifibre catheters will not overlap unless the fibres are closely packed together. As a consequence of scattering the fluence rate at the surface of the tissue was larger than the incident power density and showed a considerable decrease from the centre to the edge of the beam. However, the physics of tissue ablation by fibres in contact with tissue are different and at present not well understood.The clinical results of the first 18 patients treated with the Dymer 200+ excimer laser (Advanced Interventional Systems, Irvine, CA, USA) are given. Six patients had abrupt closure solved by balloon angioplasty, but complicated by a small myocardial infarction. One patient had emergency by-pass surgery for abrupt closure after laser followed by balloon angioplasty (probably a dissection and thrombus). In one patient we perforated in a bend of a RCA with a 2.0 catheter following a second pass. We had two in hospital deaths (4 and 14 days after treatment). At 6 months follow-up, eight patients had restenosis or occlusion at the lased segment.However, the results of the first 1000 patients enrolled in the American ELCA-Registry are more promising. In the light of these results it can be concluded that a randomized trial balloon angioplasty versus excimer laser angioplasty appears to be indicated.     

Improved criteria for the recognition of atherosclerotic plaque using fluorescence spectroscopy

To determine the fluorescence pattern for distinguishing normal (N) from calcified and fibrous plaque (P), fluorescence spectra of cadaveric aorta were measured with a spectrofluorometer. Emission (Em) and excitation (Ex) spectra corrected for instrumental response were obtained from 200 to 1000 nm. Specimens from 50 patients were measured less than 24 h after autopsy and then examined histologically. Spectra from 25 specimens demonstrated that the ratio of fluorescence intensity 460 nm/385 nm with Ex=337 nm provided separation of N from P (1.53±29 vs 0.82±0.25,p<0.01) and that a ratio of 1.25 correctly identified all N and P. A prospective test of this ratio on an additional 25 specimens yielded a significant difference between N and P (1.70±0.37 vs 0.87±0.23,p<0.0001) with a value of 1.25 correctly identifying all (10/10) N and 93% (14/15) P. Prospective analysis of previously proposed fluorescence ratios (600 nm/580 nm at Ex=480 nm; 530 nm/550 nm at Ex=459 nm; 448 nm/514 nm and 538 nm/514 nm at Ex=337 nm) all resulted in poor separation of N from P. The ratio of 460 nm/385 nm with Ex=337 nm is superior to previously reported criteria for distinguishing N from P and may be useful for guiding laser angioplasty systems.     

Myocardial revascularization in patients with end-stage renal disease: Comparison of percutaneous transluminal coronary angioplasty and coronary artery bypass grafting

Background: Ischemic heart disease is the major cause of death inpatients with end-stage renal disease. The high prevalence of coronary artery disease results in a rising number of dialysis patients requiring myocardial revascularisation. Objective: The objective of this study was to compare the outcomes of recurrent angina, myocardial infarction, rate of reinterventions and cardiovascular death following percutaneous coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) inpatients with end-stage renal disease. Patients and methods: In a retrospective investigation 40 patients with chronic renal failure undergoing primarily PTCA and 65 patients undergoing CABG were included. Both groups were comparable for gender, duration on dialysis and the number of cardiovascular risk factors per patient. Patients undergoing PTCA were younger (53 ± 12 years vs. 57 ± 8 years; p < 0.05) and more often diabetics (30% vs. 14%; p < 0.05). Results: Most patients in both groups had a multi-vessel disease (95% in the CABG group vs. 74% in the PTCA group), in the CABG group there were significantly more patients with a triple-vessel disease (62% with vs. 40%in the PTCA group; p < 0.01), PTCA was primarily successful in 95% of the patients while complete revascularization was achieved in 88% of patients undergoing CABG. The perioperative mortality after CABG was 4.8% as compared to none after interventional revascularisation. The cumulative freedom of angina after 6, 12 and 24 months after intervention was significantly lower after PTCA (54%, 40%, 29%) than after bypass grafting (97%, 94%, 90%, p < 0.001). The frequency of reinterventions following PTCA was significantly higher compared to patients following CABG (p < 0.001). After PTCA 15 patients needed further revascularisations, 8 of them underwent CABG, whereas after CABG only two patients required additional myocardial revascularisation. There was no significant difference in the overall mortality between both groups; the survival rate after 12 and 24 months was 95% and 82% after PTCA and 93% and 86% after CABG, respectively. Condition: Although patients receiving CABG had a more severe coronary artery disease the overall mortality was comparable and clinical and functional outcome was improved compared to patients after coronary angioplasty. This revised version was published online in June 2006 with corrections to the Cover Date.     

Factors influencing the ablation of atherosclerotic plaque with the argon laser

This paper describes the ablative effect of argon laser light, delivered fibre optically in vitro, on 234 segments of atherosclerotic human aorta. Variables such as energy density, type of atheroma and immersion media were taken into account. All irradiated specimens were subsequently submitted to histological examination and crater volumes in mm³ were derived from micrometer measurements made at light microscopy. Results showed: (1) a linear relationship between energy dose and crater volume in fibrous atheroma; (2) significantly greater surrounding tissue damage in the higher energy dose groups; (3) a lower dose response in calcified tissue than in fatty streaks or fibrous atheroma; (4) immersion of tissue in blood during ablation resulted in a significantly greater dose response than immersion in plasma or saline, and the corresponding surrounding tissue damage was greatest under blood. Thus, argon laser light is both effective and predictable in response when ablating atheromatous tissue, and the efficiency of the process depends on the immersion medium. The degree of surrounding tissue damage depends on the energy dose.     

Physical properties of sapphire fibretips for laser angioplasty

The physical properties of sapphire contact probes were examined with respect to their use in laser angioplasty. The rounded and bullet-shaped probes are mechanically atraumatic and provide tactile feedback during laser angioplasty. The optical transmission characteristics of the flat, rounded and bullet-shaped probes were measured and the propagated laser beam profiles photographed in air and water. These properties are largely wavelenght independent in the small part of the spectrum currently used for laser angioplasty. Sapphire contact probes may heat up from direct absorption of laser light at the interfaces, but they probably also heat up by conduction from the heated tissue with which they are in contact. The rounded and bullet shaped probes focus light to a rather diffuse waist in air, but in water this focusing effect is lost. The divergence angle of the bare fibre is reduced in water. Transmittance characteristics depend on surface reflection, absorption, probe shape and surface smoothness. The flat probes transmitted 85% of the incident light, but the rounded and bullet probes absorbed and scattered almost half of the light.     

Excimer laser coronary angioplasty (ELCA) for diffuse in-stent restenosis: beneficial long-term results after sufficient debulking with a lesion-specific approach using various laser catheters

Although brachytherapy became frequently used technique for treating in-stent restenosis (ISR) in 2000 (stenosis recurrence: 14–25%), removing the tissue (i.e., debulking) is still under evaluation. Regarding XeCl Excimer laser no randomised trials have been completed so far. The entirely attainable and published data originate from five one-centre and one multicentre registries which showed a high procedural success- (98%) and a very low complication rate (<2%), but heterogeneous results based on (I) manifold laser- and lasing technology due to evolving catheter and lasing technology during the studies and (II) inhomogeneous patient-populations, which had been documented only occasionally, although we now know that ISR-recurrence rates are significantly higher in patients with (1) high grade stenosis (>70%), (2) long lesions (>15mm in length), (3) recurrent ISR, (4) ISR in saphenous vein grafts, (5) early-ISR (<3 months after stent implantation), (6) multi-vessel disease and (7) low ejection fraction. Because all athero-ablative procedures are typically finalised by adjunctive balloon PCI, diameter stenosis before adjunctive PTCA was between 23% and 64%, reflecting the different lasing (and therefor debulking) intensity between the studies. The mean lesion-length, vessel diameter, stent-type and coronary differed significantly between the studies (i.e. mean lesion length between 14 and 32 mm) and although of major influence, the speed of lasing (=ablation) was not recorded in the various studies. Concerning eccentric ELCA the invention of the area-ablation technique provide a significant greater ablation effect and the new OS-technology provide 60% more ablating area. In summary, the feasibility, effectiveness, procedural success and presumably long-term outcome of the Excimer laser for treating ISR depend on multiple outcome-influencing aspects. The lack of recording variables make analysis of various laser-for-ISR trials difficult or even impossible. ELCA seems to have advantageous procedural and long term results in lesions, where aggressive debulking effect using eccentric ELCA catheters can be achieved. The OS-catheter can provide a maximum debulking in distal lesions and tortuous vessels, where the debulking abilities of the eccentric catheter are limited. If laser debulking is inadequate (DS 30%), the incidence of recurrent restenosis appear to be higher and brachytherapy is probably more suitable. Sufficient laser debulking can only be achieved through use of precise technique respecting the laser-specific abilities of plaque dissolution, appropriate energy levels and quantities, and possibly recovery time.     

Excimer laser angioplasty: Quantitative comparison in vitro of three ultraviolet wavelengths on tissue ablation and haemolysis

The effects of three ultraviolet excimer laser wavelengths on normal and atheromatous human cadaver aortic wall are presented. Ultraviolet radiation successfully ablates vessel wall; the dose response is greatest at 249 nm followed by 193 nm and 351 nm, where the effect is negligible for the equivalent energy dose. Wavelengths 249 and 193 nm have a selective effect on fibrous atheroma; ablation proceeds at a higher rate in this tissue. Non-linear effects observed at 249 nm may be due to thermal as well as photoablative mechanisms. In addition, blood samples were exposed to all three wavelengths and potassium concentrations were measured; the dose of energy required to produce tissue ablation may also produce significant haemolysis and hyperkalaemia at 249 and 193 nm but not with 351 nm. This finding may be important for coronary angioplasty but less so for peripheral work. The wavelength that produces the strongest dose response is 249 nm; this is the wavelength for which a fibre-optic delivery system should be developed.     

Transmission of laser energy and assessment of target temperature in an experimental model of laser balloon angioplasty

The potential application of laser balloon angioplasty (LBA) is limited because of difficulties in temperature control and dosimetry during trans-balloon laser irradiation. An experimental model of LBA was designed to help understand the polymer membrane effects of two materials on tissue temperature. The durability of two types of polymer films with different optical properties, polyethylene terephthalate (PET), a low scattering polymer and polyetheretherketone (PEEK), a high scattering polymer, were examined as potential balloon material. The PEEK film (thickness: 50 μm) was melted and perforated by light from a diode laser (wavelength: 808±10 nm, irradiance: 1469 W cm⁻², mean exposure time: 30±7 s). On the other hand, the PET film with the same thickness was completely intact after 1 min exposure at the same irradiance. Diode laser irradiation was applied to indocyanine green stained human aortic media in three different exposure methods; directly, through the free PET and through the pressed PET film. Temperatures of laser-irradiated specimens were measured using an infra-red thermal camera with an 8–12 μm bandwidth, and corrected for the emissivity of the tissue and the PET film. Results demonstrated underestimation of surface temperature because of low transmittance of radiated intensity through the free PET film and a significant (p<0.001) increase of corrected temperature (δT=169±32°C) through the pressed-PET exposure compared with the direct exposure (ΔT=81±7°C), even though the same laser irradiance (18.6W cm⁻²) was applied for 5s. That is, the tightly PET-covered tissue develops a significantly higher temperature during diode laser irradiation, and this increased thermal effect can be advantageous for laser welding with less power in laser balloon angioplasty.