Percutaneous coronary excimer laser-assisted balloon angioplasty: initial clinical and quantitative angiographic results in 50 patients

Laser coronary angioplasty: history, present and future

The efficacy of percutaneous transluminal coronary angioplasty (PTCA) is limited by remaining plaque tissue and the development of restenosis. It has been demonstrated that the restenosis rate is low if a large lumen diameter is achieved after coronary intervention. Debulking of coronary stenoses is a concept to increase the luminal diameter after intervention. Laser angioplasty debulks coronary stenoses by ablation of atherosclerotic plaque. Since the first intravascular laser intervention, the technique has been significantly improved by the use of optimized wavelength, the development of flexible optimally spaced multifiber catheters and an additional saline flush technique. These technical advancements allowed a reduction in the incidence of adverse events, such as the number of dissections and perforations, associated with the use of the laser technique. Coronary laser angioplasty is commonly combined with adjunctive balloon angioplasty to optimize the outcome. Laser coronary angioplasty was not followed by a lower restenosis rate compared with plain balloon angioplasty in lesions without stents, however, a randomized comparison of the techniques including the use of the saline flush technique is not available yet. The value of excimer (acronym for excited dimer) laser coronary angioplasty for treatment of in-stent restenosis is still under investigation. So far, nonrandomized single center studies have not suggested a relevant benefit for this technique used for in-stent restenosis. In nonstented lesions there remain niche indications for laser angioplasty such as the treatment of ostial lesions, diffuse lesions or lesions traversable with a guidewire but not with an angioplasty balloon. Laser coronary angioplasty may also be useful after a failed balloon angioplasty and in patients with chronic total occlusions. The potential advantages of combining laser coronary angioplasty with vaporization of thrombus in patients with acute coronary syndromes are currently under evaluation.

Acute results, complications, and effect of lesion characteristics on outcome with the solid-state, pulsed-wave, mid-infrared laser angioplasty system: final multicenter registry report. Holmium:YAG Laser Multicenter Investigators

BACKGROUND AND OBJECTIVE

The solid-state, mid-infrared holmium:YAG laser (2.1 microm wavelength) is a relatively new percutaneous device that has recently been evaluated in a multicenter study. Because of its unique wavelength and photoacoustic effects on atherosclerotic plaques, this laser may be useful in treatment of symptomatic patients with coronary artery disease. This study sought to evaluate the safety and efficacy of mid-infrared laser angioplasty in the treatment of coronary artery lesions.

PATIENTS AND METHODS

Laser angioplasty was performed on 2,038 atherosclerotic lesions in 1,862 consecutive patients with a mean age of 61 +/- 11 years. Clinical indications included unstable angina (69%), stable angina (20%), acute infarction (6%), and positive exercise test (5%). Complex lesion morphology included eccentricity (62%), thrombus (30%), total occlusion (27%), long lesions (14%), and saphenous vein grafts (11%).

RESULTS

This laser catheter alone successfully reduced stenosis (>20%) in 87% of lesions. With adjunct balloon angioplasty, 93% procedural success was achieved. The presence of thrombus within the target lesion was a predictor of procedural success (OR = 2.0 [95% confidence interval 2.0, 4.0], P = .04). Bifurcation lesions (OR = 0.5 [95% confidence interval 0.2, 1.0], P = .05) and severe tortuosity of the treated vessel (OR = 0.4 [95% confidence interval 0.2, 0.9], P = .02) were identified as significant predictors of decreased laser success. Calcium within the lesion was associated with reduced procedural success (OR = 0.57 [95% confidence interval 0.34, 0.97], P = .03), and calcified lesions required significantly more energy pulses than noncalcified lesions (119 +/- 91 pulses vs. 101 +/- 86 pulses, respectively, P = .0002). Complications included in-hospital bypass surgery 2.5%, Q-wave myocardial infarction 1.2%, and death 0.8%. Perforation occurred in 2.2% of patients; major dissection in 5.8% of patients, and spasm in 12% of patients. No predictor of major complications was identified. Six-month angiographic restenosis was documented in 54% of patients, and clinical restenosis occurred in 34% of patients.

CONCLUSION

Mid-infrared laser has a safety profile similar to that of other debulking devices. This laser may be useful in select patients presenting with acute ischemic syndromes associated with intracoronary thrombus; however, like other coronary lasers, it is limited by the need for adjunctive balloon angioplasty and/or stenting to achieve adequate final luminal diameter. No beneficial effects on reducing 6-month restenosis rates were observed.

Smooth excimer laser coronary angioplasty (SELCA) and conventional excimer laser angioplasty: Comparison of vascular injury and smooth muscle cell proliferation

Although the excimer laser, which utilizes 'non-thermal ablation effects', has achieved encouraging results in early clinical trials, the long-term results have failed to show any advantage over conventional percutaneous transluminal coronary angioplasty (PTCA).A new system, Smooth Excimer Laser Coronary Angioplasty (SELCA), has been developed to reduce the tissue damage in the vessel wall caused by shock waves and vapour bubbles.SELCA (wavelength 308 nm, pulse duration 115 ns, repetition rate 150 Hz and energy density 50 mJ mm(-2)) lowers the amount of shock wave formation and pressure peak amplitude in the surrounding tissue by about eight times when compared to the conventional 308 nm excimer laser (ELCA). In this preclinical evaluation, this new system was compared to ELCA. Fifty New Zealand White rabbits were stimulated by repeated weak DC impulses for a period of 28 days in order to form an atherosclerotic plaque in the right carotid artery. The vessels were excised 3, 7,14 and 28 days after laser irradiation for immunohistochemical analysis.SELCA and ELCA laser treatment lead to a decrease in maximal intimal wall thickness 3 days after intervention (control: 177+/-4 microm; SELCA: 131+/-22microm; ELCA: 120 +/-33microm). In the period between 3 and 28 days, a moderate increase in intimal wall thickness was observed after SELCA treatment compared to a significant increase after ELCA (28 days after intervention: SELCA: 157+/-22microm; ELCA: 274 +/-28microm). Bromodeoxyuridine (BrdU) was applied 18 and 12 h before excision of the vessels in order to determine the percent of cells undergoing DNA synthesis. The percent of BrdU labelled SMC in the intima (control: 13 +/- 2 cells mm(-2)) increased in both groups after 3 days (SELCA: 248 +/- 107 cells mm(-2); ELCA: 162 +/- 41 cells mm(-2)) and 7 days (SELCA: 162+/- 55 cells mm(-2); ELCA: 279 +/- 119 cells mm(-2)).The present results demonstrate that vascular wall injury and increase in intimal wall thickness following SELCA are reduced in comparison to the results achieved with the conventional technique. Further trials are necessary to assess whether these improvements will lead to more favourable long-term results after excimer laser angioplasty.

Early deterioration after excimer laser-assisted coronary angioplasty

Coronary lumen changes after excimer laser coronary angioplasty, after adjunct percutaneous transluminal coronary angioplasty, and at 24 hours after intervention were assessed using quantitative coronary angiography. Lesions treated with this combined technique showed significant early deterioration within 24 hours.

Effect of intracoronary saline infusion on dissection during excimer laser coronary angioplasty: a randomized trial. The Percutaneous Excimer Laser Coronary Angioplasty (PELCA) Investigators

OBJECTIVES

We sought to evaluate whether intracoronary saline infusion during excimer laser coronary angioplasty decreases the incidence of significant laser-induced coronary artery dissections.

BACKGROUND

Despite procedural success rates > 90%, coronary artery dissections occur in 17% to 27% of excimer laser coronary angioplasty procedures. Excimer laser irradiation of blood results in vapor bubble formation and acoustomechanical trauma to the vessel wall. Saline infusion into a coronary artery may minimize blood irradiation and consequent arterial wall damage.

METHODS

In this prospective, randomized, controlled study, consecutive patients undergoing excimer laser coronary angioplasty were randomly assigned to conventional laser irradiation in a blood medium or to laser irradiation with blood displacement by intracoronary saline infusion. In the patients randomized to intracoronary saline infusion, prewarmed normal saline was injected through the coronary artery guide catheter at a rate of 1 to 2 ml/s using a power injector. The incidence and severity of dissection after excimer laser ablation were evaluated in a core laboratory by angiographers with no knowledge of treatment assignment. The severity of coronary artery dissection was rated on an ordinal scale of 1 to 5. Dissections of grade 2 or higher were considered significant.

RESULTS

The mean (+/- SE) dissection grade after laser angioplasty in patients treated with intracoronary saline infusion was 0.43 +/- 0.13 compared with 0.91 +/- 0.26 in patients undergoing laser angioplasty in a blood medium. The incidence of significant dissection was 7% in saline-treated patients compared with 24% in conventionally treated patients (p < 0.05). No significant complications were associated with saline infusion.

CONCLUSIONS

Intracoronary saline infusion should be incorporated into all excimer laser coronary angioplasty procedures.

Solid-state, pulsed-wave, mid-infrared coronary laser angioplasty in de novo versus restenosis lesions: observations from a multicenter study

The following is a study of the response of de novo versus restenosis coronary lesions to pulsed-wave, mid-infrared (holmium:YAG) laser assisted angioplasty. De novo lesions contain thrombi, cholesterol, and fibrosis, whereas restenotic lesions are composed of smooth muscle cells corresponding to injury caused by preceding balloon inflations. It is not known whether the different composition affects results of treatment by laser. In a clinical multicenter study, a mid-infrared, solid-state, pulsed-wave laser (holmium:YAG, 2.1 microns wavelength, 250-600 mJ/pulse, 5 Hz) was applied for revascularization of de novo and restenosis coronary lesions. Analysis of data was undertaken to document laser success, complications, and restenosis rate and to define whether the type of lesion treated had an effect on laser success and related complications. A total of 1340 patients with 1465 stenoses presented with symptomatic coronary artery disease. Laser success was 87 and 86% in these lesions, respectively. Overall procedural success of 93% was achieved. Restenosis lesions, known to be composed of smooth muscle proliferation, needed more laser energy for ablation than de novo lesions, which contain an atherosclerotic plaque (130 +/- 123 pulses vs 109 +/- 31, p = 0.001). Procedure-related Q-wave myocardial infarction was significantly higher in patients with de novo lesions over patients with restenosis lesions (1.4 vs 0.2%, p = 0.05). With the mid-infrared, pulsed-wave, holmium:YAG laser, the composition of the target lesion affects the energy level required, as well as the procedure-related complications.

Effect of midinfrared holmium: YAG laser angioplasty with and without balloon angioplasty on acute outcome and restenosis in atherosclerotic femoral arteries in rabbits

BACKGROUND AND OBJECTIVE

Pulsed laser may lessen vascular damage and reduce restenosis. This study examined the acute and chronic effects of midinfrared laser angioplasty with and without balloon angioplasty in atherosclerotic femoral arteries in rabbits.

STUDY DESIGN/MATERIALS AND METHODS

Atherosclerosis was induced in arteries by air desiccation and cholesterol feeding. Arteries were assigned to one of four groups: (1) laser angioplasty with a Thullium/Holmium/Chromium:YAG infrared laser (Eclipse), (2) balloon angioplasty, (3) laser followed by balloon angioplasty, and (4) no intervention. Arteries were examined angiographically and histologically at 2 hours and 28 days.

RESULTS

Intervention groups had significant initial gain, but this gain was less with laser alone than after balloon or after laser plus balloon. At 2 hours, laser alone caused greater arterial damage and thrombosis compared to controls. At 28 days, arteries treated with laser plus balloon had greater narrowing compared with arteries treated with balloon angioplasty. By multivariate regression analysis, the severity of the pre-intervention stenosis (P = 0.001) and intervention with laser plus balloon (P = 0.01) correlated independently with the severity of luminal narrowing at 28 days.

CONCLUSION

Midinfrared Ho:YAG laser angioplasty resulted in substantial acute damage with increased frequency of thrombus formation in this rabbit model. arteries treated with laser alone had suboptimal initial gain and more obstruction by plaque at 28 days compared to nonintervened arteries. The adjunctive use of balloon angioplasty improved initial gain, but correlated with smaller luminal diameters and more severe narrowing by plaque at 28 days.

Intravascular ultrasound imaging after excimer laser angioplasty

To help elucidate the mechanism of excimer laser coronary angioplasty (ELCA), intravascular ultrasound (IVUS) imaging was performed in 19 of 29 patients who were treated with ELCA. The results were compared with a non-randomized control group of 18 patients who had IVUS studies both before and after PTCA alone. After ELCA alone, lumen diameter (1.9 x 1.7 mm) and lumen cross-sectional area (CSA) (2.9 mm2) by IVUS were not significantly different from baseline values in the patients before PTCA alone (2.1 x 1.8 mm, 3.2 mm2). After balloon dilatation in the laser treated group, lumen diameter (2.5 x 2.1 mm) and lumen CSA (4.9 mm2) were significantly greater than those post ELCA alone. However, there was no difference in lumen CSA or atheroma CSA in the group treated with excimer laser plus balloon dilatation vs. these measurements in the group treated with PTCA alone. ELCA does not ablate a large amount of atheroma (9% reduction) but creates a pathway to permit easier passage of a PTCA balloon. These quantitative and morphologic results may help explain why the restenosis rate with ELCA is similar to PTCA alone.

Acute complications of excimer laser coronary angioplasty: a detailed analysis of multicenter results. Coinvestigators of the U.S. and European Percutaneous Excimer Laser Coronary Angioplasty (PELCA) Registries

OBJECTIVES

The aim of this study was to document and analyze the incidence and consequences of complications of excimer laser coronary angioplasty.

BACKGROUND

Excimer laser coronary angioplasty has been reported to be a safe and feasible alternative or adjunct to conventional balloon angioplasty, but serious and unique complications have been observed.

METHODS

Data on 1,595 interventions of excimer laser coronary angioplasty in 1,521 patients were analyzed, using a merged data base from the U.S. and European Percutaneous Excimer Laser Coronary Angioplasty (PELCA) registries.

RESULTS

Procedural success was achieved in 89.3% of interventions. Stand-alone laser angioplasty was performed in 17.8% of interventions. Complications included dissection (22.0%), vasospasm (6.1%), filling defects (4.8%), abrupt reclosure (6.1%), embolization (2.3%), perforation (2.4%), arrhythmia (0.7%) and aneurysm formation (0.3%). Major complications were non-Q wave myocardial infarction (2.3%), Q wave myocardial infarction (1.0%), coronary artery bypass grafting (3.1%) and death (0.7%). Logistic regression analysis revealed correlation between dissections and the use of larger catheter size (p = 0.0005), high energy per pulse levels (p = 0.0001 for native vessels), lesion length > 10 mm (p = 0.001) and presence of a side branch (p = 0.01). The incidence of perforations was higher in women (p = 0.004), in treatment of total occlusions (p = 0.02) and in the presence of a side branch (p = 0.03). Fatal complications were correlated with patients with multivessel disease (p < 0.0001), patients with acute myocardial infarction (p = 0.0009) and older patients (> 70 years old, p = 0.004). The incidence of major complications decreased after performance of 50 laser angioplasty procedures at one institution (p = 0.02).

CONCLUSIONS

This analysis defines both the learning curve and the profile of complications for excimer laser angioplasty and provides insight into the selection of appropriate patients and proper performance of the procedure.

Quantitative assessment of lumen area stenosis by Doppler echocardiography and application of continuity equation

Assessment of luminal stenosis plays a central role in the clinical decision makings for patients with heart diseases. To examine the role of Doppler echocardiography in the measurement of stenotic areas, we attempted to determine the mitral valve area and coronary artery stenosis by Doppler technique with a continuity equation. Mitral valve area was determined as a product of aortic or pulmonic annular cross-sectional area and the ratio of time velocity integral of aortic or pulmonic flow to that of the mitral stenotic jet. Mitral valve area determined at catheterization by Gorlin's formula was used as a gold standard. In the determination of coronary artery stenosis, flow velocity at the site prior to the stenotic lesion and that of stenosis was measured by catheter-tipped Doppler flowmeter (3-Fr, 20 MHz). The severity of the stenosis was calculated from the ratio of time-velocity integrals from prestenotic and stenotic segments. In 41 patients with mitral valve stenosis, valve area determined by continuity equation method correlated well with catheterization measurements irrespective the presence of aortic regurgitation (r = 0.91, y = 0.84x + 0.15, P less than 0.01). Of 20 patients with coronary artery disease, flow velocity both at the stenosis and prior to the stenosis could be determined in 13 patients examined. Under these conditions, coronary artery stenosis determined by continuity equation varied from 21%-76%. When these values were compared with those determined by biplane cineangiography, there was good correlation between them (r = 0.83, y = 0.92x - 0.45, P less than 0.01). These results demonstrate that Doppler-derived luminal area stenosis is applicable to assess the severity of the stenotic lesions, providing further information which cannot be obtained by the conventional methods, although several limitations should further be resolved.

Cardiovascular applications of laser technology

Laser technology has been evaluated for the treatment of coronary artery disease, ventricular and supraventricular arrythmias, hypertrophic cardiomyopathy, and congenital heart disease. Developments in laser angioplasty, laser thrombolysis, transmyocardial laser revascularization, photochemotherapy, laser treatment of arrhythmias and/or laser diagnostics are directed at improving upon conventional non-laser approaches, and providing new therapeutic and diagnostic options. This review will summarize the current status of the multiple applications of laser technology for cardiovascular diagnosis and therapy.

Coronary laser angioplasty

With the widespread growth of percutaneous transluminal coronary angioplasty (PTCA), the realization of limitations of balloon angioplasty stimulated the development of alternative revascularization approaches such as laser angioplasty. PTCA is best suited for the treatment of discrete atherosclerotic stenoses, with lower success rates and more difficult application in patients with diffuse atherosclerotic disease or total occlusions [1-3]. Moreover, despite an initially high primary success rate, coronary angioplasty is still plagued by a restenosis rate as high as 57% [4]. The potential advantages of laser angioplasty address the limitations of PTCA. In contrast to balloon angioplasty where the plaque material is compressed or displaced, laser angioplasty ablates the plaque material [5]. This bulk removal of plaque material could improve acute procedural success rates, decrease complication rates, treat "untreatable" lesions, and decrease restenosis rates. Because laser energy can vaporize atherosclerotic plaque, there may be no requirement for a preexisting channel, and therefore laser angioplasty may have a high success rate for the treatment of coronary occlusions. In its best embodiment, laser angioplasty offers the potential for passing a fiberoptic catheter through the entire length of the coronary circulation to vaporize all atherosclerotic plaque along the arterial wall. This applicability for the treatment of diffuse atherosclerotic disease would offer treatment opportunities currently unavailable with conventional bypass surgery or angioplasty.

Formation of pressure waves during in vitro excimer laser irradiation in whole blood and the effect of dilution with contrast media and saline

Pressure waves during excimer laser ablation of vascular tissue may be responsible for complications of coronary excimer laser angioplasty. In this experimental study, pressure waves were measured during excimer laser irradiation in blood and contrast media using a polyvinilidenefluoride hydrophone. At a distance of 4 mm lateral to the tip of a 1.7 mm multifiber laser catheter, excimer laser irradiation in blood resulted in a linear increase of peak pressures from 1,365 +/- 165 kPa at 30 mJ/mm2 to 2,866 +/- 404 kPa at 60 mJ/mm2. In contrast media, peak pressure increased from 3,172 +/- 573 kPa (30 mJ/mm2) to 5,763 +/- 467 kPa (60 mJ/mm2). Contrast media and saline were added to blood. At a concentration of 60% contrast in blood, a 3.4 fold increase of peak pressures was documented as compared to pure blood. Further increase of the concentration did not result in higher pressure waves. Concentrations of saline in blood of 90% and 96% reduced the peak pressures by 16% and > 50%, respectively, as compared to pure blood.

Acute vessel closure following excimer laser coronary angioplasty: can we predict it?

Of 124 consecutive patients undergoing elective excimer laser coronary angioplasty, 33 (26%) had periprocedural occlusion following excimer laser irradiation. Successful management (reopened vessel, no death, no myocardial infarction, no emergency bypass surgery) including repeat lasing, subsequent percutaneous transluminal coronary angioplasty, use of intracoronary nitroglycerin or streptokinase was achieved in 32 of the patients with acute occlusion following excimer laser coronary angioplasty. In one patient a nonfatal anterior myocardial infarction occurred. A late event occurred in two patients despite patency at the control angiography 24 h later. Multiple logistic regression modeling was used to examine the relationship between various characteristics and the risk of acute vessel closure. The preprocedural and procedural variables analyzed included progressive spasm prior to occlusion and lesion morphology after intervention (angiographic complications after percutaneous transluminal coronary angioplasty were prospectively divided into class 0, no complication, and classes 1-3, according to purely descriptive morphological characteristics). These showed a multivariate correlation with acute occlusion during excimer laser coronary angioplasty. These results suggest that acute vessel closure during stand-alone excimer laser coronary angioplasty is a benign but unpredictable event.

A new, safer lasing technique for laser-facilitated coronary angioplasty

In vitro studies during cold pulsed-wave laser angioplasty have demonstrated production of gas bubbles within the target tissue, creation of shock wave and formation of multi-layer dissections accompanied by an increase in the plaque and vessel wall temperature. These processes account for certain complications of coronary lasing, including acute vessel closure, dissections, spasm, and even perforation. The traditional lasing technique in which a large number of pulses is continually emitted across the lesion, may in fact contribute to the development and acceleration of the above mentioned processes. To overcome the shortcomings we have developed a new, safe lasing technique that consists of multiple trains of a small number of pulses each. Between laser sessions the laser catheter is retracted into the guiding catheter and nitroglycerin is injected intracoronary, thus providing time for dispersion of produced gas bubbles, cooling of the target artery, and adequate coronary vasodilatation. This new technique results in a significant reduction of laser associated complications.

Holmium: YAG laser-assisted coronary angioplasty with multifiber delivery catheters

Mid-infrared lasers are attractive for coronary angioplasty based upon their excellent fiberoptic transmission and enhanced tissue absorption. Using a solid-state, mid-infrared holmium:YAG laser with prototype multifiber laser delivery catheters, we performed coronary laser angioplasty with or without adjunctive balloon angioplasty or directional atherectomy in 14 patients with 17 stenoses. Procedural laser success was obtained in 13/14 (93%) patients and 16/17 (94%) lesions; however clinical success was achieved in 9/14 (64%) patients and 12/17 (71%) stenoses. Angiographic restenosis at 4.6 +/- 1.6 months was found in 5/8 (63%) patients. We achieved an excellent procedural laser success rate in patients with generally unfavorable angioplasty anatomy. However, our clinical success rate was not different from that expected with conventional angioplasty alone. The holmium laser remains an attractive energy source for laser angioplasty; but as is the case for all coronary laser systems, its utility as a stand-alone therapy is limited by catheters which create small channels. In this small group, we could demonstrate no clinical benefit for laser-assisted angioplasty in complex coronary lesions. Our results suggest that a randomized trial comparing laser-assisted angioplasty and conventional angioplasty be performed to determine the clinical benefits of this more expensive therapy.

Excimer laser coronary angioplasty in The Netherlands: preamble for a randomized study

The immediate outcome of ELCA by XeCl excimer laser radiation is described in 53 patients who were selected to undergo ELCA from December 1990 to September 1991 in two centers that are currently performing ELCA in the Netherlands. Immediate success rates on the basis of visual assessment of the angiogram were as follows. Laser success (> 20% reduction of diameter stenosis after ELCA alone) was observed in 77% of patients, procedural success (< 50% residual stenosis after ELCA with or without adjunctive balloon dilatation [PTCA]) in 91%, and clinical success (procedural success without clinical complications) in 83% of patients. Quantitative coronary angiography by automated contour detection was performed in 31 patients who underwent ELCA in the Thoraxcenter. The minimal luminal diameter (mean +/- SD) of the treated coronary segments increased from 0.77 +/- 0.41 mm to 1.24 +/- 0.25 mm after ELCA and further to 1.67 +/- 0.29 mm after adjunctive PTCA in 25 patients. The present experience is put in perspective of results initially reported by other centers and compared with data from multicenter registries of ELCA. Finally, a short description is given of the design of a prospective, randomized trial of ELCA versus conventional PTCA (AMRO trial).

Excimer, Ho:YAG, and Q-switched Ho:YAG ablation of aorta: a comparison of temperatures and tissue damage in vitro

The adjacent thermal and mechanical tissue damage after normal-mode Ho:YAG (pulse length = 250 mus, lambda = 2.09 mum), Q-switched Ho:YAG (pulse length = 200 ns, lambda= 2.09 mum), and excimer (pulse length = 120 ns, lambda = 308 nm) pulsed laser irradiation of human thoracic aorta samples was studied in vitro. Surface temperatures were monitored during laser irradiation with an IR camera in air or a thermocouple in saline. Histological analysis of the irradiated sites was performed to assess thermal and mechanical damage to tissue surrounding the crater. The ablation of aortic tissue with any of the lasers resulted in a temperature buildup inside the tissue; this effect was most significant for the IR wavelength. Mechanical damage was observed in all cases but was most pronounced for the Q-switched Ho:YAG laser. Excimer ablation in air left behind a smooth surface; however, under saline the result was a much rougher surface.

Laser facilitated angioplasty and thrombolysis in acute myocardial infarction complicated by prolonged or recurrent chest pain

To date, application of laser angioplasty in acute myocardial infarction (MI) has not been reported. In nine patients with acute myocardial infarction complicated by continuous or recurrent severe ischemia and chest pain, a mid-infrared, solid-state, pulse-wave holmium/thulium:YAG coronary laser was applied. In six of these patients the laser was specifically utilized for the purpose of coronary thrombolysis. In each case a guidewire was placed across the stenosis and a multifiber laser catheter was utilized, emitting 250-600 mJ/pulse at 5 Hz, followed by adjunctive balloon angioplasty. Laser success (defined as ability to cross the lesion, reduction of > or = 20% in stenosis and thrombolysis when a thrombus is present) was achieved in all patients. Final angiograms revealed residual stenosis < or = 30%, adequate thrombolysis and no major complication (MI, perforation, emergency CABGS, CVA, death) in each patient. Clinically, all nine patients improved, survived the acute infarction and were discharged. This initial clinical experience demonstrates the feasibility and safety of holmium/thulium:YAG laser application in thrombolysis and plaque ablation in selected patients who experience acute myocardial infarction complicated by prolonged or recurrent ischemia and chest pain.

Effects of pulsed lasers on agar model simulation of the arterial wall

Coronary laser angioplasty is limited by a high rate of dissection and the occurrence of abrupt closure and perforation. The aim of this study was to visualize the mechanical effects of pulsed lasers on two chamber in vitro models. These models consisted of 1 or 2 agar layers and calcium carbonate inclusions (1-layer model) or lipid (2-layer model) simulating lipid or calcified tissue. The inclusions were irradiated with a holmium-yttrium-aluminum-garnet (Ho-YAG) laser or a xenon chloride excimer laser. The Ho-YAG laser demonstrated dissection-like expansions of the target and perforation-like cracks. The size of dissection was obtained using an the empirical formula of energy (E) and the maximal expansion distance (Dmax) of the targets, Dmax = 0.15E0,87-1,17. The excimer laser showed rare and short perforation-like cracks and little dissection-like expansion of the gaseous products originating from the ablation of material. Ho-YAG laser ablation is likely to induce target tissue dissections and/or perforations. Excimer laser-ablates targets with less traumatic effects than Ho-YAG laser.

Occurrence, extent, and implications of pressure waves during excimer laser ablation of normal arterial wall and atherosclerotic plaque

Ablation of atherosclerotic plaque and normal arterial wall was performed using a Xenon-Chloride Excimer laser with a wave-length of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 microns bare fibre and adjusted to an energy density of 3.5J/cm2. The acoustic signals generated by the laser pulse were measured with two types of hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and 0.5 mm and recorded on a dual channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband fibre-optic transmission system. Tissue was retrieved from nine cadaver human aortas and macroscopically classified as either normal or calcified atherosclerotic plaque. Histological analysis (Haematoxylin eosin, elastica van Gieson, and immunohistochemical staining) was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For normal arterial wall, maximum peak pressure was 1.28 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2k Pa +/- 5.4k Pa/ns. For calcified, atheromatous segments, a maximum peak pressure of 2.02 MPa +/- 1.16 MPa, a rise time of 69.9 ns +/- 25.8 ns, and a pressure increase of 32.3 kPa +/- 21.3 kPa/ns was found. Statistical analysis showed a significant shorter rise time (P < 0.0001) and a higher pressure increase (P < 0.0001) for calcified tissue in comparison to normal arterial wall, whereas maximum pressures alone did not allow a differentiation of tissue characteristics. Several hundred kPa are generated during Excimer laser ablation.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical success, complications and restenosis rates with excimer laser coronary angioplasty. The Percutaneous Excimer Laser Coronary Angioplasty Registry

The role of excimer laser angioplasty in treating complex coronary artery disease remains uncertain. A randomized trial comparing this new technology with balloon angioplasty cannot be designed until systematic analysis identifies the lesion types that are likely to benefit from treatment with excimer laser angioplasty. In a cohort of 764 patients who had 858 coronary stenoses treated with excimer laser-facilitated angioplasty, relative risk analysis was used to examine acute success, complications and restenosis rates, and the results were compared with those of balloon angioplasty to identify the lesion types that show the greatest benefit with the new treatment. Clinical success was achieved in 657 patients (86%), as indicated by < or = 50% residual stenosis and no in-hospital complication. A major in-hospital complication (death, bypass surgery, or Q-wave or non-Q-wave myocardial infarction) occurred in 58 patients (7.6%). Follow-up angiography was obtained in 70% of eligible patients. Combining angiographic and noninvasive restenosis rates yielded an overall restenosis rate of 46%. Relative risk analysis showed that major complications occurred frequently in lesions at an arterial bifurcation (odds ratio [OR] 5.96 [2.76, 12.6]; p = 0.001). However, certain complex lesions that are difficult to treat with balloon angioplasty (saphenous vein graft lesions, lesions > 10 mm, ostial lesions, calcified stenoses, total occlusions and unsuccessful balloon dilatations), analyzed together as a group, had lower complication rates by univariate (OR 0.59 [0.35, 1.00]; p = 0.051) and multivariate logistic regression (p = 0.006) analyses.(ABSTRACT TRUNCATED AT 250 WORDS)

Wire-guided excimer laser coronary angioplasty: instrument selection, lesion characterization, and operator technique

Laser angioplasty has now been successfully performed on over 2,000 patients worldwide. Two systems (Advanced Interventional Systems, and Spectranetics, Corp.) have now received initial approval from the Food and Drug Administration. As with all new interventional techniques designed as an alternative to balloon angioplasty, there are a variety of instrument related issues that merit consideration in terms of patient selection as well as operator technique. While the ultimate role of laser angioplasty in the percutaneous revascularization of coronary artery disease remains to be established with certainty, laser angioplasty is, in fact, being currently used on a widespread basis as an alternative or an adjunct to balloon angioplasty in a large number of centers worldwide. Industry projections suggest that the use of this technique will increase further over the next decade. Accordingly, the purpose of this article is to discuss specific issues regarding instrumentation, native anatomical considerations, operator technique, and complications that relate specifically to the applied use of this technology as it is currently being used.

Success with coronary angioplasty as seen at demonstrations of procedure

To assess the real-life results of coronary angioplasty, unidentified participants made notes on 104 cases demonstrated live at twelve international angioplasty courses in 1991. The initially planned procedure was successful in 73% with crossover to another device in 20% for an ultimate success rate of 93%. Interventions lasted an hour on average and two devices on average were used per artery tackled. Rates of success and of complication necessitating reintervention were, for balloon angioplasty (57 cases) 81% and 19%, for directional atherectomy (16 cases) 75% and 0%, for the Rotablator (12 cases) 42% and 42%, for stent implantation (10 cases) 100% and 0%, for excimer laser angioplasty (6 cases) 17% and 33%, and for Rotacs recanalisation (3 cases) 67% and 0%, respectively. The complications were occlusions (threatened, acute, or delayed) and they were usually treated by balloon angioplasty or a stent. No death or myocardial infarction was reported. The observer attending the demonstration tended to take a less favourable view of the outcome than the clinician doing the procedure and in general the results of coronary angioplasty seemed inferior to those reported in journals. Interventions done before an audience will be unusually stressful but this will be outweighed by the fact that difficult cases with a low probability of success are rarely tackled during live courses. This survey suggests that conventional balloon angioplasty, complemented by stent implantation in selected cases, is the treatment of choice.

Vascular injury and time course of smooth muscle cell proliferation after experimental holmium laser angioplasty

BACKGROUND

In vitro experiments have shown that holmium laser energy can effectively ablate even calcified plaque in human arterial vessels. Because high-energy densities from holmium lasers can easily be transmitted through quartz fibers, this solid-state laser has been suggested as an alternative intraluminal treatment of atherosclerotic plaque.

METHODS AND RESULTS

To develop an intimal plaque, 35 New Zealand White rabbits underwent electrical stimulation of their right carotid artery for 28 days. Subsequently, in 25 rabbits, holmium laser angioplasty (wavelength, 2.12 microns; pulse duration, 150 microseconds; energy density, 350 mJ/mm2) was performed. To study the morphological results, the vessels were excised after 7, 14, 28, and 42 days. Cross sections were analyzed in regard to laser-specific injury. Staining of alpha-actin was used to identify smooth muscle cells (SMCs). After bromodeoxyuridine labeling, the extent of proliferation (number of cells undergoing DNA synthesis) was determined by using a monoclonal antibody. Holmium laser ablation resulted in an initial decrease of the numbers of intimal cell layers in the early group (7 days after treatment: 5 +/- 1 cell layers with 76 +/- 39 microns; control: 13 +/- 3 cell layers with 144 +/- 44 microns). Quantification of SMCs undergoing DNA synthesis in the intima (control: 51 +/- 19 cells/mm2) showed a significant increase of labeled cells after 7 (216 +/- 74 cells/mm2, p = 0.003) and 14 days (281 +/- 139 cells/mm2, p = 0.011). Integrity of the internal elastic lamina was disrupted in all animals after intervention. Seven and 14 days after treatment, a considerable reduction of medial cell nuclei was found in 10 of 12 animals. SMC proliferation in the medial layer was increased within the first 2 weeks after laser ablation (168 +/- 113 cells/mm2; control: 8 +/- 4 cells/mm2; p = 0.023). Six weeks after holmium laser angioplasty, SMC proliferation had returned to control levels in the intima and remained increased in the medial layer. This proliferative response resulted in a significant increase of intimal thickening within 6 weeks after laser ablation (30 +/- 6 cell layers, 375 +/- 97 microns resp.; p = 0.001 each).

CONCLUSIONS

Holmium laser treatment leads to considerable vessel wall injury and results in SMC proliferation in the intimal and medial layer with a maximum of proliferative activity within the first 2 weeks. Subsequently, this results in considerable intimal and medial hyperplasia within 6 weeks after treatment.

Excimer laser ablation before autoperfusion balloon inflation: a novel therapeutic approach to high grade stenoses in vessels supplying substantial myocardium at risk

The utility of a novel approach employing excimer laser ablation to form a channel for subsequent autoperfusion balloon angioplasty is presented. Two important advantages of this strategy are highlighted: (1) applicability to severe stenoses in vessels supplying substantial myocardium at risk and (2) ability to allow prolonged inflation time to minimize procedure related ischemia and optimize revascularization of the heart. We prospectively selected and studied five patients and performed excimer laser coronary angioplasty using either a 1.3 mm or 1.6 mm laser catheter followed by autoperfusion balloon dilatation. Procedural success was documented by a significant reduction in mean percent diameter stenosis from 89 +/- 4% (S.D.) to 53 +/- 4% after laser angioplasty (p < 0.0001) and subsequently to 20 +/- 4% after autoperfusion balloon angioplasty (p < 0.0001). Clinical success was attained and characterized by resolution of anginal symptoms for at least 4 weeks after hospital discharge. There were no major acute complications encountered; however, restenosis has occurred in 2 out of 5 patients. We therefore recommend this novel pre-dilation strategy with excimer laser followed by autoperfusion balloon angioplasty in selected patients with an extensive amount of myocardium at risk.

Laser angioplasty

Laser energy has the potential for selective ablation of atherosclerotic plaque through minimally invasive means. As currently practiced, laser angioplasty requires the adjunct of balloon angioplasty in most cases and has limited application compared with more conventional methods of revascularization. However, new advances in guidance systems, delivery devices, and laser sources may allow realization of the full benefit of this technology at some point in the future.

Origin of arterial wall dissections induced by pulsed excimer and mid-infrared laser ablation in the pig

To study adjacent tissue damage after delivery of holmium, thulium and excimer laser pulses, porcine thoracic aortas were irradiated in vivo. After 3 days, microscopic analysis of 67 craters produced by all three lasers demonstrated large dissections extending from the craters. The mean diameter of the dissections was smaller for excimer-induced craters (1.38 +/- 0.42 mm; n = 22) than for holmium-induced (2.7 +/- 0.87 mm; n = 22) and thulium-induced (2.37 +/- 0.42 mm; n = 14) craters (p less than 0.01 vs. mid-infrared dissections). In addition, microscopic analysis demonstrated necrosis adjacent to the crater. The lateral necrotic zones of the thulium-induced craters were smaller than the holmium- and excimer-induced necrotic zones (p less than 0.01). To identify the origin of the excessive tissue tearing, laser-saline and laser-tissue interaction were compared in vitro by time-resolved flash photography. In saline solution, the mid-infrared lasers showed bubble formation on a microsecond time scale. The excimer laser produced similar bubbles in the vicinity of tissue. For all three lasers, elevation of the tissue surface was shown during in vitro ablation. Dimension (diameter up to 4 mm) and time course (rise time of 100 to 300 microseconds) of bubble formation and tissue elevation were strikingly similar. Thus, tissue dissections are caused by the expansion of a vapor bubble within the target tissue. Coronary dissections after excimer and mid-infrared laser angioplasty might be related to the forceful bubble expansion.

In vivo assessment of vascular pathology resulting from laser irradiation. Analysis of 23 patients studied by directional atherectomy immediately after laser angioplasty

BACKGROUND

The pathological consequences of cardiovascular laser irradiation have been studied extensively in vitro. Previous in vivo studies of laser-induced injury have included analyses of acute and/or chronic findings in experimental animals. Little information, however, is available regarding the acute effects of laser irradiation of human vascular tissues in vivo.

METHODS AND RESULTS

To determine the acute pathology resulting from laser irradiation of human vascular tissue in vivo, specimens retrieved from 23 patients by directional atherectomy immediately after laser angioplasty (19 peripheral and four coronary) were examined by light microscopy. Of the 23 patients, three (13.0%) were treated with a metal-capped ("hot-tip") fiber coupled to a continuous-wave neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using up to 18 W power and 18-305 seconds of cumulative exposure time; in all three patients (100%), thermal injury, including frank charring several cell layers thick, was seen along the luminal borders of the atherectomy specimen. In eight of the 23 patients (34.5%), laser angioplasty was performed using a 250-microseconds holmium:YAG laser at fluences up to 2,300 mJ/mm2, a repetition rate of 5 Hz, and 25-200 seconds of cumulative exposure; in seven of eight patients (85.5%), the atherectomy specimen showed signs of vacuolar injury consisting of central and satellite Alcian-blue-negative vacuoles. In two patients (25.0%), there was a "smudged" or "shredded" edge, whereas in one patient, frank signs of thermal injury were observed. Finally, in 12 of the 23 patients (52.2%), laser angioplasty was performed using a 120-nsec excimer laser at fluences up to 60 mJ/mm2, a repetition rate of 25 Hz, and a cumulative exposure time of 21-315 seconds. Pathological findings among these 12 patients were limited to nine patients (75%) in whom a weakly basophilic, smudged, and/or shredded appearance approximately one cell layer thick was observed along the luminal border of the atherectomy specimen and two patients (16.7%) with small foci of vacuolar injury. None of the atherectomy specimens retrieved after excimer laser angioplasty disclosed signs of thermal injury.

CONCLUSIONS

These findings document that acute pathological alterations resulting from in vivo laser angioplasty are variable, depending on the laser source used, and are similar to that predicted by experimental studies performed previously in vitro. The prognostic implications of these varying pathological features remain to be clarified.

Quantitative assessment of coronary artery stenosis by intravascular Doppler catheter technique. Application of the continuity equation

BACKGROUND

Quantitative assessment of coronary artery stenoses plays a central role in clinical decision making. According to the continuity equation, the ratio of the time-velocity integral of prestenotic to stenotic flow velocities represents the ratio of the cross-sectional area of the stenotic to prestenotic segments. However, no data exist regarding the application of this method to clinical assessment of human coronary artery diseases. Therefore, we attempted to determine the severity of coronary artery stenoses by applying the continuity equation to the coronary circulation.

METHODS AND RESULTS

Nineteen patients with a stenosis of the proximal left anterior descending coronary artery (LAD) and one patient with a stenosis in an aortocoronary bypass graft to the LAD were studied. Coronary flow velocities at the prestenotic and stenotic segments were measured with an end-mounted Doppler catheter (3F, 20 MHz), and the time-velocity integral ratio was calculated. Percent area stenosis was calculated as (1-time-velocity integral ratio) x 100. In three patients with severe stenosis (greater than 90% in area stenosis), velocity at the stenosis could not be determined because of aliasing of Doppler signals, and in four, Doppler signals at the stenosis were not measurable because of technical difficulties. The stenotic flow velocity was successfully recorded in 13 patients (65%) with mild to moderate stenosis. The diastolic peak flow velocity at the stenosis was 90 +/- 36 cm/sec (mean +/- SD), and was significantly greater than the velocity at the prestenotic segment, 48 +/- 18 cm/sec (p less than 0.01). Percent area stenosis determined by Doppler continuity equation correlated closely with that by biplane coronary angiography (r = 0.83, y = 0.92x-0.45, p less than 0.01).

CONCLUSIONS

Application of the continuity equation to Doppler catheter measurement of coronary flow velocity can be used to successfully compute the severity of coronary stenoses. This may be a useful alternative method to estimate functional severity of coronary artery disease, although further technical developments will be necessary to improve the sensitivity.

Success rate and incidence of restenosis following coronary excimer laser angioplasty: results of a single center experience

The initial single center experience of percutaneous coronary excimer laser angioplasty is described for the first three series of 147 patients. Sixty patients were treated with a prototype 1.4-mm laser catheter, 40 patients with improved transmission devices, and the third series of 47 patients with an increased pulse width of the laser system allowing improved energy transmission. In 17 patients (12%) laser angioplasty could not be initiated due to inability to cross the lesion with the guidewire or to place the catheter coaxially within the vessel. In 32 patients (58%) of series 1, 11 patients (31%) of series 2, and 17 patients (43%) of series 3, additional balloon dilatation following laser treatment was necessary due to vessel closure (24%) or due to an insufficient angiographic result (35%). There was one death in series 1 (2%) and 2 (3%) each, one perforation in series 2 (3%), two transmural myocardial infarctions in series 1 (4%), and one myocardial infarction in series 2 (3%). During the 6-month follow-up period one patient in series 2 (2%), and one patient in series 3 (3%) died. Angiographic restenosis was found in 22, 12, and 11 patients of series 1 (40%), 2 (34%), and 3 (27%), respectively. No patient developed a transmural myocardial infarction. Thus, percutaneous coronary excimer laser angioplasty can be performed as a safe and feasible procedure in patients with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of morphologic parameters in predicting the outcome of coronary excimer laser angioplasty

The treatment of complex coronary lesions with conventional balloon angioplasty is associated with a reduced success rate and an increased incidence of complications. To evaluate the influence of lesion morphology on the outcome of coronary excimer laser angioplasty, morphologic parameters of 148 target lesions in 147 consecutive patients were determined. Morphologic analysis included target vessel, involved vessel segment, vessel diameter, minimal lumen diameter, length of the lesion, single discrete (concentric/eccentric) or complex lesions (occlusions, bifurcational, tandem or long segmental lesions), American College of Cardiology/American Heart Association Task Force classification, lesion location in curved or straight vessel segments, prestenotic vessel tortuosity and the direction of the laser approach in curved vessels with eccentric lesions. Failure of laser angioplasty occurred in 17 patients because of failed guidewire placement (n = 8), catheter placement (n = 6), or inability to pass the lesion with the laser catheter (n = 3). Successful stand-alone laser angioplasty was achieved in 68 procedures. In 63 interventions additional balloon angioplasty was necessary (n = 60) or stand-alone laser angioplasty was not successful (n = 3). The frequency of complex lesions, particularly total occlusions (p less than 0.001) and prestenotic vessel tortuosity (p = 0.002) was significantly increased in the group with failed laser attempts. Statistical analysis of the morphologic parameters in successful stand-alone laser interventions compared with combined or unsuccessful interventions revealed no significant difference. These data suggest that failure of laser angioplasty occurs because of low catheter flexibility and the need for guidewire support in treating totally occluded vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Excimer laser-facilitated balloon angioplasty of a nondilatable lesion

Preliminary clinical experience with excimer laser coronary angioplasty shows that it is a safe and effective means of achieving nonsurgical coronary revascularization in selected patients but specific indications for its use are as yet undefined. In the present report a specific indication is proposed for the use of the excimer laser: to facilitate balloon inflation in a rigid stenosis that fails to dilate despite high balloon inflation pressures.

Percutaneous coronary excimer laser-assisted angioplasty: initial multicenter experience in 141 patients

Initial multicenter clinical experience with percutaneous coronary excimer laser-assisted angioplasty is described for 158 lesions in 141 patients. Using a xenon chloride (308 nm) excimer laser generator and 1.5 to 1.75 mm catheters, excimer laser angioplasty was attempted at 135 ns pulse width, 25 to 40 Hz repetition rate, 2 to 5 s laser delivery time and 30 to 60 mJ/mm2 energy fluence. Laser success (greater than 20% improvement in luminal diameter) was achieved in 138 (87%) of 158 lesions, with a reduction to less than 50% stenosis noted in 77 lesions (49%). Overall, laser-assisted balloon angioplasty success (less than 50% residual stenosis without major complication) was observed in 129 (91%) of 141 patients. Procedural complications (abrupt closure 1.3%, side branch occlusion 1.9%, intimal dissection 6.3%, embolization 1.3%, filling defect 1.3%, perforation 1.9% and spasm 1.3% and major complications (non-Q wave myocardial infarction 4.8%, emergency coronary bypass surgery 3.5% and death 0%) were infrequent and predominantly related to subsequent balloon angioplasty. In the early follow-up period (range 1 to 10 months, mean 7), 111 (79%) of the 141 patients remain asymptomatic, whereas symptoms have recurred in 27 (19%) and 3 patients (2.1%) have died. Thus, percutaneous coronary excimer laser angioplasty appears to be a feasible and safe procedure. Assessment of the impact of this technology on the acute complications of and restenosis rates after angioplasty awaits further follow-up analysis.

Laser angioplasty in miniature swine: advantages of a modified fiber tip delivery system

Laser angioplasty using a spherical lensed fiber-tip laser delivery catheter and a 200 mum bare silica fiber tip was performed in occluded atherosclerotic iliac arteries of miniature swine. Group I consisted of 8 animals with 11 totally occluded arteries in which the bare silica fiber was used. Group II included 22 animals with occlusive lesions in 41 arteries in which the silica lens tip was used. In vivo laser angioplasty was performed in both groups using an argon ion laser delivering 2 to 3 watts of power in 1 to 5 second intervals. Successful recanalization occurred in 7/11 (64%) in group I arteries and 35/41 (85%) in group II arteries. Vascular perforation occurred in 36% (4/11) in group I compared to 10% (4/41) in group II (P less than 0.05). Mechanical perforation due to the bare fiber alone accounted for 50% of the perforations in group I and did not occur with the silica lens-tip device (group II). We conclude that the atraumatic lensed fiber is more effective in recanalizing occlusive lesions and is a safer delivery system than the bare silica fiber.