Direct argon laser exposure for recanalization of peripheral arteries: early results

Direct laser light, in combination with percutaneous transluminal angioplasty (PTA), was used to recanalize atherosclerotic peripheral arteries. Argon laser energy was controlled with an optical assembly and aligned with a special centering/dilation balloon so that plaque tissue absorbed laser energy directly and was vaporized. A channel was thereby created with multiple 10-W laser exposures (2-10 seconds), and conventional angioplasty was then performed. Recanalization was achieved in 33 of 36 procedures (92%), in 23 femoropopliteal (mean length, 9 cm) and three iliac total occlusions and ten femoropopliteal high-grade stenoses, with the three failures occurring in the first group. Complications included two emboli, six moderate groin hematomas, and one laser perforation. While these results are preliminary (mean follow-up, 3 months), direct laser angioplasty appears to be a useful adjunct to PTA for treating atherosclerotic arteries.     

Percutaneous transluminal laser angioplasty. Progress over the past two years

The progress in percutaneous transluminal laser angioplasty (PTLA) over the past two years is presented. The technical development includes the application of new equipments to laser sources, delivery systems and monitors. We review new experimental research in rapidly establishing animal models and human postmortem specimens, as well as efforts to select adequate wave length and irradiation time for laser energy with suitable infusion media. A summary of clinical trials is given on expanding usage, complication rates and long-term patency of PTLA. The current trends in PTLA respecting guide wire assisted balloon angioplasty and other recanalization methods are described.     

Endovascular excimer laser atherectomy techniques to treat complex peripheral vascular disease: an orderly process

Peripheral vascular disease represents the largest obstructive subsegment within the vascular system. Advances in equipment, techniques, biochemical treatments, and the influx of multiple specialties into this arena indicate a coming tidal wave of change to the standard treatment plan for patients with claudication and especially critical limb ischemia. Initial attempts in the 1980s to utilize the "laser" to treat peripheral vascular disease led to a clinical debacle: wavelengths and methods were not optimized; tissue heating was excessive, resulting in restenosis. Since then the "laser" has fallen from grace for endovascular treatment, although it has an infinite set of potential wavelengths, energy levels, and delivery methods. The xenon chloride, excimer laser, a pulsed 308-nm system, has overcome many of these early catastrophes. The long, ongoing success of this method of photoablating thrombus and plaque represents a true step forward in the endovascular treatment of occlusive disease. Although only a tool, the excimer laser provides a means to utilize electromagnetic energy instead of shearing mechanical force to resolve occlusions. With its active element at the tip, the excimer laser requires much less mechanical translation force to cross total occlusions, find the distal lumen, and thereby cause less plaque destabilization. In addition, removing the firm surface layer of plaque, decapping, and some of the plaque volume, debulking, exposes the softer subsegments of the plaque to balloon angioplasty. Utilizing this method, more complex lesions can be approached safely, with a high likelihood of successful revascularization and a low risk of potentially limb-threatening complication.     

Laser-assisted percutaneous angioplasty: initial clinical experience in peripheral arteries

Experimental and animal studies have shown that laser energy can vaporize intra-vascular thrombus and atheroma, suggesting that it may have a role in percutaneous angioplasty. Argon laser energy transmitted via a flexible fibre introduced through a percutaneous catheter was used in 15 patients undergoing balloon angioplasty of femoral or popliteal arteries. Of four stenoses, laser alone produced improvement of the lumen in two. Of 11 occlusions some degree of clearance of the lumen was achieved by laser in eight prior to balloon dilatation. Extravasation of contrast medium indicating wall perforation occurred in two patients, without clinical sequelae. No other complications, such as embolism, arterial spasm or toxic effects were observed. There was one acute re-occlusion, almost certainly not related to the use of laser. There have been no late complications. The ability of laser to influence favourably vascular occlusion is confirmed, but technical advances are necessary to avoid vessel wall perforation consistently and to improve the production of an adequate lumen before its potential can be fully realized.     

Occlusive peripheral vascular disease: a multicenter trial of fluorescence-guided, pulsed dye laser-assisted balloon angioplasty.

Fluorescence-guided, laser-assisted balloon angioplasty was performed in 129 patients with iliac and femoropopliteal artery chronic occlusions (range, 0.5-50.0 cm; mean length, 9.9 cm) after failure of recanalization with standard guide-wire techniques. Laser recanalization and short-term angiographic success were achieved in 101 (72%) and 95 (68%) of 140 occlusions, respectively. Laser and balloon angioplasty failures were encountered in heavily calcified plaques or after perforations and dissections. Complications included perforations (19%), hematomas (5%), thromboses (4%), and distal embolizations (4%). Real-time fluorescence spectroscopy identified thrombus, white fibrous plaque, and media but could not avoid perforations in many cases because laser wire advancement outdistanced fluorescence sensing. Disruption of tissue by means of pressure transients and/or mechanical advancement occurred in at least 36% of lesions where the laser energy was insufficient (less than 0.4 J/cm) to ablate significant tissue. Integration of fluorescence guidance with pulsed dye laser ablation is feasible, but additional refinements are necessary to increase safety and efficacy.     

Experimental angioplasty: lessons from the laboratory

To elucidate the pathophysiologic mechanisms of transluminal angioplasty, normal coronary arteries in dogs, atherosclerotic human coronary arteries, and atherosclerotic vessels in rabbits were studied after angioplasty. Normal canine coronary arteries showed desquamation of endothelium, exposure of subendothelial connective tissue elements, and deposition of a carpet of platelets, fibrin, and occasional red blood cells. Administration of low molecular weight dextran before angioplasty decreased platelet deposition. Atherosclerotic human coronary arteries studied postmortem showed enlargement of lumen size after angioplasty due to splitting and disruption of the plaque and the underlying media. Endothelial desquamation and splitting of the plaque were also seen in atherosclerotic vessels in rabbits after angioplasty. The amount of splitting seems to depend on the relative size of the stenotic vessel and the inflated angioplasty balloon. Animals studied sequentially showed retraction of the separated intimal plaque elements and further lumen enlargement after 1-2 weeks. Two mechanisms of successful angioplasty are suggested by these studies: (1) desquamation of superficial plaque elements and (2) splitting of the plaque with retraction of intimal flaps as healing occurs. These mechanisms have important implications for the treatment of patients undergoing percutaneous transluminal angioplasty.     

Percutaneous transluminal angioplasty of the aorta. Light and electron microscopic observations in normal and atherosclerotic rabbits

Histological changes which developed after percutaneous transluminal angioplasty in normal and atherosclerotic rabbit aortas were correlated with balloon size and inflation time. In normal rabbits, progressive changes were observed in the intima and media with increasing balloon size and inflation time. The atherosclerotic aortas exhibited unpredictable fragility, with limited correlation between histological changes, balloon size, and inflation time, attributable mainly to the distribution and thickness of plaques. In atherosclerotic vessels, the mechanism of angioplasty consisted of plaque dehiscence and fracture, followed by overstretching of the plaque-free wall segments. No plaque compression was observed.     

Laser thermal angioplasty for the treatment of obstruction of the distal superficial femoral or popliteal arteries

The success rates and clinical effectiveness of percutaneous laser thermal angioplasty for obstruction of the distal superficial femoral or popliteal arteries were assessed. Laser thermal angioplasty was performed with the first commercially available laser system on 25 atherosclerotic vascular lesions in 20 lower extremities of 18 patients. Fifteen of the lesions were occlusions (average length, 5.6 +/- 3.1 cm), and 10 were high-grade stenoses (average length, 2.6 +/- 1.8 cm). Indication for angioplasty was claudication limiting life-style in 12 extremities and threatened limb loss in eight. All patients were treated with a 1.5- or 2.0-mm metal-capped optical fiber attached to a 14-W argon-ion laser. Balloon angioplasty was performed after laser recanalization in all successful cases. The patients were followed by Doppler ankle/brachial index and clinical evaluation. Laser thermal angioplasty was technically successful (vessel recanalization) in 18 (90%) of 20 of the cases. Fourteen (70%) of 20 extremities were successes by ankle/brachial index follow-up, while 15 (75%) of 20 remained clinically improved after an average follow-up of 7.8 +/- 5.3 months. Laser thermal angioplasty has a technical and clinical success rate that compares favorably with previous reports of balloon angioplasty. With proper patient selection, laser thermal angioplasty can reduce the difficulty of traversing lesions that are amenable to standard balloon angioplasty and increase the number of vascular lesions that can be treated percutaneously but could not be recanalized without the use of laser energy.     

Analysis of particle size generated during plaque ablation with a flashlamp pumped pulsed dye laser

Purpose To examine debris size generated duringin vitro plaque ablation by laser energy and estimate the risk of peripheral embolization following laser angioplasty. Methods A flashlamp pumped pulsed dye laser of 480nm wavelength was used to ablate calcified arteriosclerotic plaque, fibrous fatty plaque, and normal aortic wall on samples of human cadaver aortas. Each tissue sample was immersed in saline solution and treated with the same amounts of laser energy transmitted by a 320 μm-diameter glass fiber in direct tissue contact. The debris generated during plaque ablation was then separated from the supernatant and the particles were counted and analyzed for size. Results Depending on the underlying type of tissue and the setting of laser energy, a wide range of particles with sizes between 5.3 mm² and 64 μm² was found in samples. The largest particles were found after ablation of calcified atherosclerotic plaque, whereas fibrous, fatty plaque and normal aortic wall showed smaller particles and a lesser amount of debris. Conclusion Our study demonstrates that a considerable amount of debris is generated during laser angioplasty at 480 nm and that particle size is sufficient to cause potentially symptomatic embolic occlusions of mid- and small-sized peripheral arteries.     

Balloon expandable intraluminal vascular stent

The percutaneous, intraluminal placement of an expandable arterial stent is a new method for reducing stenosis in atherosclerotic arteries. This method, used in conjunction with balloon angioplasty, involves the placement of metallic mesh stent at the sight of the stenosis. Use of this technique has resulted in various improvements over angioplasty alone.     

Cryoplasty for the Prevention of Arterial Restenosis

Restenosis after percutaneous transluminal angioplasty remains the limiting factor for the long-term benefit of endovascular therapies of peripheral arterial occlusive disease. Despite a variety of modifications and adjuncts to angioplasty such as bare metal stents, covered stents, and drug-eluting stents as well as a number of new technologies like laser angioplasty and cutting balloon angioplasty, restenosis rates have not been significantly affected and remain inferior to those for surgery for long lesions in the femoropopliteal segment. Cryoplasty, which combines balloon angioplasty with the application of cryothermal energy to the vessel wall, was suggested as a promising approach to prevent the formation of neointimal hyperplasia after angioplasty procedures. This review discusses the basic principles of cryoplasty, summarizes the current data on restenosis rates after cryoplasty treatment, and evaluates cryoplasty as a new treatment method to solve the problems associated with restenosis development. The results of the clinical studies suggest that cryoplasty is a feasible and safe technique in the treatment of femoropopliteal disease, however, they have failed to prove any superiority of cryoplasty over conventional angioplasty.     

血管内超声在1例颈内动脉闭塞患者介入治疗中的应用

目的 探讨血管内超声(IVUS)技术在颈内动脉闭塞经皮腔内血管成形术(PTA)中的应用价值.方法 1例患者CTA明确颈内动脉闭塞,脑灌注成像见低灌注区与缺血相关症状符合,在IVUS导引下接受PTA治疗.采用微导丝及微导管同轴技术通过闭塞段,IVUS确认位于真腔内,微导管造影确认闭塞远端血管通畅,调整后放置栓塞保护器;IVUS测评斑块及管腔情况,球囊预扩张后再次测评;血管内恢复正向血流后通过IVUS虚拟组织学序列分析斑块稳定性,斑块纤维帽稳定且管腔狭窄率＜40％仅作单纯球囊扩张治疗.结果 单纯球囊扩张治疗后闭塞血管再通,恢复正向血流.IVUS全程检测狭窄段斑块纤维帽稳定,管腔狭窄率＜40％,脑灌注成像显示低灌注状态明显改善.结论 IVUS技术在PTA治疗颈内动脉闭塞中起重要导引作用,可增加再通手术成功率,降低并发症发生率.     

Thermal laser-assisted angioplasty of renal artery stenosis for renovascular hypertension

Percutaneous transluminal laser-assisted angioplasty of a renal artery stenosis was performed in a 16-year-old woman with renovascular hypertension. The stenotic portion of the renal artery was predilated by delivering Nd-YAG laser energy to the terminal tip of a laser catheter. Although the luminal diameter did not increase sufficiently with laser angioplasty alone, it allowed passage of the balloon catheter and subsequent successful balloon angioplasty. Immediately after dilatation, the patient's blood pressure fell to normal, and plasma renin activity decreased. There were no serious complications. Thermal laser angioplasty seems to be an effective adjunct technique for the treatment of severe renal artery stenosis which does not allow initial passage of a balloon catheter.     

Combined laser and balloon angioplasty of venous obstructions in patients with insufficient hemodialysis access fistulas

In 19 patients with insufficient hemodialysis access fistulas combined laser and balloon angioplasty of two occlusions and 17 stenoses of the shunt vein was performed. In 13 of those 19 cases the procedure was preceded by balloon angioplasty, which was insufficient because of resistant subintimal fibrosis. After using the pulsed dye laser a complete dilatation was possible in all cases.The new method is a valuable addition to percutaneous interventional techniques in patients with shunt problems, and better long term results may be expected in selected cases. Offprint requests to: E. Gmelin     

In vitro and clinical feasibility study with an over-the-wire delivery system for pulsed dye laser angioplasty.

The suitability of a pulsed dye laser (504 nm) in experimental and clinical angioplasty was investigated. In an experimental study, the ablation thresholds were 3 J/cm2 +/- 8 (mean +/- standard deviation) for fibrofatty plaque and 25 J/cm2 for calcified tissues under saline. At a radiant exposure of 10 J/cm2 the etch rates were 1.7 microns per pulse +/- 0.3 for media, 2.8 microns/pulse +/- 0.4 for normal intima, and 3.9 microns/pulse +/- 1.1 for fibrofatty plaque (P less than .05). Pressure wave effects with a separation of tissue layers were predominantly localized at the internal elastic lamina. Thermal injury with vacuolations extended 15 microns +/- 6 into adjacent tissue. For clinical study, laser-assisted balloon angioplasty was performed in 10 patients (64 years +/- 14) with occlusions of peripheral arteries using a 9-F multifiber ring catheter. Lesion length ranged from 2 to 12 cm (mean, 7 cm). Laser angioplasty with an 80 mJ/pulse decreased the mean stenosis from 100% to 58% +/- 12% (P less than .005). The ankle-brachial index rose from a median of 0.48 to 0.88 (P less than .001). In 33% of patients, there were subintimal dissections after laser angioplasty. After a mean follow-up of 10.2 months, the overall clinical success was 70% with a primary patency of 78%. The over-the-wire approach with a pulsed dye laser may constitute a safe and feasible tool in laser angioplasty.     

Initial clinical experience with a new pulsed dye laser device in angioplasty of limb ischemia and shunt fistula obstructions.

Selective plaque ablation with laser radiation at 405-530 nm in vitro has been reported. We investigated the possibilities of a new pulsed dye laser device for in vivo recanalization of arteries in ischemic lower limbs and stenoses/occlusions of arterio-venous hemodialysis shunt fistulae. A specially designed 9F or 7F multifiber catheter was used for treatment of 10 patients with lower limb artery obliterations and 11 patients with malfunctioning hemodialysis access fistulae (HAF). The recanalization technical success was 5/5 in the iliac arteries (IA), 4/5 in the superficial femoral arteries (SFA), and 11/11 in the HAF. Early re-occlusions occurred in one SFA and one IA, respectively, caused by very bad run-off. There was one clinically insignificant SFA perforation. Additional balloon angioplasty was considered necessary in 10/16 lesions. Mean ankle-arm index increased from 0.68 to 0.97. With two exceptions all HAF patients were re-integrated in the dialysis program. Pulsed dye laser angioplasty promises to be an effective and fast method for plaque ablation/debulking. The first clinical experience confirms previous in vitro results. In particular laser recanalization may become the method of choice for treatment of rigid HAF obstructions and it seems to be superior to vascular surgery or balloon angioplasty alone.     

Laser angioplasty of peripheral arteries: An epilogue?

This review gives a short overview of the results of 15 years of experimental and clinical work on laser angioplasty. Experimentally, photothermal and photomechanical ablation of plaque could be demonstrated. However, laser angioplasty did not cause reduction of platelet adhesion and intimai hyperplasia. Clinically, the technique of laser angioplasty was continuously improved until the initial recanalization rates and longterm patency rates in femoropopliteal artery occlusions were the same as the success rates of percutaneous transluminal angioplasty (PTA). This was proven by various randomized studies. Currently, laser angioplasty cannot be proposed as a routine procedure because it is an expensive technology. However, laser recanalization and debulking of total occlusions should be further developed, especially in combination with endoluminal graft placement.     

Radiofrequency balloon angioplasty. Rationale and proof of principle

Post-angioplasty restenosis (PARS) in atherosclerotic lesions of medium and small arteries occurs in about one-third of cases in the first year following percutaneous transluminal angioplasty (PTA) (early PARS). PARS includes acute spasm, dissection with reclosure, elastic recoil, fibrocellular proliferative response, and progressive atheromatous disease. Fibrocellular proliferation (possibly initiated by platelet derived growth factor) is felt to be culpable in many cases of early PARS (months). Pharmacologic regimens, stents, and thermal welding of the intimal-medial cracks of PTA are among the interventions being developed to deal with PARS. Radiofrequency (RF) current as a source of thermal energy may be useful in combination with balloon angioplasty to reduce PARS. Ideally, this combination would (1) weld intimal-medial cracks of PTA; (2) mold plaque and normal vessel to increase lumen diameters without creating intimal-medial cracks; and (3) destroy medial smooth muscle cells and multipotential cells (cellular substrate of PARS). Canine in vivo studies have established the feasibility of RF-mediated vascular tissue welding. Human aortic specimens (N = 28) were manually dissected into intima-media and media-adventitia layers. Bipolar RF energy (650 KHz, total 300 J) and mechanical pressure (1 atm) (experimental group, N = 24) or mechanical pressure alone (control group, N = 4) were applied to the reapposed specimen layers in a special chamber. The chamber was modified with a bipolar electrode designed to reproduce that planned for an RF balloon angioplasty catheter. Welding was demonstrated in normal and atherosclerotic treated specimens (23/24 or 96%) but not controls (0/4).(ABSTRACT TRUNCATED AT 250 WORDS)     

Follow-up of conventional angioplasty versus laser thermal angioplasty for total femoropopliteal artery occlusions: results of a randomized trial.

Sixty-eight patients with 68 femoropopliteal occlusions were entered into a randomized trial of conventional guide-wire and catheter percutaneous angioplasty versus laser thermal angioplasty. Thirty-four occlusions were randomized to conventional angioplasty and 34 to laser thermal angioplasty. After successful recanalization and balloon dilation, the patients were followed up for 1 year. Follow-up consisted of obtaining measurements of the ankle-arm indexes at 1, 3, 6, and 12 months. The increase in the mean resting ankle-arm index 1 year after conventional angioplasty (0.26) was greater than that after laser angioplasty (0.12). At 1-year follow-up, the cumulative success rate was 47% for patients treated with conventional angioplasty versus 39% for those treated with laser angioplasty. Statistical analysis showed no significant difference in clinical success between the two treatment groups.     

Percutaneous intravascular US as adjunct to catheter-based interventions: preliminary experience in patients with peripheral vascular disease

Catheter-based ultrasound (US) transducers may be introduced into the vascular system to record high-resolution images of the vessel wall and lumen. The potential advantages and existing liabilities of percutaneous intravascular US as an adjunct to transluminal vascular recanalization were investigated. A 6.6-F braided, polyethylene catheter enclosing a rotary drive shaft with a single-element, 20-MHz transducer at the distal tip was used in 17 patients undergoing percutaneous transluminal (balloon) angioplasty (PTA) alone (10 patients), PTA with implantation of an endovascular stent (two patients), atherectomy alone (two patients), or laser angioplasty with PTA and/or atherectomy (three patients). The arteries treated and examined included the common iliac in five patients, the external iliac in two, the superficial femoral in nine, and a vein graft-arterial anastomosis in one. In 14 cases PTA was employed as sole or adjunctive therapy; plaque cracks were clearly delineated with intravascular US in all 14 (100%) and dissections were observed in 11 (78%). Plaque-arterial wall disruption was less prominent in the arteries treated with mechanical atherectomy. The results of laser angioplasty reflected the adjunctive modality employed. After stent implantation, serial intravascular US documented effacement of PTA-induced plaque cracks and/or dissections. Intravascular US also aided in the quantitative assessment of luminal cross-sectional areas after the procedures (19.0-51.8 mm2). The observations recorded in this preliminary group of 17 patients illustrate the potential utility of intravascular US as an adjunct to conventional angiography in patients undergoing percutaneous revascularization.