Human percutaneous and intraoperative laser thermal angioplasty: Initial clinical results as an adjunct to balloon angioplasty

Percutaneous Transluminal Laser Angioplasty

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.

Argon Laser-Assisted Peripheral Angioplasty

Pioneered several years ago by cardiologists and interventional radiologists, laser-assisted angioplasty for the ablation of occlusive atherosclerotic lesions in the peripheral and coronary circulations is now entering the domain of the vas cular surgeon, who has the ability to progress beyond the limitations of the percutaneous approach.

In the initial 38 patients undergoing 51 lower extremity laser angioplasty/ balloon dilatation procedures for peripheral vascular occlusive disease, pedal pulses were restored in 32 (63%) limbs. The tandem procedure failed in 16 (31%); however, when improvement was assessed objectively by postoperative ankle/arm index evaluation, a positive outcome was achieved in 72 % of the patients. Three (6%) patients required femoral-popliteal bypass after balloon- related arterial dissection was identified.

Although laser angioplasty can successfully open occluded arteries, new in traoperative angiographic equipment compatible with laser angioplasty and a variety of incrementally sized laser probes will facilitate refinement of the tech nology and enhance its application.

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.

Management of Failed or Failing Infrainguinal Bypasses with Distal Correctable Lesions

The goal of this study was to assess the management of failed or failing infrainguinal bypasses with distal correctable lesions. A retrospective analysis of 94 procedures was performed for 72 (77%) failed and 22 (23%) failing infrainguinal bypasses with distal correctable lesions in 94 patients. The 94 procedures included 50 (53%) balloon angioplasties and 44 (47%) distal vein graft extensions from the previous graft to the distal artery. Preprocedural thrombolytic therapy was performed in 62 of 94 limbs with a failed graft, and complete thrombolysis was achieved in 30 of 94. The results of thrombolytic therapy (complete or incomplete thrombolysis) or the means of revision procedure (balloon angioplasty or distal vein graft extension) did not affect the patency. Lower patency was observed for women, patients with a secondary bypass, and grafts with multiple episodes of revision. We conclude that the patency of failing infrainguinal bypasses after revision of distal lesions was affected not by means of therapy but by previous vascular procedures, the usual risk factors, and female gender.

No additional benefit from laser in balloon angioplasty of the superficial femoral artery

OBJECTIVES

To evaluate the efficacy of the addition of plaque ablation by hot-tip laser to balloon angioplasty.

DESIGN

Prospective randomised clinical trial.

MATERIALS AND METHODS

Patients with either occlusion orf > 50% diameter stenosis less than 3 cm in length in the superficial femoral artery, and with two or three calf vessel run-off were eligible and randomised to receive either balloon angioplasty alone or with laser assistance. Treatment failure in follow-up was defined as reocclusion or recurrence of greater that 50% stenosis at the site of angioplasty.

RESULTS

Ninety limbs (82 patients) were entered into the study. Forty-four patients had mild claudication, 32 more severe symptoms and 6 rest pain or ulceration. More patients with diabetes (5 of 5, p = 0.04, Fisher's exact test) and occlusions (16 of 22, p < 0.05, chi(2)) were randomised to the laser group. Initial technical success was obtained in all lesions. The median duration of follow-up was 1 year. Failure occurred in 40 limbs during follow-up. Three segments, all with initial occlusions and undergoing laser angioplasty re-occluded within 2 days, one requiring immediate thrombectomy. Another 20 limbs underwent further intervention. Overall success (+/- S.D.) (Kaplan-Meier) at 1 year was 67% (+/- 5%) and at 2 years 43% (+/- 7%). Only increased age, initial occlusion, female sex, and not smoking were significantly (p < 0.05, Cox's proportional hazards) associated with failure; on multivariate analysis, age and occlusion were the best independent predictors. There was no significant difference (p > 0.05) in outcome between limbs undergoing laser assisted balloon angioplasty and balloon alone either overall of within the stenosis or occlusion subgroups.

CONCLUSIONS

This study found no significant benefit was gained by the addition of laser to balloon angioplasty and that the long term success was modest for lesions considered to be suitable for angioplasty.

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.

Initial results of laser angioplasty under angioscopic guidance for salvage of an ischemic lower limb: preliminary report

From March to July 1989, nine patients at risk for peripheral artery disease underwent intraoperative Nd:YAG laser angioplasty using angioscopy at the Veterans General Hospital (Taipei, Taiwan, Republic of China). Following the laser angioplasty, balloon dilatation was performed in all cases. Eight men and one woman at an average age of 68 were included in the study (range: 58 to 78 years old). Ischemic symptoms included five patients with disabling claudication, four with pain at rest and one with gangrene on the toes. Eight of the nine patients had complete occlusions ranging from 2 to 19 cm in length. Two patients had high degree multiple segmental stenosis of the superficial femoral artery from 1 to 2 cm in length. Initial clinical success (indicated by relief of symptoms and increase in Doppler ankle pressure and index) and improvement in the angiographic luminal diameter was noted in 9 of 10 occluded vessels (90%) that underwent Nd:YAG laser treatment which was delivered at 10 to 12 watts through laser probes. Prelaser intraluminal diameter increased from 0.05 +/- 0.07 to 0.53 +/- 0.07 mm, Doppler ankle pressure index rose from 0.51 +/- 0.12 to 0.81 +/- 0.12, Doppler ankle pressure increased from 62.44 +/- 16.10 to 104 +/- 21.21 mmHg and the amplitude of pulse volume recorder at ankle level rose from 5.77 +/- 2.80 to 12.11 +/- 2.77 mm as compared with prelaser therapy (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Laser thermal angioplasty for early repair of anastomotic stenosis after lower extremity arterial reconstruction: initial experience

Laser thermal angioplasty with a sapphire hot-tip Nd-YAG laser system was effectively used for five grafts with anastomotic stenotic lesions which occurred after femoro-popliteal arterial reconstructions. Stenotic lesions were detected by a combination of Doppler flow waveform analysis and ankle/brachial index measurement in 32 femoro-popliteal and five femoro-tibial arterial bypass grafts in the postoperative period. The laser probe used was 3 to 4 mm in diameter. There were no perforations of the arterial wall caused by thermal ablation, even with repeated pulses of 40 watts of laser energy for 3 s. Contact Nd-YAG laser thermal angioplasty using this rounded, 3-4 mm hot-tip facilitated effective widening of the lumen of the anastomotic stenotic lesion. All patients remain well at follow-up from 9 to 20 months after laser thermal angioplasty.

Early experience with the smart laser in the treatment of atherosclerotic occlusions

A dual-laser system (helium-cadmium and pulsed dye) capable of continuous computer analysis of spectroscopic characteristics of tissue fluorescence, which can distinguish atherosclerotic plaque from components of normal arterial wall, was used to deliver laser energy to ablate plaque. During a 1-year period this system was used to facilitate balloon angioplasty of short (3 to 17 cm) total occlusions of the superficial femoral or popliteal arteries only when standard angioplasty techniques were ineffective. During the year of the study, in one institution 415 patients were subjected to arteriography of the lower extremities for leg ischemia (397 for limb salvage indications). Standard angioplasty techniques were used in 94 of these patients; 218 patients were unsuitable for standard angioplasty, did not fulfill criteria for "smart" laser treatment, and underwent standard bypass operations. Only 11 patients (plus six others in the second institution) requiring treatment fulfilled the criteria for use of the "smart" laser. In 10 patients the occluding lesion was traversed by the laser wire (diameter 0.021 inch), and luminal patency was effectively restored by balloon angioplasty to greater than or equal to 70% of the most normal-appearing segment of that artery. Satisfactory luminal patency has persisted for 2 to 12 months (mean 6 months) in nine patients; the lesion in the tenth patient restenosed at 3 months. The laser procedure was unsuccessful in all three patients with occlusions greater than 10 cm and in four others. Although there were three microperforations with the laser wire, there were no clinically significant complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental treatment of thrombotic vascular occlusion

The role of laser energy in the treatment of thrombotic vascular occlusion was evaluated in two sets of experiments. First, 10 polytetrafluoroethylene grafts were used to replace segments of the superficial femoral arteries in dogs and were thrombosed by distal ligation. Occlusion was maintained for one hour, or for 7, 14, 21, and 28 days in each of two grafts. Patency was restored in all 10 grafts without perforation or anastomotic disruption using a 2 mm hot tip probe powered by an Argon laser. However, increased organization of thrombus related to the duration of occlusion lead to decreased laser channel diameters, and 75% of the 28 day thrombus remained in the graft after recanalization. The second experiments tested the added benefit of thrombolytic infusion following laser recanalization. Bilateral external iliac artery thrombosis was induced in dogs by operative vessel isolation, de-endothelialization, and thrombin injection. At 7 days the efficacy of laser-assisted thrombolysis (LAT) versus enzymatic thrombolysis (ET) alone was compared. Eight vessels underwent ET by urokinase (4000 I.U./min.); 14 vessels were laser recanalized prior to thrombolytic infusion. LAT was performed from a carotid artery approach in 8 vessels (antegrade) and from a femoral artery in 6 vessels (retrograde). In contrast to studies using the hot tip alone, both ET and LAT accomplished complete thrombus removal. However, LAT lead to significant iliac arterial flow in 9 +/- 8 min. (antegrade) and 25 +/- 8 min. (retrograde) while ET required 109 +/- 47 min (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of balloon angioplasty and laser thermal angioplasty in the treatment of femoropopliteal atherosclerotic disease: initial results of a prospective randomized trial. Work in progress

The authors recently initiated a prospective randomized trial in which results of standard balloon angioplasty were compared with those of laser thermal angioplasty in the treatment of patients with symptoms of femoropopliteal occlusive disease. The data regarding their initial technical success are reported herein. Twenty-five patients with moderate to severe claudication have thus far undergone 27 procedures. The type of lesions treated varied from short focal stenoses to occlusions up to 10 cm in length; 12 stenoses and 15 occlusions were treated. Fourteen procedures were randomized to laser therapy and 13 to standard balloon angioplasty. If the primary randomized treatment failed, the alternative procedure was then attempted. Of the 14 laser procedures, five were initial failures; three of these failures were subsequently treated successfully with the balloon technique. Three of 13 balloon procedures were failures; none were subsequently successful with use of the laser. While these data are limited, initial experience indicates that technical success is directly related to the ability to pass an angiographic wire through the lesion and the length and type of lesions. It does not appear to depend on whether the laser or the balloon is used.

Recent changes in the treatment of aortoiliac occlusive disease by the Oxford Regional Vascular Service

Over the four years from 1 January 1985 to 31 December 1988, 192 patients were treated for aortoiliac occlusive disease by the Oxford Regional Vascular Service. The number of patients treated by percutaneous transluminal angioplasty increased from two in the first year of the study to 34 in the third year of the study. This increase was accompanied by a decrease in the proportion of patients treated by aortobifemoral bypass but the proportion of patients treated by extra-anatomic bypass remained constant at around 30 per cent. Twice as many patients were treated in the fourth year as in the first year of the study so that the number of surgical operations increased despite many patients being treated exclusively by percutaneous transluminal angioplasty. The number of patients requiring mandatory treatment for limb salvage increased by 109 per cent and optional treatment for intermittent claudication by 85 per cent. The introduction of percutaneous transluminal angioplasty in Oxford has coincided with an increase in the number of patients presenting with symptomatic aortoiliac occlusive disease and has allowed twice as many people to be treated while the number of aortobifemoral bypass operations has remained unchanged. It is concluded that the introduction of percutaneous transluminal angioplasty has not only generated its own workload but has also led to an increased demand for surgical reconstruction for aortoiliac occlusive disease.

Initial results and subsequent outcome of laser thermal-assisted balloon angioplasty of 56 consecutive femoropopliteal lesions

Laser thermal-assisted balloon angioplasty (LABA) was prospectively applied in the treatment of 56 atherosclerotic femoropopliteal occlusive lesions in 51 consecutive patients. All procedures were performed in the operating room using a neodynium:yttrium-aluminum-garnet (Nd:YAG) laser source, and patients were evaluated for immediate and long-term hemodynamic and clinical improvement. Technically successful recanalization was achieved in 82% of cases, with 57% of all patients (32 of 56) obtaining early hemodynamic and clinical improvement. Long-term clinical success (by life-table analysis) was obtained by only 22.5% at 6 months, and only 13.5% at 12 months. Patients presenting with intermittent claudication did significantly better than those presenting for limb salvage (p = 0.01), and trends toward improved outcome were noted for short versus long lesions as well as for patients with "good" versus "poor" distal runoff (NS). Procedure-related morbidity occurred in 14%, and there was one peri-procedural mortality (1.8%). We conclude that the use of LABA is associated with long-term clinical success in only a small proportion of patients, and that widespread clinical application of this technique is not indicated at the present time.

Heparin-resistant thrombus formation by endovascular stents in baboons. Interruption by a synthetic antithrombin

Intravascular mechanical support has been proposed as a solution to the frequent occurrence of vascular narrowing and occlusion after transluminal balloon angioplasty or surgical endarterectomy. Although several endovascular stents are currently in clinical use for angioplasty of larger vessels, acute thrombosis is a troublesome complication of their use with coronary angioplasty. To study thrombus formation associated with metallic mesh endoprostheses, we have evaluated stents placed inside 3-mm expanded polytetrafluoroethylene (ePTFE) grafts incorporated into chronic exteriorized arteriovenous silicone rubber shunts in baboons. We have also compared the antithrombotic capacities of heparin and the synthetic antithrombin D-phenylalanyl-L-prolyl-L-arginyl-chloromethylkene (D-FPRCH2Cl) to interrupt this platelet-dependent process for two different endovascular stents. Acute platelet deposition was continuously measured during 1 hour using gamma camera imaging of platelets labeled with indium-111 oxine. On untreated control ePTFE grafts (n = 11), 0.87 +/- 0.15 x 10(9) platelets/cm were deposited during 60 minutes. In contrast, balloon-expandable endovascular stents within ePTFE (n = 6) accumulated 4.37 +/- 0.68 x 10(9) platelets/cm (p = 0.003 compared with controls), and self-expandable stents (n = 6) accumulated 3.91 +/- 0.42 x 10(9) platelets/cm (p = 0.006 compared with controls); no difference between stents was detected in this test system (p greater than 0.5). Systemic heparin treatment did not reduce platelet deposition (4.20 +/- 0.41 x 10(9) platelets/cm at 60 minutes; p greater than 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental argon laser thermal angioplasty as an adjunct to balloon angioplasty in peripheral arteriosclerotic disease

Laser thermal recanalization has been used clinically as an adjunct to balloon angioplasty in the treatment of peripheral arteriosclerotic disease, with improved initial success rates in total peripheral occlusions and greater 1 yr vessel patency suggested, as compared to balloon angioplasty alone. However, the morphological effects of laser-assisted balloon angioplasty are unknown. Therefore, the goals of the present study were to evaluate 1) the angiographic and histologic effects of laser thermal recanalization followed by balloon angioplasty and 2) the hypothesis that balloon-catheter-induced neointimal fracture could be sealed by subsequent laser thermal angioplasty in an experimental rabbit iliac artery atherosclerotic model. In Group 1 (7 vessels), a 1.5 mm metal capped argon laser fiberoptic was introduced via femoral arteriotomy and 10 W of thermal power was applied to the iliac artery stenosis for 5 sec while maintaining constant back-and-forth motion. Thereafter, balloon angioplasty was performed in the same vessel segment with a 2.5 mm balloon catheter inflated 3 times at 5 atm for 30 sec each. Mean angiographic luminal diameter increased from 1.1 mm to 2.0 mm after both procedures, and mean final post balloon dissection grade was 0.6 on a scale of 0, 1+, and 2+. Perforation occurred once with the laser probe and once with the balloon catheter. Histologic examination of these vessels was characterized by irregular thermal erosions with minimal reactive thrombosis. In Group 2 (10 vessels), the sequence was reversed, with laser thermal angioplasty following balloon dilation. Mean angiographic luminal diameter improved from 1.2 mm to 1.8 mm after both procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of lasers in the management of peripheral vascular disease

Although it has been almost twenty-five years since the first studies of McGuff et al, who employed the laser for atheroablation, problems still require resolution. The various laser wavelengths from ultraviolet through visible to infrared have been employed for atheroablation. The laser's greatest appeal and the most spectacular results have been in reopening channels in totally occluded vessels. The laser's greatest problem has been damage of the arterial wall and even perforation. The purpose of this presentation is to clarify the present status of available lasers for the treatment of peripheral vascular disease of the lower extremities. To this end, the initial experience with angioscopically guided laser-assisted angioplasty with a new hybrid laser probe is reported.

Optothermal mathematical model and experimental studies for laser irradiation of arteries in the presence of blood flow

We have developed an optothermal model for the interaction of laser light and the tissue of arterial walls and have checked its validity with animal experiments. The mathematical model consists of a laser diffusing tip positioned intraluminally in a cylindrical artery, in which the diffused laser light is incident on a blood-tissue interface at a distance from the tip. A temperature profile throughout the interface is obtained by considering the optical interaction and the thermal conduction and convection of the blood and tissue. The distribution of light in the media is determined using both Beer's law and the Kubelka-Munk two-flux theory in cylindrical coordinates. For experimental in vivo verification, a diffusing tip was inserted in canine arteries and the temperature profile varied by restricting the volume of blood; this simulated degrees of occlusion to determine the influence of blood flow on heat transport. The measured temperature profiles compared favorably to the theoretical results. Temperature profiles are also predicted for a water-filled lumen. The theoretical model will be useful in predicting the depth of ablation and extent of normal tissue damage during laser angioplasty treatment of atherosclerosis.

Applications and limitations of laser-assisted angioplasty

Laser-assisted angioplasty is rapidly evolving into a promising adjunct to or replacement for standard vascular procedures. A protocol was devised to evaluate the technique in a non-selected, consecutive patient population to define the applications and limitations of the technique. In a 12-month period, 358 lower-limb atherosclerotic lesions were treated with laser/balloon angioplasty [percutaneously (52%) or open (48%)] in 206 consecutive patients. Overall, the laser/balloon technique recanalised 234 lesions (65% laser success), judged clinically effective by a greater than 0.15 improvement in the ankle/brachial index and elimination of symptoms. Operative complications included: perforation (15, 4.2%); thrombosis (16, 4.5%); spasm (5, 1.4%); and false aneurysm at the puncture site (7, 2.0%). Of the 124 failures (35%) categorised for analysis, the most common cause was inability to cross the lesion in 20 cases. This experience has identified three significant clinical limitations to successful laser recanalisation: calcification, inadequate distal circulation, and inability to control restenosis/reocclusion (collapsible lesions and accelerated plaque deposition). Further research is needed to determine if thermal injury seriously compromises the safety and long-term outcome of laser-assisted angioplasty.

The effects of argon laser on in vitro aggregation of platelets in platelet rich plasma and whole blood

The effects of an Argon laser on platelet aggregation were studied, since platelets may be exposed to laser energy when used intravascularly. Various preparations of platelets in platelet rich plasma (PRP) and whole blood, with or without aspirin, were tested with the aggregating agents ADP, collagen, thrombin, and epinephrine. Simultaneous release of ATP was also measured in PRP. At relatively low levels of irradiation, platelet aggregation was potentiated. Enhancement was evidenced by an increase in percent aggregation, earlier onset of the reaction, and reduction in the amount of aggregating agent required. In PRP, the mechanism of laser potentiation appeared to be the release of endogenous ATP from platelets. At relatively high levels of irradiation, platelets were destroyed and aggregation abolished. In whole blood, the mechanism was somewhat more complicated since release of ATP occurred from RBCs as well as platelets. Spontaneous aggregation following laser treatment occurred in isolated instances in PRP and in every trial in whole blood preparations. Aspirin ingestion inhibited the laser's effects in PRP but not in whole blood. These results may have important clinical implications for laser angioplasty, and the potentiated aggregation response may prove useful in laboratory studies of platelet function.

Rotational endarterectomy in normal canine coronary arteries: preliminary report

Endarterectomy was performed in vivo using a high speed rotating abrasive-tipped catheter device in 11 normal canine coronary arteries. The device is designed to remove atheromatous material from diseased arteries by the abrasive action of its rotating tip. It was operated percutaneously from a femoral approach using conventional angioplasty guiding equipment. The rotating device was advanced over a guide wire from just beyond the tip of the guide catheter into the distal vessel. Six arteries were harvested immediately after endarterectomy and five were left in place for 7 +/- 2.8 days; in the latter group, the animals were maintained on a regimen of aspirin, 325 mg/day. Angiography before and after treatment demonstrated vessel patency in all cases. Caliper-measured luminal diameters were not significantly changed after endarterectomy. Histologic examination of pressure-fixed vessels showed extensive intimal loss and 20 to 30% loss of the internal elastic lamina. Medial damage was superficial and never exceeded 40% of the total medial thickness. There were no vessel perforations. Results of histologic study of the myocardium supplied by the treated vessels were normal without evidence of distal embolization or infarction. It is concluded that a high speed rotating abrasive device can be safely operated percutaneously in normal coronary arteries and results in minimal vessel damage and continued patency at 7 +/- 2.8 days.