Laser Endarterectomy Research Articles

A novel ultrasound-assisted laser technique to remove atherosclerotic plaques

Atherosclerosis is a medical condition in which arteries hardens and narrows due to the buildup of fat, cholesterol, calcium, and other substance. It can affect arteries of heart, brain, arms, legs, pelvis, and kidney, resulting in ischemic heart disease, carotid artery disease, peripheral artery disease, and chronic kidney disease. Laser based treatment techniques like laser angioplasty and carotid artery laser endarterectomy can be used to treat most common atherosclerosis disease like ischemic heart disease and carotid artery disease. Excimer laser coronary angioplasty (ELCA) is a clinical technique to remove the arterial plaque. However, the use of ELCA remains low due to higher risk of complication and its low efficacy in removing plaques as compared with balloon angioplasty. In this study, we developed a novel technology that uses ultrasound along with laser to assist the removal of atherosclerotic plaque. Spatio-temporally synchronized pulsed laser and ultrasound was used. The preliminary experiments were performed on pig belly fat sample to find the optimal ultrasound and laser parameters. The final experiment was performed on the plaque samples collected from patient during carotid endarterectomy procedure. Our results show that the addition of ultrasound can effectively reduce the needed laser power, which could result in improved treatment safety and efficiency.

Vascular Applications of Lasers

There have been major advances in laser technology and in our understanding of the effects of laser energy on blood vessels. This, in turn, has led to the many clinical applications of lasers in patients with vascular disease. The clinical results of laser endarterectomy, laser angioplasty, laser-assisted balloon angioplasty, laser-assisted vascular anastomoses, and the future of lasers in cardiovascular disease are discussed.

Initial results of endothelial cell seeding following argon laser carotid endarterectomy.

This study evaluates the initial results of endothelial cell (EC) seeding following argon laser carotid endarterectomy. Venous endothelial cells were harvested from 12 dogs and cultured. A laser endarterectomy was performed on both carotids of each dog. One side was seeded with endothelial cells. Six dogs had both carotids harvested 1 hour after restoring blood flow. The others were harvested in 24 hours. The percentage of lumen covered with EC was evaluated by scanning electron microscopy. At 1 hour, the seeded arteries demonstrated 35 +/- 3 percent EC coverage, whereas the unseeded arteries had no EC coverage (P = 0.0002). At 24 hours, the seeded arteries had 58 +/- 15 percent EC coverage, whereas the unseeded arteries had no coverage (P = 0.01). Significant gross thrombus developed only in unseeded arteries (P = 0.047), two of which were occluded at 24 hours. EC seeding is beneficial following argon laser carotid endarterectomy resulting in improved patency and less surface thrombogenicity.

A Color Atlas of Endovascular Surgery

Part 1 Natural history of the atherosclerotic lesions: the atherosclerotic lesion relationship of the distribution of lesions and the application and development of interventional methods. Part 2 Angioplasty devices techniques and applications: intraluminal access techniques balloon angioplasty lasers atherectomy stents additional endovascular techniques. Part 3 Angioscopy. Part 4 Additional imaging techniques and guidance methods: angiography ultrasound spectroscopy. Part 5 Evolving related technologies in vascular surgery: laser endarterectomy laser vascular tissue fusion.

Excimer Laser Radiation for Endarterectomy of Experimental Atheromas

Open laser endarterectomy produces a smooth arterial surface with welded distal end points. This report evaluates 308-nm excimer laser radiation for the laser endarterectomy operation. Arteriosclerotic New Zealand white rabbits (N = 15) were studied. A thoraco-abdominal exploration was performed, the aorta was isolated, heparin was administered, and multiple endarterectomies were performed in each rabbit. A line of laser craters was created at the proximal and distal ends of an atheroma. Laser radiation was used to connect the craters to form the proximal and distal end points. The atheromas were dissected from the aorta with laser light and the end points were fused. The aortas were removed for light and electron microscopy and the animals were sacrificed. Excimer radiation was delivered by a 600-microns fiber at 50 mJ/pulse, 120-ns pulses and either 15- or 20-Hz frequency. At 15 Hz excimer laser endarterectomies showed no perforations along the surface or at the end points. The surfaces were smooth but the end points were not welded in place. At 20 Hz, perforations were seen along 7/11 surfaces and at 5/11 end points. Excimer laser endarterectomy is best performed at 15 Hz. The end points, however, cannot be welded with excimer laser radiation.

Initial clinical evaluation of carotid artery laser endarterectomy

Initial clinical evaluation of carotid artery laser endarterectomy

Initial clinical evaluation of carotid artery laser endarterectomy

Clinical study of carotid artery laser endarterectomy began April 15, 1988. This report describes the first 10 cases that were performed in nine patients (five men and four women, mean age 70 years). Indications were asymptomatic stenosis (5), transient ischemic attacks (4), and stroke in evolution (1). There were two emergency cases and eight elective cases (including one reoperative case). Surgical exposure, systemic heparinization, vascular control, and a longitudinal arteriotomy were used. The cleavage plane between atheromas and media was developed with argon ion laser radiation (488 and 514.5 nm) directed through a 300 μm quartz fiber at power 1.0 W. Laser radiation was used to cut the atheromas out of the arteries and weld the end points. Residual atheromatous debris were vaporized with individual laser exposures. Arteriotomies were closed with sutures, and blood flow was restored. The endarterectomies were 3.9 ± 1.1 cm long and required 330 ± 97 joules. Mean clamp time was 22.5 ± 7.9 minutes. Shunts were used in two cases. There were no arterial perforations or injuries as a result of laser light. Complications were hematoma (1), respiratory arrest (1), and transient neurologic deficit (1). Carotid endarterectomy is technically feasible with argon ion laser radiation. In the present series, postoperative observations, averaging 12 months and ranging from 5 to 19 months, have shown satisfactory results. No angiographic follow-up examinations were carried out.

Initial Trial of Argon Ion Laser Endarterectomy for Peripheral Vascular Disease

In the initial of open laser endarterectomy, 16 patients underwent 18 reconstructions for claudication (13 patients), rest pain (3 patients), and gangrene (2 patients). The mean (+/- SD) preoperative ankle arm index was 0.53 +/- 0.18. The laser endarterectomies were aorto-bi-iliac (1 patient), iliac (1 patient), superficial femoral (7 patients), profunda femoral (7 patients), and popliteal-posterior tibial (2 patients). All operations included surgical exposure, vascular control, administration of heparin, and an arteriotomy. Atheromas were dissected from arteries with argon ion laser radiation (power, 1.0 W). End points were welded with laser light. Arteries were closed primarily. The laser endarterectomies were 6 to 60 cm long and required 168 J to 2447.5 J. All patients had symptomatic relief, with a postoperative ankle arm index of 0.97 +/- 0.10. There were no arterial perforations from laser radiation. Surgical complications included early thrombosis requiring thrombectomy (3 patients) and hematoma requiring evacuation (1 patient). The laser endarterectomies have an 88% patency at 1 year. Open endarterectomy can be performed with laser radiation. A larger clinical trial is necessary to define the indications for laser endarterectomy in peripheral vascular disease.

Laser-Assisted Balloon Angioplasty: Analysis of 132 Clinical Cases

From September, 1987, to September, 1988, 132 laser endarterectomies with or without balloon angioplasty were performed on 113 patients who presented with lower limb occlusive disease. Overall success rate as determined by intra operative angiogram and Doppler measurements signifying a patent lumen was 80% (106 laser-assisted procedures). In 26 procedures (20%), laser-assisted balloon angioplasty was unsuccessful. Complications associated with 132 laser thromboendarterectomies were arterial spasm (9.1%), perforation requiring surgery (3.0%), and thrombosis in the first forty-eight hours (1.5%) following the procedure. There was no limb loss, stroke, myocardial infarction, or death associated with this procedure.

Comparison of contact and free beam laser endarterectomy

Free beam laser endarterectomy (LE) and contact laser endarterectomy (CLE) were compared in 15 arteriosclerotic New Zealand white rabbits. The rabbits underwent balloon catheter trauma to the thoracoabdominal aorta and were fed a 2% cholesterol diet for 18 weeks. Thoracoabdominal exploration was performed under general anesthesia and multiple endarterectomies were performed in each rabbit. Atheromas were dissected from arteries with laser radiation and end points were welded in place with laser radiation. LEs ( N = 8) were performed with argon ion radiation delivered through a 400 μm fiberoptic. Power was kept constant at 1 W and the average fluence was 97.5 ± 6.6 J/cm 2. CLEs were performed with conical sapphire probes powered by either argon ion radiation ( N = 12) or Nd-YAG radiation ( N = 10). Power used was 1 W to 4 W for each laser. Average argon ion fluence was 117.8 ± 3.1 J/cm 2 and average Nd-YAG fluence was 611.1 ± 34.4 J/cm 2. Following the operations, aortas were removed, fixed, serially sectioned, and stained. Microscopic study revealed welded end points with LE but not with CLE. There were no perforations with LE. There were 11 12 perforations with argon ion CLE and 8 10 perforations with Nd-YAG CLE. Free beam laser endarterectomy is superior to contact laser endarterectomy for experimental atheromas.

Excimer Laserを用いたEndarterectomyおよびその治癒過程に関する研究

Excimer laser endarterectomy (ExLE) was compared with conventional surgical endarterectomy (SE), about early response in atherosclerotic rabbit aortas and about late healing response in normal canine arteries.In the first experiment, surfaces following ExLE were rougher than those after SE, but ExLE end points, without any intimal flaps, were smoother than those of SE exhibiting rough transitions and intimal flaps. And then thrombus formation in the ExLE was less than in the SE.In the second experiment endotherial cells appeared at 3 weeks and completely covered surfaces at 3 months in the both techniques. But some of arterial walls following ExLE showed aneurysmal changes at 3 months.In conclusion, it was demonstrated that ExLE exhibited no intimal flaps at the end points, lower thrombogenicity than SE, and favorable healing response. And so it is expected that ExLE will find a place in the future treatment of coronary artery disease.

63 エキシマレーザーを用いたlaser endarterectomyの組織学的検討

63 エキシマレーザーを用いたlaser endarterectomyの組織学的検討

Increased preferential absorption in human atherosclerotic plaque with oral beta carotene. Implications for laser endarterectomy.

Patients undergoing carotid endarterectomy were pretreated with low-dose, oral beta carotene to determine whether the carotenoid content of plaque could be increased in vivo. Beta carotene-treated patients had a 50-fold increase in their plaque beta carotene level from 0.066 to 3.3 micrograms beta carotene/g plaque. Microscopy and microspectrophotometry demonstrated that plaque from beta carotene-treated patients had higher carotenoid levels and higher absorption (450-500 nm) compared with control specimens, but normal media was unaffected. This demonstration of increased preferential absorption by plaque suggests that selective ablation of atherosclerotic plaque may be enhanced by pretreating patients with oral beta carotene.

Intraoperative laser coronary angioplasty.

After the first intraoperative application of an Argon-laser by Choy in 1983, a special trial on laser angioplasty was started in Houston in 1985. Under the indications of tandem stenoses, diffuse atherosclerotic alteration or peripheral stenoses, laser endarterectomy was performed with a hand-held CO2-laser in addition to conventional bypass surgery. Between January 1985 and December 1986, 20 patients were treated with this combined method. Laser endarterectomy was successful in 37 out of 40 diseased vessels. After an interval of one week to 6 months after operation, 18 patients underwent a reangiography, showing a patency rate of 76% in the lased arterial segments. This result is comparable to conventional endarterectomy or intraoperative balloon angioplasty in similar cases. Further improvements can be expected by modifications in antiplatelet drug therapy.

Preferential ablation of calcified arterial plaque with laser-induced plasmas

Laser endarterectomy, a promising new method of reopening stenotic or occluded arteries, has been limited by difficulties in ablating calcified plaque. This study demonstrates that pulsed, visible laser radiation (482 nm, 1 μs duration, 40-80 mJ/pulse) can ablate calcified plaque at intensities (50 MW/cm2) that are readily transmit, ted down flexible (320 μm diameter) optical fibers and at fluences which are below the threshold for ablating normal artery. The ablative process is characterized by a loud snapping sound, a luminescent plume, ejection of fine debris, and an ablation efficiency as high as 10 mg/J, suggesting that removal of material occurs primarily by formation of a plasma and fracturing of the plaque, rather than by thermal vaporization. The presence of a plasma associated with ablation of calcified plaque was documented by emission spectrum measurements.

Comparison of continuous-wave lasers for endarterectomy of experimental atheromas

The standard surgical lasers, argon ion, neodymium-yttrium aluminum garnet, and carbon dioxide, are often operated as continuous wave lasers with specific uses. Clinical trials of laser therapy for arteriosclerotic cardiovascular disease are underway with all three lasers. Therefore, we compared these three lasers under controlled experimental conditions. A thoracoabdominal exploration was performed in 17 arteriosclerotic rabbits. The aorta was isolated, heparin administered, and multiple endarterectomies were performed in each rabbit with each of the lasers. A line of laser craters was created at the proximal and distal ends of an atheroma. Continuous-wave laser radiation was used to connect the craters and thereby form proximal and distal end points. The plaques were dissected free from the aorta with laser light and the end points were fused by laser. The aortas were removed for light microscopy and the animals were killed. The endarterectomy surfaces and end points were serially sectioned and graded according to light microscopic findings (1 = worst, 4 = best). Argon ion laser endarterectomy (N = 16) required 106 +/- 10 J/cm2. The surface score was 3.5 and end point score 3.4. Neodymium-yttrium aluminum garnet laser endarterectomy (N = 13) required 1,289 +/- 115 J/cm2 with a surface score of 2.4 (p less than 0.001 from argon ion) and an end point score of 1.3 (p less than 0.001 from argon ion). Carbon dioxide laser endarterectomy (N = 9) required 30 +/- 5J/cm2 with a surface score of 2.0 (p less than 0.001 from argon ion) and and end point score of 1.6 (p less than 0.001 from argon ion). Perforation occurred in one of 16 argon ion studies (technical error, not laser), in 11 of 13 neodymium-yttrium aluminum garnet studies, and in six of nine carbon dioxide studies. This study demonstrates that of the currently available clinical continuous-wave lasers, the argon ion laser is superior for endarterectomy of experimental atheromas.

The argon contact laser scalpel: a study of its effect on atherosclerosis.

A new argon laser scalpel (ALS) that delivers radiation to tissue by direct contact was used to perform endarterectomies on atherosclerotic rabbit aortas in vivo. The resultant effects were compared to those induced by CO2 laser (CO2) and conventional surgical endarterectomy (END) to determine whether this instrument might be useful in the treatment of occlusive cerebrovascular disease. Light microscopy of the treated aortic segments revealed significantly more atheroma removed and less damage to the underlying media in the ALS segments compared to the CO2 segments. Electron microscopy showed that the ALS surface and distal intima-media interface were smoother and more even than those of the CO2 or END groups. Prostacyclin synthesis, as measured by 6-keto-prostaglandin F1a levels, was significantly reduced in the ALS compared to the END and control segments. These results indicate that the ALS is superior to CO2 in performing open laser endarterectomies, but such treatment places the atherosclerotic blood vessel at greater risk for thrombotic complications during the early postoperative period that does surgical endarterectomy. It is conceivable that a contact laser may be useful in the smooth welding of the distal edge of an atheroma (i.e., during carotid endarterectomy) and for the transcatheter ablation of surgically inaccessible obstructions of the cerebral circulation.

Photosensitization of experimental atheromas by porphyrins

Arteriosclerotic arteries have been shown to fluoresce when treated with hematoporphyrin derivative. This study investigates the incorporation and distribution of a partially purified form of hematoporphyrin derivative (Photofrin II) in normal and arteriosclerotic rabbit aortas. A thoracoabdominal exploration was performed in 15 rabbits. Group I comprised normal rabbits, Group II normal rabbits given 5 mg/kg Photofrin II 48 hours before surgery, Group III arteriosclerotic rabbits and Group IV arteriosclerotic rabbits given 5 mg/kg Photofrin II 48 hours before surgery. Multiple aortic biopsy specimens for frozen section were taken from all rabbits. In addition, open laser endarterectomy (with an argon ion laser) was performed on Group III and Group IV rabbits. Frozen sections were studied by digital video fluorescence microscopy to determine the distribution of Photofrin II within the layers of the aortic wall. The fluorescence of the intima of Group IV rabbits was found to be significantly greater than that of the intima, internal elastic lamina, media or adventitia of the other groups (p less than 0.01) and significantly greater than that of the internal elastic lamina, media or adventitia of Group IV rabbits (p less than 0.01). When open laser endarterectomy was performed, Group III rabbits required 103 +/- 14 J/cm2 and Group IV required 33 +/- 3 J/cm2 (p less than 0.01). It is concluded that porphyrins are selectively localized within the intima of arteriosclerotic arteries. This localization sensitizes atheromas to argon ion laser light and facilitates laser endarterectomy.

The thrombogenic potential of argon ion laser endarterectomy

The surface thrombogenicity of atheromas, conventional endarterectomy (CE), laser endarterectomy (LE), and laser angioplasty (LA) were compared in the rabbit arteriosclerosis model. Normal ( N = 6) and arteriosclerotic ( N = 15) rabbits underwent thoracoabdominal exploration. Multiple CEs and LEs were performed in 12 arteriosclerotic rabbits leaving a segment of intact atheroma between each endarterectomy. Multiple LAs were performed in three arteriosclerotic rabbits. Argon ion laser radiation was used for all laser procedures. Blood (0.05 ml) from normal rabbits was placed on the CE surface, LE surface, LA surface, atheroma, and normal intima and clotting times were determined. Surface thrombogenicity was calculated as the ratio of the clotting time of the CE, LE, LA, or atheroma to normal intima. Surface thrombogenicity was 1.0 ± 0.03 for normal intima (control), 0.58 ± 0.06 for atheromas ( P < 0.001), 0.46 ± 0.08 for CE ( P < 0.001 from atheromas), 0.46 ± 0.08 for LE ( P = NS from CE), and 0.27 ± 0.09 for LA ( P < 0.001 from CE and LE). The thrombogenicity of LE is the same as the thrombogenicity of CE. Both forms of endarterectomy are less thrombogenic than LA in the rabbit model.

Arterial healing in rabbits following carbon dioxide laser endarterectomy

CO2 laser open endarterectomy of small atherosclerotic vessels appears feasible. Under the conditions described, the endarterectomized arterial wall is not smooth but the thrombogenicity of the laser-treated surface is low, and the endothelial healing rapid. These advantages are to be weighed against the consequence of thermal injury, in particular, the late development of aneurysms. Before human clinical trials are made, further experimental studies are required to determine the best type of laser and optimal wave length to limit thermal injury.