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The feasibility of welding thin-walled microvessels by laser has been established. This report summarizes our experience using laser welding to repair thick-walled, high-pressure, 4 to 8-mm canine arteries using CO2, Nd:YAG, and argon lasers. The CO2 laser did not produce seals that could withstand arterial pressure. Nd:YAG laser welds were initially successful, but the majority failed within 20 to 40 minutes. The argon laser uniformly sealed 2-cm-length arteriotomies that healed rapidly within 4 to 6 weeks and had less foreign body response compared to sutured controls. Laser welding may represent an alternative for repair of small- and large-diameter vessels with several advantages compared to conventional suture techniques.

Clinical observations have suggested that low-energy lasers might stimulate wound healing. To understand the mechanism of the biostimulation, we previously examined the effects of low-energy lasers on collagen production by human skin fibroblasts and reported an increase of collagen synthesis in vitro. To examine the effects of low-energy lasers in vivo, hairless mice were experimentally wounded, sutured, and subjected to laser irradiation by a helium-neon laser with a power output of 1.56 mW and an energy fluence of 1.22 Joules/cm2. Experimental wounds were subjected to laser treatment every other day for 2 months; control wounds remained untreated. Specimens from the wounds were then examined for histological findings, tensile strength, and total collagen content. Results demonstrated a considerable improvement in the tensile strength of the laser-irradiated wounds at 1 and 2 weeks. Furthermore, the total collagen content was significantly increased at 2 months when compared with control wounds. These results suggest a beneficial effect of the helium-neon laser on wound healing in vivo.

To determine the effects of laser irradiation upon human coronary atherosclerotic disease, coronary plaques were extracted from fresh human cadaver hearts. Seventy-four diseased artery samples were sectioned either transversely or longitudinally and subjected to laser treatment from argon-ion and carbon dioxide sources. The laser beam affected vaporization and patency in fibrous, lipoid, and calcified plaques as observed histologically. Calcified blockage showed greater extent of charred remnants following controlled thermal injury than did fibrous or lipoid obstructions. The area and depth of penetration varied directly with intensity and duration of photoirradiation and inversely with the density of the atherosclerotic tissue. This study supports further research work on the use of lasers to effect relief of atherosclerotic obstructions.

The prograde and retrograde approaches to the treatment of malignant esophageal obstruction with the Nd:YAG, or neodymium: yttrium, aluminum, garnet, laser are compared. With the prograde technique, tumor destruction proceeds from the proximal to the distal tumor margin. In retrograde treatment, the endoscope is passed to the distal tumor margin so that the treatment can proceed in the reverse direction, thereby completing therapy in a single treatment session. This is usually accomplished by passage of a guide wire down the biopsy channel of the endoscope, tumor dilatation, and then passage of the endoscope over the guide wire to the distal tumor margin, where laser destruction is begun. Twenty nonrandomly selected patients with malignant esophageal obstruction were studied. The first ten patients were treated with the prograde technique, the next ten with the retrograde technique. The two groups were similar with respect to age, sex, and tumor histologies. Patients treated retrogradely had narrower pretreatment lumens (average 2.3 vs. 4.1 mm) as well as longer tumor lengths (average 8.9 vs. 4.8 cm). The posttreatment luminal diameters were similar for each group: 18.0 mm for prograde; 16.3 for retrograde. In the retrograde group, therapy was completed in fewer treatments (1.6 vs. 2.9) and over a shorter period of time (3.6 vs. 7.8 days), despite the longer tumor lengths. All patients in both groups were able to tolerate a regular diet at the completion of therapy. The complication rate was low in both groups. It is felt that the retrograde technique (single session therapy) is the preferred method because it allows more-rapid treatment without increased complications and thereby shortens hospital stay and reduces hospital costs.

Skin incisions 6 mm in length were made on the backs of hairless mice. Control wounds were closed with interrupted 5-0 Prolene sutures, and experimental wounds were approximated and closed by laser welding using a Nd: YAG laser. The wounds were examined daily, and specimens were excised at weekly intervals for histopathologic study, transmission electron microscopy, tensile strength determination, and type I collagen-specific messenger ribonucleic acid measurements. The laser-welded wounds demonstrated rapid healing. Histologic study showed a functional scar tissue at day 7 and a minimal residue of the original wound at day 14. Tensile strength of the control and experimental wounds was similar at all time points. The levels of collagen-specific messenger ribonucleic acid were significantly higher in the sutured group in comparison with the laser group or with normal control skin. This study suggests that laser welding might have advantages over suturing, since the former is sterile and nontactile, does not require introduction of foreign material into the wound, and provides subjectively improved cosmetic results.

Malignant esophageal obstruction in 24 patients was treated using the neodymium:ytrium, aluminum, garnet laser. There were 15 males and nine females; the average age was 70.9 years. There were 17 adenocarcinomas and seven squamous cell carcinomas, with two of these being recurrent after radiation therapy. Tumor lengths ranged from 2.5–19.0 cm, with an average of 6.7 cm. The average energy delivered per centimeter of tumor was 6,309 joules for the squamous cell carcinomas and 5,598 for the adenocarcinomas. Energy delivered per treatment ranged from 3,152 to 70,527 joules. Total energy delivered per patient depended on the volume of tumor destroyed. Esophageal lumens increased from 3.4 to 16.7 mm, and 23 patients had their diets advanced, 22 to regular and one to soft solids. Reobstruction did not occur in patients who received adjunctive therapy after laser therapy. This consisted of chemotherapy in five, surgery in two, and radiation therapy in one. Complications consisted of aspiration pneumonia in three patients, including one who developed a tracheoesophageal fistula, and one documented and two suspected perforations. Hospital stay averaged 5.4 days overall and 3.5 days in those treated with the single-session techniques. This increased to 8.0 days in patients with proven or suspected perforations. Endoscopic laser therapy is a safe and effective method for palliating esophageal cancer.

• Malignant esophageal obstruction in patients with carcinoma of the esophagus and adenocarcinoma of the distal esophagus usually indicates far-advanced disease. Palliative therapy with the neodymium—yttrium, aluminum, garnet laser has been proposed as an alternative to more invasive procedures that do little to improve the quality of life or prolong survival. Fifteen patients were treated with endoscopic laser therapy. A previously described technique was used to treat the first ten patients; the remaining five were treated with a single-session therapy method. This new technique allowed more rapid completion of therapy (1.4 treatments over 2.2 days vs 2.9 treatments over 7.8 days) without sacrificing safety. Single session therapy using this laser is recommended as the treatment of choice in patients with carcinoma of the esophagus with obstruction that is surgically or radiotherapeutically incurable. ( Arch Surg 1986;121:395-400)

The use of lasers in gastrointestinal diseases is becoming more commonplace, yet there are several major issues about which there is not unanimous agreement. I thought it would be valuable to review with the discussants some of the major undecided issues regarding the use of lasers today. Through the course of the following discussion we will address the issues listed below: 1) which endoscope should be used and for what reason, 2) where should the endoscopic laser procedure be performed, 3) what type of anesthesia should be used, 4) which bleeding lesion should be treated, which bleeding lesion should not be treated, 5) in the case of the recently bleeding ulcer that has ceased bleeding under what circumstances is laser therapy indicated, 6) how do you train endoscopists to perform laser therapy, 7) should there be any limitations upon who should be allowed to purchase lasers, 8) are controlled trials necessary for the treatment of acute gastrointestinal bleeding, 9) is further animal work with lasers necessary and if so in what areas, 10) which gastrointestinal malignancies are amenable to laser treatment and which of these should be treated.

This study compared the histology, biochemistry, tensile strength, and extensibility of Nd:YAG laser-welded and sutured venotomies. Two-centimenter-length bilateral canine femoral or jugular venotomies were evaluated with one vessel (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral vessel (experimental) welded with the Nd:YAG laser (1 W power and 30- to 40-sec exposure). Specimens were removed and examined immediately after fashioning (t0) and at 1, 4, or 5 weeks post-operatively to compare the progression of healing. Histologic examination of the 4- and 5-week sutured wounds had granulomatous reaction around the sutures with areas of excessive collagen accumulation. In contrast, the laser-welded wounds had minimal inflammatory response, near normal collagen content, and minimal residual disorientation and break in the elastic fiber continuity. The rate of collagen synthesis in laser-welded wounds was approximately twice that of sutured wounds at 1, 4, and 5 weeks, and correlated with increased tensile strengths of lasered wounds. The extensibility of the 5-week specimens was 0.19 for sutured and 0.29 for laser-welded wounds as compared to 0.29 for normal vein. These preliminary data suggest that laser welding of venotomies may have several advantages over conventional suture techniques.

• We investigated the histologic and biochemical effects of carbon dioxide and neodymium (Nd)-YAG laser welding on the healing of venotomies. Ten canine femoral venotomies 2 cm in length were approximated and welded with 10 600-nm wavelength, 1-W power over 20 to 25 s for CO 2 laser, and 1060-nm wavelength, 1-W power over 30 to 40 s for Nd-YAG laser. On removal at one to three weeks, all veins (4/4 welded by CO 2 and 6/6 by Nd-YAG) were patent without hematomas. Histologic and biochemical analyses of the venous tissues demonstrated active healing at the venotomy sites. We conclude that the CO 2 and Nd-YAG lasers can be used successfully to weld venotomies and may provide an alternative to conventional suture techniques for repair of vascular lesions. ( Arch Surg 1986;121:905-907)

Various laser modalities are currently in extensive use in dermatology and plastic surgery, particularly for treatment of vascular and pigmented lesions. A relatively new area of laser utilization involves the possible biologic effects of the lasers. In this overview, we are summarizing our recent studies, which indicate that lasers at specific wavelengths and energy densities modulate the connective tissue metabolism by skin fibroblasts both in vitro and in vivo. Specifically, the neodymium-yttrium-aluminum-garnet (Nd: YAG) laser was shown to selectively suppress collagen production both in fibroblast cultures and in normal skin in vivo, thus suggesting that this laser modality may be useful for the treatment of fibrotic conditions such as keloids and hypertrophic scars. Furthermore, two low-energy lasers, helium-neon (He-Ne) and gallium-arsenide (Ga-As), were shown to stimulate collagen production in human skin fibroblast cultures, suggesting that these lasers could be used for enhancement of wound healing processes. These experimental approaches illustrate the future possibilities for applying lasers for the modulation of various biologic functions of cells in tissues and attest to the potential role of lasers in the treatment of cutaneous disorders.

• An argon-ion laser, coupled to a flexible fiberoptic endoscope, was used to photocoagulate experimentally produced bleeding gastric ulcers in dogs. Argon-ion laser phototherapy rapidly and effectively achieved hemostasis in all bleeding ulcers. Bleeding arteries up to 2 mm in diameter were photocoagulated. Intact normal gastric mucosa was exposed to laser energy for varying periods of time to determine if transmural photothermal injury occurred. Exposure for greater than 15 seconds at 1.0 w of throughput power caused microscopical evidence of transmural injury. Healed, laser-treated ulcers could not be differentiated from nontreated control ulcers or normal stomach one month after injury. The Beer law and the heat-transfer factors relating to soft tissues are discussed. The coupled argon-ion laser-endoscope may be a safe tool to treat self-limited superficial bleeding gastric lesions. ( Arch Surg 111:750-755, 1976)

As recently as 1981, fewer than 12 medical centers in the United States were using lasers in the treatment of gastrointestinal (GI) disease. By 1984, 200 hospitals were using lasers for this purpose,1 and by the end of 1986,2 there were approximately 1,000. The reasons for such proliferation include increased applications of the use of lasers in GI problems, the relative ease with which they can be used, and the recent ruling by the Food and Drug Administration that the Nd:YAG laser is safe and effective and is therefore no longer considered to be an investigational device. Furthermore, lasers provide a multidisciplinary and multispecialty modality as well as therapeutic options where such choices did not exist or were limited previously.3 More importantly, they have been found to be safe, efficient, and cost-effective in most cases.

This study compared the histology, biochemistry, and tensile strength of laser-welded and sutured canine venotomies, arteriotomies, and arteriovenous fistulas. Twelve animals had bilateral femoral vessels studied, with one repair (control) closed with interrupted 6-0 polypropylene sutures, and the contralateral repair (experimental) welded with the argon laser. Specimens were examined at weekly intervals from 1 to 4 weeks (four animals for each type of repair), and were evaluated histologically by hematoxylin and eosin, elastin, and trichrome stains; biochemically by the formation of [3H]hydroxyproline as an index of collagen synthesis; and mechanically by tensile strength determinations. At removal, all experimental closures were patent without hematomas, aneurysms, or luminal dilatation. Histologic and biochemical examination and tensile strength determinations suggest that laser welding may be an alternative to sutures for repair of large-diameter venotomies, arteriotomies, and arteriovenous fistulas, as healing is comparable to that seen with suture repairs up to 4 weeks postoperatively.

LASER energy has previously been shown to control bleeding from superficial gastric erosions in the dog. In the initial report by Goodale et al, 1 carbon dioxide laser energy was transmitted through a rigid, hollow endoscope. Subsequently, Nath et al 2 described a flexible fiberoptic delivery system through which argon laser energy could be transmitted. In 1975, Dwyer et al 3 reported the successful use of such a system to treat hemorrhage from superficial gastric erosions in dogs. This communication describes the use of argon ion laser phototherapy for the treatment of acute upper-gastrointestinal bleeding in man. Materials and Methods An argon ion retinal photocoagulator with a flexible fiberoptic delivery system was attached to the outside of an endoscope as previously reported. 3 The tip of the fiberoptic cable was covered by a protective cap, and the cap was equipped with two channels, one for water to wash the quartz

Endoscopic laser therapy for malignant esophageal obstruction is rapidly gaining widespread acceptance by the medical community. The standard approach utilizing the neodymium: yttrium, aluminum, garnet (Nd: YAG) laser was first described by Fleischer for squamous cell carcinoma of the esophagus and subsequently for adenocarcinoma of the gastroesophageal junction. According to his technique, treatment was begun at the proximal tumor margin and proceeded distally; as many as 13 treatments were necessary to complete therapy and relieve the obstruction. A new technique has been developed utilizing tumor dilatation so that treatment can be started at the distal tumor margin working retrogradely. This new technique has allowed treatment to be completed in a single session in most patients. This rapid completion of therapy has reduced the length of hospitalization and thereby hospital costs. It has also allowed patients to aliment earlier, thereby minimizing the metabolic consequences of prolonged intravenous feedings, has allowed patients to receive other forms of therapy on an outpatient basis, and has obviated the need for the chronic placement of tubes for drainage and feeding. The technique is described and discussed.

Reprint requests: Garrett 1,~. M.D., Cardiovascular Medicine, Suite 202. LICD Professional Bldg.. 4301 S St., Sacramento, CA 95817. therapy” of heart and circulatory disorders is virtually unexplored. To determine the in vivo feasibility of transmitting laser energy intravascularly for the purposes of visualizing and treating peripheral artery pathoanatomy, a flexible fiberopticscope (Trimedyne, Inc., Arlington Heights, Ill.), equipped with a quartz fiber, was inserted via the left subclavian artery to the aortoiliac bifurcation in open-chest dogs (Fig. 1, A). For improved viewing, blood was diverted by normal saline infusion through the flushing channel of t,he fiberopticscope (Fig. 2, A). In addition, an area within the origin of the right iliac artery was then photoirradiated by a neodymium-YAG laser (five 2 to 3 second bursts of 60 W) (Fig. 2, B). Following these studies, the intervened vessels were removed, thereby verifying that the photoirradiation had indeed produced a lesion of coagulation necrosis (Fig. 1, A and B). Thus this investigation provides the initial demonstration of the practicality of conducting laser energy into living blood vessels and related structures as a new modality in the management of cardiovascular diseases.

• We compared the histologic features, tensile strength, and collagen synthesis of laser-welded and sutured arteriotomies. Four bilateral canine femoral or carotid arteries, 2 cm long, were studied at one through four weeks postoperatively, with one vessel (control) closed with interrupted 6-0 polypropylene sutures and the contralateral vessel (experimental) welded with an argon laser (0.5 W [1417 J/cm 2 ], four-minute exposure per 1-cm length of incision). Histologic examination revealed that laser-welded arteriotomies had less inflammatory reaction, more normal collagen and elastin reorientation, and similar endothelial continuity when compared with the control, sutured wounds. The tensile strength of the one- and two-week laser-welded specimens was less than that of sutured wounds and became approximately equal to sutured repairs at three and four weeks. There were no significant differences in the rate of collagen synthesis. There was no evidence of abnormal healing in the laser-welded specimens, suggesting that argon laser welding may be an alternative to suture repair of arteriotomies. ( Arch Surg 1986;121:1133-1135)

A flexible fiberoptic system has been used to deliver visible laser light into the upper gastrointestinal tract to arrest bleeding from various induced lesions. This procedure has achieved hemostasis at bleeding sites in the gastrointestinal tract of animals and suggests that bleeding lesions in the heman may be treated similarly without resort to surgical intervention or intensive medical management.