In an experimental animal model of femoral artery thrombosis, contrast angiography was compared to intravascular angioscopy. Additionally, the effect of mechanical, rotational thrombectomy and the additive benefit of the administration of intravascular streptokinase were assessed by means of both procedures. After external forceps crush injury alone, contrast angiograms were generally normal (6 of 14) or showed minimal luminal irregularity (3 of 14), and 5 of 14 had 30% to 50% stenosis. With angioscopy, none appeared normal, and 14 of 14 showed thrombi layered along the wall, as well as intimal flaps, and 6 of 14 had partially occlusive thrombi (p less than 0.001 angiography vs angioscopy). After 2-hour occlusion and injection of thrombin into the injured segment, angiographic total (5 of 14), subtotal (3 of 14), or partial thrombotic occlusions (5 of 14) were created. Angioscopy showed similar results, except that total occlusions were classed as subtotal occlusions. After rotational thrombectomy, most arteries again appeared normal by contrast angiography (6 of 11) but none were angioscopically normal (p less than 0.006). Streptokinase, administered after rotational thrombectomy in seven arteries, normalized one 30% angiographic stenosis; there were no other angiographic changes. Findings with angioscopy were also unchanged. We conclude that in the diagnosis and treatment of intravascular thrombosis, angioscopy is generally more sensitive in the detection of intravascular thrombi, with the exception of total thrombotic occlusions. Angioscopy was uniquely effective in identifying subintimal flaps, which were never identified by angiography. In this model, streptokinase provided little or no additional thrombolytic benefit to mechanical thrombectomy alone.

Percutaneous coronary rotational angioplasty was attempted in 12 patients. The procedure was performed with a flexible rotating shaft with an abrasive tip, varying in diameter from 1.25 to 3.5 mm, tracking along a central guide wire. Among the 12 patients (mean age 58 years), 4 had a stenosis in the left anterior descending coronary artery and 8 a stenosis in the right coronary artery. After the guide wire crossed the stenosis, the abrasive tip was slowly advanced and several passes across the stenosis were made. The residual stenosis was measured with computerized automatic quantitative coronary angiography. Success was defined as a reduction of percent stenosis by greater than 20%. If residual stenosis remained significant (greater than 50%), the procedure was completed by balloon dilation. The device could not be inserted in 2 of the 12 patients. Five of the 10 patients underwent rotational angioplasty alone, and 5 had the procedure completed by balloon dilation. The stenosis was significantly enlarged from 0.56 +/- 0.31 mm to 1.26 +/- 0.28 mm. The outline of the vessel appeared smooth and regular. There were no complications related to the procedure and all patients were free of symptoms when discharged 2 to 3 days after the procedure. Thus, coronary rotational angioplasty is a simple and safe procedure allowing marked dilation of the narrowed segment. However, long-term follow-up is required for further evaluation.

We have developed a mechanical thrombolytic catheter which defibrinates a fresh intra-arterial thrombus by wrapping fibrin about its rotating shaft. Defibrination results in liquification of the thrombus and reperfusion of the thrombotically occluded vessel. In this study, we employed this catheter-based approach in dogs with coronary thrombosis to simulate possible clinical use in acute myocardial infarction. Total coronary thrombosis was generated in 11 dogs. Spontaneous reperfusion did not occur over a 30-minute control period. All vessels studied were initially totally thrombosed. After mechanical thrombolysis, there was a significant improvement in percent diameter stenosis from 100% to 28 +/- 26% (P less than 0.001). After thrombolysis, angiographically graded blood flow was normal in 9 of 11 arteries and was mildly delayed in 2 of 11. Complications included perforation of 2 vessels. We conclude that mechanical thrombolysis, with a rotating catheter, results in prompt reperfusion of the infarct vessel and significant improvement in distal blood flow. This approach, unlike angioplasty, removes the thrombus and might serve as an alternative to or supplemental form of mechanical thrombolysis.

The application of laser sources for cutting and coagulation of tissue has enjoyed widespread notoriety. Frequently the physician directing laser energy does so with minimal understanding of the response of the tissue to penetrating radiation, the buildup of heat in the tissue, and the propagation of thermal energy during and after the actual laser irradiation. Lengthy animal modeling studies have been performed which have greatly aided the development of good estimates of laser coagulation necrosis when used within tightly confined parameters of space, time, energy, and wavelength. Unfortunatly, much of the enthusiasm which has been showered upon laser coagulation and cutting has occurred because of a generalized fascination with lasers rather than because of some proven character advantage. Older methods of radio-frequency coagulation have experienced a rekindling of interest because of the interest in laser surgery.

The use of concentrated laser irradiation for evaporation of tissue has been well accepted. In particular, the CO2 laser with its very high absorption coefficient permits surface ablation or linear excavation, providing a well controlled surgical device. Its use through the operating microscope enables non-contact management of surgical therapy with unparalleled convenience and precision. However, in other areas of surgery where deeper tissue coagulation is valuable for better hemostasis, the CO2 laser falls short of the clinical need. The use of deeper penetrating laser wavelengths necessarily reduces the superficially evaporative cutting in much the same manner that coagulating waveforms reduce cutting efficienty in electrosurgical scalpels. We have developed a series of transparent quartz scalpel blades which allow delivery of visible and near infrared laser irradiation to a mechanically incised tissue margin resulting in vastly improved hemostasis.

Conclusion Many methods are being considered for the endoscopic control of upper gastrointestinal bleeding. These techniques can stop experimental bleeding without adverse clinical effects in animals. Some techniques penetrate more deeply than others and therefore have a higher incidence of full-thickness wall injury, but these techniques may also be most useful for a deep-lying vessel which requires greater penetration of energy through tissue. There are many questions that will only be answered in carefully controlled clinical trials comparing new methods with standard therapy and new therapies with each other; however, each method must first be found to be effective and safe in animal studies. We hope that eventually one or more endoscopic hemostatic method will prove clinically safe and effective and improve the outcome for patients with upper gastrointestinal bleeding.

This paper presents the physical theory and engineering development of a new hemostatic scalpel, the photocoagulating dielectric waveguide scalpel. (laser blade). This device has demonstrated a marked reduction in blood loss during surgery of organs where bleeding is normally a major problem, such as the debridement of third-degree burns. The scalpel utilizes an argon laser for optical power (25 W) and a fiber-optic waveguide to flexibly transport the laser radiation to a fused silica scalpel blade. The blade is a dielectric waveguide which carries the laser radiation to a tapered cutting edge which is used for the mechanical incision of tissue and provides the means by which the laser radiation couples (tapered waveguide coupling) into the surrounding tissue for photocoagulation. The optical characteristics of the blade are analyzed and experimentally verified.

We have developed a new method for coupling the hemostatic capabilities of argon laser light with the mechanical advantages of a sharpened quartz blade using fiberoptics. Using the new laser-assisted scalpel, a series of symmetrical skin excisions was done in 20- to 30-kg pigs on one side and with electrosurgery on the other. The laser scalpel was superior in its hemostatic properties (p less than 0.01) with no statistically significant difference in surgical speed. Take of split-thickness skin grafts was 90% in beds excised with either the laser or the electrosurgical device. Histologic sections showed less tissue damage with the laser-assisted scalpel than with electrocautery.

Hemostasis remains a major technical problem in surgery of the liver and spleen. A high power neodymiumdoped yttrium aluminum garnet (Nd:YAG) laser has been coupled with a fiberoptic delivery system and quartz blade designed to yield maximal hemostasis and minimal tissue injury. In a series of experiments we were unable to demonstrate a significant advantage of its use in partial hepatic lobectomy.

The advent of flexible fiberoptic endoscopy has stimulated the development of numerous nonsurgical methods to stop bleeding in patients with upper gastrointestinal hemorrhage. Our laboratory has evaluated several of these techniques in studies using standard-sized bleeding canine gastric ulcers. Gas-assisted argon and the neodymium YAG laser photo-coagulation, computer-assisted monopolar and bipolar electrocoagulation, and a new device, the heater probe, are all highly effective for stopping bleeding from this model. Of these, the gas-assisted argon laser produces the least injury to tissue underlying the treated ulcer. A topical hemostatic spray, Flucrylate, proved ineffective in this model. Uncontrolled clinical experience with laser photocoagulation and monopolar electrocoagulation indicates that each stops upper gastrointestinal hemorrhage in more than 90% of treated patients. Based on available experimental and clinical data, we are now undertaking a controlled clinical trial of gas-assisted argon laser photocoagulation in patients with bleeding gastric, stomal, or duodenal ulcers.

During the past five years we have evaluated argon laser photocoagulation in various canine models of upper gastrointestinal hemorrhage. In gastric erosions, the eight-watt argon laser was uniformly effective in stopping bleeding. In our standard acute ulcer model the seven-watt argon laser was effective in stopping bleeding from most ulcers and only occasionally produced deep injury. With the addition of a jet of CO2 exiting the laser catheter coaxial to the laser beam, the argon laser was 100% effective and no deep injury resulted. The application of the argon laser in a more physiologic canine bleeding model using a single bleeding vessel in an ulcer base is currently under study. The development of improved animal models of gastrointestinal bleeding should contribute to the identification of effective and safe endoscopic hemostatic methods.

A hybrid optical fiber catheter has been developed which is capable of simultaneously emitting from its distal end 20 W of continuous laser radiation and a jet stream of CO2 gas. The catheter can be readily inserted into the biopsy channel of conventional flexible endoscopes for control of gastric bleeding. Experiments on bleeding animal ulcers and an artificial bleeding vessel model show that a catheter which delivers a simultaneous jet of gas with laser radiation is much more effective in achieving hemostasis than laser radiation alone. The laser/gas catheter also incorporates other improvements in device durability. Results of controlled animal trials are discussed.

Endoscopic laser photocoagulation is one of the exciting developments in the field of gastrointestinal endoscopic therapy. However, much work needs to be done before these techniques should be allowed to proliferate into widespread use. There are few controlled randomized clinical studies evaluating any endoscopic treatment of bleeding, including argon laser and Nd:YAG laser photocoagulation. Despite this, uncontrolled clinical trials of both argon and Nd:YAG laser photocoagulation have begun. Laser photocoagulation of bleeding upper gastrointestinal lesions should be considered a procedure in an experimental stage of development, to be performed only under protocol studies at endoscopic research centres. Only after this or any other haemostatic technique has been proven effective and safe in thorough animal trials and then in controlled clinical trial should it be considered ready for general clinical use.

The purpose of this study is to evaluate the efficacy and safety of a new argon laser system for stopping bleeding from experimental canine gastric ulcers. This system consists of a catheter which can be inserted via an endoscopic biopsy channel to deliver a jet of CO2 coaxially with an argon laser beam. The efficacy of this system in stopping bleeding was tested in two acute experiments at laparotomy in heparinized dogs using our gastric ulcer model. At 7 w of power the gas-jet-assisted laser proved 100% effective in stopping bleeding with an average of three 5-sec exposures, as compared to the same laser without added CO2, which required an average of 11 5-sec exposures. Furthermore, the 7-w laser without added CO2 did not stop all bleeding ulcers. The safety of the CO2 laser system was tested in a chronic experiment at sterile laparotomy using the same ulcer model. No ulcer treated with the 7-w gas-jet-assisted argon laser showed histologic evidence of full thickness injury. A final acute experiment compared the efficacy of various wattages of the gas-jet-assisted laser in stopping bleeding from the ulcer model; the wattages used in this series of experiments and in previous experiments proved to be in the efficacious range. We conclude that CO2 added coaxially to a 6- to 7-w argon laser increases the efficacy of coagulation while reducing the depth of injury.

A single quartz fiber delivery system capable of remotely depositing in excess of 9 watts of continuous laser radiation has been developed and tested. Of particular interest in this development was the achievement of a catheter that can be inserted into the biopsy channel of a conventional flexible endoscope for noninvasive control of gastric bleeding. In animal testing, the prototype device was found capable of producing a large useful area of superficial tissue coagulum, effectively controlling gastric hemorrhage. Future clinical application is highly encouraging.