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In a prospective study, we assessed the diagnostic and therapeutic applications of intraoperative angioscopy for peripheral vascular procedures. Sixty-seven vessels and 17 bypass grafts were examined with a flexible, multichannel, fiberoptic endoscope (outer diameter 2.8 mm), with video projection of a magnified image used during the following operations: femoropopliteal or femorotibial bypass (14), aortofemoral (six), axillopopliteal bypass (one), and femoral embolectomy (three). Preoperative angiograms were compared with the findings at prebypass intraoperative angioscopy. Immediately after bypass, angioscopic appearances of the graft, anastomosis, and distal runoff artery were compared with a completion angiogram. Significant disparity between angioscopy and arteriography occurred in five patients (21%), with resultant change of management in three (12.5%). In comparison to angioscopy, the arteriograms gave a false negative rate of 12.5% (3 of 24) and a false positive rate of 8% (2 of 24). Angioscopy was accurate for assessment of anastomoses in all cases and was particularly beneficial for monitoring balloon catheter embolectomy. Complications were limited to three instances of vasospasm when the scope was used in narrow vessels. No embolization, intimal trauma, infection, or vessel perforation occurred. We conclude that angioscopy promises to be a safe and accurate alternative technique for intraoperative assessment, monitoring anastomotic results and controlling therapeutic procedures.

The thrombogenicity of argon laser—assisted vascular anastomoses (LAVAs) was compared with that of sutured vascular anastomoses (SVAs) by measurement of platelet aggregation at the site of repair in a canine model. Sequential 1 cm longitudinal carotid and femoral arteriotomies (n = 80) or jugular and femoral phlebotomies (n = 80) were performed, with each vessel having two tandem, randomly positioned arteriotomies or phlebotomies separated by a 4 cm length of intact vessel. One incision was repaired by SVA with continuous 6-0 polypropylene sutures and the other by argon LAVA. For the laser fusions, argon laser energy was applied to the adventitial surface of the vessel with a 300 μm fiberoptic probe with 0.5 W power, 1100 joules per square centimeter energy fluence, and 150 second exposure per 1 cm length. The arterial and venous segments of SVAs and LAVAs and an equivalent length of normal vessel were harvested at 48 hours (n = 16, 16, 16), 2 weeks (n = 12, 12, 12), and 4 weeks (n = 12, 12, 12). Autologous indium 111 oxine—labeled platelets were injected intravenously 48 hours before removal of the vascular repairs and the radioactivity of the specimens was determined on removal with a NaI (T 1 ) well-type scintillation counter. Anastomotic platelet adherence index (APAI) was calculated as the ratio of emissions of SVA or LAVA to normal reference vessel. Argon arterial LAVAs had significantly less platelet deposition when compared with SVAs in the canine model at 48 hours (APAI = 161 ± 76 and 93 ± 41, respectively; p

The objective of this study was to evaluate the use of an angioscope-assisted laser hot-tip probe for performing valvulotomies in in situ nonreversed canine veins used for arterial bypasses. In Group 1, 9 valvulotomies were performed in 7 bypass veins with a 2-mm probe activated by 12 W power, resulting in 4 vein perforations, 1 vein thrombosis, and 4 in situ grafts patent at removal after 2-28 days. In Group 2, 10 valvulotomies in 9 bypass veins were performed with a 1.5-mm probe at 14 W with no vein perforations, 3 vein thromboses, and 6 in situ grafts patent at removal after an interval of 1 to 6 weeks. We conclude that valvulotomy within in situ vein bypasses can be successfully performed using a 1.5-mm laser hot-tip probe at 14 W power, with patency of the grafts demonstrated at 6 weeks. Angioscope-assisted laser valvulotomy using a laser probe may significantly reduce the length of incisions and the time required for in situ vein bypasses and improve the technical accuracy of the procedure.

This study compared the healing of laser-welded and sutured canine femoral arteriovenous anastomoses. Arteriovenous fistulas 2 cm in length were created bilaterally in the femoral vessels of 10 dogs and were studied at 1 (n = 2), 2 (n = 2), 4 (n = 3), and 8 (n = 3) weeks. In each animal, one anastomosis (control) was closed with running 6-0 polypropylene sutures, and the contralateral anastomosis (experimental) was sealed with an argon laser (0.5 watt, 4 minutes of exposure, 1830 J/cm2/1 cm length of anastomosis). At removal all experimental anastomoses were patent without hematomas, aneurysms, or luminal narrowing. Histologic examination at 4 weeks revealed that laser-welded anastomoses had less inflammatory response and almost normal collagen and elastin reorientation. At 8 weeks sutured anastomoses had significant intimal hyperplasia whereas laser repairs had normal luminal architecture. Tensile strength and collagen production, measured by the synthesis of hydroxyproline and the steady-state levels of type I and type III procollagen messenger ribonucleic acids, at the anastomoses and in adjacent vein and artery specimens were similar in sutured and laser-welded repairs at 2, 4, and 8 weeks. We conclude that argon laser welding of anastomoses is an acceptable alternative to suture techniques, with the advantage of improved healing without foreign body response and possible diminished intimal hyperplasia at the anastomotic line. (J V ASC S URG 1987;6:447-53.)

In order to elucidate the biochemical mechanism of laser welding of tissues, we have compared protein profiles from argon laser-treated specimens with controls. Extracellular matrix components from untreated and laser-welded skin and blood vessels were extracted with guanidine hydrochloride and separated by SDS polyacrylamide gel electrophoresis. When compared with matched, untreated tissues, protein electrophoretic profiles from laser-treated samples showed several changes. In both tissue types, argon laser treatment decreased the concentration of a 235 kd protein that migrates between the alpha and beta chains of type I collagen. Laser-treated blood vessels showed significantly more low molecular weight protein at the dye front than in control tissue, whereas significantly more high molecular weight protein appeared in laser-treated skin samples when compared with untreated tissue. These results suggest that the argon laser may either degrade or crosslink proteins in vivo. Laser-induced protein crosslinks may be the biochemical basis of argon laser welding.

Forearm Brescia-Cimino arteriovenous fistulas were chosen for the initial clinical evaluation of argon laser-assisted anastomosis of human vessels. Ten patients with chronic renal failure had side-to-side radial artery/cephalic vein fistulas fused by laser. Incisions 1.2 to 1.5 cm in length were made in adjacent segments of artery and vein and were aligned for application of laser energy by four 6-0 polypropylene sutures. The sutures divided each fistula into four segments that were 5.0 to 6.5 mm long. Each segment was sealed satisfactorily in 75 to 100 seconds by use of 0.5 W, 1130 to 1520 joule/cm2 argon laser energy fluence. Seven (17.5%) of 40 bonds required an additional 7-0 biodegradable suture to close small gaps that did not fuse adequately. Serial prospective follow-up studies of the patients by physical examination and duplex scanning for periods of 12 to 20 months (15.4 +/- 2.8, n = 7) postoperatively have shown uniformly patent, compliant anastomoses with no evidence of hematomas, false aneurysms, or luminal narrowing. Histologic examination of two patent fistulas that were excised during revision procedures at 4 and 5 months postoperatively showed healing of the entire circumference of the anastomosis similar to that noted in extensive preclinical canine studies. We conclude from these preliminary results that argon laser vascular tissue fusion is possible in humans when reliable primary sealing of vascular anastomoses is achieved, and that healing occurs without aneurysmal dilatation during follow-up of up to 20 months.

The development of arteriosclerotic peripheral vascular lesions following balloon catheter and mechanical fragmentation of the arterial myointima combined with an atherogenic diet was studied in a canine model. The ileofemoral arteries of five mongrel dogs (mean wt 22 +/- 2 kg) were selectively cannulated and subjected to balloon catheter and mechanical myointimal injury by repeated longitudinal and transverse shearing forces. Twenty grams of hydrogenated coconut oil and a 5.0% cholesterol diet were fed to the animals daily during the study period. Followup angiographic studies obtained at 4 weeks (n = 2), 10 weeks (n = 3), 16 weeks (n = 3), and 24 weeks (n = 2) demonstrated changes of progressive peripheral vascular occlusion. Concurrent duplex Doppler studies correlated well with the angiographic results. At 10 (n = 1), 18 (n = 2), and 24 (n = 2) weeks, the animals were sacrificed and the vessels were perfusion-fixed in situ with 2% glutaraldehyde or formaldehyde solutions and excised. Histological examination demonstrated extensive arteriosclerotic changes including (i) fragmentation and reduplication of the internal elastic membrane, (ii) myointimal hyperplasia with fibroblastic proliferation including the development of fibrous intimal plaques, and (iii) transmigration and proliferation of smooth muscle cells with scattered monohistiocytes. The specimens showed a range of stenotic changes from 25% to total occlusion of the vascular lumen. These preliminary data demonstrate the feasibility of providing intense arteriosclerotic myointimal histologic changes in the canine peripheral vasculature within a 24-week period. Further refinement of this methodology may provide a practical model for studies of localized peripheral vascular occlusive disease.

CO2 and argon lasers have been used successfully for vascular welding in both experimental and clinical settings. This study compared the thermodynamics during CO2 and argon laser welding of 1-cm longitudinal arteriotomies in a canine model. Continuous recordings using an AGA 782 digital thermographic system with spatial and thermal resolution of ±0.2 mm and ±0.2°C, respectively, were analyzed. A HGM argon laser using a 300-μm optic fiber held at 1 cm from the vessel edges (spot diameter = 2.8 mm) with concomitant room temperature saline irrigation (1 drop/sec) was used for argon welds. Total exposure time was 150 sec/cm. CO2 welds were performed with a Sharplan CO2 laser (spot diameter = 0.22 mm) with no irrigation for total exposure time of 10 sec/cm. Thermodynamic results and laser parameters are summarized as follows: Argon–n = 20; power = 500 mW; energy fluence = 1,400 J/cm2; Tmax = 48.8°C; T mean ± S.D. = 45.1 ± 2.7°C; CO2–n = 20; power = 150 mW; energy fluence = 3,000 J/cm2; Tmax 84.0°C; T mean ± S.D. = 60.7 ± 9.8°C. There was a significant difference (P < .05) in thermal measurements between successful CO2 and argon vascular welds. Temperature rise during the argon welds was limited by saline irrigation. In contrast, during CO2 laser welding, the temperature rose quickly to its maximum and was maintained at a relatively high level as the laser progressed (0.1 cm/sec) along the anastomosis. Histologic examination revealed charring at the CO2 weld site but absence of thermal damage at the argon laser weld. These thermodynamic differences may account for the different welding mechanisms currently described.

This study was designed to determine the optimal laser power (watts) for maximal strength of argon laser vascular fusions by measuring bursting pressures of repairs. Longitudinal incisions (n = 105) measuring either 2.5 or 5 mm in length were performed in canine femoral, carotid, and jugular veins and arteries and were fused with the argon laser at 0.3, 0.5, 0.7, or 0.9 W power. Total exposure time for each repair (50 to 80 sec/0.5 cm) was adjusted to yield identical energy fluences of 1,100 J/cm2. Bursting pressure of the fusions was determined by monitored infusion of anticoagulated blood into an isolated segment of the vessel that contained the fusion. Mean bursting pressures for venous and arterial repairs were significantly higher in the 2.5 mm incisions compared with the 5 mm incisions (P less than 0.05). Venous and arterial repairs of equal length performed at each power resulted in equivalent bursting strengths, except that 5 mm venous segments fused with 0.9 W withstood lower pressures than all other venous repairs (P less than 0.05), and 5 mm arterial segments were in turn significantly weaker at 0.3 W (P less than 0.02). We conclude that argon laser fusion is equally suitable for repair of medium-sized veins and arteries and that immediate strength decreases with increasing length of repair. To maximize strength of longer repairs, venotomies should be welded at power settings between 0.3 and 0.7 W while arteriotomies should be fused at power settings between 0.5 and 0.9 W. The differences in optimal power may be explained by variable wall composition and thickness between veins and arteries.

The mechanism of laser vascular tissue welding remains unknown. This study compared the acute tissue response and long-term healing of sutured and laser-welded anastomoses of vein segments used to bypass ligated canine femoral arteries. For each procedure, one anastomosis was formed using running 6-0 polypropylene suture (control), and the other anastomosis was formed using argon laser tissue welding (experimental). The vein grafts were harvested at 4 (n = 2), 8 (n = 1), 12 (n = 1), and 16 (n = 2) weeks, and selected samples were evaluated by histologic examination, electron microscopy, tensile strength testing, and by measuring the formation of [3H]hydroxyproline as an index of collagen synthesis. Examination of successful laser fusions immediately after they were formed showed bonding of collagen to collagen and elastin to collagen. Follow-up evaluations showed that the precision of tissue apposition affected the rate of healing and tensile strength. Laser-welded anastomoses demonstrated a progression of healing similar to sutured repairs, with remodeling of fibrous tissue and collagen being the primary component of weld integrity. This study demonstrates that sutured and argon laser-welded vein-artery anastomoses heal comparably up to 16 weeks postoperatively, and that laser welding is a satisfactory alternative to sutured anastomoses.

The role of angioscopic monitoring and aiming for control of laser intervention in the vascular system was initially investigated in 48 vessels in 33 dogs, and the techniques were then applied to 30 patients undergoing intraoperative or percutaneous laserprobe angioplasty treatment for long atherosclerotic occlusions of the femoral and popliteal arteries or well-localized lesions of the superficial femoral artery. Experimental bare argon fiber laser application in 20 normal canine arteries in vivo demonstrated that small-diameter laser fibers could be accurately aimed by manipulations of the scope. However, advancement of the fiber resulted universally in perforation, with extravasation and thermal damage of surrounding tissues after 2 seconds of argon laser energy at low power. In 28 canine and 2 human veins, angioscopically guided metallictipped laserprobes were used to divide 82 valve cusps in preparation for in-situ bypass, with satisfactory aiming and monitoring achieved expeditiously by manipulations of the angioscope. We conclude that angioscopic aiming of lasers is feasible in normal vessels or localized lesions. In contrast, angioscopy has a restricted role for guidance of laser angioplasty in atherosclerotic, occluded arteries, and does not prevent perforation. Postprocedural inspection allows immediate detection of complications and may avert or predict poor outcome.

There are conflicting opinions regarding the mechanism of welding or fusion of vascular tissue by lasers. In this study, we measured the effects of saline irrigation on tissue temperature and fusion produced by argon laser welding of eight femoral and four carotid arteriovenous fistulas. Temperatures were continuously recorded using a digital thermographic camera. Forty 1-cm. welds were performed using powers of 0.50 (n = 24), 0.75 (n = 8), and 1.00 (n = 8) watt (W), with an energy fluence of 1100 J/cm2 per 1 cm segment, and cooling of the anastomotic site by saline irrigation (3 ml/minute). The "success" of fusions was determined by testing integrity of the repairs by exposure to blood flow. At 0.50 and 0.75 W, successful welds were formed when the temperatures were 44.2 +/- 1.6 (n = 28) and 55.0 +/- 3.6 degrees C (n = 20), with maximum temperatures of 47.9 and 59.9 degrees C respectively. At 1 W, the tissue was desiccated and the welds disrupted when exposed to blood flow with temperatures measured at 63.7 +/- 10.0 degrees C (n = 22) and maximum of 88.0 degrees C. Eight welds were also attempted without saline irrigation at 0.25 (n = 4) and 0.50 W (n = 4). At 0.25 W, tissue fusion was achieved but disrupted when exposed to intraluminal pressures with temperatures 50.3 +/- 2.0 degrees C (n = 10) and maximum of 52.6 degrees C. At 0.50 W, the fusion failed after only minimal exposure to the laser energy because of tissue drying and retraction with temperatures measured at greater than 125 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

We describe the regression of a 6.5 cm diameter abdominal aortic aneurysm in a 71-year-old patient within 1 year of aortic endograft placement. The aneurysm decreased in size to 4 cm at 3 months and was 3.3 cm at 8 months on duplex examination. By 1 year a spiral computed tomographic study confirmed complete regression of the aneurysm, with mild shortening and angulation of the unsupported body of the aortoiliac endoluminal prosthesis. The case demonstrates a potential of endograft treatment of aortic aneurysms and describes the changes in prosthesis configuration and position that occurred after implantation. (J Vasc Surg 1997;26:133-7.)

Objectives The operative mortality and morbidity of patients with complicated acute type B aortic dissection remain high. The endovascular approach has been proposed as a potential alternative. The purpose of this study is to review the contemporary outcome of patients undergoing endovascular treatment for complicated acute type B aortic dissection. Methods A retrospective analysis of 28 patients undergoing endovascular interventions for acute type B aortic dissection was performed. Kaplan–Meier survival analysis was used for statistical computation. Results Indications for emergency endografting were rupture in 4 (14%) patients, severe lower body malperfusion in 8 (29%) patients, visceral/renal malperfusion in 7 (25%) patients, persistent chest pain despite proper anti-impulsive therapy in 5 (18%) patients, uncontrollable hypertension in 1 (4%) patient, and acute dilatation of false lumen with impending rupture in 3 (11%) patients. Three (11%) patients died early. Three patients died during follow-up of non–aorta-related causes. Overall survival was 82% and 78% at 1 and 5 years' follow-up, respectively. The aorta-related mortality was 10% for the entire follow-up period. Complete thrombosis of the false lumen in the thoracic aorta was achieved in 22 (85%) members of the surviving cohort, and partial thrombosis was achieved in the remainder. The rate of treatment failure according to Stanford criteria was 18% at 5 years. Mean follow-up was 36 months, and follow-up was complete in 28 (100%) patients. Conclusions Thoracic aortic endografting for complicated acute type B aortic dissection can be performed with a relatively low postoperative morbidity and mortality in experienced hands. The endovascular approach to life-threatening complications of acute type B aortic dissection appears to have a favorable outcome in midterm follow-up.

ObjectivesEvaluating the success of endoluminal repair of abdominal aortic aneurysms (AAAs) is frequently based on diameter measurements and determining the presence of endoleaks. The use of three-dimensional volumetric data and observation of morphologic changes in the aneurysm and device have been proposed to be more appropriate for postdeployment surveillance. The purpose of this study was to analyze the long-term volumetric and morphologic data of 161 patients who underwent endovascular AAA exclusion and to assess the utility of volume measurements for determining successful AAA repair.MethodsPatients with spiral computed tomography scans obtained preoperatively, within the first postoperative month, at 6 months, and annually thereafter, were included in this analysis. Computerized interactive three-dimensional reconstruction of each AAA scan was performed. Total aneurysm sac volume was measured at each time interval (mean preoperative volume 169.0 ± 78.5 mL), and the significance of volume changes was determined by mixed linear modeling, a form of repeated measures analysis, to account for longitudinal data clustered at the individual level. Sixty-two patients (38%) developed endoleaks at some time during follow-up—15 type I leaks, 45 type II leaks, and 2 type III leaks. The patients with type I and type III leaks were treated with cuffs, and the type II leaks were treated either with observation, side-branch embolization, or required open conversion.ResultsAneurysm sac volume increased slightly at 1-month follow-up (+3.3%), and then decreased steadily to −12.9% at 5 years (P < .0001). This effect remained unchanged after controlling for the three device types used in our study population. Patients who did not exhibit an endoleak (n = 99) showed a significant decrease in aneurysm volume across the entire follow-up duration when compared with those who did exhibit an endoleak (n = 62) (P < .0001). The presence of a 10% or greater decrease in volume at 6 months demonstrated a sensitivity of 64%, a specificity of 95%, a positive predictive value of 95%, a negative predictive value of 62%, and an accuracy of 75% for predicting primary clinical success defined by successful deployment of the device; freedom from aneurysm- or procedure-related death; freedom from endoleak, rupture, migration, or device malfunction; or conversion to open repair.ConclusionsVolumetric analysis may be used to predict successful endoluminal exclusion of AAAs. Volume regression appears to be device-independent and should be expected in most clinically successful cases. The presence of volume increases in the first 6 months is suspicious for an endoleak that is pressurizing the aneurysm sac and heralds the need for closer evaluation and possible intervention. A volume decrease of 10% or greater at 6 months and continuing regression over time is associated with successful endovascular repair.

Two mechanisms of laser tissue fusion, thermal and photochemical, are currently being proposed in several types of tissue. In this study we examined the thermal and histologic components of laser fusion in blood vessels and bowel. CO2 and Argon lasers were used to fuse 1 cm canine arteriotomies and 1 cm rabbit enterotomies. Thermal images were concurrently recorded with an AGA Thermovision camera and computer analyzed. Tissue samples from each weld were subsequently prepared for histologic examination.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Forearm Brescia-Cimino arteriovenous fistulas were chosen for the initial clinical evaluation of argon laser-assisted anastomosis of human vessels. Ten patients with chronic renal failure had side-to-side radial artery/cephalic vein fistulas fused by laser. Incisions 1.2 to 1.5 cm in length were made in adjacent segments of artery and vein and were aligned for application of laser energy by four 6-0 polypropylene sutures. The sutures divided each fistula into four segments that were 5.0 to 6.5 mm long. Each segment was sealed satisfactorily in 75 to 100 seconds by use of 0.5 W, 1130 to 1520 joule/cm2 argon laser energy fluence. Seven (17.5%) of 40 bonds required an additional 7-0 biodegradable suture to close small gaps that did not fuse adequately. Serial prospective follow-up studies of the patients by physical examination and duplex scanning for periods of 12 to 20 months (15.4 +/- 2.8, n = 7) postoperatively have shown uniformly patent, compliant anastomoses with no evidence of hematomas, false aneurysms, or luminal narrowing. Histologic examination of two patent fistulas that were excised during revision procedures at 4 and 5 months postoperatively showed healing of the entire circumference of the anastomosis similar to that noted in extensive preclinical canine studies. We conclude from these preliminary results that argon laser vascular tissue fusion is possible in humans when reliable primary sealing of vascular anastomoses is achieved, and that healing occurs without aneurysmal dilatation during follow-up of up to 20 months.

Extracellular matrix components from untreated and laser-welded skin and blood vessels were extracted with guanidine hydrochloride and separated by SDS polyacrylamide gel electrophoresis. When compared to matched, untreated tissues, protein electrophoretic profiles from laser-treated samples showed several changes. In both tissue types, the concentration of a protein normally migrating between alpha and beta chains of type I collagen decreased in laser-treated samples. However, laser-treated blood vessels showed significantly more low molecular weight protein, whereas significantly more high molecular weight protein appeared in laser-treated skin samples when compared to untreated tissue. These results suggest that the argon laser either degrades or crosslinks proteins in-vivo. Laser induced protein crosslinks may be the biochemical basis of laser welding.

The biocompatibility, osteoconduction and biodegradation characteristics of calcium phosphate ceramics is controversial. Few comparative studies have controlled for material properties as well as biological influences. In this study, we compared the in-vivo response of implants made porous (500 μm pores) using the Replamineforu™ process and composed of hydroxyapatite (HA), sintered hydroxyapatite (SHA), tricalcium phosphate (TCP) or calcium carbonate (CC). In ten rabbits, rod-shaped implants (5mm d × 10m 1) of each material were randomly press-fit into two bilateral defects of either the bicortical iliac crest or unicortical proximal tibial metaphysis. Explants were harvested at 1 to 9 months, sectioned midsagitally with half embedded in plastic for qualitative histomorphometry, and the other half decalcified and stained for histology. The acute and chronic inflammatory response was minimal for all implants. The osteoconduction properties were similar for the calcium phosphate materials, resulting in repair of the cortical defects within three months with partial bony fill of the medullary canal. CC completely degraded by three months, causing incomplete defect closure in some cases. TCP partially degraded in the medullary canal, but remained when surrounded by bone in the cortex. HA and SHA did not degrade. In summary: $\begin{array}{*{20}{l}} {{\text{Biocompatibility}}:}&{{\text{HA}}\,{\text{ = }}\,{\text{SHA}}\,{\text{ = }}\,{\text{TCP}}\,{\text{ = }}\,{\text{CC}}} \\ {{\text{Osteoconduction}}:}&{{\text{HA}}\,{\text{ = }}\,{\text{SHA}}\,{\text{ = }}\,{\text{TCP}}\,{\text{ > }}\,{\text{CC}}} \\ {{\text{Biodegradation:}}}&{{\text{HA}}\,{\text{ = }}\,{\text{SHA}}\,{\text{ < }}\,{\text{TCP}}\,{\text{ < < }}\,{\text{CC}}} \end{array}$

Video angioscopy was employed in 12 patients to monitor thrombectomy or embolectomy within prosthetic bypass grafts (n = 4), saphenous vein grafts (n = 2), and native femoropopliteal arteries (n = 6). A flexible, 2.8 mm diameter angioscope was introduced into the vessel for confirmation and accurate localization of the diagnosed embolus. A Fogarty embolectomy balloon catheter was passed alongside the angioscope and balloon inflation was visually calibrated to the exact vessel lumen. Thromboembolic debris was then retrieved under direct visualization. Intraoperative angiograms were obtained in all cases and results were compared with the finding at angioscopy. After conventional thrombectomy, angioscopic inspection revealed residual thrombus within the lumen or adherent to the wall in 10 of 12 cases. Residual debris was also identified in tributary vessels in two cases, and the embolectomy catheter was successfully guided into these channels by the tip of the scope. Limb salvage was achieved in all but one patient, with early followup of up to 18 months. As a result of this experience we conclude that angioscopic thromboembolectomy has several advantages over the traditional blind technique: (1) accurate detection and localization of thrombus or embolus; (2) monitoring and control of the degree of balloon inflation, thereby preventing vessel wall damage caused by overinflation; (3) detection and retrieval of residual clot after blind embolectomy; (4) manipulation of the balloon catheter to selected vessels; (5) decreased requirement for repeated arteriograms; (6) increased speed, convenience, and accuracy when compared with intraoperative angiography; and (7) avoidance of surgical exposure of the distal popliteal and tibial vessels. (J VASC SURG 1988;7:318-25.)

• 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)

There is a need for new materials which attach to bone. Attachment can occur through bioactive surfaces or porosity. The Replamineform process can be used to produce polymers, metals and ceramics with these properties. In this study, porous implants were manufactured in cobalt-chromemolybdenum (Co-Cr-Mo) vitreous carbon and silicone rubber. The pores were 200 pm in diameter and fully interconnected. The biocompatibility and osteoconduction of these materials was compared to porous hydroxyapatite (Interpore 200 HA). In 10 rabbits, blocks (2mm×3mm×5mm) of each material were implanted subperiosteally onto the femur, or rods (5mm D×10 L) were press-fit into unicortical defects of the proximal tibia. Explants were harvested at 1–6 months, sectioned midsagitally and embedded in plastic for histomorphometry using SEM or bright field microscopy. Bone grew up to and into all implants by two months. However, implants of porous Co-Cr-Mo, vitreous carbon and silicone rubber had less bone than implants of hydroxyapatite. Also, bone formed in direct apposition to hydroxyapatite, but secondly incorporated the other materials. Moreover, implants containing hydroxyapatite in the pores of the Co-Cr-Mo induced more complete and intimate bone ingrowth. This study demonstrates the potential for bone ingrowth and bonding into a range of biocompatible materials with interconnected porosity and the superior osteconduction of porous hydroxyapatite.

Vascular tissue fusion by lasers is performed by directing a low energy beam at the apposed edges of the repair. The tissues are approximated with stay sutures or non-reflective instruments and laser energy is passed back-and-forth over the anastomotic site until fusion is achieved. Vessel welding is apparent to the trained eye, as is nonunion caused by inadequate energy delivery. Conversely, excessive energy delivery results in obvious tissue coagulation or vaporization. Fiberoptic laser transmission and hand-eye coordination are adequate for repair or anastomosis of vessels with diameters greater than 3 mm, whereas magnification and precise mechanical control of the laser beam are necessary for microanastomoses of smaller vessels. The laser power (watts, W), and the amount of energy and time required (energy fluence or power density) vary according to the type of laser and the size of the vessels. Although laser repairs can be fashioned in time intervals equal to or slightly longer than those required for suture repairs, the optimum wavelengths and laser parameters for different types of seals are not yet established.

This study evaluated the histology and electron microscopy of four samples of 2 cm long venotomies and artery-vein anastomoses formed in canine femoral arteries and veins using the argon laser (0.5 W power, 1 800 J/cm2, 4 min exposure/1 cm length of anastomosis). Welds were continuously irrigated with saline during the procedure to limit maximal temperatures to 44.2 +/- 1.6 degrees C (mean +/- SD), and the specimens were removed immediately following fusion and preserved for examination. Histologic and electron microscopic examination of different areas of the welds revealed various mechanisms of fusion including a) apposition of denatured collagen and elastin in the media and adventitia; b) bonding of vein medial collagen and elastin to the internal elastic membrane of the artery; and c) fusion consisting of a coagulum of platelets and fibrin depending on the alignment and apposition of the vessel edges. This study demonstrates that vascular tissue fusion by the argon laser occurs by various mechanisms. Future experiments should delineate which types of seal produce the optimal strength at the time of fusion, and enhance long-term healing.

CO2, neodymium:yttrium -aluminum- garnet (Nd:YAG), and argonlaser welding of vascular. tissueRodney A. White, R. Patrick Abergel *, Richard Lyons *, Stanley R. Klein,George Kopchok, Richard M. Dwyer *, Jouni Uitto*Departments of Surgery and Medicine *, Harbor -UCLA Medical Center1000 W. Carson Street, Torrance, California 90509AbstractTne feasibility of welding thin- walled microvessels by laser has been established.This report summarizes our experience using laser welding to repair thick -walled, large-diameter, 4 to 8 mm canine veins and arteries using CO2, Nd:YAG and argon lasers. Weldingof venotomies is uniformly successful using CO2 and Nd:YAG lasers, and Nd:YAG venotomiesappear to heal more rapidly than sutured controls. Arterial welding has been accomplishedwitn the Nd:YAG and argon laser. Our preliminary experience shows promise for weldingboth large diameter veins and arteries using lasers. Laser welding may represent analternative for repair of small and large diameter vessels with several advantagescompared to conventional suture techniques.IntroductionVascular surgery has rapidly developed as a specialized field over the past 30 years.Many of the advances have relied on development of blood compatible synthetic polymers foruse as suture and prosthetic materials. Current areas of development in the repair ofvascular lesions require miniaturization of sutures, needles, prosthetic materials andinstruments to yield continued satisfactory results. Development of an expedientnonsuture technique for repairing arterial lesions and making anastomoses would be costand time effective, would reduce the technical difficulty of procedures and would improvethe quality of patient care.Several new techniques have been evaluated for repairing vessels. Automated suturingand stapling devices show some promise for increasing the speed and precision ofprocedures. Biologic adhesives, in particular fibrin glue, show encouraging results forrepair of arteriotomies and are useful adjuncts in forming anastomoses. Recentindications in the literature and preliminary experiments in our laboratory suggest thatlasers are applicable to vascular repair and may have several advantages over conventionaltechniques.This paper reviews our experience using CO2, Nd:YAG and argon lasers to repair otomiesin 4 to 8 mm canine arteries and veins. Previous studj,es "pave established the ability to

Laserprobe thermal-assisted balloon, angioplasty (LTBA) has demonstrated promising initial clinical results in recanalizing stenotic or occluded superficial femoral and popliteal arteries. Over the past year we have obtained six specimens of laserprobe thermal (LT) and LTBA treated total occlusions (avg. length 12 cm) for histopathologic examination from patients who were treated for limb salvage. Three tissue specimens were obtained acutely, and one was obtained at 6, 8, and 13 days, respectively, after laser angioplasty at the time of revision for complications or failed procedures. Serial histologic sections of the treated LT segments demonstrated recanalization of atherosclerotic lesions to approximately 60-70% of the probe diameter. The LT channels were lined by a thin layer of carbonized or coagulated tissue and several layers of cell necrosis. The histology of the thermal injury was similar regardless of whether it was produced by the heated metal cap or by free argon laser energy. Stellate balloon angioplasty fractures were frequently filled with thrombus. Analysis of these human LT and LTBA specimens revealed that the thermal device produces a confined injury through the path of least resistance. Balloon dilatation produces fragmented cracks in the vessel wall, which appear to be more thrombogenic than the carbonized LT surface. With improved guidance methods, LTBA shows potential for continuing development.

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.

The utility of enterotomy closure with the argon and CO2 lasers was examined in New Zealand white rabbit ileum. Thermal properties of 10 argon (0.5 W power for 30 s, energy fluence 230 J/cm2) and 10 CO2 (1.0 W power for 30 s, energy fluence 2700 J/cm2) laser-fused enterotomies were determined during acute fusion experiments using an AGA 782 digital thermographic camera. Healing of the fusions created by the two lasers was subsequently assessed in an additional group of 28 rabbits by comparing three 1.0-cm longitudinal ileal enterotomies, with each rabbit having both types of laser-welded closures and a sutured control. Thermal measurements made from the 10 closures with each laser revealed that the CO2 fusions generated significantly higher temperatures (max. 198 degrees C, mean 106 +/- 37 degrees C, n = 100) than argon (max. 85.2 degrees C, mean 60.5 + 8.1 degrees C, n = 100) p less than 0.001. In the healing studies, four rabbits died from weld failures (one argon and one CO2 disruption, two rabbits with both welds disrupted). Two additional rabbits died at 1 day and one at 10 days for undetermined reasons. The remainder of the animals were sacrificed at 1 (n = 11), 2 (n = 2) and 4 (n = 9) weeks postoperatively. Sutured closures exhibited more granulation tissue and adhesions surrounding the wounds than did welded closures and seven microabscesses were noted adjacent to sutured repairs. One of the CO2 repairs had an abscess at 4 weeks and none of the argon laser fusions had evidence of disruption or abscess.(ABSTRACT TRUNCATED AT 250 WORDS)

In this study, we examined short-term strength and histology of experimental argon and CO2 laser-welded and control-sutured enterotomies in a rabbit model. Longitudinal 1.0-cm enterotomies were closed with the argon laser at 0.5 (n = 10) or 1.0 (n = 10) W power and a spot diameter of 2.8 mm resulting in energy fluences of 230 and 450 J/cm2, respectively. Similar enterotomies were closed using the CO2 laser at 0.5 (n = 10) or 1.0 (n = 10) W power and a spot diameter of 1.2 mm, resulting in energy fluences of 1,360 and 2,730 J/cm2. In all closures, continuous wave laser was delivered for 30 seconds. Using a pressuremonitored infusion system with normal saline, the pressure required to burst each weld as well as sutured controls (n = 10) was recorded approximately 1 minute following fusion. Mean bursting pressures for the argon laser at 0.5 W and 1.0 W were 34.1 ± 19.4 mm Hg (mean ± SD) and 17.3 ± 8.3 mm Hg, respectively, and for the CO2 laser were 23.5 ± 12.0 mm Hg and 31.8 ± 15.6 mm Hg, respectively. Sutured controls leaked at 45.2 ± 12.0 mm Hg. With the exception of argon-laser welds at an energy fluence of 450 J/cm2, which were less than sutured repairs, the bursting pressures for welded closures were not significantly different from the sutured controls (Student's t distribution, P < .05). Histologic examination of both types of welds demonstrated a fibrin and red blood cell coagulum bridging the anastamosis, with some evidence of mild thermal injury at the mucosa. These findings suggest that both the argon and the CO2 lasers present an alternative means to suturing in closure of small-bowel enterotomies.

The thermal properties and maximum temperatures attained during CO 2 (n=20) and Argon (n=20) laser welded repair of arteries were compared in a canine model. An AGA 782 digital thermographic system with spatial and thermal resolution of +0.2mm and +0.2°C was used to continually record and analyze the measurements. Longitudinal incisions of 1 cm length were made in each vessel with a 6-0 prolene stay suture at each apex and the midpoint, forming two 5mm segments. A Sharplan CO 2 laser was used at an energy fluence of 1500 J/cm 2 , 150mw power, spot size of .00049 cm 2 and exposure of 5 seconds to induce fusion of each 0.5 cm of vessel wall. Argon fusion was accomplished with the HGM Argon laser using a 300 micron diameter fiber held 1 cm from the surface of the vessel, energy fluence of 570 J/cm 2 , 500mw power, spot size of 0.066cm 2 and total exposure of 75 seconds per 0.5cm length. Continuous irrigation of room temperature saline at 1 drop/second (approx. 3m1/min) was used during argon welding. With CO2 laser welding temperature increased quickly to its maximum (MAX=84.0, MEAN=60.7+ 9.8°C) which was maintained as the laser energy moved slowly (0.1cm/sec) along the vessel edges. In contrast the argon laser welding temperatures rose to a maximum (MAX=48.8, MEAN=45.1+2.7°C) and returned to a baseline temperature with each drop of saline. The thermal difference with these two laser wavelengths may bring about different welding mechanisms and provide an explanation for the increased incidence of thrombus aneurysm formation that has been reported in CO 2 laser fusion.

• 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)

Studies have documented abdominal aortic aneurysm (AAA) enlargement in up to 41% of patients 5 years after endovascular repair (EVAR). Noting limitations of patient selection and length of follow-up, the current analysis was undertaken to assess AAA enlargement in an unselected patient cohort with follow-up for up to 15 years after repair.