Geoffrey H. White

Initial human evaluation of argon laser—assisted vascular anastomoses

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.

Argon laser-welded arteriovenous anastomoses

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.

Intraoperative video angioscopy compared with arteriography during peripheral vascular operations

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.

Angioscopic thromboembolectomy: preliminary observations with a recent technique.

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 follow-up 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.

Laser Vascular Welding - How Does It Work ?

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.

Thermal Studies of In-Vivo Vascular Tissue Fusion by Argon Laser

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)

Intraluminal Vascular Ultrasound: Preliminary Report of Dimensional and Morphologic Accuracy

The role of intraluminal ultrasound for diagnosis and monitoring treatment of vascular disease has yet to be defined. This study evaluated the dimensional precision and morphologic accuracy of an intraluminal ultrasound system which consists of a 5.5 French external diameter ultrasonic catheter with a central lumen for passage of a guidewire. Ultrasound images from five in-vitro human and three porcine arterial segments and two in-vivo arteriosclerotic canine arteries were compared to dimensions obtained from arteriograms and from sections of the specimens. Each gross and histological specimen and ultrasound image was scaled, photographed and enlarged up to 20 times and measured for vessel intraluminal and adventitial or outer diameter and wall thickness. Intraluminal and outer diameters and wall thickness from normal in-vitro specimens correlated significantly with dimensions obtained from histologic specimens (r=0.99, p<0.005 for internal and outer diameters and r=0.73, p<0.005 for wall thickness). The mean differences of luminal diameters measured from the vessels supported within a silicone rubber mold was 0.05±0.09 mm (n=20). Diameters of outer diameter and wall thickness were less reliably defined, the average margin of error being 0.49±0.39 mm and 0.29±0.26 mm, respectively. The mean difference between in-vivo ultrasound and arteriographic diameters was 0.61±0.38 mm (n=12). Correlation of luminal diameters between ultrasound and arteriogram was significant (r=0.76, p<0.02). The ultrasound images also differentiated a laminated appearance of normal vessel anatomy from non-uniform or dense signals seen in atherosclerotic lesions. We conclude that the definition of arterial wall morphology and accuracy of dimensions obtained using intraluminal ultrasound compared favorably to those obtained by histology and arteriography. This technology may be valuable for precise intraluminal guidance of angioplasty devices by identifying the location and consistency of atherosclerotic lesions.

Experimental and early clinical evaluation of vascular anastomoses with argon laser fusion and the use of absorbable guy sutures: A preliminary report

This study investigated the feasibility of forming vascular anastomoses by use of argon laser tissue fusion and absorbable, monofilament polydimethylsiloxane guy sutures. In initial animal studies femoral arteriovenous fistulas approximately 1.5 cm in length were created bilaterally in each of 10 dogs and were studied histologically at 2, 4, 8, 16, and 24 weeks (two animals in each interval). In each animal, one anastomosis (control) was formed with continuous 6-0 polypropylene suture, and the contralateral anastomosis (experimental) was performed with an argon laser (0.5 watt, 5 to 7 minutes exposure, energy fluence 1100 to 1500 joules/cm2 per 1 cm length) with stay sutures of 5-0 polydimethylsiloxane at 0.5 to 0.65 cm intervals. At removal, all anastomoses were patent without hematomas, aneurysms, or luminal narrowing. Histologic examination at 2 to 16 weeks demonstrated resorption of the biodegradable suture material by a local inflammatory reaction. By 24 weeks, laser-fused specimens had no evidence of suture material at the anastomotic line, and healing consisted of a bond between artery and vein wall tissues. Control suture specimens at the same intervals exhibited an organized fibrous tissue response to the suture. Clinical adaptability of this technology has subsequently been evaluated in five patients at 10 to 27 months (21.6 +/- 5.8) by physical examination and duplex scanning and demonstrate no evidence of abnormal healing. This study establishes the experimental and preliminary clinical feasibility of laser-fused anastomoses aligned by biodegradable guy sutures and supports further investigation and refinement of the technique.

Argon Laser Vascular Welding: The Thermal Component

Various mechanisms have been proposed for laser induced vascular welding. The conflict is partly due to the different laser parameters being used, different techniques, and the possible dual thermal and photochemical effects of lasers on tissues. This study examines the thermal aspects of welding medium diameter (4-8 mm) blood vessels. Six canine arteriovenous (A-V) fistulas were created by argon laser vessel fusion. Thermal images were concurrently recorded with a AGA thermal camera and computer analyzed. The welding was done at an energy fluence of 1100 J/cm2, using continuous saline irrigation for cooling. The thermal profiles revealed a maximum temperature of 48° C. In previous experiments, welding of microvessels has been achieved with CO2 , Na:YAG and argon lasers. In our experience, welding of medium diameter arteriotomies and A-V fistulas was possible only with argon lasers. The thermal component induced by different laser wavelengths may be partly accountable for these observed differences in welding properties. Further studies are required to delineate the role of photochemical and thermal reactions in vascular tissue fusion by lasers.

Blunt traumatic dissection of the internal carotid artery treated by balloon occlusion

An extensive traumatic intimal dissection of the internal carotid artery was successfully managed by permanent occlusion of the vessel with percutaneously-placed, inflatable balloons in a young patient who had suffered transient ischemic neurological attacks despite anticoagulation. This technique has not been previously reported for treatment of dissection. Review of 34 published reports of symptomatic intimal dissection associated with non-penetrating trauma to the head and neck revealed that most did not have a direct injury to the carotid region and that development of symptoms was often delayed. Only 50% of these patients had onset of neurological symptoms within six hours of the episode of trauma, while 33% remained asymptomatic for more than one week before complications occurred. In 15 patients who were treated surgically, only nine (60%) achieved full recovery. Operative repair was considered unduly hazardous in our patient because of extension of the spiral dissection to the base of the skull. Successful use of percutaneous balloon occlusion of the carotid in this patient suggests that this technique should be considered a worthy alternative for management of selected cases.