Biomedical subjects

G Kopchok

Publications and source records attributed to G Kopchok.

29 records · Page 2Linked to original sources

PubMed1987

Valvulotomy in in situ vein bypasses performed by angioscope-assisted laser probe.

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.

Animals↗

PubMed1987

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.

Animals↗

PubMed1987

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.

Animals↗

PubMed1986

Laser welding of venotomies.

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 CO2 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 CO2 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 CO2 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.

Animals↗

PubMed1986

Comparison of laser-welded and sutured arteriotomies.

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/cm2], 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.

Animals↗

PubMed1986

Biological effects of laser welding on vascular healing.

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.

Animals↗

PubMed1986

Laser welding: an alternative method of venous repair.

This study compared the histology, biochemistry, tensile strength, and extensibility of Nd:YAG laser-welded and sutured venotomies. Two-centimeter-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.

Animals↗

PubMedDate not supplied

A canine iliac artery occlusion model.

This report describes an occlusive canine iliac artery model for use in experimental angioplasty procedures. Lesions were induced by overdistending and breaking the internal elastic lamina of the artery and implanting a 2-cm long occlusive collagen plug. The collagen plug diameter was varied to fit the iliac artery and caused immediate bilateral iliac occlusions. Histology of the lesions at 9 and 14 days (n = 2) showed that the lumen was filled with a mixture of fresh thrombus and collagen pad material (more collagen than thrombus) with focal disruptions of the internal elastic lamina. At 36 days (n = 2) the lumen was obliterated with a mixture of organizing thrombus and collagen pad material (more organizing thrombus than collagen). At 60 (n = 4) and 80 (n = 8) days the collagen pad had been completely replaced with organizing thrombus consisting of collagen fibers and hemosiderin-laden macrophages with persistent focal disruptions of the internal elastic lamina. These initial data demonstrate the ability to create fibrotic arterial occlusions in as short a time as 60 days and to provide a practical model to study methods for treating localized peripheral vascular occlusive disease.

Animals↗

PubMedDate not supplied

Laser-fused biologic vascular graft anastomoses.

Tissue fusion using laser energy is a promising new technology that may improve the healing of anastomoses. This study evaluated the feasibility of using argon laser energy to fuse vascular tissue and biologic vascular prostheses (St. Jude Medical, Inc.) in a canine arteriovenous (A-V) fistula model. Five animals had 4-cm length, 3-mm internal diameter grafts (n; eq 10) placed bilaterally as side-to-side A-V interpositions from the femoral artery to femoral vein. One A-V graft was placed using argon laser energy with the vessel edges aligned by 6-0 polypropylene traction sutures at 3 to 4 mm intervals. The contralateral graft was sutured using running 6-0 polypropylene suture. Anastomoses were successfully fashioned in all animals except for episodes of delayed bleeding at two laser-fused segments (15 min and 2 hrs) and one segment in a suture control (6 days). The implants were removed to evaluate the integrity and healing of the anastomoses at 2 hrs, 8 days, and at 7, 9, and 11 weeks. In all instances, there was no evidence of anastomotic dehissance or enlargement. Histologic examination of the anastomoses revealed coapted vessel and prosthetic edges in laser-fused specimens and a limited foreign-body response to the permanent sutures in the suture controls. In the longer term specimens there was marked intimal proliferation at the venous anastomosis in all implants, with recent bilateral occlusions of the 7 and 11 week implants at the venous connection. We conclude that laser fusion of biologic vascular prostheses to autogenous vessel is possible with healing and no evidence of anastomotic dehissance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Anterior patch aortic aneurysm model for the study of endoluminal grafts.

Endovascular graft repair for aortic aneurysms has led to concerns regarding the healing characteristics of the graft within a thrombus-lined aneurysm and the effect that collateral flow may have on the endoluminal prosthesis and the aneurysm. An anterior aortic patch aneurysm model that preserved collateral arteries was examined and modified to address these issues. In canines (n = 30) a Dacron knitted patch (n = 27) or a rectus fascia patch (n = 3) was sutured into a 3.5-cm anterior aorotomy. Dacron patch aneurysm diameter was an average of 21.8 +/- 2.2 mm (mean canine normal aortic diameter 9.06 +/- 0.79 mm). Canines underwent angiogram, computed tomography, and/or intravascular ultrasound from 1 to 11 weeks later, at which time an endoluminal prosthesis was deployed and followed 30 to 60 days until harvest. Aneurysms accumulated minimal thrombus through the initial 11 weeks. Significant stenosis (mean 21.2% +/- 19%) occurred at aneurysm necks in association with a patch imbrication suture technique (n = 11). Following modification (n = 16), this decreased to a mean of 3.6 +/- 9.7%. Collateral lumbar artery patency was 95% at the time of imaging prior to graft placement. Following successful graft implantation, 16 of 18 aneurysms were filled with thrombus and in most cases the collateral circulation occluded. One of three fascial patch aneurysms ruptured 21 days after creation. This model more accurately depicts abdominal aortic aneurysms with the inherent thrombus and collateral flow that is important when studying aspects of endovascular aortic graft repair.

Animals↗

PubMedDate not supplied

Laser welding of large diameter arteries and veins.

Based on our preliminary studies and the results of this study, we conclude that argon laser welding of 4-8 mm internal diameter veins, arteries, and arteriovenous fistulas may have several potential advantages compared to conventional suture techniques. The benefits of laser repairs may include improved mechanical properties, and absence of the foreign body response related to sutures. Laser welding is sterile, nontactile and possibly time conserving, and the wounds heal rapidly without aneurysms or excess tissue proliferation.

Animals↗