A Novel Microporous Polyurethane Vascular Graft: In Vivo Evaluation of the UTA Prosthesis Implanted as Infra-Renal Aortic Substitute in Dogs

A novel microporous polyurethane blood conduit developed at the University of Texas at Arlington was implanted as an infra-renal substitute in dogs. The prosthesis was fabricated by precipitating a solution of the polymer with dry nitrogen onto a rotating mandrel. The grafts were sterilized either by gamma radiation (series I) or ethylene oxide (series II); they were implanted for the following prescheduled periods: 4, 24, 48 hours, and J week (short-term) and 2, 4 weeks, 3 and 6 months (medium-term). The thrombohematological characteristics of each animal were evaluated prior to implantation and confirmed that the index of blood coagulability was normal. In the short-term group, five out of eight grafts were patent and three were partially occluded; four grafts in the medium-term group were patent; one was partially occluded; and three were thrombosed at retrieval. One week after implantation, the prostheses were surrounded by an external capsule, which was present mainly at the two anastomoses. The external capsule covered the entire graft at 3 months. No kinking of the grafts was observed and the presence of a mild yellow stain related to bilirubin uptake was detected at 2 weeks, 1, 3, and 6 months. Histological studies have revealed the formation of a thin internal capsule at both anastomoses, 2 weeks postimplantation, which was not anchored to the graft wall. In the medium-term group, the thrombosed grafts failed to develop an internal capsule, whereas the patent graft exhibited a thick internal capsule made of neocollagenous tissue over the entire graft. This new microporous polyurethane prosthesis did not perform satisfactorily as an infra-renal substitute in dogs and its in vivo stability requires further assessment. Thus, the concept of a polyurethane with closed pores does not achieve what was anticipated.     

Comparative study of microepineurial anastomoses with the use of CO2 laser and suture techniques in rat sciatic nerves: Part 1. Surgical technique, nerve action potentials, and morphological studies

The possibility of utilizing the CO2 laser for neural anastomoses was investigated in a rat sciatic nerve model. One nerve in each animal was acutely divided and anastomosed using 10-0 nylon epineurial sutures, while the opposite side was joined by "welding" the opposed nerve ends together with CO2 laser pulses. The surgical incisions were reexplored 60 days postoperatively, action potentials were recorded across the anastomoses, and the nerves were removed for light and electron microscopy. The operative patency rate in the suture group was 100%, compared to 87% in the laser group. Among those animals with bilaterally intact nerves, action potentials could be recorded across the anastomotic site in 78% of the sutured preparations and in 85% of nerves spot-welded with the CO2 laser. Morphological studies showed a greater degree of scar tissue formation and constriction in the anastomotic zone of the nerves joined by sutures than was present in laser-treated animals. We believe these preliminary observations suggest that the CO2 laser may have a role to play in peripheral nerve surgery. Further study of this technique is warranted.     

Nonreversed saphenous vein grafts for coronary artery bypass grafting

Between August 1985 and December 1988, valvotomized saphenous vein grafts were used in 365 patients undergoing coronary artery bypass grafting (CABG). In this operation, the femoral end of the vein is attached to the aorta and the pedal end is attached to the coronary artery. Vein diameters measured 8 +/- 2 mm at the femoral end, 4.5 +/- 1.2 mm at the knee level, and 3.5 +/- 1.3 mm at the ankle. Ratios between levels were as follows: knee to femoral end, 0.56, and ankle to femoral end, 0.43. The ratio of knee to femoral end was 0.42 in cases with vein midthigh bifurcation. There were 1,310 grafts implanted (3.6 per patient). In 341 patients, CABG alone was performed, and 24 patients had combined procedures: 11 had CABG with mitral valve replacement, 9 had CABG with aortic valve replacement, 2 had CABG with repair of postinfarct ventricular septal defect, and 2 had CABG with automatic defibrillator implantation. Follow-up (up to 3.5 years) was attained in 97% of patients. For various reasons, 34 patients had a second angiogram between 3 and 41 months postoperatively. Of 120 vein grafts, 108 (90%) were patent. At autopsy, 11 patients with 45 vein grafts had 43 patent and clean grafts and two thrombosed. Use of nonreversed saphenous vein for coronary bypass is recommended. It assures a large proximal anastomosis, natural vein bifurcations can be used with fewer proximal anastomoses, better vein-coronary artery size matching is obtained, and the patency rate is satisfactory.     

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.     

Vascular anastomoses in growing vessels: the use of absorbable sutures

Primary end-to-end infrarenal aortic anastomoses were performed in 36 piglets using two synthetic absorbable suture materials: polydioxanone and coated polyglactin. Animals were killed at 1, 4, and 11 weeks and 6 months following operation. Each aorta was removed, burst-tested to 300 mm Hg, radiographed, and examined histologically. All anastomoses were patent, and no burst-test failures occurred. Stenosis occurred in 14 of 17 animals at 1 and 4 weeks, respectively. One of 5 animals exhibited stenosis at 11 weeks, and none of the 14 animals had stenosis 6 months postoperatively. Histological examination revealed fibrosis replacing areas of disrupted elastica at 6 months in both suture groups. This study suggests that absorbable suture material, in particular polydioxanone, because of its excellent handling characteristics and prolonged tensile strength retention, will be useful for the repair of vascular and cardiac anomalies where growth of the suture line is required.     

Initial results on the use of mechanical devices for proximal saphenous vein graft anastomoses: a clinical and angiographic evaluation

Objective: To report on our initial clinical experience of the utilization of a mechanical anastomotic device (MAD) to perform saphenous vein graft to aorta anastomosis. Method: Between June 2002 and May 2003, 17 patients, including 13 male, with a mean age of 64.4 +/- 9.4 years, were selected for coronary artery bypass grafting using MAD. A total of 49 anastomoses, 19 arterial and 30 vein grafts, were performed with a mean of 2.9 +/-0.5 anastomoses per patient. Eleven (36.7%) vein-graft anastomoses were performed with conventional sutures and 19 (63.3%) using MAD. The clinical evolution, enzymatic and electrocardiographic alterations as well as an angiographic study were analyzed in the postoperative period. Results: Of the 17 patients, the mechanical device was used on 16 (94.1%). Six (37.5%) patients were operated on under cardiopulmonary bypass with a mean time of 102.9 +/-16.9 minutes. The postoperative evolution was satisfactory in all patients. No patient presented with enzymatic, myocardial infarction or other ischemic electrocardiographic alterations in the immediate postoperative period. Early postoperative angiography was performed in 9 (52.9%) patients. The anastomoses of the left internal thoracic artery to left anterior descending artery were patent in all cases. Of the 15 saphenous vein grafts studied, 11 (73.3%) were performed using MAD, 9 (81.8%) of which were patent. All the 4 conventionally sutured vein anastomoses were patent. No hospital deaths occurred. In the late follow-up, 88.2% of the patients were free of cardiac-related events. Conclusions: MAD for vein graft-to-aorta anastomoses proved to be feasible, but a wider analysis of the benefits of its utilization regarding operative time, aggression to the patient, patency of the grafts and final cost are necessary.     

Laser-assisted microsurgical anastomosis

A low power carbon dioxide laser was used to perform 212 end-to-end laser-assisted microvascular anastomoses (LAMA) of femoral arteries (mean diameter, 1.2 mm) in Sprague-Dawley rats. Eighty-two conventional microvascular suture anastomoses (CMSA) utilizing 10-0 monofilament interrupted sutures were done for comparison of techniques and wound healing. The mean duration of each anastomosis procedure was 16 minutes for the LAMA repairs, compared to an average of 27 minutes for the CMSA repairs (P less than 0.05). All anastomoses were patent at the completion of the procedure. Each laser-assisted anastomosis required an average of seven intermittent laser exposures of 0.1 to 0.3 seconds each with approximately 80 mW of CO2 (wavelength = 10.6 micron) radiation at a spot size of 150 micron. A patency rate of 95% was obtained on the LAMA vessels (202 of 212) compared to 96% for the CMSA repairs (79 of 82). A total of 14 aneurysms were noted in the LAMA group (7%) compared to 11 in the CMSA (13%). All aneurysms were in patent vessels. Histological analysis indicates that the progression of wound healing of LAMA and CMSA anastomoses follows similar paths chronologically and morphologically with increased scar tissue formation around the suture. Scanning electron microscopy confirms the comparable luminal healing of the LAMA and CMSA vessels, with complete reendothelialization occurring by 3 weeks postoperatively. The tensile strength of the LAMA repair, although low immediately after operation, is comparable to that of the intact artery at 21 days. These findings suggest that a low energy carbon dioxide microsurgical laser has potential beneficial clinical application for anastomosis of small vessels.     

Combined internal mammary artery graft for coronary artery revascularization

Five patients with multiple-vessel coronary artery disease underwent isolated coronary artery bypass grafting with a technique involving both internal mammary arteries and a small piece of interposed saphenous vein. The combined internal mammary artery grafts were used for sequential grafting. A total of 20 anastomoses were performed (average number, 4 anastomoses per patient). There were no operative deaths. Postoperative complications included reoperation for bleeding in 1 patient and diaphragmatic dysfunction in another. Postoperative coronary angiography 2 days before discharge (mean time, 10 days postoperatively) revealed that all the sequential anastomoses with the combined IMA graft were patent. Exercise tolerance tests performed 3 and 11 months postoperatively indicated excellent results and no ischemia. Based on this experience, we conclude that this method appears promising for multivessel coronary artery bypass grafting.     

Aorta-coronary bypass grafting with polytetrafluoroethylene conduits. Early and late outcome in eight patients

During 1982 and 1983 we performed aorta-coronary bypass grafts on eight patients using 4 mm polytetrafluoroethylene conduits and predominantly the multiple sequential graft technique. Angiography was performed 1 week postoperatively and seven of eight patients had patent grafts and were angina free. At 1 year's follow-up 18 of 28 distal anastomoses were patent and five of eight patients were angina free. At 45 month's follow-up four of 28 distal anastomoses were patent and one of eight patients was angina free.     

Laparoscopic aortofemoral bypass. Initial experience in an animal model.

OBJECTIVE: The study objective was to evaluate the feasibility of laparoscopic aortofemoral bypass in a porcine model. SUMMARY BACKGROUND DATA: Laparoscopic techniques have been applied to numerous general and thoracic surgical procedures. Their application to vascular surgery has been virtually nonexistent. Open surgery for aortoiliac occlusive disease is accompanied by significant morbidity rates, and minimally invasive procedures have the disadvantage of reduced patency rates. Laparoscopic aortofemoral replacement has the theoretical advantage of long-term patency with reduced postoperative complications. METHODS: Between January and September 1993, laparoscopic surgery was performed on 16 pigs: 6 underwent transperitoneal laparoscopic aortic dissection and vessel control alone; 7 underwent complete transperitoneal laparoscopic aortofemoral bypass; and 3 underwent a retroperitoneal approach. The aortic anastomosis was performed using a combination of sutures and titanium clips in an end-to-side fashion in five pigs, and a custom-made nonsutured graft was secured with use of an end-to-end method in five pigs. Femoral anastomoses were performed with the standard open technique. RESULTS: Technical success was achieved in all 10 animals and with no major complications. Mean blood loss was 20 ml (range, 5-50 ml), and mean operative time was 2.45 hours (range, 2-4 hrs). On aortic-clamp release, 2 of the end-to-side anastomoses required additional sutures to stop bleeding between oversized staples, and 2 of the end-to-end anastomoses required additional ties to reinforce loose ties. All 10 grafts and anastomoses were patent and free of leaks after completion of the procedure. CONCLUSIONS: Laparoscopic aortofemoral bypass is technically feasible in a porcine model. Further experimental work with new instrumentation and technical refinement will make laparoscopic surgery feasible for the treatment of vascular disease in humans.     

Sequential grafts for limb salvage in the presence of widespread occlusive vascular disease. A review of twenty patients.

Twenty patients with widespread occlusive vascular disease received sequential bypass grafts for lower-limb salvage. In 16 patients an isolated common femoral or profunda segment was perfused by a proximal graft and run-off was augmented by femoropopliteal bypass. In 4 a femoropopliteal bypass constituted the proximal component perfusing an isolated popliteal segment, run-off being increased by a popliteal-to-tibial graft. Dacron, expanded polytetrafluoroethylene (PTFE) (Gore-Tex), and autogenous vein grafts were used. The mean period of follow-up was 10.6 +/- 7 months and 70% of the limbs were salvaged. Thirteen graft systems remain currently patent, 4 have thrombosed, 2 patients died with patent grafts, and 1 required amputation despite graft patency.     

Patency of laser-assisted anastomoses in small vessels: one-year follow-up

Laser-assisted arterial anastomoses can now be performed with satisfactory short-term patency. This study was undertaken to evaluate patency and aneurysm formation with a 1-year follow-up. A microscopically guided CO2 laser was used to anastomose 1.5 to 2.0 mm carotid arteries in 24 rabbits. Under X6 to X40 magnification, 60 to 70 mW were delivered with a spot size of approximately 0.32 mm. One carotid artery underwent laser anastomosis; the opposite served as a sutured control (10-0 nylon sutures). The 48 end-to-end anastomoses were evaluated for patency and aneurysm formation at 3, 6, and 12 months. Aneurysms were defined as a 1.5 times increase in diameter at the anastomotic site. The vessels underwent microscopic examination. All laser-assisted and sutured anastomoses were patent up to 1 year. At 3 months, one of eight sutured and one of eight laser anastomoses were aneurysmal; stenosis was noted in one laser anastomosis. At 6 months, one of eight laser and 0 of eight sutured anastomoses were aneurysmal. At 12 months, one of eight rabbits had died; of the remaining seven, three of seven laser and zero of seven sutured anastomoses were aneurysmal. In total, five of 23 (21.7%) aneurysms developed with the laser technique and one of 23 (4.3%) with the suture technique (p less than 0.05). Laser-assisted anastomoses are technically feasible, and patency at 1 year is equal to those performed with the suture technique. Aneurysm formation is a consistent problem that demands further investigation.     

Intraoperative coronary artery imaging with infrared camera in off-pump CABG

To achieve high quality off-pump coronary artery bypass grafting (CABG), thermal coronary artery imaging using a new generation infrared camera was used and anastomotic status was assessed intraoperatively. In 12 patients who underwent off-pump CABG, 18 grafts (11 internal thoracic, 2 radial, 2 gastroepiploic arteries, and 3 saphenous veins) were evaluated following completion of anastomoses. All grafts were clearly visualized and anastomotic and flow status were observed with local epicardial cooling by CO2 blower in the normothermic heart. Seventeen grafts had no problems and one internal thoracic artery graft showed anastomotic failure that was successfully revised. All grafts were restudied by conventional catheter angiography postoperatively, and all were patent. Intraoperative coronary imaging with a highly sensitive infrared camera is noninvasive and effective for real time evaluation in the operating room. This results in more successful off-pump CABG.     

Comparison of the telescoping anastomotic technique with the end-to-end technique utilizing vein grafts for venous defects: Short- and long-term results

The telescoping anastomotic technique was used for both anastomoses of vein grafts placed in the rat left epigastric vein in an effort to make the anastomosis easier and faster. Vein grafting in the right epigastric vein was completed using the conventional technique. The 20 rats with 20 left and 13 right vein grafts, which were patent at 3 weeks, were seen again 3 months postoperatively to compare the two techniques with regard to long-term stenosis and histological changes. Patency of the grafts 2 hr postoperatively was also compared between the two techniques in another 25 rats to eliminate the influence of recanalization on patency. All the vein grafts, which had been patent 3 weeks postoperatively, remained patent after 3 months and no statistically significant difference was found between the telescoping and conventional technique in the degree of stenosis. The vein grafts 2 hr postoperatively were all patent in both groups. © 1995 Wiley-Liss, Inc.     

Experimental laser-assisted end-to-side microvascular anastomosis

The authors present a new technique of end-to-side microvascular anastomosis in a rat carotid artery model, employing a milliwatt CO2 laser. Both carotid arteries were isolated and approximated in an end-to-side fashion by the placement of four 10-0 nylon stay sutures. The milliwatt CO2 laser was used to effect vessel anastomosis between the sutures, using 70-100 mW of power. Animals were killed 8 weeks postoperatively. Angiography of each anastomosis was performed in all animals. All anastomoses were then harvested, and submitted for histological analysis. Anastomotic patency was 100%, both intraoperatively and angiographically. There was no evidence of intravascular thrombus, anastomotic stenosis, or pseudoaneurysm formation. Early in the experiment, some anastomoses showed localized dilatation at the anastomotic site. The histologic changes at the anastomotic site are described. Laser-assisted microvascular anastomosis is a feasible technique, and a potential alternative to conventional suture techniques.     

Duplex imaging of in situ saphenous vein bypass grafts and late failure reduction

Duplex ultrasonic scanning was applied prospectively to 20 consecutive cases of in situ saphenous vein infrainguinal bypass 1, 3, 6, and 12 months postoperatively. All 20 (100 percent) and 17 of 19 (90 percent) of the proximal and distal anastomoses, respectively, could be imaged satisfactorily. Graft velocity ranged from 30 to 100 cm/s. Of three grafts with low velocity, one had impending graft failure and two had inherently low velocity but remained patent. Five defects in three grafts were detected. In three cases, intervention prevented graft failure. The primary patency rate was 80 percent, but was improved to 95 percent as a result of graft surveillance and simple revisions. Duplex scanning is a superior method for postoperative in situ saphenous vein bypass surveillance. We recommend that patients be studied 1 month postoperatively and every 3 to 6 months thereafter.     

CO2-welded venous anastomosis: enhancement of weld strength with heterologous fibrin glue

The milliwatt CO2 laser was used to perform end-to-end anastomoses in canine jugular veins. There was a high disruption rate (50%) in laser-welded veins (n = 10). Fibrin glue (n = 17), formed from human fresh-frozen plasma, enhanced the weld strength decreasing the disruption rate (18%), resulting in an 82% patency which nearly equaled the contralateral sutured vein patency (93%). The bursting strength was improved with fibrin glue. Transmural necrosis was present initially in all groups but extended for a longer distance in the vessel wall in laser-welded anastomoses. Sutured anastomoses exhibited a greater inflammatory response. In laser-welded anastomoses endothelial cells were not as confluent as in sutured anastomoses by six weeks. Carbon dioxide laser-welded end-to-end vein anastomoses appear to be impractical because they disrupt too easily. However, the addition of heterologous fibrin glue to the weld results in a reasonably strong anastomosis with histologic properties that may be beneficial in vein bypass grafts.     

Heparin-bonded Dacron or polytetrafluoroethylene for femoropopliteal bypass grafting: a multicenter trial

BACKGROUND: Dacron (polyester fiber) was largely abandoned for femoropopliteal bypass grafts 30 years ago because saphenous vein achieved better patencies. However, in patients taking aspirin, patency in above-knee femoropopliteal bypass grafts has recently been shown to be equivalent to that with saphenous vein. We compared heparin-bonded Dacron (HBD) and polytetrafluoroethylene (PTFE) in a randomized multicenter trial including below-knee popliteal or tibioperoneal trunk bypass graft where the long saphenous vein was absent or inadequate. METHODS: Over 28 months, 209 patients undergoing femoropopliteal bypass grafts (180 above-knee, 29 below-knee) were randomized to HBD (n = 106) or PTFE (n = 103). Each patient was given aspirin (300 mg/d) before surgery, and this continued unless the patient had intolerance to the aspirin. RESULTS: The mean follow-up was 42 months (range, 28-55). Fifteen (7.1%) patients died with patent grafts, and three (1.4%) infected grafts were removed. Patency (measured with Kaplan-Meier survival analysis) at 1, 2, and 3 years for HBD was 70%, 63%, and 55% compared with 56%, 46%, and 42%, respectively, for PTFE (P =.044). A total of 67 secondary interventions were performed on 48 thrombosed grafts; long-term patency was achieved in only three. Risk factors for arterial disease did not significantly influence patency. Amputations have been performed in 23 patients, six after HBD and 17 after PTFE bypass grafts (P =.015). CONCLUSIONS: HBD achieved better patency than PTFE, which carried a high risk of subsequent amputation.     

Experimental aortocoronary artery bypass grafting using a CO2 laser on the dog: acute experiment

This study was designed to evaluate the feasibility of using laser tissue welding in aortocoronary bypass operation. Simulated aortocoronary bypass operations were performed on 10 dog hearts supported by extracorporeal circulation. Distal anastomoses between internal mammary artery and coronary artery were achieved using the laser technique, which includes four stay sutures of 7-0 polypropylene and tissue welding between the stays by the laser at a power level of 65 mW. Short-term luminal patency was 100% without stenosis by angiography. Microscopy and histology showed that CO2 laser caused medial change resulting in fusion with preservation of normal intimal morphology. The aortocoronary bypass operation using a CO2 laser is technically feasible, and this technique may open up a new method for patients with small peripheral coronary artery obstruction and for pediatric patients with certain conditions (eg, Kawasaki disease).     

Effect of blood flow rate and donor vessel diameter on the patency of carotid venous bypass grafts in dogs

A saphenous vein graft was implanted from the right subclavian to the right common carotid artery in seven dogs (group I) and between the right and left common carotid arteries in another seven dogs (group II). The recipient artery was ligated proximally to augment blood flow through the graft. Immediately after the anastomoses were completed, the average blood flow through the graft was 32 +/- 25 mL/min in group I and 122 +/- 22 mL/min in group II. At sacrifice 30 days later, angiography showed that all grafts in group I were thrombosed, whereas six (87.5%) of seven grafts in group II were patent. These findings suggest that a larger donor vessel diameter and higher graft flow rates may improve patency in venous bypass grafts that are 3 to 5 mm in diameter.