Biomedical subjects

B T Uchida

Publications and source records attributed to B T Uchida.

At least 19 recordsLinked to original sources

PubMed2005

Small intestinal submucosa sandwich Zilver stent-grafts for TIPS: experimental pilot study in swine.

The aim of this study was the evaluation of preliminary suitability of the piglet small intestinal submucosa (SIS) sandwich Zilver endograft for experimental transjugular intrahepatic portosystemic shunt (TIPS) creation. TIPS was created in six swine. The five surviving animals underwent the follow-up portogram and were sacrificed at four weeks after TIPS creation. Gross and histologic examination was performed in all animals. TIPS creation was successful in all animals. One animal died four days after TIPS creation. In the five surviving animals, one shunt was occluded and four shunts were stenosed on the follow-up portogram. The mean percentage narrowing of the most advanced stenoses was 72% (range, 60%-100%). The most advanced stenosis was located in the parenchymal tract in three shunts and in the hepatic vein portion in one shunt. Gross and histologic examination showed abundant neointimal formation composed mainly of fibroblasts leading to the significant shunt stenoses. The piglet SIS sandwich Zilver stent-graft was found to offer only limited TIPS patency and should not be used for the definitive long-term TIPS study.

Journal Article↗

PubMed2001

Effects of intraarterial thrombin in the swine model.

PURPOSE: To evaluate the effects of catheter-directed thrombin in the peripheral arterial circulation of swine. MATERIALS AND METHODS: Thrombin was injected into a single femoral artery in 20 domestic swine. Each of five animals from four dose groups received 50, 150, 250, or 1,000 U as a single dose. Bilateral femoral arterial flow was monitored for as long as 4 hours and evaluated relative to baseline and contralateral limb flow. Interval arteriographic results were evaluated by segmental patency and a numeric angiographic score. RESULTS: Mean baseline flow was 136 mL/min +/- 44, with an internal arterial diameter of 3.4 mm +/- 0.5. A transient increase in blood flow after thrombin administration was followed by diminished flow and thrombosis. These findings varied directly with dose and inversely with baseline flow. Angiographic and flow abnormalities generally improved with time and recovery was generally better in swine that received 50 or 1,000 U than in other groups. However, one animal that received 1,000 U (13.2 U/mL/min) developed stable, complete limb thrombosis. The degree of recovery varied with thrombin dose and thrombus location. At doses greater than 50 U (0.33 U/mL/min +/- 0.05), abnormalities were commonly persistent. Animals receiving the 150-U dose (1.33 U/mL/min +/- 0.41) had a higher incidence of persistent distal occlusion. Distal occlusions were less likely to resolve than proximal occlusions. CONCLUSIONS: The effect of intraarterial thrombin is directly related to dose and inversely related to baseline blood flow. In swine, a threshold for significant flow disruption and thrombosis exists above a dose of 50 U (0.33 U/mL/min +/- 0.05). A threshold dose for irreversible occlusion may also exist. Although small amounts of thrombin in a high-flow vessel may not cause significant complication, administration into the arterial circulation should be avoided.

Angiography↗

PubMed2001

Intravascular US-guided direct intrahepatic portacaval shunt with a PTFE-covered stent-graft: feasibility study in swine and initial clinical results.

PURPOSE: To determine the feasibility of the creation of a direct intrahepatic inferior vena cava (IVC)-to-portal-vein shunt with puncture guided by a transfemorally placed intravascular ultrasound (IVUS) probe and use of a polytetrafluoroethylene (PTFE)-covered stent-graft. MATERIALS AND METHODS: In five swine, transjugular access was used to perform a direct puncture from the IVC to the portal vein with use of a modified Rosch-Uchida Portal Access set directed with real-time IVUS (9 MHz) introduced from a transfemoral venous approach. The direct intrahepatic portocaval shunt (DIPS) was then created with single or overlapping PTFE-covered Palmaz stents placed through a 10-F sheath and dilated to a diameter of 8 mm. Follow-up was performed with transhepatic portography at 2, 4, and 8 weeks. Animals were killed when shunts occluded or at the termination of the study at 8 weeks. Gross and microscopic histologic study was performed on sacrificed animals. A similar technique was used to create DIPS in five patients with intractable ascites, with follow-up by US and venography. RESULTS: All experimental DIPS created in swine were created without complications. Portal vein punctures were achieved in four of five swine on the first or second pass of the needle. Follow-up transhepatic portography at 2 weeks demonstrated occlusion of two shunts, both explained by technical reasons at sacrifice. At 4 and 8 weeks, the remaining three shunts were patent on portography. Histology showed a thin neointimal lining with no significant tissue ingrowth or hyperplasia. Clinically, in five patients, successful puncture of the portal vein from the IVC was achieved in one to three passes. Creation of DIPS led to a reduction of mean portosystemic gradient from 18-29 mm Hg (mean, 24 mm Hg) to 9-10 mm Hg (mean, 9 mm Hg). One patient died of liver failure 2 days after creation of DIPS. The other four patients were doing well 2-15 months (mean, 8 months) after the procedure, with patency confirmed by US and venography. CONCLUSION: Creation of DIPS is technically feasible, and the direct IVC-to-portal-vein puncture can be done accurately with real-time IVUS guidance. Further studies and longer follow-up are necessary to determine if the short length of the PTFE-covered stent-graft and avoidance of the hepatic vein will increase the long-term patency compared to standard transjugular intrahepatic portosystemic shunt creation.

Animals↗

PubMed2001

Bifurcated drum occluder endograft for treatment of abdominal aortic aneurysm: an experimental study in dogs.

PURPOSE: To evaluate a new, low profile, home-made, bifurcated drum occluder endograft (BDOEG), designed for percutaneous, transcatheter treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAA was created in 10 dogs with over-dilated Palmaz stents. To prevent back filling, the lumbar arteries, inferior mesenteric artery, and common internal iliac arteries were embolized. The BDOEG was constructed of a drum occluder device and two PTFE endografts. The drum device consisted of a modified Z stent with Dacron stretched across and held within the ends of the stent, each with two 8 x 6-mm slits through which PTFE endografts were delivered. The PTFE endografts were 8 mm in diameter and 9.5 cm in length. Preloaded, the BDOEG was delivered through a 10-F sheath from both femoral arteries in a three-step procedure. All 10 animals were treated with BDOEG. Aortography was performed immediately, 6 weeks, and 12 weeks after stent-graft placement. Five animals were killed at 6 weeks and five were killed at 3 months. Gross and histologic evaluation was performed. RESULTS: The infrarenal aortic diameters and both external iliac arteries ranged from 8.0 mm to 10.3 mm (mean, 9.4 mm +/- 0.6) and from 5.2 mm to 6.8 mm (mean, 5.8 mm +/- 0.5), respectively. Creation of the AAA was successful in all 10 dogs. AAA diameters ranged from 13.7 mm to 15.9 mm (mean, 14.9 mm +/- 0.7). Complete exclusion of the AAA was achieved immediately after BDOEG placement and aneurysms remained excluded without perigraft leak to the time of killing in all 10 animals. There was a high incidence of aortoiliac limb occlusion. Occlusion of 12 aortoiliac limbs (60%) caused by intimal hyperplasia at the distal end of the endografts in iliac arteries developed in nine animals (90%). In six animals (60%), one limb occluded and, in three animals (30%), there was occlusion of both limbs. CONCLUSION: This study suggests a new approach for treatment of AAA. BDOEG use reduces sheath size for endograft delivery and may eliminate the need for a surgical cut down on femoral arteries. Tapering of the iliac ends of endografts to the size of the artery will be needed to prevent distal intimal hyperplasia.

Animals↗

PubMed2000

The square stent-based large vessel occluder: an experimental pilot study.

PURPOSE: The purpose of this study is in vitro and in vivo experimental evaluation of a square stent-based vascular occlusion device for large vessels. MATERIALS AND METHODS: Square stent-based large vessel occluders (LVO) 5 mm-50 mm in size were constructed from stainless-steel square stents covered by porcine small intestine submucosa (SIS). The LVOs with two back-side barbs were delivered through a guiding catheter. The LVOs with two back-side barbs and two frontal barbs were front-loaded and delivered coaxially. A pusher with a retention mechanism at its end was used for deployment. In vitro testing for competency was performed with use of a flow model with pressure increases. In an experimental pilot study in seven pigs and five dogs, 16 LVOs were placed into the aorta (n = 4), common iliac artery (n = 2), pulmonary artery (n = 4), and medial sacral artery (n = 6). Four animals received two LVOs in different locations. Angiography was performed before and after placement of each LVO. Animals were followed for as long as 3 months with use of angiography and were then killed for gross and histologic evaluation. RESULTS: In vitro LVOs with two and four barbs were easily collapsed and pushed through or front-loaded into guiding catheters (6-F for a 5-mm occluder, 10-F for a 50-mm occluder). A 20-mm LVO adapted to tubular structures 10-15 mm in diameter, forming polygons 17-18.5 mm in length. In the flow model, LVOs endured pressure increases to 300 mm Hg. In vivo, the LVOs self-expanded and adapted to the vessel without migration in all cases. The locking pusher allowed precise LVO placement and engagement of its barbs into the vessel wall before complete deployment, preventing dislodgment by blood flow. Complete arterial occlusion occurred within 10-20 minutes and arteries remained occluded until the animal was killed in all cases. After 2 months, histologic evaluation revealed replacement of SIS by host tissue and its remodeling with variable fibrocytes, fibroblasts, and some inflammatory cells. Complete endothelialization was seen on both sides of the LVO. CONCLUSION: The SIS LVO is effective and reliable for acute and chronic occlusion in a high flow model in an experimental animal.

Angiography↗

PubMed1999

Long-term results of treatment of benign central venous obstructions unrelated to dialysis with expandable Z stents.

PURPOSE: To evaluate long-term patency of self-expanding Z stents for treatment of benign central venous obstructions unrelated to dialysis. MATERIALS AND METHODS: Z stents were placed in 19 patients, (ages 26-72 years) with severe symptomatic obstructions of the superior or inferior venae cavae and their large branches and portal vein caused by surgical or catheter injury (n = 8), fibrosis (n = 5), cirrhosis (n = 3), Budd-Chiari syndrome (n = 2), and extrinsic compression (n = 1). Fourteen patients underwent stent placement primarily, five after local urokinase infusion for superimposed thrombosis. Follow-up was performed with ultrasound and venography. RESULTS: Venous congestive symptoms quickly resolved in all patients after stent placement. The follow-up period was from 1 to 94 months. Twelve patients have died during follow-up from 1 to 37 months although all remained asymptomatic until death. Six patients remain alive, asymptomatic, with patent stents, and with follow-up from 24 to 94 months. Primary patency was 83%, and secondary patency was 100%. One patient with a patent stent at 12 months was lost to follow-up. No stent migrations, perforations, infections, or significant complications occurred. CONCLUSION: Benign central venous obstructions are effectively treated by the placement of self-expandable Z stents. Placed percutaneously into obstructive lesions with a minimum risk, these stents offer long-term durability and patency.

Adult↗

PubMed1999

Twin-tube endografts for aortic aneurysms: an experimental feasibility study.

PURPOSE: To explore feasibility of twin-tube endografts (TTEGs) for treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAAs were created in six dogs by overdilation of Palmaz stents. TTEGs made of seven 9.5-mm-diameter Gianturco Rösch Z (GRZ) stents and covered with PTFE were deployed simultaneously from both femoral arteries through 10-F sheaths to exclude the AAA. Follow-up aortography was performed immediately and at 2, 4, and 8 weeks. Two dogs were killed at 4 weeks and four were killed at 8 weeks. Gross and histologic examinations were performed. RESULTS: AAA creation and TTEG placement were successful in all six dogs. TTEGs completely excluded AAAs in five dogs. Minor temporary perigraft leak was seen in one dog immediately after stent placement. Four dogs had TTEGs patent to termination at 8 weeks. In two dogs with oversized TTEGs, one of the twin endografts occluded at 2 weeks. At autopsy, TTEGs were formed in semicircular shape and histology did not show any significant inflammatory reaction. CONCLUSION: TTEGs show promise for treatment of AAA, with the potential of reducing the introductory sheath size. Further experimental studies, particularly with TTEGs extended into iliac arteries, are warranted.

Angiography↗

PubMed1999

Percutaneous transjugular kidney biopsy in swine with use of a side-cutting needle with a blunt-tipped stylet.

PURPOSE: To evaluate a new 19-gauge blunt-tipped, side-cutting, single throw transjugular biopsy needle for transvenous kidney biopsies. MATERIALS AND METHODS: Transjugular transvenous kidney biopsies were performed with a modified 70-cm biopsy needle utilizing fluoroscopic guidance in nine swine. Three tissue specimens were obtained with four biopsy device passes in five animals and three biopsy device passes in four animals. Renal arteriography and venography were performed immediately before and after renal biopsy. Five animals were killed immediately after biopsy. Four animals were allowed to recover and underwent arteriography and venography prior to being killed, which varied from 1 to 6 weeks. Gross and histologic examinations of the biopsied kidney were performed after euthanasia. A pathologist reviewed all biopsy specimens for quality based on the number of glomeruli present. RESULTS: Results of immediate and delayed arteriography and venography were normal in all cases. Histologic evaluation of all biopsy specimens demonstrated a range of two to 13 glomeruli per sample (mean, 6.5), with successful acquisition of the cortex. In one animal killed immediately after biopsy, a small subcapsular hematoma was present. CONCLUSION: The 19-gauge, side-cut biopsy needle with a blunt-tip stylet proved to be efficacious for obtaining renal cortical samples in right swine kidneys via a transjugular approach.

Animals↗

PubMed1998

Percutaneous retroperitoneal splenorenal shunt: an experimental study in swine.

PURPOSE: To evaluate the technical possibility of creating a percutaneous retroperitoneal splenorenal shunt (PRESS) in swine as a minimally invasive treatment of portal hypertension. MATERIALS AND METHODS: Five normal domestic swine underwent creation of a PRESS. A modified transjugular intrahepatic portosystemic shunt puncture set was introduced from the right femoral vein into the left renal vein. The proximal splenic vein was punctured transvenously through the retroperitoneal cavity. Noncovered metallic stents were then placed to connect both veins. The animals were sacrificed 1 hour after the procedure, after follow-up splenic venography and necropsy were performed. RESULTS: Puncture of the splenic vein and stent placement were successfully completed in all cases. In four of five cases, the splenic venogram revealed good flow from the splenic vein to the left renal vein through the shunt track 1 hour after creation of the PRESS, and there was no evidence of leakage. No changes in vital signs were noticed. At necropsy, a small retroperitoneal hematoma along the stent and minimal intraperitoneal bleeding were observed. The stents were found in the retroperitoneal cavity connecting both veins in all animals. CONCLUSION: Creation of a PRESS is technically possible, and further experimental studies of its efficacy are warranted.

Animals↗

PubMed1997

Transjugular intrahepatic portosystemic shunt with silicone-covered Wallstents: results in a swine model.

PURPOSE: To evaluate the use of impermeable silicone-covered Wallstents for transjugular intrahepatic portosystemic shunt creation. MATERIALS AND METHODS: A transjugular intrahepatic portosystemic shunt was created in 14 young swine (weight, 20-32 kg) by using impermeable silicone-covered Wallstents. In eight animals, the silicone covering extended from the portal vein to the inferior vena cava. In two swine, the silicone covering ended short of the inferior vena cava, in two it ended short of the portal vein wall, and in two it ended short at each end. Follow-up transhepatic portal venography was performed weekly for 6 weeks or until the shunt was occluded. Animals were then sacrificed for gross and histologic evaluation. RESULTS: Only two of 14 shunts were patent after 3 weeks; both were stenosed with luminal narrowing of more than 50% in the middle of the shunt. By 6 weeks, all shunts were occluded. At histologic evaluation, a marked foreign-body reaction with superimposed thrombosis was demonstrated. CONCLUSION: In comparison with uncovered Wallstents, impermeable silicone-covered Wallstents are associated with decreased patency at transjugular intrahepatic portosystemic shunt creation. This is likely due to increased thrombogenicity and a foreign-body reaction.

Animals↗

PubMed1995

Improved transjugular intrahepatic portosystemic shunt patency with PTFE-covered stent-grafts: experimental results in swine.

PURPOSE: To evaluate the ability of stent-grafts made with polytetrafluoroethylene (PTFE) graft material to improve transjugular intrahepatic portosystemic shunt (TIPS) patency. MATERIALS AND METHODS: TIPS were created in 13 swine by using PTFE-covered stent-grafts. Uncovered TIPS were placed in 13 other swine. Twenty-one of 26 animals were followed up with portal venography for 3 months or until the shunt became severely stenotic. Five animals without severe stenosis were sacrificed before 3 months because of illness. RESULTS: At 4 weeks after TIPS placement, nine of 13 stent-graft TIPS were patent (< 50% diameter narrowing) compared with only one patent stent in 13 uncovered TIPS. Six of 13 stent-graft TIPS remained patent until the animals were sacrificed. In 11 of 12 uncovered TIPS, stenosis was most prominent in the parenchymal tract. In five of seven stent-graft TIPS, stenosis was most prominent in the hepatic vein above the end of the graft material. Bile leaks were discovered in six occluded uncovered TIPS and in two of the stent-graft TIPS. CONCLUSION: PTFE-covered stent-grafts significantly improved TIPS patency in swine (P < .01). However, stenosis in the hepatic vein led to late shunt malfunction in selected cases.

Animals↗

PubMed1994

Transcatheter tubal sterilization in rabbits. Technique and results.

RATIONALE AND OBJECTIVES: A potential method of nonsurgical tubal sterilization was tested in rabbits. METHODS: Metal coils were designed which could be placed into the uterotubal junction using transvaginal fluoroscopic fallopian tube catheterization. These metal coils were successfully placed unilaterally in the uterotubal junction of 32 rabbits. The contralateral fallopian tube and uterus were used as a control. The rabbits were bred, and the presence of pregnancies was confirmed by palpation. RESULTS: In 21 rabbits (66%), the coil stayed in place. Sixteen rabbits had multiple gestations on the side without the coil and no gestations on the side with the coil. Three rabbits had gestations on both sides, even though the coil was in place, and two rabbits never conceived. In 11 rabbits (34%) the coil was dislodged as early as 5 days and as late as 18 weeks after the procedure. Five of these 11 rabbits had bilateral embryos, 4 had embryos only on the side contralateral to where the coil had been, and 2 never conceived. CONCLUSIONS: The metal coil does prevent conception if it stays in place at the uterotubal junction. However, the coil failed to prevent pregnancy in 3 of 19 rabbits, and was dislodged in 11 rabbits, giving an overall failure rate for contraception of 44%.

Animals↗

PubMed1992

In vitro comparison of the spiral Z stent and the Gianturco Z stent.

A new spiral Z stent is described, and its characteristics are compared in vitro with those of the modified Gianturco Z stent. The spiral Z stent has a more uniform expansile force throughout its effective length; is more compressible, thus allowing for use of a smaller introductory catheter; and is more stable than the modified Z stent. Flexibility of both stent types is similar. Advantages of the spiral Z stent promise to be beneficial for clinical use.

Equipment Design↗

PubMed1992

Venous stenoses in patients who undergo hemodialysis: treatment with self-expandable endovascular stents.

During a 32-month period, 25 modified self-expandable endovascular stents were placed in 20 hemodialysis access sites to treat 21 stenoses and four occlusions in 19 patients. All stenoses were initially dilated with a high-pressure balloon. The initial success rate was 90% (18 of 20 access sites). The stents were patent from 0 to 960 days (mean duration of follow-up, 309 days). At 2 years follow-up, the patency rates were as follows: primary, 25%; secondary, 34%; and tertiary, 42%. The morbidity rate associated with this procedure was 15% (three of 20 sites); the mortality rate, 5% (one of 19 patients). All five complications (graft or native-vein thrombosis [n = 2], nerve deficits [n = 2], and death secondary to sepsis [n = 1]) occurred in three patients early in the study, before the use of prophylactic antibiotics and refinements in technique. The best results occurred in patients in whom the stenosis or occlusion affected a large vein that had no acute angle and was away from venous confluences such as the femoral and iliac regions.

Constriction, Pathologic↗

PubMed1990

Device for hysterosalpingography and fallopian tube catheterization.

A device was developed for hysterosalpingography and fallopian tube recanalization. It differs from the previously used vacuum-cup device in that the central shaft slides and has an acorn-shaped tip. Optimal results were obtained in all 14 women (100%) who underwent catheterization with the new device; optimal results were achieved in only five of eight women (62%) who underwent catheterization with the fixed-shaft device during the same time period.

Catheterization↗

PubMed1988

Transvaginal fallopian tube catheterization in an animal model.

A rabbit model for testing the safety and effectiveness of diagnostic and interventional techniques of fallopian tube catheterization is presented. Hysterography with injection into the terminal portion of the uterine horn visualized the fallopian tube in only 6% of cases; however, this increased from 33% to 50% by pretreatment with progesterone, administration of glucagon or phentolamine, or increased pressure of injection with balloon obstruction of the uterine horn. Salpingography with a catheter introduced in the tubal ostium or directly inside the tube was most effective and resulted in a consistent (100%) visualization of the fallopian tube. The technique also allowed coaxial introduction of small diameter guidewires and catheters deep into the fallopian tube.

Animals↗

PubMed1988

Superior vena cava syndrome associated with massive thrombosis: treatment with expandable wire stents.

Two patients with superior vena cava syndrome (SVCS) associated with massive thrombosis were treated by means of local thrombolytic therapy and placement of modified Gianturco expandable wire stents. Treatment resulted in complete resolution of the SVCS symptoms. The combination of local thrombolytic therapy and stent placement allows a more aggressive approach to treatment of SVCS and provides longer-term palliation of symptoms even for patients with later stages of the disease.

Aged↗

PubMed1988

Selective transcervical fallopian tube catheterization: technique update.

A technique of transcervical fallopian tube catheterization involving use of a new vacuum hysterograph and coaxial catheter set is described. In 25 women, selective catheterization of the uterine cornua was accomplished with a 94% success rate. Ostial salpingography permitted visualization of 26% of the 46 tubes found to be obstructed or poorly visualized with conventional hysterosalpingography. Recanalization was successful in 96% of 28 proximal tubal obstructions and in 33% of six midisthmic obstructions unrelated to surgery. Recanalization attempts resulted in tubal perforations without apparent clinical effects in four tubes, one with proximal and three with midisthmic postsurgical obstructions. The new hysterograph with coaxial catheter set is more suitable for recanalization of the obstructed fallopian tubes than is the previously used balloon catheter set.

Adult↗