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%.

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.

Diagnosis of cornual obstruction by transcervical fallopian tube cannulation.

Interstitial fallopian tube obstruction (IFTO) occurs in 15% of hysterosalpingograms (HSG) performed for infertility. Conventional HSG or laparoscopy may not differentiate cornual spasm or other temporary cause from true obstruction. We used transcervical cannulation of the proximal oviduct with a 3-F Teflon catheter and flexible guidewire 0.018 inch (0.043 cm) in diameter under hysteroscopic or fluoroscopic guidance to evaluate IFTO in 28 patients. Fluoroscopic catheterization techniques with selective salpingography demonstrated patency in 84% of obstructed tubes. Hysteroscopic cannulation with direct visualization by laparoscopy or laparotomy was successful in 92%. In one patient, perforation of the isthmus occurred without sequelae. Transcervical coaxial cannulation of the proximal oviduct is an effective method for evaluating cornual obstruction.

Aortic and venous valve for percutaneous insertion.

The purpose of this paper is to present in vitro and in vivo experimental evaluation of a new, artificial, bicuspid, aortic and venous valve. Valves were constructed from square stents with barbs covered by porcine small intestine submucosa (SIS). A valve 15 mm in diameter was tested in a flow model (2.5 l/min) with pressure measurement. A 100-ml rubber bag attached to a side arm of the flow model simulated heart ejection fraction. In acute (n=6) and short-term (n=3) experiments conducted in four swine and four dogs, valves ranging from 16-28 mm in diameter were placed into the ascending aorta through 10 F sheaths; three were placed subcoronary and six in a supracoronary position. Function and stability of the valves were studied with pressure measurements and aortograms. Three short-term animals were sacrificed for gross and histologic evaluation at one, two and four weeks respectively. In an acute experiment, venous valves with four barbs were placed into the IVC through an 8 F guiding catheter in three dogs. For longer-term testing, valves were placed into the IVCs and iliac veins of three young swine. The animals were followed up after two weeks with venograms, then were sacrificed for gross and histologic evaluation.

Reverse endoventricular artificial obturator in tricuspid valve position. Experimental feasibility research study.

The concept of vena contracta space reduction in tricuspid valve position was tested in an animal model. Feasibility of specific artificial obturator body (REMOT) fixed to the right ventricular apex and interacting with tricuspid valve leaflets was evaluated in three different animal studies. Catheter-based technique was used in three series of experiment in 7 sheep. First acute study was designed for evaluation if the screwing mode of guide wire anchoring to the right ventricular apex is feasible for the whole REMOT body fixing. Longer study was aimed to evaluate stability of the REMOT body in desired position when fixing the screwing wire on its both ends (to the right ventricular apex and to the skin in the neck area). X-ray methods and various morphological methods were used. The third acute study was intended to the REMOT body deployment without any fixing wire. In all of 7 sheep the REMOT was successfully inserted into the right heart cavities and then fixed to the right ventricular apex area. When the REMOT was left in situ more than 6 months it was stable, induced adhesion to the tricuspid valve leaflet and was associated with a specific cell invasion. Releasing of the REMOT from the guiding tools was also successfully verified. Deployment of the obturator body in the aim to reduce the tricuspid valve orifice is feasible and well tolerated in the short and longer term animal model. Specific cell colonization including neovascularization of the obturator body was observed.

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.

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.

"Atraumatic" transjugular needle for portal vein puncture in swine.

A new coaxial needle-catheter system was designed for transjugular portal vein puncture in young domestic swine. It was tested in 32 animals and successfully entered the portal circulation via a hepatic vein or intrahepatic portion of the inferior vena cava. No complications were encountered.

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.

Portal decompression after transjugular intrahepatic portosystemic shunt creation with use of a spiral Z stent.

PURPOSE: An experimental swine model of acute presinusoidal portal hypertension was used to investigate the feasibility of a spiral Z stent for transjugular intrahepatic portosystemic shunt (TIPS) placement and the correlation between the shunt (stent) size and degree of portal pressure decrease. MATERIALS AND METHODS: Twelve young swine were used. Acute portal hypertension was induced by means of selective injections of absolute alcohol, ethiodized oil, and polyvinyl alcohol sponge particles into intrahepatic portal branches. RESULTS: TIPS was successfully created in all swine by using spiral Z stents that were 6, 8, and 10 mm in diameter; each size stent was deployed in four animals. Being sufficiently flexible, spiral Z stents accommodated for curved shunt tracts. An average of 48% portal pressure decrease was achieved with 6-mm-diameter stents, 61% with 8-mm-diameter stents, and 87% with 10-mm-diameter stents. CONCLUSION: These results are in agreement with our clinical experience with use of Gianturco-Rösch Z stents for TIPS formation.

Gianturco-Rösch Z stents in tracheobronchial stenoses.

PURPOSE: To evaluate expandable metallic Gianturco-Rösch Z (GRZ) stents for treatment of benign and malignant tracheobronchial stenoses. PATIENTS AND METHODS: Six patients, ages 45-73 years, were treated for severe dyspnea with placement of GRZ stents. Three patients had benign tracheal lesions (one tracheomalacia, two postoperative) and received uncovered GRZ stents. Three patients had malignant stenoses at the level of the carina; one received an uncovered stent and the other two received silicone-covered GRZ stents. RESULTS: Two patients with benign lesions responded well to stent placement. One was asymptomatic for a year and then was lost to follow-up; the other improved substantially but died of end-stage lung disease 5 months after stent placement. A third patient with a benign high tracheal lesion did poorly; symptoms recurred secondary to inferior migration of a stent, which was removed surgically at 4 months. All patients with malignant lesions improved symptomatically after stent placement and remained without significant dyspnea until death (from 1 to 6 months). CONCLUSION: Expandable GRZ stents are promising devices for treatment of benign lesions and offer effective palliation of malignant tracheobronchial stenoses.

Experimental TIPS with spiral Z-stents in swine with and without induced portal hypertension.

PURPOSE: To assess the suitability of spiral Z-stents for transjugular intrahepatic portosystemic shunt (TIPS) and the influence of portal hypertension on shunt patency in young swine. METHODS: TIPS were established using spiral Z-stents in 14 domestic swine. In 7 animals, the portal venous pressure was normal; in the other 7, acute portal hypertension was induced by embolization of portal vein branches. Follow-up portal venography and histologic evaluations were done from 1 hr to 12 weeks after TIPS. RESULTS: Follow-up transhepatic portal venograms showed progressive narrowing of the shunt, most prominent in the midportion of the tract. Ingrowth of liver parenchyma between the stent wires found after 3 weeks led to progressive shunt narrowing and shunt occlusion by 12 weeks. A pseudointima grew rapidly inside the stent, peaked in thickness around 4 weeks, and decreased later. Acutely created portal hypertension rapidly returned to normal and there was no difference in TIPS patency between the two groups of animals. CONCLUSION: Although the spiral Z-stent can be used as a device for creation of TIPS in patients with cirrhotic livers, it is associated with extensive liver ingrowth in swine that leads to rapid shunt occlusion. Portal hypertension was only transient in this model.

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.

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.

Retrievable IVC square stent filter: experimental study.

PURPOSE: In vitro and in vivo evaluation of a new retrievable, home-made, inferior vena cava (IVC) Square stent filter (SSF) with two trapping levels. METHODS: In vitro, the SSF was compared in a flow model with the stainless steel Greenfield filter (SGF) for emboli-trapping efficiency by serially passing 300 emboli of 3 and 6 mm in diameter and 15-30 mm in length in each type of filter. Nine swine were used for the in vivo testing of the SSF for deployment and retrievability, emboli-trapping efficiency, stability, and self-centering ability and two were used (total of 11 swine) for testing repositioning and retrievability of the SSF at 2 weeks and for gross and histologic IVC changes at 2 months. RESULTS: In vitro, the SSF and SGF had similar efficiency in trapping large emboli but the SSF had significantly better efficiency than the SGF for trapping all sizes of emboli (91.7% vs 81%), medium size emboli (93% vs 80%), and small emboli (86% vs 69%). Efficiency decreased in both filters from the first to the fifth embolus in each series but was still significantly better for the SSF. With the SSF, 89% of emboli were caught at the primary and 11% at the secondary filtration level. In the nine animals used for acute studies, the SSF was easily placed in all 27 attempts, assumed a central position 26 times, and was easily retrieved in 21 of 22 attempts. One tilted filter needed additional manipulation for retrieval. During emboli injection in five swine, the SSF had 97.2% emboli-trapping efficiency and demonstrated good stability. In the two animals used for longer-term evaluation, the filters were easily retrieved 2 weeks after implantation. Histologic evaluation at 2 months showed neointimal proliferation around the SSF wires in contact with the IVC wall, which was otherwise normal. CONCLUSION: The SSF is a promising filter. It is easy to place and retrieve, is stable after placement, and has high efficiency for trapping emboli. Promising results justify further experimental and eventual clinical studies with a commercially manufactured SSF.

Fallopian tube obstruction: selective salpingography and recanalization. Work in progress.

Seven infertile women, in whom interstitial fallopian tube obstruction (IFTO) was suspected at hysterosalpingography and who were recommended for surgical evaluation and treatment, were treated with catheterization techniques. Selective salpingography with ostial injection demonstrated tubal patency in two patients; direct intratubal salpingography demonstrated patency in another patient. Four patients with a true IFTO underwent fallopian tube recanalization: in the first two, a small soft-tipped guide wire was used, and in the other two, a guide wire and 3-F catheter were used. The suggested catheterization techniques have the potential to make evaluation and treatment of IFTO more efficient, safer, and less expensive than presently used methods.

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.

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.

Polyurethane-coated Dacron-covered stent-grafts for TIPS: results in swine.

PURPOSE: To evaluate shunt patency after placing a new polyurethane-coated Dacron-covered spiral Z stent-graft to create a transjugular intrahepatic portosystemic shunt (TIPS). METHODS: TIPS stent-grafts were placed in six young swine, using polyurethane-coated, Dacron-covered spiral Z stent-grafts. Animals were followed weekly by transhepatic portal venography until shunt occlusion or up to 6 weeks, then were sacrificed for gross and histologic evaluation. RESULTS: Five of six TIPS stent-grafts were found to be occluded by 3 weeks and none were patent at 6 weeks. Histologic evaluation demonstrated a marked foreign body reaction with superimposed thrombosis occluding the graft lumen. CONCLUSION: Polyurethane-coated Dacron-covered stent-grafts do not improve TIPS patency.

Attempted induction of chronic portal venous hypertension with polyvinyl alcohol particles in swine.

PURPOSE: Creation of presinusoidal chronic portal venous hypertension by means of repeated portal vein (PV) embolization was explored in an attempt to improve a porcine model of transjugular intrahepatic portosystemic shunt (TIPS) patency. MATERIALS AND METHODS: Six microswine underwent weekly PV embolization for 5 weeks with a total of 10.4-12.6 g of polyvinyl alcohol (PVA) particles (0.149-0.250 mm in size). Portography, liver function tests, pressure measurement in the PV and inferior vena cava (IVC) before and after PV embolization, and histopathologic evaluation of the livers were performed. RESULTS: Transhepatic portal venography performed after each embolization demonstrated diffuse PV branch occlusion in all cases. At weekly follow-up, reconstitution of flow was demonstrated in these branches; permanent occlusion of PV branches was not achieved. The mean PV pressure elevated acutely from 17.3 mm Hg +/- 0.9 to 24.5 mm Hg +/- 4.2 (P < .01) after each embolization. However, the pressure always returned to baseline on the follow-up studies 1 week later. Liver function tests were normal. Histopathologic evaluation of the liver showed, in multiple PV branches, central plugs of PVA with peripheral recanalization. The liver parenchyma was otherwise normal. CONCLUSION: Massive embolizations of PV with PVA at weekly intervals failed to create permanent portal hypertension or induce hepatic fibrosis.