A simplified arteriovenous malformation model in sheep: feasibility study.

BACKGROUND AND PURPOSE: Recently, a swine model of a cerebral arteriovenous malformation (AVM) has been developed that closely resembles a human AVM of the brain. The creation of such a model requires sophisticated neurointerventional techniques. The purpose of this study was to develop a simple and cost-effective AVM animal model that does not require additional endovascular techniques. METHODS: A surgical anastomosis was created in seven sheep between the common carotid artery and the ipsilateral jugular vein, followed by ligation of the jugular vein above the anastomosis and of the proximal common carotid artery below the anastomosis. The anastomosis was created on the left side in four animals and on the right side in three. Cerebral angiography from the contralateral carotid artery was performed before and immediately after surgery to delineate the relevant cerebral vascular anatomy and to determine the direction of blood flow. RESULTS: An angiographic appearance simulating an AVM was found in all the animals. The ramus anastomoticus and arteria anastomotica functioned as the feeding vessels to the rete mirabile, which represented the nidus in our model, and to the jugular vein, which represented the draining vein from the malformation. Extensive collateral flow through the rete mirabile into the distal segment of the external carotid artery above the ligature was observed angiographically, with retrograde flow through the surgical anastomosis into the jugular vein. CONCLUSION: A simple surgically created experimental model for cerebral AVMs was developed in sheep without the need for additional complex endovascular catheter manipulations of intracranial branches. Such an animal model can substantially reduce the cost of research and training in the neurointerventional or radiosurgical management of AVMs.

Percutaneous implantation of non-small-cell lung carcinoma: technique and observations.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether intrathoracic inoculation of non-small-cell lung carcinoma with fluoroscopic guidance would provide for more accurate implantation. MATERIALS AND METHODS: A tumor cell inoculum (2 x 10(6) cells per 0.15 mL) was injected percutaneously under fluoroscopic guidance at the posterior midaxillary line in 22 athymic nude mice. The mice underwent imaging with a mammographic unit at 3, 5, and 8 weeks after implantation. The mice were sacrificed at 8 weeks, and autopsy was performed to determine tumor yield. RESULTS: The use of a percutaneous technique under fluoroscopic guidance greatly facilitated the accurate implantation of xenografts. Tumor growth was seen at radiography in 18 of the 22 (82%) mice at 8 weeks. Necropsy revealed a 100% tumor yield. Histologic examination confirmed adenocarcinoma of the lung. The average number of tumors found in the lung parenchyma was 1.05 +/- 0.35; the average number of tumors found in the mediastinum was 0.59 +/- 0.67. The average tumor weight was 389 mg +/- 64.3. The average tumor size was 300 mm3 +/- 66.23. CONCLUSION: With fluoroscopic guidance, percutaneous implantation of tumor cells in athymic nude mice is simple and effective.

Cragg Endopro System I: early experience. I. Femoral arteries.

PURPOSE: This work describes the early experience with the Cragg Endopro System I. The safety and efficacy of this device in the treatment of atherosclerotic lesions of the femoral arteries are evaluated. MATERIALS AND METHODS: Eleven patients with complex femoral artery lesions were treated. Ten patients presented with femoral artery occlusion and one had a 90% stenosis. All patients had life-style limiting claudication. Associated comorbid states included smoking (n = 10), hypertension (n = 4), hyperlipidemia (n = 5), coronary artery disease (n = 3), and diabetes (n = 1). The stents were dilated to the size of the native artery in the first three patients. The protocol was modified and stents were overdilated by 1 mm in the remaining eight patients. An anticoagulation regimen was used in the first three patients and modified per protocol requirements in the remaining eight. Prophylactics antibiotics were given before the procedure. Follow-up studies included Doppler ultrasound and intravenous and intraarterial digital subtraction angiography. RESULTS: An antegrade femoral approach was used. Stent placement was successful in all patients. The mean lesion length was 9.9 cm (4-18 cm). Mean ankle/brachial index before treatment was 0.65 and increased to 0.87 after treatment. Mean follow-up was 17.2 months, and one patients was lost to follow-up. Complications included sepsis (n = 1), fever (n = 2), severe pain (n = 4), thrombosis (n = 5), and hematoma (n = 2). Stent patency was improved after protocol modifications. Overall primary patency rate was 45% and secondary patency was 56%. CONCLUSION: This early experience with the Cragg Endopro System I shows that recanalization of long femoral occlusions and stent-graft placement is feasible. The primary and secondary patency rates are low and the complication rate is high. Improved patency rates are expected with a more aggressive anticoagulation regimen and stent overdilation.

Effect of transjugular intrahepatic portosystemic shunt on quality of life.

OBJECTIVE: The objective of this study was to determine the effect of the transjugular intrahepatic portosystemic shunt (TIPS) procedure on the quality of life. SUBJECTS AND METHODS: Data were collected on 99 patients who underwent the TIPS procedure between September 1991 and September 1995. Quality of life was assessed by the Karnofsky scale before and at intervals after the procedure. Procedure-related complications and other aspects of the patients' overall well-being, as reflected in liver and kidney function and nutritional status, were reviewed immediately before and after TIPS creation. Finally, mortality and TIPS patency rates were tabulated. RESULTS: We observed significantly improved quality of life. The quality of life remained significantly improved throughout the 24-month follow-up period. During the 1- to 3-month interval after the TIPS procedure, we observed in patients a significant decrease in blood urea nitrogen and an increase in albumin and bilirubin. During this period, patients had no significant change in liver enzymes, prothrombin time, ammonia, or creatinine. Complications of the TIPS procedure included a 30% incidence of new or worsened encephalopathy and a 15% incidence of other severe complications (intraperitoneal hemorrhage, severe accelerated liver failure). The procedure-related death rate was 5%. Longer term follow-up showed an overall sustained decrease in blood urea nitrogen, an increase in albumin, and a return of bilirubin to the pre-TIPS levels or below. CONCLUSION: For patients who survive longer than 1 month, TIPS results in an overall, sustained improvement in the quality of life. Improved quality of life may result from a low incidence of repeat variceal bleeding, decreased ascites, and improved nutritional status.

Venous recanalization by metallic stents after failure of balloon angioplasty or surgery: four-year experience.

PURPOSE: This retrospective study describes our updated experience in treating venous stenoses and occlusions with metallic endovascular stents. METHODS: Gianturco, Palmaz, and Wallstent stents were placed in 55 patients over a 4-year period. Stent sites included the subclavian veins (9), innominate veins (3), superior vena cava (4), inferior vena cava (3), iliac veins (29), femoral veins (5), and portal veins (6). The most common indications for stent placement were malignant stenoses and chronic pelvic venous occlusions. Venoplasty and/or urokinase were used as ancillary therapy. Patients were anticoagulated for 3-6 months. Follow-up included clinical assessment and duplex ultrasound. RESULTS: Lifetable analysis shows 59%, 63%, and 72% primary, primary assisted, and secondary 1-year patency rates, respectively. The 4-year primary patency rates were the same. Duration of patency depended on the venous site. Death was a complication of stent placement in 2 patients and 12 patients died within 6 months after stent placement from primary disease progression. Although early failures were more common in stents placed across occlusions than stenoses, 1-year secondary patency rates were comparable. Primary patency rates were only slightly lower in patients with malignant obstruction than in patients with benign disease. CONCLUSION: Endovascular stent placement provides a nonsurgical alternative for reestablishment of venous flow and symptomatic relief in patients with benign as well as malignant venous obstruction.

Duplex sonography after transjugular intrahepatic portosystemic shunts (TIPS): normal hemodynamic findings and efficacy in predicting shunt patency and stenosis.

OBJECTIVE: Portal hemodynamics are altered by placement of a transjugular intrahepatic portosystemic shunt (TIPS). Normal duplex sonographic findings after TIPS placement and hemodynamic alterations indicating shunt failure have not yet been well described. The purposes of this study were to determine normal hemodynamic changes on duplex sonography after TIPS placement and to assess the efficacy of duplex sonography in detecting shunt dysfunction. SUBJECTS AND METHODS: Forty patients underwent TIPS placement and were entered into a study that included routine sonographic evaluation and portal venography at regular intervals. Portal venography was also performed if shunt velocities on duplex sonography changed from the baseline, which raised the question of shunt stenosis or occlusion. The pre-TIPS duplex sonographic study included determination of patency, velocity, and flow direction in the main, right, and left portal veins and in the hepatic artery. Follow-up sonography included the pre-TIPS examination in addition to velocity determinations in three segments of the shunt. Correlation was made between 82 concurrent sonographic and portal venographic studies. RESULTS: High-velocity blood flow (mean peak velocity, 135-200 cm/sec) was consistently seen within patent, well-functioning shunts. Hepatic artery peak systolic velocities increased from 79 cm/sec before TIPS placement to 131 cm/sec after TIPS placement (p < .001). Main portal vein velocities increased from 21.8 cm/sec before TIPS placement to 41.5 cm/sec after TIPS placement (p < .001). When compared with portal venography, duplex sonography was 98% sensitive and 100% specific in predicting the presence of blood flow within the stent. Sonography was highly sensitive and specific for detecting stent stenosis. Final sonographic criteria for shunt stenosis in angiographically documented cases were low-velocity shunt flow (< or = 60 cm/sec) in the entire stent, or low-velocity shunt flow with an associated focal velocity elevation. CONCLUSION: Consistent changes in portal venous and hepatic arterial hemodynamics are normally seen on duplex sonography after placement of a TIPS. Duplex sonography accurately predicts shunt patency and dysfunction when compared with portal venography. Duplex sonography is an effective, noninvasive method of evaluating shunt function and should be considered for use as the primary imaging technique in routine follow-up after TIPS placement.

The forgotten indwelling ureteral stent: a urological dilemma.

Ureteral stents are an integral part of urological practice. However, stents that migrate, fragment or are forgotten pose a management and legal dilemma. Our series consists of 31 patients, 22 with forgotten stents that were left indwelling for more than 6 months (mean 22.7) and 9 migrated stents. Of the forgotten stents 15 (68%) were calcified, 10 (45%) were fragmented, and 3 (14%) were calcified and fragmented. Procedures to render the patient stent-free were ureteroscopy in 16 (52%), percutaneous nephroscopy in 8 (26%), cystoscopic electrohydraulic lithotripsy in 6 (19%), extracorporeal shock wave lithotripsy in 10 (32%), open cysto-litholapaxy in 1 (3%) and simple nephrectomy in 1 (3%). Multiple procedures were required in 6 patients (19%). Management of such complicated ureteral stents requires a multimodal therapeutic approach incorporating the latest in extracorporeal shock wave lithotripsy and endourological techniques. These patients are at increased risk for loss of renal function. A computerized tracking registry of ureteral stents may help prevent this urological travesty.

Femoral neuropathy following percutaneous nephrolithotomy of a pelvic kidney.

Management of nephrolithiasis within a pelvic kidney presents a novel challenge to the urologist. We report on a patient who underwent ureteral stent placement prior to extracorporeal shock-wave lithotripsy (ESWL). Following ESWL, the ureteral stent calcified at the vesical and renal ends, requiring "sandwich therapy" of percutaneous nephrolithotripsy, ESWL, and percutaneous nephroscopy. Percutaneous access to the pelvic kidney through a posterior approach was complicated by femoral neuropathy manifested by an ability to walk. With 6 months of aggressive physical therapy, the patient is now able to ambulate with difficulty using a walker.

Chronic iliac artery occlusions: primary recanalization with endovascular stents.

PURPOSE: The authors describe treatment of chronic iliac artery occlusions with primary stent placement without prior thrombolysis or angioplasty. PATIENTS AND METHODS: Eight patients with chronic iliac artery occlusions (six men and two women) underwent primary stent placement without prior use of thrombolytic agents or angioplasty. Palmaz stents were placed in seven patients and a Wallstent device was placed in one. RESULTS: In all patients, revascularization was successful without residual stenoses or pressure gradients. There was no angiographic evidence of distal embolization. CONCLUSION: Primary stent placement for chronic iliac artery occlusions without prior thrombolysis or angioplasty appears to be safe and efficacious and is potentially cost effective.

In vitro metal fatigue testing of inferior vena cava filters.

RATIONALE AND OBJECTIVES: Inferior vena cava filter fractures have been described in vivo on several occasions. No studies have compared the fatigue life of the different filter types. Four different, frequently used filters (Vena-Tech filters [VTF], stainless-steel Greenfield filters [SSGF], Simon nitinol filters [SNF], and titanium Greenfield filters [TGF]) were, therefore, tested with regard to fatigue life. METHODS: Ten filters of each type were tested by compressing the filter legs repeatedly. A travel distance of 1.5 cm was used, setting minimal and maximal filter leg separations of 1.0 cm and 2.5 cm, respectively. The endpoint was filter fracture or 10,000,000 compressions. The test was then repeated on five of the filters from each group, but on a different filter leg pair. RESULTS: Seven of 10 VTFs fractured during the first part of the study, and all five VTFs fractured during the second part of the study. One SSGF fractured in each part of the study. None of the SNFs or the TGFs fractured. Significant difference in fracture frequency was found. CONCLUSION: The VTFs appear to have the shortest fatigue life. The TGF and the SNF have a fatigue life exceeding the test limits. The consequences of filter fracture are unknown.

Color Doppler sonography of transjugular intrahepatic portosystemic shunts (TIPS).

Transjugular intrahepatic portosystemic shunts (TIPS) have largely replaced surgically created shunts in the treatment of life-threatening sequelae of portal venous hypertension [1-5]. Conventional duplex and color Doppler sonography are proving to be useful tools in the assessment of the stents and their associated hemodynamic changes [2-5]. A thorough Doppler survey before and immediately after TIPS placement provides a baseline for evaluation of shunt function and procedure-related complications. Routine follow-up studies at regular intervals after the procedure provide noninvasive assessment of shunt patency and late complications. This pictorial essay illustrates the anatomic and hemodynamic abnormalities present with portal hypertension before TIPS and discusses the expected duplex and color Doppler findings after TIPS. The sonographic characteristics of immediate and delayed complications, as well as potential diagnostic pitfalls, are discussed.

Development of stenoses in transjugular intrahepatic portosystemic shunts.

PURPOSE: To evaluate the frequency and significance of stenoses or occlusions developing within transjugular intrahepatic portosystemic shunts (TIPS) and identify predictive factors. MATERIALS AND METHODS: Medical records of 52 patients who underwent TIPS placement between September 1991 and October 1993 were reviewed. Various shunt parameters were correlated with the development of shunt abnormalities. Findings at follow-up portography and frequency of variceal bleeding and paracentesis were also noted. RESULTS: Twenty-four patients were followed up for at least 6 months. In eight patients, stenoses developed within 6 months; one shunt occluded. No clear correlations were found between shunt parameters and development of shunt abnormalities. Two of four patients with recurrent variceal bleeding had associated shunt abnormalities. The frequency of stenosis of TIPS was high. CONCLUSION: Early detection and prompt revision of stenotic shunts may decrease the frequency of recurrent variceal bleeding and ascites.

Intraureteral metallic self-expanding endoprosthesis (Wallstent) in the treatment of difficult ureteral strictures.

Intractable and recurrent ureteral stricture presents a continuous challenge to the urologist. We report on 5 patients with severe ureteral stricture who were successfully treated with self-expanding metallic stents. Ureteral stricture occurred at ureteroileal anastomotic sites after neoplasm resection in 2 cases, multiple upper ureteral strictures were related to multiple surgical procedures for correction of bladder exstrophy in 1 and a ureteral kink developed in 1. Treatment with transluminal balloon dilation provided poor results but self-expanding metallic stents were used successfully with no major complications. In the last patient the stent and the overlying ureter were removed due to recurrent reflux; the gross and histological ureteral changes are discussed in detail. The technical approach is described, alternative therapeutic options are considered and pertinent literature is reviewed.

In vitro and in vivo experimental evaluation of a new vena caval filter.

PURPOSE: A new stainless steel (MP35N alloy) vena cava filter without a central stasis point was evaluated in vitro and in vivo. MATERIALS AND METHODS: The clot-trapping efficiency and hemodynamic flow pattern of the filter were assessed in a flow model and were compared with those of currently available commercial filters including the Vena Tech-LGM, Simon nitinol, Greenfield, and Bird's Nest filters. The new filter was placed in the inferior vena cava (IVC) of 31 dogs; 21 of the 31 dogs were followed up with cavography for up to 3 months. At the termination of the study, the filters and IVCs were examined grossly and histologically. An in vivo clot-trapping test was carried out in five dogs. RESULTS: The least turbulence was noted with the new filter and the titanium Greenfield filter. The stainless steel Greenfield and Simon nitinol filters caused major flow disturbances. Migration within 5 cm of initial placement occurred in two animals (9.5%). There were no IVC thromboses, perforations, or filter embolizations. An in vivo clot-trapping study showed an 80% efficiency for small thrombi (3 x 20 mm) and 100% efficiency for large thrombi (6 x 20 mm) with the new filter. The Simon and the new filter had the best clot-trapping capabilities. The Vena Tech-LGM and Bird's Nest filters were slightly inferior and the Greenfield filter demonstrated by far the lowest trapping capacity. CONCLUSION: The new vena cava filter is easily introduced percutaneously through a 12-F sheath and appears to be very promising due to its high filtering capability, low turbulence, nonmagnetic properties, good mechanical stability, and hypothrombogenicity. Clinical trials are warranted.