On Studying the Interaction Between Different Stent Models and Rabbit Tracheal Tissue: Numerical, Endoscopic and Histological Comparison.

Stenting technique is employed worldwide for treating atherosclerotic vessel and tracheal stenosis. Both diseases can be treated by means of metallic stents which present advantages but are affected by the main problem of restenosis of the stented area. In this study we have built a rabbit trachea numerical model and we have analyzed it before and after insertion and opening of two types of commercial stent: a Zilver(®) Flex™ Stent and a WallStent™. In experimental parallel work, two types of stent were implanted in 30 New Zealand rabbits divided in two groups of 10 animals corresponding to each stent type and a third group made up of 10 animals without stent. The tracheal wall response was assessed by means of computerized tomography by endoscopy, macroscopic findings and histopathological study 90 days after stent deployment. Three idealized trachea models, one model for each group, were created in order to perform the computational study. The animal model was used to validate the numerical findings and to attempt to find qualitative correlations between numerical and experimental results. Experimental findings such as inflammation, granuloma and abnormal tissue growth, assessed from histomorphometric analyses were compared with derived numerical parameters such as wall shear stress (WSS) and maximum principal stress. The direct comparison of these parameters and the biological response supports the hypothesis that WSS and tensile stresses may lead to a greater tracheal epithelium response within the stented region, with the latter seeming to have the dominant role. This study may be helpful for improving stent design and demonstrates the feasibility offered by in-silico investigated tracheal structural and fluid dynamics.

The CIRSE Retrievable IVC Filter Registry: Retrieval Success Rates in Practice.

CIRSE established a registry of retrievable filter use with the primary aim of determining the success of IVC Filter retrieval and associated complications. Secondary endpoints included filter indications, imaging strategies before retrieval, filter dwell times, and anticoagulation status. A web-based electronic registry was hosted between 01/12/2010 and 30/06/2012. Data entry occurred at the date of IVC filter retrieval and included items such as filter type, indication for filter insertion, access route, dwell time, retrieval success, complications, reasons for failed retrieval, and anticoagulation status. 671 filter retrievals were entered (male:female 333:295, mean age 55, median 57). Retrieval data were not entered in 43/671 leaving 628 patients for analysis. The 4 commonest retrievable filters used were the Celect in 182 patients, the OPTEASE in 161, ALN in 120, and Gunther Tulip in 98. Filters were inserted for absolute indications 40%, relative indications in 31%, and prophylactic in 24%, with 5% missing. Mean filter dwell time was 90 days. Filters were successfully retrieved in 576/628 patients (92%). The mean dwell time for successful retrievals was 85 days versus 145 days for unsuccessful retrievals (p = 0.001). Major complications occurred in 2 patients (0.03%). In summary, the CIRSE retrievable filter registry demonstrates a retrieval rate of 92% across a range of filter types, with a low major complication rate, reflecting current practice. There is an increase in trend of retrievable filter use for relative and prophylactic indications.

Evaluation of migration forces of a retrievable filter: experimental setup and finite element study.

The aim of this paper is to provide a computational study of migration forces of a retrievable filter (Günther Tulip inferior vena cava filter). Using an experimental setup and finite element simulation, the migration forces and stress at the end of the anchored hooks in the struts were estimated. After that, the estimation value of migration stress (τ(rup)) was used to analyze the effect of different mechanical factors (strut thickness, vena cava diameter) in the migration of the IVC filter. Our results show that the migration stress is τ(rup)=4.37 N/mm(2). Using this value we obtain that the filter with higher strut diameter (ϕ(strut)=0.45 mm) shows the maximal migration forces in every cava diameter. On the other hand, the value of the migration force decreases when the cava diameter increases. In addition, the finite element simulations also show that there are contact between the struts of the filter and the vein in regions close to the anchors.

Experimental study and constitutive modelling of the passive mechanical properties of the porcine carotid artery and its relation to histological analysis: Implications in animal cardiovascular device trials.

The present study focusses on the determination, comparison and constitutive modelling of the passive mechanical properties of the swine carotid artery over very long stretches in both proximal and distal regions. Special attention is paid to the histological and mechanical variations of these properties depending on the proximity to the heart. The results can have clinical relevance, especially in the research field of intravascular device design. Before the final clinical trials on humans, research in the vascular area is conducted on animal models, swine being the most common due to the similarities between the human and swine cardiovascular systems as well as the fact that the swine size is suitable for testing devices, in this case endovascular carotid systems. The design of devices usually involves numerical techniques, and an important feature is the appropriate modelling of the mechanical properties of the vessel. Fourteen carotid swine arteries were harvested just after sacrifice and cyclic uniaxial tension tests in longitudinal and circumferential directions were performed for distal and proximal samples. The stress-stretch curves obtained were fitted with a hyperelastic anisotropic model. Stress-free configuration states were also analyzed. Finally, human and swine samples were processed in a histological laboratory and images were used to quantify their microconstituents. The statistical analysis revealed significant differences between the mechanical behavior of proximal and distal locations in the circumferential but not in the longitudinal direction. Circumferential direction samples show clear differences both in residual stretches and tensile curves between the two locations, while the features of longitudinal specimens are independent of the axial position. The statistical analysis provides significant evidence of changes depending on the position of the sample, mainly in elastin and SMC quantification.

Percutaneous treatment of intrabdominal abscess: urokinase versus saline serum in 100 cases using two surgical scoring systems in a randomized trial.

The purpose of this study was to assess whether regular instillation of urokinase during abscess drainage leads to an improved outcome compared to saline irrigation alone. One hundred patients referred for image-guided abdominal abscess drainage were randomized between thrice daily urokinase instillation or saline irrigation alone. At the end of the study, patient medical records were reviewed to determine drainage, study group, Altona (PIA II) and Mannheim (MPI) scoring, duration of drainage, procedure-related complications, hospital stay duration, and clinical outcome. The technical success rate of the percutaneous abscess drainage was 100%. The success or failure of abscess remission did not differ significantly between groups (success rate of 91.5% in the urokinase group vs. 88.8% in the saline group; failure rate was of 8.5 vs. 21.2%, respectively); however, days of drainage, main hospital stay, and overall costs were significantly reduced in patients treated with urokinase compared to the control group (P < 0.05). No adverse effects from urokinase were observed. Surgical scores were a useful homogeneity factor, and MPI showed a good correlation with prognosis, while PIA results did not have a significant correlation. For drainage of complex abscesses (loculations, hemorrhage, viscous material), fibrinolytics safely accelerate drainage and recovery, reducing the length of the hospital stay and, therefore, the total cost.

A radiofrequency-assisted device for bloodless rapid transection of the liver: a comparative study in a pig liver model.

BACKGROUND: Efficient and safe liver parenchymal transection is dependent on the ability to address both parenchymal division and hemostasis simultaneously. In this article we describe and compare with a saline-linked instrument a new radiofrequency (RF)-assisted device specifically designed for tissue thermocoagulation and division of the liver used on an in vivo pig liver model. METHODS: In total, 20 partial hepatectomies were performed on pigs through laparotomy. Two groups were studied: group A (n=8) with hepatectomy performed using only the proposed RF-assisted device and group B (n=8) with hepatectomy performed using only a saline-linked device. Main outcome measures were: transection time, blood loss during transection, transection area, transection speed and blood loss per transection area. Secondary measures were: risk of biliary leakage, tissue coagulation depth and the need for hemostatic stitches. Tissue viability was evaluated in selected samples by staining of tissue NADH. RESULTS: In group A both blood loss and blood loss per transection area were lower (p=0.001) than in group B (70+/-74 ml and 2+/-2 ml/cm(2) vs. 527+/-273 ml and 13+/-6 ml/cm(2), for groups A and B, respectively). An increase in mean transection speed when using the proposed device over the saline-linked device group was also demonstrated (3+/-0 and 2+/-1cm(2)/min for group A and B, respectively) (p=0.002). Tissue coagulation depth was greater (p=0.005) in group A than in group B (6+/-2 mm and 3+/-1 mm, for groups A and B, respectively). Neither macroscopic nor microscopic differences were encountered in transection surfaces between both groups. CONCLUSIONS: The proposed RF-assisted device was shown to address parenchymal division and hemostasis simultaneously, with less blood loss and faster transection time than saline-linked technology in this experimental model.

Stent-graft treatment of trauma to the supra-aortic arteries. A review.

Trauma to the carotid, subclavian, vertebral, or innominate arteries may be blunt or penetrating. Some injuries, such as those caused by central venous catheterization, are iatrogenic. Trauma-induced fistulas and pseudoaneurysms of the supra-aortic arteries are relatively rare, but may result in disabling neurologic symptoms or death. Traditional surgical approaches to supra-aortic artery trauma have high morbidity and mortality rates, especially in patients with multiple injuries and patients with a serious concomitant illness. The minimally invasive endovascular approach may offer an alternative that avoids the tissue damage, bleeding, infectious complications, pain and disability, long recovery time, and high financial cost associated with surgery. In the past 15 years, stent-grafts have evolved from bare-metal stents to which the operator attached autologous vein or a prosthetic material to manufactured balloon-expandable or self-expanding endoprosthetic systems. No devices designed specifically for use in the supra-aortic arteries are yet available. Nevertheless, the reported experience with stent-graft treatment of supra-aortic artery trauma is growing rapidly, although it remains limited to case reports and small series with relatively short follow-up times. Results have been very promising: complete lesion exclusion from the circulation and resolution of symptoms has been achieved in almost all cases, and few procedural complications and stent-graft stenoses and thromboses have been reported. The stent-graft approach warrants additional research on its long-term outcomes, as well as continued development of enhancements for the devices used.

[Endovascular treatment of massive hemoptysis by bronchial artery embolization: short-term and long-term follow-up over a 15-year period]. / Tratamiento endovascular mediante embolización arterial bronquial en la hemoptisis masiva. Seguimiento a corto y largo plazo durante 15 años.

OBJECTIVE: To present our experience of using arterial embolization for the endovascular treatment of massive hemoptysis along with the results of follow-up over a 15-year period. PATIENTS AND METHODS: A total of 401 patients with hemoptysis were referred to the minimally invasive surgery unit of the Hospital Universitario Lozano Blesa de Zaragoza between April 1989 and September 2004 for diagnosis and possible endovascular treatment. Of those patients, 314 met criteria for massive hemoptysis and treatment was attempted using embolization in 287 (91.4%). The most common cause of hemoptysis was bronchiectasis (n=99, 31.5%), followed by lesions due to tuberculosis (n=57, 18.1%) and chronic bronchitis (n=47, 14.9%). RESULTS: Angiography of the bronchial arteries provided evidence to account for the hemoptysis in 287 patients (91.4%). The affected arteries were satisfactorily embolized in 281 (97.9%). Endovascular treatment was clinically successful in 256 of those patients (91.1%). Embolization had to be repeated during the hospital stay in 19 patients (6.7%) and was effective in 52.6% of those cases. The 6 patients in whom embolization was not satisfactory underwent thoracotomy. The mean follow-up in 201 patients (71.5%) was 2372.5 days (range, 61-5475 days). Eighty patients (28.4%) were lost to follow-up for various reasons and at different points. Recurrence of hemoptysis occurred on 1 or more occasions in 45 patients (22.3%) but only 21 (10.4%) required repeat embolization. Minor complications that did not require treatment were observed in 88 patients (28.0%). CONCLUSIONS: Embolization of bronchial arteries is a nonsurgical treatment that is safe and effective in patients with massive hemoptysis.

[Nasolacrimal stent: modifications to Ho-Young Song's technique]. / Stent nasolacrimal: variaciones en la técnica de Ho-Young Song.

PURPOSE: To introduce modifications to Song's technique in the treatment of nasolacrimal occlusion by means of a polyuretane stent. MATERIAL AND METHOD: Thirty five polyuretane stents were placed under fluoroscopic guidance in 32 patients diagnosed with total and partial nasolacrimal occlusion. CONCLUSION: Technical success rate was 90%. Sixteen right and nineteen left nasolacrimal systems were probed. The introduction of a guidewire through the lower punctum, the use of a Ritleng guide, a Crawford hook and ocular protectors are modifications of Song's procedure that may help in successfully performing this technique in a fast and easy way.

Jugular venous malformation in an 8-year-old boy: treatment with endovascular sclerotherapy.

UNLABELLED: An 8-year-old male presented with a mass in the left supraclavicular region first noted 3 months earlier and which gradually became more prominent. Ultrasound showed a lobular, well-delineated hypoechoic lesion which increased in size on Valsalva manoeuvre. Doppler waveform analysis suggested a slow flow vascular lesion. Venography showed a saccular, multilobular venous malformation which connected with the external jugular and subclavian veins. With an angiographic catheter, the venous malformation was treated by endovascular sclerotherapy. Four weeks later, ultrasonography showed a resolution of the lesion. CONCLUSION: Endovascular sclerotherapy appears to be an effective and safe treatment for jugular venous malformation.

Use of venous thromboembolism prophylaxis for surgical patients: a multicentre analysis of practice in Spain.

OBJECTIVE: To assess the use of venous thromboembolism prophylaxis in surgical patients. DESIGN: Retrospective multicentre study. SETTING: Eight acute-care teaching hospitals with more than 400 beds, Spain. PATIENTS: Medical records of all consecutive patients undergoing operations in the general surgical and trauma and orthopaedic services during the month of April, 1997, were randomly selected. INTERVENTION: The sample size for each type of operation (general, trauma-orthopaedic) was calculated from the number of operations done at each hospital (with an absolute precision of 5%, and an alpha error of 5%) and the prevalence of the use of venous thromboembolism prophylaxis obtained from a random sample of 50 records (25 from patients in general surgery and 25 from patients in orthopaedic surgery) from each centre. MAIN OUTCOME MEASURES: Appropriate and inappropriate pharmacological prophylaxis defined according to a combination of risk categories for venous thromboembolism, doses of antithrombotic agents given, time of starting prophylaxis, and its duration. RESULTS: A total of 1848 medical records (general surgery, n = 1025; trauma-orthopaedic surgery, n = 823) were included. Physical methods (elastic stockings, intermittent pneumatic compression) were used in only 0.3% of patients. Pharmacological prophylaxis consisted of low molecular weight heparin in 99% of cases. The percentage given heparin-based prophylaxis was 54%. Overall, appropriate prophylaxis was given in 1175 patients (64%). Use of thromboprophylaxis ranged from 27% to 70% among the participating hospitals. Prophylaxis was more likely to be appropriate in orthopaedic patients (577, 70%) than in general surgical patients (598, 58%) in both the high and moderate risk categories. CONCLUSIONS: Given the large variability between the participating hospitals, more specific protocols and recommendations about prophylaxis of thromboembolism in surgical patients are needed.

Nasolacrimal polyurethane stent placement: preliminary results.

PURPOSE: To present our initial results in the treatment of nasolacrimal obstruction by placing a polyurethane stent. METHODS: 74 nasolacrimal stents were implanted under fluoroscopic guidance in obstructed nasolacrimal systems of 64 patients. Dacryocystography and CT were used to verify the position and patency of the stents. Mean follow-up was 15 months. Clinical examinations were done at the first week, first month, third month and sixth month after stent placement. RESULTS: Polyurethane stents were successfully inserted and permeable in 59 patients (92.1%), but could not be inserted in 5 patients (7.8%). Epiphora was solved and permeable in 53 cases (82.8%), it was not permeable but asymptomatic in 2 cases (3.1%), and was not permeable but symptomatic in 4 (6.2%). In 5 cases (7.8%) stents remained permeable although patients complained of epiphora. CONCLUSIONS: Polyurethane stent placement is a non-invasive technique that can replace dacryocystorhinostomy, giving better results and tolerance.

Animal experience in the Günther Tulip retrievable inferior vena cava filter.

PURPOSE: To assess the retrievability of the Günther Tulip temporary inferior vena cava filter from a technical viewpoint, and consider the histopathologic changes that occur at the anchoring site of the filter prongs to the vein endothelium in Landrace pigs. METHODS: Twenty-two Günther Tulip retrievable filters were inserted in 22 experimental Landrace pigs via the jugular vein. Device implantation time was 0, 3, 7, 12, 14, 15, 16, 20, 30, 35 and 56 days. Study subjects were divided into two groups. In one group the filter was retrieved percutaneously via the jugular vein whereas in the other group it was removed surgically. The specimens obtained (vena cava and filter) were histopathologically examined. Prior to filter retrieval, a venacavography was obtained in all cases. Degree of retrieval difficulty was rated as follows: no difficulty (N), slight (S), mild (M), high (H) and unretrievable (U). RESULTS: Of the 22 implanted filters, 11 should have been removed percutaneously but this was impossible in three cases (U). In four cases the device was retrieved with no difficulty (N); in two cases the degree of difficulty was mild (M) and in other two it was high (H) and slight (S) respectively. Retrieval difficulties were observed after 16 days. Starting from day 20, there was evidence of fibrosis with thick intimal proliferation and total filter prong involvement, which accounts for the difficulty in retrieving the device. CONCLUSIONS: It is advisable not to exceed a filter retrieval time of 16 days in view of the fibrotic changes reported. It might be necessary to perform a larger study with more animals and with retrieval times between 14 and 20 days.