Nitinol Guidewire Research Articles

Computational modelling of the mechanical performance of nitinol guidewires in an idealised tortuous path for medical device applications

Guidewires are critically important components in medical implant and device delivery systems and their desired clinical performance or “steerability” requires a good torque response, i.e., the rotation of the (distal) guidewire tip should follow exactly the (proximal) applied input rotation. However, guidewires can suffer from phenomena known as lag (tip rotation is significantly less than the input rotation) and whip (the lag is suddenly recovered). Nitinol is a common guidewire material that can give superior performance but has been known to exhibit lag and whip depending on the specific material formulation and processing route. In this study, the torsional response of Nitinol guidewires is investigated using computational modelling (the finite element method) and analytical approaches, with a view to gaining a fundamental understanding of the mechanisms behind the lag and whip phenomena and how these relate to the specific material properties of a range of Nitinol variants and the geometrical configuration of the wire during torsion. An idealised vascular geometry is considered; this consists of a curved section and a straight section of varying length where the curved section is representative of geometries that are encountered in tortuous path navigation in the vasculature.The results capture the experimentally observed phenomena and reveal the relationship between material properties and guidewire performance. The stress state in the wire, which is dictated by the stress plateaus in the Nitinol material response, leads to the generation of a net moment within the wire which requires net work to be done during rotation of the wire. Analysis of idealised hypothetical materials show that the transformation strain is also an important parameter. The analysis reduced the performance of the guidewire material to a single metric that is given in terms of the energy dissipated during transformation, i.e., the area of the hysteresis loop. The results show that the combination of torsion and the bending of the wire in the curved path are critically important in the generation of lag and whip, and that both are accentuated by increasing the length of the straight section once the phenomena are active.

V02-10 LIMITED RESOURCES IMPROVISED BASKETS FOR PCNL

You have accessJournal of UrologyCME1 Apr 2023V02-10 LIMITED RESOURCES IMPROVISED BASKETS FOR PCNL Mohammed Lezrek, Mohammed Lezrek, Hicham Tazi, Oussama El Yazami, Souhail Yacoubi, Abdeladim Mikou, Jihad El Anzaoui, and Hamid Mawfiq Mohammed LezrekMohammed Lezrek More articles by this author , Mohammed LezrekMohammed Lezrek More articles by this author , Hicham TaziHicham Tazi More articles by this author , Oussama El YazamiOussama El Yazami More articles by this author , Souhail YacoubiSouhail Yacoubi More articles by this author , Abdeladim MikouAbdeladim Mikou More articles by this author , Jihad El AnzaouiJihad El Anzaoui More articles by this author , and Hamid MawfiqHamid Mawfiq More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003232.10AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: We present a video of how a difficult situation was resolved by on the spot improvisation of a basket made form a standard Nitinol hydrophilic guidewire, to extract a lateral stone, during percutaneous renal surgery. Are there other alternatives materials to improvise a basket? Is it possible to improvise a basket from 2/0 nylon suture? we present ideas of how to do it. Then it is tried in our endoscopic glove model. METHODS: Improvisation of a Nitinol basket: The floppy tip of a standard hydrophilic guidewire is looped twice, forming a 3 cm diameter loop. The distal ends of the loops are placed crosswise. They are fixed in this position with knots. The guidewire tail is back-loaded into the operating channel of the nephroscope until the proximal knot is introduced into the operating channel. The whole complex nephroscope-basket is moved as one in order to maneuver and catch the stone. After introduction through the Amplatz sheath, and into the calyx, the basket is moved around until the stone is caught and attracted through the Amplatz sheath. Improvisation of the nylon basket: The tip of the 2/0 nylon suture is looped twice, forming a 3 cm diameter loops. The distal ends of the loops are placed crosswise, and fixed with knots. The other end of the nylon suture is passed through the inner catheter of the Coaxial double-J stent pusher. Then, it is fixed to the distal end of the pusher with ligations. Thus, the basket and the inner catheter are forming a unit. The basket is closed or opened by attracting or pushing the inner catheter through the outer one. Endoscopic Glove model: a surgical glove is filled with water and a 24 Amplatz sheath is inserted into its opening and fixed with ligations. Stones are inserted into the glove. The basket is tried through the nephroscope. RESULTS: it is possible to improvise a basket, from a Nitinol guidewire, or from a 2/0 nylon suture and a coaxial double-J stent pusher, to use through the nephroscope. It was easy and quick to make. These baskets have been tried successfully in PCNL. The guidewire basket was successfully used in 2 patients, when the nitinol basket was not available. The nylon basket was effective to mobilize and extract the stones, in the glove model. It was also successfully tried in a PCNL case. CONCLUSIONS: to improvise an on the spot handmade basket, form a guidewire or a Nylon suture is possible and easy to prepare. This idea to improvise an on the spot handmade basket had allowed to solve an intraoperative problem or complication. To overcome different situations during percutaneous renal surgery a spirit of innovation can be helpful. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e171 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Mohammed Lezrek More articles by this author Mohammed Lezrek More articles by this author Hicham Tazi More articles by this author Oussama El Yazami More articles by this author Souhail Yacoubi More articles by this author Abdeladim Mikou More articles by this author Jihad El Anzaoui More articles by this author Hamid Mawfiq More articles by this author Expand All Advertisement PDF downloadLoading ...

A technical review of bail-out procedures to place Najuta stent-graft into the ascending aorta

BackgroundThe Najuta stent-graft (Kawasumi Laboratories Inc., Tokyo, Japan) is usually easily advanced to the correct deployment position in the ascending aorta thanks to the pre-curved delivery J-sheath with all fenestrations automatically oriented towards the supra-aortic vessels. Aortic arch anatomy and delivery system stiffness could however represent limitations for proper endograft advancement, especially when the aortic arch bends sharply. The aim of this technical note is to report a series of bail-out procedures that could be useful to overcome the difficulties encountered during the Najuta stent-graft advancement up to the ascending aorta.Main bodyThe insertion, positioning and deployment of a Najuta stent-graft requires a through-and-through guidewire technique using a .035″ 400 cm hydrophilic nitinol guidewire (Radifocus™ Guidewire M Non-Vascular, Terumo Corporation, Tokyo, Japan) with right brachial and both femoral accesses. When standard maneuver to put the endograft tip into the aortic arch, some bail-out procedures can be applied to obtain proper positioning. Five techniques are described into the text: positioning of a coaxial extra-stiff guidewire; positioning of a long introducer sheath down to the aortic root from the right brachial access; inflation of a balloon inside the ostia of the supra-aortic vessels; inflation of a balloon inside the aortic arch (coaxial to the device); and transapical access technique. This is a troubleshooting guide for allowing physicians to overcome various difficulties with the Najuta endograft as well as for other similar devices.Short conclusionTechnical issues in advancing the delivery system of Najuta stent-graft could occur. Therefore, the rescue procedures described in this technical note could be useful to guarantee the correct positioning and deployment of the stent-graft.

MP40-19 HOW TO IDENTIFY PATIENTS SUITABLE FOR CONSERVATIVE MANAGEMENT OF UPPER TRACT UROTHELIAL CARCINOMA (UTUC) ACCORDING TO TUMOR SIZE: IMPLICATIONS FOR CLINICAL GUIDELINES

You have accessJournal of UrologyCME1 May 2022MP40-19 HOW TO IDENTIFY PATIENTS SUITABLE FOR CONSERVATIVE MANAGEMENT OF UPPER TRACT UROTHELIAL CARCINOMA (UTUC) ACCORDING TO TUMOR SIZE: IMPLICATIONS FOR CLINICAL GUIDELINES Eugenio Ventimiglia, Christian Corsini, Margherita Fantin, Mario de Angelis, Pietro Dioni, Marco Moschini, Daniele Raggi, Maurilio Ponzoni, Umberto Capitanio, Andrea Necchi, Roberta Lucianò, Olivier Traxer, Alberto Briganti, Francesco Montorsi, Luca Villa, and Andrea Salonia Eugenio VentimigliaEugenio Ventimiglia More articles by this author , Christian CorsiniChristian Corsini More articles by this author , Margherita FantinMargherita Fantin More articles by this author , Mario de AngelisMario de Angelis More articles by this author , Pietro DioniPietro Dioni More articles by this author , Marco MoschiniMarco Moschini More articles by this author , Daniele RaggiDaniele Raggi More articles by this author , Maurilio PonzoniMaurilio Ponzoni More articles by this author , Umberto CapitanioUmberto Capitanio More articles by this author , Andrea NecchiAndrea Necchi More articles by this author , Roberta LucianòRoberta Lucianò More articles by this author , Olivier TraxerOlivier Traxer More articles by this author , Alberto BrigantiAlberto Briganti More articles by this author , Francesco MontorsiFrancesco Montorsi More articles by this author , Luca VillaLuca Villa More articles by this author , and Andrea SaloniaAndrea Salonia More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002600.19AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Tumor size <2 cm is the upper dimensional limit for conservative management of upper tract urothelial carcinoma (UTUC). Within this indication, we aimed to analyze the risk of adverse oncological outcomes of this approach according to specific tumor size. METHODS: Data from 151 consecutive ureteroscopies (n=39 patients) performed for UTUC at a single academic center between 2015 and 2021 were included in this analysis. Two experienced endo-urologists performed all the procedures. Ureteroscopies were performed using a digital flexible ureterorenoscope (Flex XC, Karl-Storz). Ureteroscopic biopsy forceps (3 Fr Piranha, Boston Scientific) were used in every case. Biopsy specimens were assessed by a dedicated uro-pathologist according to 2016 WHO grading classification and classified into low- vs high-grade. Tumor Ho:YAG laser ablation was performed in any case whenever feasible (VersaPulse PowerSuite 100W, Lumenis) using 1 J and 10 Hz. Tumor size was evaluated at pre-operative contrast-enhanced CT-scan; for non-CT visible lesions, size was endoscopically estimated by comparing with a 0.038” nitinol guidewire. We analysed the association between tumor size and histopathological grade according to different size cut-offs (≥1 and <1.5, ≥1.5, and ≥2 cm). Moreover, we explored the graphical relationship between tumor size and the multivariable adjusted probability of having high-grade tumor at biopsy (LOWESS curve). RESULTS: Mean [IQR] tumor size was 1.5 [0.8-2.0] cm. High grade disease was found in 34 cases (23%). At multivariable logistic regression analysis tumor size ≥1.5 cm (OR 2.46 [1.06-5.88], p=0.04) and ≥2.0 cm (OR 2.90 [1.24-6.93]) were associated to increased risk of having high-grade disease, whereas tumor size between 1 and 1.5 cm was not (p=0.80). We then graphically modelled the multivariable adjusted risk of high-grade disease according to different tumor size cutoffs. The risk of high-grade disease (∼20%) remained stable for tumors <1.5 cm, then linearly increased up to 30% for tumors >2 cm. CONCLUSIONS: The probability of diagnosing high-grade UTUC during fURS marginally increases for tumor size ≥ 1.5 cm as compared to smaller lesions. These patients need to be accurately counselled regarding the risk of not being enrollable in conservative management protocols. Source of Funding: none © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e682 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Eugenio Ventimiglia More articles by this author Christian Corsini More articles by this author Margherita Fantin More articles by this author Mario de Angelis More articles by this author Pietro Dioni More articles by this author Marco Moschini More articles by this author Daniele Raggi More articles by this author Maurilio Ponzoni More articles by this author Umberto Capitanio More articles by this author Andrea Necchi More articles by this author Roberta Lucianò More articles by this author Olivier Traxer More articles by this author Alberto Briganti More articles by this author Francesco Montorsi More articles by this author Luca Villa More articles by this author Andrea Salonia More articles by this author Expand All Advertisement PDF DownloadLoading ...

Artificial ascites using the guidewire technique during microwave ablation in the liver dome: technique and analysis of fluid repartition.

To describe the guidewire technique to perform hydrodistension and create artificial ascites during liver microwave ablation (MWA) of tumors located in the hepatic dome and evaluate the effectiveness of repartition of peritoneal fluid along segments VII and VIII with this technique. A retrospective review of all 18 consecutive patients who benefited from MWA combined with hydrodistension causing artificial ascites performed with the guidewire technique was conducted. The technique involves inserting a 20G spinal needle in the liver parenchyma and catheterizing the peritoneum with a 0.018 nitinol guidewire while retrieving the needle from the liver. Technical success was defined by the successful insertion of a sheath over the wire in the peritoneal cavity and identification of peritoneal fluid on CT images, with repartition of ascites around segments VII and VIII. Target tumors were located in segments VII and VIII and had a mean size of 27.7mm with a mean distance from the diaphragm of 1.7mm. Technical success of artificial ascites was 14/18 (78%). In the four cases where artificial ascites failed, patients had undergone previous liver surgery. In the 14 cases for which artificial ascites were successful, complete separation of the diaphragm from the ablation zone was noted in 9/14 cases and partial separation in 5/14 cases. Hydrodistension with the guidewire technique is effective and safe to accomplish artificial ascites. The extent of repartition of peritoneal fluid is variable, especially in the peritoneal recess in contact with the bare area where diffusion of fluid was variable.

Preparation and evaluation of a UV-curing hydrophilic semi-IPN coating for medical guidewires

Guidewires have crucial roles in intravascular, critical care, and urological applications. In recent years, the demand for guidewires with lower friction surfaces has arisen for medical applications. Among various surface lubrication strategies for guidewires, the most promising is the use of a hydrophilic coating. However, obtaining a hydrophilic coating on guidewires with strong adhesion remains difficult owing to the surface energy difference between the substrate and hydrophilic coating. Herein, we present a UV-curing semi-interpenetrating polymer network coating for medical thermoplastic polyurethane (TPU)-sheathed nitinol guidewires. A polyurethane acrylate (PUA) was synthesized and cured as a transition layer on the TPU substrate to provide strong adhesion. Then, polyvinyl pyrrolidone (PVP) and polyethylene glycol diacrylate (PEGDA) permeated into the PUA layer and cured to form the composite coating. The PUA–PEGDA–PVP coating exhibited excellent lubricity and satisfactory adhesion force. The surface coefficient of friction decreased to approximately 0.02 after modification with the coating, and the coating was stable during long-term soaking in water and repeated friction. In vitro toxicity tests revealed that the coating had good biocompatibility. Thus, our PUA–PEGDA–PVP coating has the potential for application as super-lubricity guidewires and other medical devices.

Susceptibility artifacts from metallic markers and cardiac catheterization devices on a high-performance 0.55 T MRI system

IntroductionVisualization of passive devices during MRI-guided catheterizations often relies on a susceptibility artifact from the device itself or added susceptibility markers that impart a unique imaging signature. High-performance low field MRI systems offer reduced RF-induced heating of metallic devices during MRI-guided invasive procedures, but susceptibility artifacts are expected to diminish with field strength, reducing device visualization. In this study, field strength and orientation dependence of artifacts from susceptibility markers and metallic guidewires were evaluated using a prototype high-performance 0.55 T MRI system. Materials and methodsArtifact volume from nitinol and stainless steel passive susceptibility markers was quantified using histogram analysis of pixel intensities from three-dimensional gradient echo images at 0.55 T, 1.5 T and 3 T. In addition, visibility of commercially available clinical catheterization devices was compared between 0.55 T and 1.5 T using real-time bSSFP in phantoms and in vivo. ResultsA low-tensile strength stainless-steel marker produced field strength- and orientation-dependent artifact size (1.7 cm3, 1.95 cm3, 2.21 cm3 at 0.55 T, 1.5 T, 3 T, respectively). Whereas, a high-tensile strength steel marker, of the same alloy, produced field strength- and orientation-independent artifact size (3.35 cm3, 3.41 cm3, 3.42 cm3 at 0.55 T, 1.5 T, 3 T, respectively). Visibility of commercially available nitinol guidewires was reduced at 0.55 T, but imaging signature could be maintained using high-susceptibility stainless steel markers. Discussion and conclusionHigh-susceptibility stainless-steel markers generate field-independent artifacts between 0.55 T, 1.5 T and 3 T, indicating magnetic saturation at fields <0.55 T. Thus, artifact size can be tailored such that interventional devices produce identical imaging signatures across field strengths.

Transseptal puncture performed with the new needle-free 'SafeSept' guidewire: a multicentre experience.

Increasing numbers of transseptal punctures (TSP) are performed for different cardiac interventions, especially for left atrial (LA) ablation of atrial fibrillation (AF). Significant TSP-related complications may occur even by experienced operators. Any strategies to mitigate these should be adopted. Previous reports have confirmed the safety and efficacy of the first generation nitinol guidewire for TSP. The objective was to assess the safety and efficacy of a new nitinol 'needle free' SafeSept guidewire (NFSG) for TSP. The distal J-shaped tip (0.014in.) of the NFSG is unchanged in design; however, the shaft is thicker (0.0315in.) and stiffer. This is a multicentre study evaluating TSP without a transseptal needle, using the NFSG via a standard transseptal sheath-dilator, in patients with an indication for TSP. A total of 145 consecutive unselected patients were studied. The mean patient age was 59 ± 15. Thirty-one (21.4%) were female and 43 (29.7%) had a previous procedure requiring TSP. The mean transverse LA diameter was 4.0 ± 0.8cm. AF or LA tachycardia comprised the major indication for TSP (n = 115). Transesophageal echocardiography for direct guidance of TSP was utilised in cases performed under general anesthesia (n = 66, 45.5%). LA access by TSP using the NFSG was achieved successfully in 100% of cases after 1.6 ± 2.3 passes. There were no TSP or other major procedural complications. Use of the NFSG appears to be a safe and effective method in performing TSP. The major improvement in the design of the NFSG is that TSP can be performed without a transseptal needle and exchange for a standard guidewire is not required upon establishing LA access.

Pulmonary nodule localization guided by computed tomography using a nitinol guidewire before video-assisted thoracoscopic surgery.

Pulmonary nodule localization guided by computed tomography using a nitinol guidewire before video-assisted thoracoscopic surgery.

A new urethral catheterisation device (UCD) to manage difficult urethral catheterisation

The cost of urethral catheterisation injury (UCI) is significant, but the true incidence of patient care error is difficult to establish in the absence of specific hospital codes recording difficult urethral catheterisation (DUC) and UCI. For many years urologists are familiar passing a non-traumatic hydrophilic guidewire blindly into the bladder to aid urethral catheter insertion in difficult circumstances. However, so far, no purpose-built regulated medical device was available on the market and clinicians had to improvise. Urethrotech filled that gap and developed the Urethral Catheterisation Device (UCD®), which integrates a standard hydrophilic Nitinol guidewire into a 3-way 16F Silicone urethral catheter design to enable safe second-line urethral catheterisation when first-line catheterisation with a standard urethral catheter is unsuccessful. The safety and efficacy of UCD® catheterisation were evaluated in consecutive cohorts of men undergoing cardiac surgery and compared to the incidence of DUC and UCI with standard Foley catheterisation. A simple new Male Catheterisation Algorithm is proposed that can deliver a safe male urethral catheterisation treatment protocol for all clinical settings of healthcare services, which is easy to implement and integrate into standard catheterisation training programs to manage DUC and avoid UCI, empowering a frontline workforce to deliver better patient care.

MP68-03 COMPARISON OF EIGHT DIGITAL (REUSABLE AND DISPOSABLE) FLEXIBLE URETEROSCOPES DEFLECTION PROPERTIES: IN-VITRO STUDY IN 10 DIFFERENT SCOPE SETTINGS

You have accessJournal of UrologyStone Disease: Surgical Therapy IV1 Apr 2018MP68-03 COMPARISON OF EIGHT DIGITAL (REUSABLE AND DISPOSABLE) FLEXIBLE URETEROSCOPES DEFLECTION PROPERTIES: IN-VITRO STUDY IN 10 DIFFERENT SCOPE SETTINGS Laurian Dragos, Sandra M. Martis, Bhaskar K. Somani, Maria Rodriguez-Monsalve Herrero, Etienne X. Keller, Vincent M.J. De Coninck, Catalin Iacoboaie, Steeve Doizi, Ewa Bres-Niewada, Livius C. Daminescu, Razvan T. Bardan, Emre T. Sener, Salvatore Buttice, Silvia Proietti, and Olivier Traxer Laurian DragosLaurian Dragos More articles by this author , Sandra M. MartisSandra M. Martis More articles by this author , Bhaskar K. SomaniBhaskar K. Somani More articles by this author , Maria Rodriguez-Monsalve HerreroMaria Rodriguez-Monsalve Herrero More articles by this author , Etienne X. KellerEtienne X. Keller More articles by this author , Vincent M.J. De ConinckVincent M.J. De Coninck More articles by this author , Catalin IacoboaieCatalin Iacoboaie More articles by this author , Steeve DoiziSteeve Doizi More articles by this author , Ewa Bres-NiewadaEwa Bres-Niewada More articles by this author , Livius C. DaminescuLivius C. Daminescu More articles by this author , Razvan T. BardanRazvan T. Bardan More articles by this author , Emre T. SenerEmre T. Sener More articles by this author , Salvatore ButticeSalvatore Buttice More articles by this author , Silvia ProiettiSilvia Proietti More articles by this author , and Olivier TraxerOlivier Traxer More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.2207AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Due to the high cost and fragility of the reusable digital flexible ureterorenoscopes (fURSs), several single use alternatives have emerged. The goal of our in-vitro study was to determine the deflection properties of these scopes with the working channel empty and occupied by different accessories. METHODS Four single-use (LithoVue, Boston Scientific, USA; Pusen, China; Neoflex, Neoscope, USA; YouCare Tech, China) and four reusable (URF-V2, Olympus, Japan; Flex Xc, Karl Storz, Germany; Cobra vision and Boa vision, Richard Wolf, Germany) fURSs were compared in a total of 10 different settings. The maximal up and down deflection was measured with the working channel empty and then occupied with various tools (200μm, 273μm, 365μm laser fibres; 1.5Fr, 1.9Fr and 2.2Fr baskets; 0.038″ PTFE and 0.035″ nitinol guidewires; Piranha biopsy forceps). Each measurement was performed three times. Deflection angles were calculated using a protractor. A scoring system by adding the total deflection degrees for each scope and each setting was used to compare the fURSs. RESULTS When the channel was occupied, the most cumulative deflection was achieved by NeoFlex (5043°) and the least by YouCare Tech (3912°) (Fig.1,2). The least affect on deflection was caused by the 200μm laser fibre (2198°) for the disposable fURSs, and by 1.5 Fr basket (1971°) for the reusable fURSS. In both reusable and disposable fURSs, the PTFE guidewire caused the maximum impact on scope deflection (Fig.3). Overall, single-use fURSs had better deflection in most settings, except when 365μm laser fibre or guidewires (either PTFE or nitinol) were occupying the working channel (Fig.3). CONCLUSIONS The single-use fURSs seem to have better in-vitro deflection than the reusable scopes. But when thicker, less flexible tools occupied the working channel, the reusable fURSs deflected better. Further evaluation of our findings in clinic settings will help to confirm our findings. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e917 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Laurian Dragos More articles by this author Sandra M. Martis More articles by this author Bhaskar K. Somani More articles by this author Maria Rodriguez-Monsalve Herrero More articles by this author Etienne X. Keller More articles by this author Vincent M.J. De Coninck More articles by this author Catalin Iacoboaie More articles by this author Steeve Doizi More articles by this author Ewa Bres-Niewada More articles by this author Livius C. Daminescu More articles by this author Razvan T. Bardan More articles by this author Emre T. Sener More articles by this author Salvatore Buttice More articles by this author Silvia Proietti More articles by this author Olivier Traxer More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Right heart catheterization using metallic guidewires and low SAR cardiovascular magnetic resonance fluoroscopy at 1.5 Tesla: first in human experience

BackgroundCardiovascular magnetic resonance (CMR) fluoroscopy allows for simultaneous measurement of cardiac function, flow and chamber pressure during diagnostic heart catheterization. To date, commercial metallic guidewires were considered contraindicated during CMR fluoroscopy due to concerns over radiofrequency (RF)-induced heating. The inability to use metallic guidewires hampers catheter navigation in patients with challenging anatomy. Here we use low specific absorption rate (SAR) imaging from gradient echo spiral acquisitions and a commercial nitinol guidewire for CMR fluoroscopy right heart catheterization in patients.MethodsThe low-SAR imaging protocol used a reduced flip angle gradient echo acquisition (10° vs 45°) and a longer repetition time (TR) spiral readout (10 ms vs 2.98 ms). Temperature was measured in vitro in the ASTM 2182 gel phantom and post-mortem animal experiments to ensure freedom from heating with the selected guidewire (150 cm × 0.035″ angled-tip nitinol Terumo Glidewire). Seven patients underwent CMR fluoroscopy catheterization. Time to enter each chamber (superior vena cava, main pulmonary artery, and each branch pulmonary artery) was recorded and device visibility and confidence in catheter and guidewire position were scored on a Likert-type scale.ResultsNegligible heating (< 0.07°C) was observed under all in vitro conditions using this guidewire and imaging approach. In patients, chamber entry was successful in 100% of attempts with a guidewire compared to 94% without a guidewire, with failures to reach the branch pulmonary arteries. Time-to-enter each chamber was similar (p=NS) for the two approaches. The guidewire imparted useful catheter shaft conspicuity and enabled interactive modification of catheter shaft stiffness, however, the guidewire tip visibility was poor.ConclusionsUnder specific conditions, trained operators can apply low-SAR imaging and using a specific fully-insulated metallic nitinol guidewire (150 cm × 0.035” Terumo Glidewire) to augment clinical CMR fluoroscopy right heart catheterization.Trial registrationClinicaltrials.gov NCT03152773, registered May 15, 2017.

TAVI WITH A SINGLE FEMORAL APPROACH: PRELIMINARY SINGLE-CENTRE EXPERIENCE

To describe our initial experience with the transradial approach as secondary access site in TAVI. As of April 2016, a strategy of systematic transradial approach as secondary access site for TAVI was adopted in our centre. A 5 F 125 cm multipurpose catheter was navigated from the left or right radial artery into the common iliac artery to assist in main access puncture. The catheter was then exchanged for a pigtail, which was positioned on the aortic valve to guide TAVI. The multipurpose catheter was used again at the end of the procedure to assess ilio-femoral integrity. In case of an iliac or femoral access complication, the radial sheath was exchanged for a 120 cm long 5F sheath. A 0.018’/400 cm nitinol guidewire was introduced beyond the lesion and a compatible long shaft (180 cm) 5F balloon or nitinol self-expandable stent was introduced and used accordingly. In case of a perforation, a balloon was inflated proximal to the lesion in order to stop the bleeding and contralateral femoral access was obtained in order to deploy a covered stent via a 6F sheath. From April 2016, 184 patients underwent TAVI using this strategy. Patients had a mean age of 83±5.9 years, 52.2% were male, mean Logistic Euroscore and STS score were 16.5±11.6% and 5.3±4.7%, respectively. 97 (52.7%) patients received a balloon-expandable valve and 87 (47.3%) received a self-expandable valve. Transradial access as secondary approach was not used in 30 of 184 patients (16.3%) for the following reasons: absence of radial pulse or unsuitable artery size (n=14; 7.6%), prohibitive patient height (n=1; 0.8%), physician preference n=15; 8.1%). TAVI was successful in all cases. No complications occurred due to transradial access. Transfemoral vascular access site complications occurred in 8 cases (4.3 %): three occlusion, two flow-limiting stenoses and three perforations of the common femoral artery. Five complications were successfully managed using self-expanding stents from the transradial access. The 3 cases of perforation (1.6%) were successfully treated with a covered stent delivered via femoral crossover. There were no additional major vascular complications at 30 days. Use of the radial approach for secondary access in TAVI is safe and feasible. Most primary access site complications were manageable from the radial access site. A low rate of crossover to the contralateral femoral approach (1.6 %) was necessary. Further large-scale studies are necessary to confirm the benefits of this approach.

Holmium:Yttrium Aluminum Garnet Laser and Guidewires: Is There a Durability Difference Among Guidewires Against Laser Energy? An In Vitro Experimental Study.

To evaluate the durability differences between five different type of guidewires against laser energy in an in vitro experimental ureteral model. The study was performed at the Department of Urology, Medicine Faculty of Ahi Evran University. An in vitro experimental ureteral model was created for the work; a silicon ureteral model in a saline-filled container. Experiments were performed on five different type of guidewires; ZIPwire, Sensor polytetrafluoroethylene (PTFE) Nitinol guidewire, Roadrunner® PC wire guide, Amplatz Super Stiff, and Zebra Urologic Guidewire. These guidewires were grouped from one to five, respectively. Laser fibers were contacted to the guidewire, and laser energy was fired to the premarked tip and body parts in different adjustments. The breakage of the guidewires was detected only on the flexible tip parts in group 1a, group 1b, group 2a, group 2b, group 4a, and group 4b. The body parts of the guidewires were resistant to laser energy in all groups and did not break. The breakage of the guidewires occurred after 3 J × 10 Hz (30 W) experiment. Group 1a and 1b were different from group 2a, 2b, 4a, and 4b according to Kruskal-Wallis H test. The body parts of the guidewires in all study groups were resistant to laser energy. The tip parts of Zipwire™, Sensor™ PTFE Nitinol, and Amplatz Super Stiff™ guidewire should be kept away from the surgical field when the high power settings of the laser are being used. The body parts of the guidewires can be utilized in the surgical field safely.

Glass-Fiber-based MR-safe Guidewire for MR Imaging-guided Endovascular Interventions: In Vitro and Preclinical in Vivo Feasibility Study.

Purpose To evaluate glass-fiber-based guidewires that are safe for magnetic resonance (MR) imaging-guided endovascular interventions by using a phantom and an in vivo swine model. Materials and Methods MR imaging-safe guidewires were made from micropultruded glass and/or aramid fibers and epoxy resin with diameters of 0.89 mm (0.035 inch) for standard and stiff guidewires and 0.36 mm (0.014 inch) for micro guidewires. MR imaging visibility and mechanical properties were assessed in a pulsatile flow model. After approval was obtained from the institutional animal care and use committee, MR imaging guidewires were evaluated for standard endovascular procedures in nine pigs. Real-time steady-state free-precession sequences were used for MR imaging-guided catheterization, balloon dilation, and stent implantation into aorto-iliac/visceral arteries and the vena cava (temporal resolution, five images per second; and spatial resolution, 150-mm field of view, and 128 × 128 matrix) with a 1.5-T clinical imager. Visualization with the guidewires was rated on a four-point scale, handling was rated on a three-point scale, and catheterization times for different vessel regions were determined by two interventional radiologists. Afterward, handling ratings and catheterization times were obtained for standard nitinol guidewires during x-ray-based fluoroscopy. Cannulation times, signal intensity in each vessel region, and visualization and handling ratings were measured for the MR imaging guidewires. Bland-Altman analysis was performed for inter- and intraobserver variability of cannulation time. Spearman rank correlation was used to compare handling of MR imaging guidewires and standard nitinol guidewires. Results MR imaging guidewires were characterized by good to excellent visibility, with a continuous artifact of 2 mm in diameter and 4 × 8-mm ball-shaped tip marker. Stiffness, flexibility, and guidance reflected comparable times for all in vitro and in vivo procedures with both the MR imaging and standard nitinol guidewires. Standard and micro MR imaging guidewires were most suitable for the iliac crossover maneuver. Phantom visceral artery cannulation was easier with standard and micro MR imaging guidewires. The stiff MR imaging guidewire provided the best support for cannulation of the swine aorta and vena cava. All interventional procedures were performed successfully without complications. Conclusion Preliminary results showed that the use of glass-fiber-based guidewires for evaluation of MR imaging-guided endovascular interventions is technically feasible and safe in a swine model, and potentially, in humans. © RSNA, 2017 Online supplemental material is available for this article.

3D-microdevice for the in vivo capture of cancer-associated circulating cells.

e579 Background: Circulating tumor cells (CTCs) are cancer cells that have detached from a tumor and have entered into the blood circulation at a very low concentration (D. Shook, Mech. Dev., Nov 2003). CTCs have a strong prognostic value, as their number has been correlated to overall survival in different metastatic cancers (J. S. de Bono, Clin. Cancer Res., Oct 2008). Considering the rareness of CTCs in blood, capturing them in vitro is very challenging. CTCs being mainly larger and less deformable than most of blood cells, ISET was the first system exploiting their physical traits using a filtration membrane to enrich 10mL blood samples (G. Vona, Am. J. Pathol., Jan 2000). However, placing the trapping system directly within the bloodstream would increase the amount of blood screened and ensure no sampling bias. To our knowledge, the only system developed for in vivo capture of CTCs relies on an immunologic detection targeting CTCs with specific epithelial-cell adhesion molecules (N. Saucedo-Zeni, Int. J. Oncol., Oct 2012). The major drawback of this technique is the selection bias induced, given the strong heterogeneity of antigen expression profiles in CTC population as confirmed by several studies. Methods: Our device combines the advantages of in vivo capture and physical trapping of CTCs. A polymeric 3D net-like microdevice is fabricated using a Direct Laser Writing technique (Nanoscribe) and integrated onto a Nitinol guidewire to be introduced into the basilic vein through a routine 20G catheter. To optimize the design, we conducted simulation studies and in vitro assays using a fluidic platform reproducing in vivo conditions. Results: We succeeded in capturing PC3 human prostate cancer cells from 20 mL healthy donor blood spiked with 1,000 PC3 cells in 2 minutes, demonstrating the capability to capture CTCs in conditions close to those found in vivo, in terms of pressure and flow rate and without any additional treatment or dilution of the blood. Conclusions: This device could facilitate treatment personalization and follow-up. Its versatility should render it transposable to the capture of single or clustered CTCs, derived from all types of cancer and, by extension, to other circulating cellular and molecular biomarkers.

Spiral imaging with off-resonance reconstruction for MRI-guided cardiovascular catheterizations using commercial off-the-shelf nitinol guidewires

Spiral imaging with off-resonance reconstruction for MRI-guided cardiovascular catheterizations using commercial off-the-shelf nitinol guidewires

Prospective Study of Novel Peripheral Intravenous Catheter System With Nitinol Guidewire Compared to Published Literature for Conventional Intravenous Catheters

The use of intravenous (IV) cannulas is an integral part of patient care in hospitals. These intravenous cannulas are a potential route for microorganisms to enter the blood stream resulting in a variety of local or systemic infections. Studies showing the actual prevalence of colonization of peripheral IV cannulas and its role in BSI are lacking. Hence, this study was aimed to estimate the prevalence of colonization of the injection ports of peripheral IV cannulas.This cross sectional study was conducted on patients admitted in ICU and wards in an 800 bedded tertiary care hospital. Swabs were taken from lumens of peripheral IV cannulas and cultured. Patient demographic data and practices followed for maintenance of IV line were noted.A total of 196 injection port samples were taken, out of which 11 tested positive for microbial growth (5.61%). Staphylococcus aureus was the predominant organism contributing 64% of the microbial growth. A significant association was seen between presence of local signs, old age and positive cultures. Flushing IV cannula every 6 h was associated with negative cultures.Peripheral IV cannulation has significant potential for microbial contamination and is largely ignored. Most of the risk factors associated with growth of microorganisms in the injection ports of peripheral intravenous cannulas (which has a potential to cause catheter-related blood stream infections) can be prevented by improving protocols for management. To prevent infection from occurring, practitioners should be educated and trained about the care and management of IV.

Externalized Guidewires to Facilitate Fenestrated Endograft Deployment in the Aortic Arch

Purpose: To describe a precannulated fenestrated endograft system utilizing externalized guidewires to facilitate aortic arch endovascular repair and to report its use in 2 patients with challenging anatomy. Technique: For distal arch repair, a fenestration for the left subclavian artery (LSA) is made onsite in a standard thoracic endograft tailored to the patient anatomy; it is precannulated with a nitinol guidewire (NGw), which is passed from the femoral artery and externalized from the left brachial artery prior to endograft delivery system introduction over a parallel stiff guidewire. Steps are then taken to remove guidewire intertwining, prevent NGw wrapping around the delivery system, and orient the LSA fenestration superiorly when the delivery system moves into the arch. Gentle traction on the ends of the NGw during endograft deployment facilitates proper fenestration alignment. A covered stent is deployed in the LSA fenestration. The technique is illustrated in a patient with congenital coarctation of the aorta and descending aortic aneurysm. For total arch repair, endograft fenestrations are made for all 3 arch branches; the left common carotid artery (LCCA) and LSA fenestrations are each cannulated with NGws, which travel together from the femoral artery, pass through a LSA snare loop, and are exteriorized from the LCCA. After endograft deployment, the innominate artery fenestration is separately cannulated using right brachial access. Placement of a parallel externalized hydrophilic guidewire passing through the LCCA fenestration (but not the LSA snare loop) and removal of the LCCA fenestration NGw allows exteriorization of the LSA fenestration NGw from the left brachial artery by pulling the LSA snare. Covered stents are deployed in all 3 fenestrations. The technique is presented in a patient with type B aortic dissection. Conclusion: Use of the precannulated fenestrated endograft system described is feasible and has the potential to make aortic arch endovascular repair simpler, more reliable, and safer.

Smart Guidewires for Smooth Navigation in Neurovascular Intervention

Smart nitinol guidewires have been proposed to improve trackability, facilitating the advancement of catheters through complex vascular anatomies during neurovascular interventions. A smart 0.015 in. diameter nitinol guidewire was actualized through Joule heating of one-way and two-way shape memory alloys (SMA). The device functionalities in terms of bending performance were analyzed: (1) trackability of a 4 Fr catheter as determined in an anatomically correct in vitro environment; (2) time and spatial response of the smart guidewire as a function of material temperature and applied current; and (3) thrombogenic effects as a function of temperature and applied voltage. The results suggest that smart guidewires have substantially improved trackability (i.e., deflection of 15 deg) to overcome the “ledge effect” with the absence of thrombogenicity via a smart guidewire–catheter combined transcatheter based procedure which keeps the catheter surface temperature at 30–33 °C.