A novel bipolar electrocautery-enhanced delivery system with a lumen-apposing metal stent for EUS-guided drainage: A porcine study.

BACKGROUND: An electrocautery-enhanced delivery system with a lumen-apposing metal stent (LAMS) is available for one-step endoscopic ultrasound-guided transmural drainage (EUS-TD). Bipolar electrosurgery has several potential clinical advantages, including reduced collateral thermal damage, enhanced hemostasis, and no requirement for a return electrode plate. In this study, we compared the technical feasibility and safety of a newly developed bipolar electrocautery-enhanced delivery system with a conventional delivery system for EUS-TD using a LAMS in a porcine model. METHOD: Ten days before the study, 12 mini pigs underwent common bile duct ligation for EUS-guided gallbladder drainage. Transenteric puncture was performed, followed by placement of a guidewire. In six pigs, a bipolar electrocautery-enhanced delivery system with LAMS (Hot SPAXUS) was inserted over the guidewire and advanced into the gallbladder, without prior dilation of the tract, by applying a bipolar cut current. In the remaining six pigs, a conventional delivery system with LAMS (Cold SPAXUS) was inserted after tract dilatation using a cystotome. The stent was removed after 4 weeks. RESULTS: In all pigs, the stent was successfully inserted and deployed in the gallbladder without adverse events. The mean procedure time of EUS-TD was significantly lower in the Hot SPAXUS group than that of the Cold SPAXUS group (mean ± standard deviation: 188.7 ± 5.2 vs 449.5 ± 97.5 s, P = .0019). Stent migration was not observed, and all stents were removed successfully. CONCLUSIONS: Endoscopic ultrasound-guided transmural drainage using a bipolar electrocautery-enhanced LAMS is feasible for reducing the procedure time while maintaining the high success rate and safety of conventional LAMS.

A novel electrocautery-enhanced delivery system for one-step endoscopic ultrasound-guided drainage of the gallbladder and bile duct using a lumen-apposing metal stent: a feasibility study.

BACKGROUND: The use of a lumen-apposing metal stent (LAMS) capable of one-step endoscopic ultrasound-guided transmural drainage (EUS-TD) can increase the effectiveness of the procedure. We evaluated the newly developed electrocautery-enhanced (EC) delivery system with a LAMS for one-step EUS-guided gallbladder drainage (EUS-GBD) or choledochoduodenostomy (EUS-CDS). METHODS: In the animal experiment, an EC-LAMS was advanced into the gallbladder without prior tract dilation in four pigs. A conventional LAMS was inserted in another four pigs as a control group. After the animal experiment, 17 patients underwent EUS-TD using the EC-LAMS (EUS-GBD in 10 patients, EUS-CDS in 7). The primary outcome was the technical success rate. RESULTS: In the animal study, the mean procedure time was significantly shorter in the EC-LAMS group than in the conventional LAMS group. In the human study, the overall technical success rate was 94.1 %, with one EUS-GBD failure. The clinical success rate was 100 %. The overall adverse event rate was 17.6 %. CONCLUSIONS: One-step EUS-GBD or EUS-CDS using the novel EC-LAMS is a feasible approach that achieves a high success rate and maintains safety.

Modiolus-hugging intracochlear electrode array with shape memory alloy.

In the cochlear implant system, the distance between spiral ganglia and the electrodes within the volume of the scala tympani cavity significantly affects the efficiency of the electrical stimulation in terms of the threshold current level and spatial selectivity. Because the spiral ganglia are situated inside the modiolus, the central axis of the cochlea, it is desirable that the electrode array hugs the modiolus to minimize the distance between the electrodes and the ganglia. In the present study, we propose a shape-memory-alloy-(SMA-) embedded intracochlear electrode which gives a straight electrode a curved modiolus-hugging shape using the restoration force of the SMA as triggered by resistive heating after insertion into the cochlea. An eight-channel ball-type electrode array is fabricated with an embedded titanium-nickel SMA backbone wire. It is demonstrated that the electrode array changes its shape in a transparent plastic human cochlear model. To verify the safe insertion of the electrode array into the human cochlea, the contact pressures during insertion at the electrode tip and the contact pressures over the electrode length after insertion were calculated using a 3D finite element analysis. The results indicate that the SMA-embedded electrode is functionally and mechanically feasible for clinical applications.

Design for a simplified cochlear implant system.

A simplified cochlear implant (CI) system would be appropriate for widespread use in developing countries. Here, we describe a CI that we have designed to realize such a concept. The system implements 8 channels of processing and stimulation using the continuous interleaved sampling (CIS) strategy. A generic digital signal processing (DSP) chip is used for the processing, and the filtering functions are performed with a fast Fourier transform (FFT) of a microphone or other input. Data derived from the processing are transmitted through an inductive link using pulse width modulation (PWM) encoding and amplitude shift keying (ASK) modulation. The same link is used in the reverse direction for backward telemetry of electrode and system information. A custom receiver-stimulator chip has been developed that demodulates incoming data using pulse counting and produces charge balanced biphasic pulses at 1000 pulses/s/electrode. This chip is encased in a titanium package that is hermetically sealed using a simple but effective method. A low cost metal-silicon hybrid mold has been developed for fabricating an intracochlear electrode array with 16 ball-shaped stimulating contacts.

Three-dimensional analysis of electrode behavior in a human cochlear model.

Three-dimensional (3D) finite element analysis is used in this study to model the mechanical effects of the electrode in a cochlear implant. We employ six electrodes with different stiffness produced by different arrangements of metal wires. Different wire arrangements are generated by changing the fitness function of a genetic program. The human cochlea is modeled by the spiral-approximation method. Reconstructed three-dimensional CT images are used to model the real insertion condition. The contact pressure at the tip and the insertion force are found to be highest when the wires are stacked horizontally. Axial rotation of the electrode has minimal effect on the stimulating current spread. The electrode does not contact the basilar membrane. The results indicate that considering the electrode stiffness is important to minimizing mechanical trauma in cochlear implantation.