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Fulltext Cochlear implantation in children with labyrinthitis ossificans

Abdullah, A., Shaharudin, M.H., Amin, M., Marhaban, J.A., Awang, M.A., Zulfiqar, M.A., et al.

Medicine & Health, 2006;1(1):61-66.
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Evidence of ossification was previously considered a relative contraindication to cochlear implantation. It was considered difficult or impossible to achieve safe electrode insertion because of bony obstruction. Either the electrodes or the inner ear structures could be damaged. Moreover, obstructed scala tympani could limit the number of electrodes that can be inserted. The efficacy of the electrical stimulation was also questioned, as a higher current would be needed on an ossified cochlea. Finally, the neural survival in ossified cochlea is unknown. This may complicate the surgical procedure and affect the long-term outcome. However, depending on the experience of the surgeon, cochlear implantation has been attempted even in grossly ossified cochlea. Here we illustrate that cochlear implantation is safe in labyrinthitis ossificans.

Matched MeSH terms: Electrodes, Implanted
Successful placement of left ventricular pacing lead despite coronary sinus perforation into the pericardial space with an obstructive flap

Tamin SS, Hussin A, Za I, Halmey N, Azman W

Pacing Clin Electrophysiol, 2007 Feb;30(2):276-9.
PMID: 17338728

Coronary sinus perforation is a relatively uncommon but much feared complication that may occur during the placement of left ventricular pacing lead. Coronary sinus perforation, especially in the presence of an obstructive flap, usually indicates the need to abandon the implantation attempt, as there are difficulties in crossing the obstructive flap as well as uncertainty of whether the lead is in the true lumen or into the pericardial space. We describe our experience in successfully placing the left ventricular lead safely despite the problems arising from these circumstances.

Matched MeSH terms: Electrodes, Implanted/adverse effects*
Optimal approach for complete liver tumor ablation using radiofrequency ablation: a simulation study

Givehchi S, Wong YH, Yeong CH, Abdullah BJJ

Minim Invasive Ther Allied Technol, 2018 Apr;27(2):81-89.
PMID: 28612670 DOI: 10.1080/13645706.2017.1330757

PURPOSE: To investigate the effect of radiofrequency ablation (RFA) electrode trajectory on complete tumor ablation using computational simulation.
MATERIAL AND METHODS: The RFA of a spherical tumor of 2.0 cm diameter along with 0.5 cm clinical safety margin was simulated using Finite Element Analysis software. A total of 86 points inside one-eighth of the tumor volume along the axial, sagittal and coronal planes were selected as the target sites for electrode-tip placement. The angle of the electrode insertion in both craniocaudal and orbital planes ranged from -90° to +90° with 30° increment. The RFA electrode was simulated to pass through the target site at different angles in combination of both craniocaudal and orbital planes before being advanced to the edge of the tumor.
RESULTS: Complete tumor ablation was observed whenever the electrode-tip penetrated through the epicenter of the tumor regardless of the angles of electrode insertion in both craniocaudal and orbital planes. Complete tumor ablation can also be achieved by placing the electrode-tip at several optimal sites and angles.
CONCLUSIONS: Identification of the tumor epicenter on the central slice of the axial images is essential to enhance the success rate of complete tumor ablation during RFA procedures.

Matched MeSH terms: Electrodes, Implanted
Novel active fixation mechanism permits precise placement of a left ventricular lead: early results from a multicenter clinical study

Yee R, Gadler F, Hussin A, Bin Omar R, Khaykin Y, Verma A, et al.

Heart Rhythm, 2014 Jul;11(7):1150-5.
PMID: 24801899 DOI: 10.1016/j.hrthm.2014.04.020

Left ventricular (LV) lead implantation for cardiac resynchronization therapy (CRT) is associated with lead dislodgement rates ranging from 3% to 10%, and some implant approaches to prevent dislodgement may contribute to suboptimal CRT response. We report our early human experience with an LV lead with a side helix for active fixation to the coronary vein wall.

Matched MeSH terms: Electrodes, Implanted*
Development of an implantable D-serine biosensor for in vivo monitoring using mammalian D-amino acid oxidase on a poly (o-phenylenediamine) and Nafion-modified platinum-iridium disk electrode

Zain ZM, O'Neill RD, Lowry JP, Pierce KW, Tricklebank M, Dewa A, et al.

Biosens Bioelectron, 2010 Feb 15;25(6):1454-9.
PMID: 19945264 DOI: 10.1016/j.bios.2009.10.049

D-serine has been implicated as a brain messenger, promoting not only neuronal signalling but also synaptic plasticity. Thus, a sensitive tool for D-serine monitoring in brain is required to understand the mechanisms of D-serine release from glia cells. A biosensor for direct fixed potential amperometric monitoring of D-serine incorporating mammalian D-amino acid oxidase (DAAO) immobilized on a Nafion coated poly-ortho-phenylenediamine (PPD) modified Pt-Ir disk electrode was therefore developed. The combined layers of PPD and Nafion enhanced the enzyme activity and biosensor efficiency by approximately 2-fold compared with each individual layer. A steady state response time (t(90%)) of 0.7+/-0.1s (n=8) and limit of detection 20+/-1 nM (n=8) were obtained. Cylindrical geometry showed lower sensitivity compared to disk geometry (61+/-7 microA cm(-2) mM(-1), (n=4), R(2)=0.999). Interference by ascorbic acid (AA), the main interference species in the central nervous system and other neurochemical electroactive molecules was negligible. Implantation of the electrode and microinjection of D-serine into rat brain striatal extracellular fluid demonstrated that the electrode was capable of detecting D-serine in brain tissue in vivo.

Matched MeSH terms: Electrodes, Implanted*
Fulltext A leadless intracardiac transcatheter pacing system

Reynolds D, Duray GZ, Omar R, Soejima K, Neuzil P, Zhang S, et al.

N Engl J Med, 2016 Feb 11;374(6):533-41.
PMID: 26551877 DOI: 10.1056/NEJMoa1511643

BACKGROUND: A leadless intracardiac transcatheter pacing system has been designed to avoid the need for a pacemaker pocket and transvenous lead.
METHODS: In a prospective multicenter study without controls, a transcatheter pacemaker was implanted in patients who had guideline-based indications for ventricular pacing. The analysis of the primary end points began when 300 patients reached 6 months of follow-up. The primary safety end point was freedom from system-related or procedure-related major complications. The primary efficacy end point was the percentage of patients with low and stable pacing capture thresholds at 6 months (≤2.0 V at a pulse width of 0.24 msec and an increase of ≤1.5 V from the time of implantation). The safety and efficacy end points were evaluated against performance goals (based on historical data) of 83% and 80%, respectively. We also performed a post hoc analysis in which the rates of major complications were compared with those in a control cohort of 2667 patients with transvenous pacemakers from six previously published studies.
RESULTS: The device was successfully implanted in 719 of 725 patients (99.2%). The Kaplan-Meier estimate of the rate of the primary safety end point was 96.0% (95% confidence interval [CI], 93.9 to 97.3; P<0.001 for the comparison with the safety performance goal of 83%); there were 28 major complications in 25 of 725 patients, and no dislodgements. The rate of the primary efficacy end point was 98.3% (95% CI, 96.1 to 99.5; P<0.001 for the comparison with the efficacy performance goal of 80%) among 292 of 297 patients with paired 6-month data. Although there were 28 major complications in 25 patients, patients with transcatheter pacemakers had significantly fewer major complications than did the control patients (hazard ratio, 0.49; 95% CI, 0.33 to 0.75; P=0.001).
CONCLUSIONS: In this historical comparison study, the transcatheter pacemaker met the prespecified safety and efficacy goals; it had a safety profile similar to that of a transvenous system while providing low and stable pacing thresholds. (Funded by Medtronic; Micra Transcatheter Pacing Study ClinicalTrials.gov number, NCT02004873.).

Matched MeSH terms: Electrodes, Implanted
Fulltext Long-term outcomes in leadless Micra transcatheter pacemakers with elevated thresholds at implantation: Results from the Micra Transcatheter Pacing System Global Clinical Trial

Piccini JP, Stromberg K, Jackson KP, Laager V, Duray GZ, El-Chami M, et al.

Heart Rhythm, 2017 05;14(5):685-691.
PMID: 28111349 DOI: 10.1016/j.hrthm.2017.01.026

BACKGROUND: Device repositioning during Micra leadless pacemaker implantation may be required to achieve optimal pacing thresholds.
OBJECTIVE: The purpose of this study was to describe the natural history of acute elevated Micra vs traditional transvenous lead thresholds.
METHODS: Micra study VVI patients with threshold data (at 0.24 ms) at implant (n = 711) were compared with Capture study patients with de novo transvenous leads at 0.4 ms (n = 538). In both cohorts, high thresholds were defined as >1.0 V and very high as >1.5 V. Change in pacing threshold (0-6 months) with high (1.0 to ≤1.5 V) or very high (>1.5 V) thresholds were compared using the Wilcoxon signed-rank test.
RESULTS: Of the 711 Micra patients, 83 (11.7%) had an implant threshold of >1.0 V at 0.24 ms. Of the 538 Capture patients, 50 (9.3%) had an implant threshold of >1.0 V at 0.40 ms. There were no significant differences in patient characteristics between those with and without an implant threshold of >1.0 V, with the exception of left ventricular ejection fraction in the Capture cohort (high vs low thresholds, 53% vs 58%; P = .011). Patients with an implant threshold of >1.0 V decreased significantly (P < .001) in both cohorts. Micra patients with high and very high thresholds decreased significantly (P < .01) by 1 month, with 87% and 85% having 6-month thresholds lower than the implant value. However, when the capture threshold at implant was >2 V, only 18.2% had a threshold of ≤1 V at 6 months and 45.5% had a capture threshold of >2 V.
CONCLUSIONS: Pacing thresholds in most Micra patients with elevated thresholds decrease after implant. Micra device repositioning may not be necessary if the pacing threshold is ≤2 V.

Matched MeSH terms: Electrodes, Implanted
Amperometric microbiosensor as an alternative tool for investigation of D-serine in brain

Mohd Zain Z, Ab Ghani S, O'Neill RD

Amino Acids, 2012 Nov;43(5):1887-94.
PMID: 22865247 DOI: 10.1007/s00726-012-1365-0

This paper discusses the application of a reagentless, selective microbiosensor as a useful alternative tool for monitoring D-serine in neural samples. The main components of the 125-μm-diameter disk biosensor were D-amino acid oxidase for D-serine sensitivity (linear region slope, 61 ± 7 μA cm(-2) mM(-1); limit of detection, 20 nM), and poly-phenylenediamine for rejection of electroactive interference. The response time of the biosensor was of the order of 1 s, ideal for 'real-time' monitoring, and detection of systemically administered D-serine in brain extracellular fluid is demonstrated. Exploitation of this probe might resolve queries involving regulation of D-serine in excitotoxicity, and modulation of N-methyl-D-aspartate receptor function by D-serine and glycine in the central nervous system.

Matched MeSH terms: Electrodes, Implanted