scholarly journals Characterization of Atrial Propagation Patterns and Fibrotic Substrate With a Modified Omnipolar Electrogram Strategy in Multi-Electrode Arrays

2021 ◽  
Vol 12 ◽  
Author(s):  
Jennifer Riccio ◽  
Alejandro Alcaine ◽  
Sara Rocher ◽  
Laura Martinez-Mateu ◽  
Sergio Laranjo ◽  
...  

Introduction: The omnipolar electrogram method was recently proposed to try to generate orientation-independent electrograms. It estimates the electric field from the bipolar electrograms of a clique, under the assumption of locally plane and homogeneous propagation. The local electric field evolution over time describes a loop trajectory from which omnipolar signals in the propagation direction, substrate and propagation features, are derived. In this work, we propose substrate and conduction velocity mapping modalities based on a modified version of the omnipolar electrogram method, which aims to reduce orientation-dependent residual components in the standard approach.Methods: A simulated electrical propagation in 2D, with a tissue including a circular patch of diffuse fibrosis, was used for validation. Unipolar electrograms were calculated in a multi-electrode array, also deriving bipolar electrograms along the two main directions of the grid. Simulated bipolar electrograms were also contaminated with real noise, to assess the robustness of the mapping strategies against noise. The performance of the maps in identifying fibrosis and in reproducing unipolar reference voltage maps was evaluated. Bipolar voltage maps were also considered for performance comparison.Results: Results show that the modified omnipolar mapping strategies are more accurate and robust against noise than bipolar and standard omnipolar maps in fibrosis detection (accuracies higher than 85 vs. 80% and 70%, respectively). They present better correlation with unipolar reference voltage maps than bipolar and original omnipolar maps (Pearson's correlations higher than 0.75 vs. 0.60 and 0.70, respectively).Conclusion: The modified omnipolar method improves fibrosis detection, characterization of substrate and propagation, also reducing the residual sensitivity to directionality over the standard approach and improving robustness against noise. Nevertheless, studies with real electrograms will elucidate its impact in catheter ablation interventions.

2003 ◽  
Vol 773 ◽  
Author(s):  
Shalini Prasad ◽  
Mo Yang ◽  
Xuan Zhang ◽  
Yingchun Ni ◽  
Vladimir Parpura ◽  
...  

AbstractCharacterization of electrical activity of individual neurons is the fundamental step in understanding the functioning of the nervous system. Single cell electrical activity at various stages of cell development is essential to accurately determine in in-vivo conditions the position of a cell based on the procured electrical activity. Understanding memory formation and development translates to changes in the electrical activity of individual neurons. Hence, there is an enormous need to develop novel ways for isolating and positioning individual neurons over single recording sites. To this end, we used a 3x3 multiple microelectrode array system to spatially arrange neurons by applying a gradient AC field. We characterized the electric field distribution inside our test platform by using two dimensiona l finite element modeling (FEM) and determined the location of neurons over the electrode array. Dielectrophoretic AC fields were utilized to separate the neurons from the glial cells and to position the neurons over the electrodes. The neurons were obtained from 0-2-day-old rat (Sprague-Dawley) pups. The technique of using electric fields to achieve single neuron patterning has implications in neural engineering, elucidating a new and simpler method to develop and study neuronal activity as compared to conventional microelectrode array techniques.


1993 ◽  
Vol 78 (2) ◽  
pp. 233-239 ◽  
Author(s):  
Giancarlo Barolat ◽  
Fulvio Massaro ◽  
Jiping He ◽  
Sergio Zeme ◽  
Beth Ketcik

✓ A database is presented of sensory responses to electrical stimulation of the dorsal neural structures at various spine levels in 106 subjects subjected to epidural spinal cord stimulation. All patients were implanted for chronic pain management and were able to perceive stimulation in the area of pain. All patients entered in this study were able to reliably report their stimulation pattern. Several patients were implanted with more than one electrode array. The electrode arrays were placed in the dorsal epidural space at levels between C-1 and L-1. The structures that were likely involved include the dorsal roots, dorsal root entry zone, dorsal horn, and dorsal columns. At the present time, exact characterization of the structure being stimulated is possible only in limited instances. Various body areas are presented with the correspondent spine levels where implanted electrodes generate paresthesias. Areas that are relatively easy targets for stimulation are the median aspect of the hand, the abdominal wall, the anterior aspect of the thigh, and the foot. Some areas are particularly difficult to cover with stimulation-induced paresthesias; these include the C-2 distribution, the neck, the low back, and the perineum.


2021 ◽  
Vol 109 ◽  
pp. 103537
Author(s):  
Li Cai ◽  
Qiang Hu ◽  
Jianguo Wang ◽  
Xin Zou ◽  
Quanxin Li ◽  
...  

2021 ◽  
Vol 11 (9) ◽  
pp. 4144
Author(s):  
Ohad Cohen ◽  
Jean-Yves Sichel ◽  
Chanan Shaul ◽  
Itay Chen ◽  
J. Thomas Roland ◽  
...  

Although malpositioning of the cochlear implant (CI) electrode array is rare in patients with normal anatomy, when occurring it may result in reduced hearing outcome. In addition to intraoperative electrophysiologic tests, imaging is an important modality to assess correct electrode array placement. The purpose of this report was to assess the incidence and describe cases in which intraoperative plain radiographs detected a malpositioned array. Intraoperative anti-Stenver’s view plain X-rays are conducted routinely in all CI surgeries in our tertiary center before awakening the patient and breaking the sterile field. Data of patients undergoing 399 CI surgeries were retrospectively analyzed. A total of 355 had normal inner ear and temporal bone anatomy. Patients with intra or extracochlear malpositioned electrode arrays demonstrated in the intraoperative X-ray were described. There were four cases of electrode array malposition out of 355 implantations with normal anatomy (1.1%): two tip fold-overs, one extracochlear placement and one partial insertion. All electrodes were reinserted immediately; repeated radiographs were normal and the patients achieved good hearing function. Intraoperative plain anti-Stenver’s view X-rays are valuable to confirm electrode array location, allowing correction before the conclusion of surgery. These radiographs are cheaper, faster, and emit much less radiation than other imaging options, making them a viable cost-effective tool in patients with normal anatomy.


2000 ◽  
Vol 73 (1-3) ◽  
pp. 230-234 ◽  
Author(s):  
M Ichimura ◽  
M Hirano ◽  
A Tada ◽  
E Arai ◽  
H Takamatsu ◽  
...  

2007 ◽  
Vol 17 (01) ◽  
pp. 173-176 ◽  
Author(s):  
BARBAROS ASLAN ◽  
LESTER F. EASTMAN ◽  
WILLIAM J. SCHAFF ◽  
XIAODONG CHEN ◽  
MICHAEL G. SPENCER ◽  
...  

We present the experimental development and characterization of GaN ballistic diodes for THz operation. Fabricated devices have been described and gathered experimental data is discussed. The major problem addressed is the domination of the parasitic resistances which significantly reduce the accelerating electric field across the ballistic region (intrinsic layer).


AIP Advances ◽  
2015 ◽  
Vol 5 (9) ◽  
pp. 097181 ◽  
Author(s):  
Ghada H. Dushaq ◽  
Amro Alkhatib ◽  
Mahmoud S. Rasras ◽  
Ammar M. Nayfeh

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