Mini Electrodes Research Articles

The advantage of the mini-electrode-equipped catheter for the radiofrequency ablation of paroxysmal supraventricular tachycardia.

Novel ablation catheters equipped with mini-electrodes (ME) offer high resolution mapping for target tissue. This study aimed to evaluate the mapping performance and efficacy of ME catheters in radiofrequency ablation (RFA) of paroxysmal supraventricular tachycardias (PSVTs). We prospectively enrolled 136 patients undergoing RFA of PSVT including 76 patients with atrioventricular nodal reentrant tachycardia (AVNRT) and 60 patients with atrioventricular reentrant tachycardia (AVRT) or Wolff-Parkinson-White (WPW) syndrome. Patients were randomized to the ME group (ablation using ME catheters) or the control group (ablation using conventional catheters). The number of ablation attempt and cumulative ablation time to ablation endpoints, which was defined as an emergence of junctional rhythm in AVNRT or accessory pathway (AP) block in AVRT/WPW syndromes were compared. During ablation procedures, discrete slow pathway or AP electrograms were found in 27 (39.7%) patients in the ME group and 13 (19.1%) patients in the control group. The primary study outcomes were significantly lower in the ME group (ablation attempt number: 2.0 [1-4] vs. 3.0 [2-7] in the ME and control group, p = .032; ablation time: 23.5 [5.0-111.5] vs. 64.5 [16.0-185.0] s, p = .013). According to the PSVT diagnosis, ablation time to junctional rhythm was significantly shorter in the ME group in AVNRT. In AVRT/WPW syndrome, both ablation attempt number and ablation time to AP block were nonsignificantly lower in the ME group. The novel ME catheter was advantageous for identifying pathway potentials and reducing initial ablation attempt number and ablation time to reach acute ablation endpoint for PSVTs(ClinicalTrials.gov number, NCT04215640).

Value of Mini Electrodes for Mapping Myocardial Arrhythmogenic Substrate—The Influence of Tip-to-Tissue Angulation and Irrigation Flow on Signal Quality

Background: The use of mini electrodes with a small surface and narrow electrode-to-electrode spacing is believed to lead to a higher electrical resolution. Until now, the effects of tip-to-tissue contact, angulation, and irrigation on signal quality and morphology are unknown. Methods: The beating heart of an open-chest pig was examined while controlling the angulation and contact between the catheter tip and myocardial tissue, as well as the irrigation of the catheter tip. The mini electrodes were mounted onto commercially available 8 mm non-irrigated and 4 mm irrigated tip catheters. Different electrode interconnections, angulations, contact forces, and irrigation flow were analyzed and compared to signals recorded from conventional electrodes. Results: A total of 63 electrode samples of 21 defined, stable settings, each lasting 30 s, were analyzed. (1) Tissue contact of mini electrodes was given as soon as the conventional tip electrode showed tissue contact. (2) Angulation of the tip-to-tissue contact showed a trend towards changes in the integral of signals derived from mini electrodes, and no significant changes were seen in signals derived from conventional or mini electrodes. (3) Irrigation flow surrounding the mini electrodes did not influence signals derived from mini electrodes, whereas conventional electrodes showed signals with a longer duration under higher irrigation. Conclusion: Mini electrodes are robust to contact force and irrigation flow regarding signal quality, whereas signals of conventional electrodes are affected by irrigation flow, leading to substantial changes in signal duration and kurtosis. Signals of mini electrodes are sensitive to local electrical changes because of a high local resolution.

B-PO05-133 ROLE OF ELECTROGRAMS RECORDED FROM THE MINI ELECTRODES IN CATHETER ABLATION OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA

Analysis of electrograms recorded from mini electrodes (MEs) (IntellaTip MiFi, Boston Scientific) has not been reported. We evaluated the additional value of MEs during ablation of atrioventricular nodal reentrant tachycardia (AVNRT). Consecutive patients with AVNRT who underwent slow pathway ablation using a MiFi catheter were included. A combined electroanatomic approach was used to identify the target site. During ablation, operators were blind to ME electrograms, and ME electrograms immediately before initiation of the first radiofrequency (RF) application were evaluated retrospectively. A total of 62 patients (47 ± 17 years, 46.8% male) with typical (n=58) and atypical (n=4) AVNRT were included. Slow pathway ablation or modification was achieved in all patients. Thirty-two patients (51.6%) showed accelerated junctional rhythm (JR) during the first RF application. Immediately before the first RF, atrial signals at the MEs were observed in 37 patients (59.7%). There was a significant association between presence of atrial signals in MEs and the occurrence of JR (OR 5.36, P=0.002). The positive and negative predictive values of the atrial signals in MEs for the JR induction during the first RF were 67.6% (25/37) and 72.0% (18/25), respectively. Amplitudes of atrial signals of the MEs were not different between patients with and without an inducible JR (0.20 ± 0.13 mV versus 0.14 ± 0.11 mV, P=0.18). Signals recorded from the MEs could be helpful in targeting the ablation point during slow pathway ablation. Ablation should be discouraged in regions with optimal bipolar electrograms not followed by adequate ME electrograms.

Effects of Anode Design and Configuration on the Growth Dynamics and Surface Morphologies of Electrodeposited Copper Films

The influence of different anode configurations on the growth mechanisms, transient currentsand surface morphologies of copper film using localized electrodeposition technique have been studied. Measured transient currents during electrodeposition wereused to investigate the underlying growth dynamics. SEM images were obtained and the surface morphologies of the deposited copper films were analyzed. It was found that the transient current increased when copper ions were able to grow directly on the empty surface of the copper film that was located away from the mini electrodes. This caused the copper ions to be deposited sporadically via the instantaneous growth mechanism and formed cluster of atoms on the empty surface of the copper film which led to rougher surfaces. In contrast, progressive growth was observed to occur at a faster rate for thedeposition performed using insulated mini electrodes, especially in the case of collinear double insulated mini electrodes as indicated by the reduction of the transient current with time. Besides, copper films with uniform and smoother surfaces were obtained when the depositions were performed using multiple or a large number of closely spaced mini electrodes. This was due to the fact that large number of closely spaced mini electrodes produced parallel and uniform electric field patterns.

P1448Ablation of cti-dependent flutter using a novel advanced mini-electrodes technology: preliminary results from Leonardo registry

Abstract Funding Acknowledgements NO FUNDING OnBehalf LEONARDO study group Background Ablation of cavotricuspid isthmus (CTI) represents the standard therapeutic approach for the creation of bidirectional conduction block (BDB) across the isthmus and the prevention of recurrences, yet recurrence of arrhythmia is common. Objective To evaluate the acute and long-term outcome of CTI ablation through a novel ablation catheter equipped with three radially distributed mini-electrodes (ME) compared with standard ablation catheter technology (ST). Methods Atrial Flutter Ablation in a Real World Population (LEONARDO) is a prospective, multicenter cohort study aimed at providing an estimate of acute to long-term outcome in a large population of pts indicated for AFL ablation from 2015 to 2017. The procedural endpoint was the creation of a BDB. Presence of widely split double potentials (DP) along the ablation line and assessment of the atrial activation sequence (AAS) were used as criteria for complete BDB. Recurrence of AFL and complications were assessed at 12-month follow-up. Results 205 consecutive pts undergoing typical AFL ablation were included (74% male, 50.6% with history of AF, median of 7[4–11] ablation lesions, median ablation time of 20[10-30] min). Complete BDB was achieved in 175 (85.4%) pts (10 pts had DP only criterion, 19 pts had AAS only criterion whereas in 1 pt we failed to reach a BDB). 15 (7.3%) pts experienced AFL recurrence during follow-up. 102 pts (49.8%) underwent ablation procedure with ME catheters whereas 103 (50.2%) pts were treated by ST catheters. The median number of lesions/pt was significantly lower in the ME group compared to the ST one (4[3-6] vs 8.5[6-12], p < 0.0001), whereas no differences were found in terms of fluoroscopy time (10.5[7-15] min vs 10[5.8 ± 15] min, p = NS) or ablation time (22.5[10-30.5] min vs 18[10-26] min, p = NS). No complications were reported. The acute procedural success was comparable between groups (81.4% vs 89.2%, p = NS) whereas the time to AFL recurrence was significantly longer among pts targeted with ME catheters (HR = 0.343; 0.12 to 0.97; log-rank p = 0.044). Conclusions In our preliminary experience, the use of the ME technology seemed safe and effective. It resulted in fewer lesions/pt and a lower AFL recurrence rate at 1-year follow-up compared with ST ablation catheters.

Laboratory characterization of sandy soil water content during drying process using electrical resistivity/resistance method (ERM)

Drought-induced evaporation can reduce soil water content and significantly alter soil hydro-mechanical behavior. Understanding the temporal and spatial distribution characteristics of soil water content during evaporation is of great significance for evaluating the encountered geotechnical and geo-environmental problems in arid or semi-arid regions. In this study, an electrical resistivity/resistance method (ERM) with a high spatial resolution of centimeter-level was developed for a small-scale laboratory test and applied to quantitatively characterize the evaporation-induced water content variations along a depth gradient. A total of 8 groups of initially saturated sandy soil columns (84 mm in diameter and 290 mm in height) were prepared, and eight pairs of mini electrodes (3.5 mm in diameter) were installed in each soil sample with a vertical distance of 30 mm. The soil columns were subjected to continuous drying. The changes in soil electrical resistance at different depths were monitored by the electrode couples. The gravimetric water contents at different depths were also measured at the end of drying. It is found that soil water content decreases exponentially with increasing electrical resistance. Based on the obtained data, a calibration relationship between soil gravimetric water content and corrected electrical resistance was well established with consideration of temperature effect. This relationship was validated successfully by the experimental results, indicating the feasibility of the developed ERM to characterize the soil water content dynamics during the drying process. Besides, the drying process with the movement of the evaporation front was discussed. The results of this study demonstrate the good performance of ERM in the estimation of temporal and spatial variations of soil water content and its potential application in arid or semi-arid regions with frequent droughts.

Laboratory modeling for contaminant migration monitoring using electrical resistivity method

The rate at which contaminants migrate in the soil, such as hydrocarbons and saltwater, has long been studied. The contaminants might be as a result of spilled oil from the failed pipeline, sabotaged pipeline in Niger Delta, and saltwater intrusion. A laboratory modeling 2D electrical resistivity experiment was carried out to model the migration pattern of soil contaminants in a sand formation. The electrical resistivity methods are often being used to detect the contaminants’ plume in the subsurface using mini electrodes electrical resistivity imaging. This geophysical method was adopted before (baseline) and after the injection of the contaminant. The model tank was filled with sand, and the contaminants [petroleum and sodium chloride (NaCl)] were injected in four points into the model tank to a depth of 5 cm. A total of three (3) traverses for each segment were established within the tank. The dipole–dipole array was used for the investigation with electrode spacing (a) of 5 cm (0.05 m) and expansion factor (n) varying from 1 to 5. The traverse interval was 11.1 cm apart. A constant station separation of 5 cm (0.05 m) was adopted. The injected contaminants are organic (hydrocarbon) and inorganic (saltwater intrusion), and they are injected at station 9 and station 30 in between traverse 1 and 2 and traverse 2 and 3. Subsequently, the injection of the contaminant into the model tank was undertaken at 24 h. Experimental results obtained from this study show that 24 h after the injection of the organic substance, high resistivity value ranging from 350 to 800 Ωm buildup in some stations, which is directly related to organic (hydrocarbon) accumulation and low resistivity value, is because the porosity in these regions has been affected. 24 h after the injection of the NaCl, the three (3) traverses depict very low resistivity value ranging from 1.2 to 45 Ωm which is related to the presence of saltwater but in traverse 3 station 23 to 25 and traverse 2 station 17 to 18 depict high resistivity value ranging between 105 and 215 Ωm which indicates that the porosity in this region has been affected by the injected fluid. In general, the injected contaminant affected the porosity of the host material, which leads to the high resistivity value in the saltwater zone and low resistivity in the hydrocarbon zone.

How to avoid unnecessary RF applications in cavo-tricuspid isthmus: common atrial flutter ablation using 8-mm-tip mini-electrode-equipped catheter

Eight-millimeter-tip ablation catheters are characterized by poor mapping resolution as they depend on electrode size and spacing. IntellaTip MiFi XP 8-mm (Boston Scientific) catheters offer high mapping resolution due to 3 mini-electrodes (ME) located at the distal tip of the catheter and are dedicated for cavo-tricuspid isthmus (CTI) radiofrequency ablation (RFA). The aim of the study was to evaluate the usefulness, effectiveness and safety of novel IntellaTip MiFi XP catheter for CTI RFA and its ability to localize anatomical structures of the heart. The study included 10 patients referred for atrial flutter ablation. The 3D mapping system EnSite Velocity was utilized for catheter visualization. The ME signals were used for tricuspid annulus visualization, RF delivery effectiveness assessment defined as ME signal attenuation, and localization of the gaps in the ablation line. The use of ME signals for TV annulus localization resulted in a 13.9mm (35.5 ± 4.8mm vs 49.4 ± 7.8mm; p < 0.01) shorter ablation line in comparison with the potential ablation line designed using standard bipol. The ablation endpoint, bidirectional block, was achieved in all 10 cases (100%) and lasted for at least 15min after the last RF delivery. The ablation endpoint was reached after 5.1 ± 1.67 RF applications. The total RF time was 220 ± 61s. Total procedure time was 66 ± 13.5min, fluoroscopy time 3.92 ± 4.21min, and total fluoroscopy dose 40.3 ± 56.5mGy. In 3 out of 10 cases, there was a need of filling the gap with 1-2 additional applications after the first linear lesion set. No additional RF applications were required at the annular end of the ablation line. The indirect comparison with previously conducted studies using a standard 8-mm ablation catheter shows that the studied catheter has at least the same or even better performance. The use of the novel IntellaTip MiFi XP may help to avoid unnecessary RF application especially at the annular part of cavo-tricuspid isthmus and enables a purely electrophysiological approach to atrial flutter ablation, as high-resolution ME signals help to understand local electrophysiological phenomena.

Electrogram voltage and pacing threshold before ablation, measured by mini-electrodes, predict parameters indicative of transmural lesions in the human atrium

PurposeAn important attenuation of the atrial signal recorded with mini-electrodes (ME) embedded in an 8-mm tip was associated with a transmural radiofrequency lesion. Our aim was to assess if parameters obtained from ME or conventional bipoles before applications predict successful atrial lesions.MethodsWe prospectively included 33 consecutive patients undergoing cavotricuspid isthmus (CTI) ablation. Electrogram voltages and pacing thresholds were measured with ME and conventional bipoles before and after radiofrequency (RF) applications. The time before the loss of capture during applications was recorded. Lesions were considered successful, in accordance with preclinical data, if ME voltage decreased > 54%.ResultsOf 207 applications, 107 could be analyzed. During applications, voltages decreased more in the ME than in the conventional bipoles (66.8 ± 26.1% vs 37.5 ± 42.5%, P = 0.001). Likewise, pacing threshold increased significantly more using the ME (86.3 ± 22.9% ME, 52.6 ± 35.6% conventional, P = 0.001). ME pre-ablation voltages were significantly higher and pacing thresholds significantly lower in successful lesions (voltage 0.88 ± 0.71 vs 0.26 ± 0.18 mV, P = 0.0001; threshold 1.6 ± 1.7 vs 2.8 ± 3.0, P = 0.04). Neither of these parameters with conventional bipoles nor time to loss of capture showed differences. A ME voltage > 0.33 mV and a pacing threshold < 1.5 mA predicted a successful lesion with 0.78 and 0.6 sensitivity and 0.78 and 0.59 specificity.ConclusionsCertain pre-ablation parameters derived from ME such as electrogram voltage and pacing threshold differ from those obtained by a conventional configuration and can predict a successful atrial lesion.

A Bioelectronic System to Measure the Glycolytic Metabolism of Activated CD4+ T Cells.

The evaluation of glucose metabolic activity in immune cells is becoming an increasingly standard task in immunological research. In this study, we described a sensitive, inexpensive, and non-radioactive assay for the direct and rapid measurement of the metabolic activity of CD4+ T cells in culture. A portable, custom-built Cell Culture Metabolite Biosensor device was designed to measure the levels of acidification (a proxy for glycolysis) in cell-free CD4+ T cell culture media. In this assay, ex vivo activated CD4+ T cells were incubated in culture medium and mini electrodes were placed inside the cell free culture filtrates in 96-well plates. Using this technique, the inhibitors of glycolysis were shown to suppress acidification of the cell culture media, a response similar to that observed using a gold standard lactate assay kit. Our findings show that this innovative biosensor technology has potential for applications in metabolic research, where acquisition of sufficient cellular material for ex vivo analyses presents a substantial challenge.

Additional Diagnostic value of Mini Electrodes in an 8-mm Tip in Cavotricuspid Isthmus Ablation.

Eight-mm ablation catheters are widely used in cavotricuspid isthmus ablation (CTI) for treatment of right sided atrial flutter. However a high success rate, these large ablation tips comes with adisadvantage of lower resolution of fractionated signals. The aim of this study was to evaluate the additional diagnostic value of the electrograms recordedfrom mini electrodes (MEs) in an 8-mm ablation catheter tip during CTI. CTI-ablation procedures were compared retrospectively in two groups, namely, group A: the Abbott Safire 8-mm tip with a 3D mapping system (n =37) and group B: the Boston Scientific MiFi IntellaTip XP 8-mm tip without a 3D mapping system (n=13). We analyzedacute procedural success, ablation characteristics and recurrence rate at one-year follow-up. Electrograms from MEs were analyzedright before the onset of the critical ablation application that resulted in acute CTI-block. We determined whether these ME electrograms had additional diagnostic value in addition to of the 8-mm tip derivedelectrogram. At the onset of the critical ablation application, the MEs had an important additional value in 3 out of 13 cases as local signals were sensed on the MEs that were not recorded by the 8-mm tip electrode. In 2cases the ME did not show local electrogramsalthough the ablationwas still effective. Acute procedural and long-term success wereobserved in all patients. No differences were found in time to bidirectional block, procedure time or fluoroscopic exposure. Our data show that signals recorded from the MEs had additional diagnostic value, but only in asmall percentage of the patients. We did not observe, although omitting 3D-mapping in the ME group, any differencebetween groups with regard to procedural or ablation characteristicsduring CTI-ablation.

Mini-electrodes help identifying hidden slow conduction during ventricular tachycardia substrate ablation

A 69-year-old male with dilated non-ischemic cardiomyopathy and history of sustained monomorphic VT (SMVT) underwent an unsuccessful VT substrate ablation due to the proximity of the earliest activation site to the conduction system. A second attempt was performed using an ablation catheter with mini-electrodes (ME) and multiple extrastimuli to unveil hidden slow conduction (HSC) sites, allowing the performance of a successful ablation. No SMVT was induced thereafter.ME-obtained electrograms permit to accurately localize areas of HSC sites within ventricular tachycardia (VT) substrates. In our case, this allowed safe ablation during sinus rhythm to eliminate the VT substrate.

First data on cardiac mapping and outcome of pulmonary vein isolation using a novel ablation catheter with tip mini electrodes

AimsPulmonary vein isolation (PVI) is a standard treatment of atrial fibrillation (AF). AF recurrence after PVI occurs in a substantial number of cases. A novel ablation catheter equipped with mini-electrodes (ME) may facilitate PVI. Our study evaluated outcome after PVI with the ME catheter compared to a standard catheter. MethodsPatients undergoing PVI with the ME catheter were compared to a control group ablated with a standard contact force sensing catheter. Freedom of AF after 12 months was the study endpoint. Additionally, low voltage areas (LVA) <0.5 mV were identified with a circular mapping catheter (CMC) and the ablation catheter in each group. LVA were compared between the maps obtained with the CMC and the ME or standard catheter, respectively. ResultsA total of 110 patients underwent PVI with ME catheter (n = 59) or the standard catheter (n = 51). Procedure duration (117.4 ± 43 vs. 103.1 ± 32.8 min, p = 0.15), radiation dose (1135.6 ± 1125.7 vs. 1078.8 ± 951.4 μGy/m2, p = 0.91), incidence of complications and 12-month success rate (64.4 vs 72.5%, p = 0.36) were not significantly different between the groups. LVA were significantly smaller when obtained with the standard catheter compared to the CMC (14 ± 13 vs. 58.5 ± 22.1 cm2, p < 0.001), while no such difference was seen for mapping with the ME compared to the CMC (37 ± 30.3 vs. 33.4 ± 39 cm2, p = 0.4). ConclusionClinical outcomes are comparable between ME catheter and a standard contact force sensing catheter. Furthermore, better LVA detection points to improved mapping capabilities of the ME catheter.

P890Electrogram voltage and pacing threshold before ablation, measured by mini electrodes embedded in an ablation catheter, predict subsequent transmural lesions at the cavotricuspid isthmus in humans

P890Electrogram voltage and pacing threshold before ablation, measured by mini electrodes embedded in an ablation catheter, predict subsequent transmural lesions at the cavotricuspid isthmus in humans

Cardiac mapping and pulmonary vein isolation using a novel ablation catheter with tip minielectrodes.

Pulmonary vein isolation (PVI) is a standard treatment for atrial fibrillation (AF). Identification of gaps in the ablation line is difficult. Tip-ring electrograms from ablation catheters represent relative large areas of myocardial tissue. Recently, an ablation catheter with three minielectrodes (ME) on the catheter tip with closer interelectrode spacing was introduced. The aim of our study was to evaluate the novel electrodes during PVI. PVI was performed with an irrigated ablation catheter equipped with conventional electrodes and three additional radial tip electrodes. Detection of pulmonary vein potentials (PVPs), local signal amplitude, amplitude reduction during ablation, and loss of capture after ablation were compared between the ME and the conventional tip-ring electrodes. Thirty-one patients (mean age 67.8 ± 10.3 years, 45.2 % men) were included. A total of 306 mapping/lesion points were analyzed. A PVP was significantly more often obtained with the ME compared to the conventional tip-ring electrodes (99.2%vs 83.5%, P<0.001). Local amplitude was significantly higher on the ME (0.8 ± 0.6mV vs 0.67 ± 0.46mV, P=0.003). Amplitude reduction during 1 RF pulse was significantly greater on the ME (82.9 ± 19.5%vs. 61.8 ± 26.9%, P<0.001). During pace mapping, loss of capture after 1 RF pulse was observed significantly more often on ME (98.3%vs 63.3%, P<0.001). Signal amplitude is higher and sensitivity during PVP mapping and ablation is increased when ME are used. ME may facilitate catheter ablation of AF in the future.

Relationship between lesion formation and electrophysiological responses using catheters equipped with mini-electrodes in chronic atrial fibrillation

The study focuses on the electrophysiological changes associated with lesion formation using 4.5-mm irrigated and 8-mm standard catheters equipped with mini-electrodes (MEs) positioned circumferentially on the tip. The aim of the study was to test the relationship between the maximal electrogram (EGM) reduction, frequency spectrum shift, and their impact on atrial lesion formation in the atrial fibrillation (AF) model. Furthermore, we hypothesize that the high fidelity recording from the MEs allows improved discrimination of ablated tissues from nonablated tissues. Under fluoroscopic and NavX guidance, atrial ablation lesions were placed in 4 canines in chronic AF (>12 months in AF) to achieve intercaval, cavotricuspid isthmus, and left atrial contiguous lesions. Lesion times were titrated to the maximal loss of EGM amplitude as recorded from the MEs. Radiofrequency (RF) lesions were sequentially connected on the basis of the ME recordings of tissue viability. In lesions formed using a 4.5-mm irrigated catheter (172 lesions) and in those formed using an 8-mm catheter (155 lesions), the time to nadir of the EGM reduction was 22 ± 12 and 22 ± 9 seconds (NS:p>0.05). Contiguous transmural lesions were successfully placed and guided by the ME EGMs and confirmed by frequency spectra. In the chronic AF model, EGM reduction and frequency spectrum shift recorded from the MEs are twice the reduction recorded using the 4.5mm and 8mm tip to ring electrodes. RF titration based on the maximal EGM diminution is an effective approach to monitor lesion formation and may improve safety by preventing unnecessarily prolonged RF application. The ME EGM recording greatly facilitates placement of contiguous transmural linear lesions.

Mini Electrodes on Ablation Catheters: Valuable Addition or Redundant Information?-Insights from a Computational Study.

Radiofrequency ablation has become a first-line approach for curative therapy of many cardiac arrhythmias. Various existing catheter designs provide high spatial resolution to identify the best spot for performing ablation and to assess lesion formation. However, creation of transmural and nonconducting ablation lesions requires usage of catheters with larger electrodes and improved thermal conductivity, leading to reduced spatial sensitivity. As trade-off, an ablation catheter with integrated mini electrodes was introduced. The additional diagnostic benefit of this catheter is still not clear. In order to solve this issue, we implemented a computational setup with different ablation scenarios. Our in silico results show that peak-to-peak amplitudes of unipolar electrograms from mini electrodes are more suitable to differentiate ablated and nonablated tissue compared to electrograms from the distal ablation electrode. However, in orthogonal mapping position, no significant difference was observed between distal electrode and mini electrodes electrograms in the ablation scenarios. In conclusion, catheters with mini electrodes bring about additional benefit to distinguish ablated tissue from nonablated tissue in parallel position with high spatial resolution. It is feasible to detect conduction gaps in linear lesions with this catheter by evaluating electrogram data from mini electrodes.

The Relationship between Insulin Resistance, Resting EEG Alpha Wave Asymmetry, and Eye Blink Startle Reflex during International Affective Picture System Presentation

According to the CDC, it is estimated that more than one in three U.S. adults have pre‐diabetes. Pre‐diabetes etiology is characterized by insulin resistance (IR), which is a reduced cellular response to insulin and characterized by lower glucose uptake in the brain. IR is also related to deficits in cognitive and affective processing, particularly reactivity to psychological stress. The goal of our analysis was to determine how IR or hyperglycemia predict eye blink startle reflex (EBR) magnitude and amplitude, an objective index of the startle response, in response to positive, negative and neutral pictures using the International Affective Picture System (IAPS). We similarly assessed if IR predicted resting right frontal asymmetry using electroencephalography (EEG), an established biomarker of predisposition toward negative affect. We hypothesized that individuals with higher IR or hyperglycemia would show greater EBR and EEG right frontal asymmetry.The analysis incorporated healthy adults (N=331 participants), aged 36–84 years old, from the University of Wisconsin‐Madison's MIDUS (Midlife in the United States) II longitudinal study. As described in the MIDUS protocol, fasted blood samples were collected during an overnight stay. EBR in response to IAPS visual stimuli paired with acoustic startle was measured by placing two mini electrodes below the eye. Picture duration was 4,000ms. For a given trial, the acoustic startle stimulus occurred for 50ms during one of three phases: 1) The “early” phase at 2,900ms after picture onset while the picture was on the screen to assess reactivity; 2) the “middle” phase at 400ms after picture offset and removal to assess short‐term recovery; and 3) the “late” phase at 1,900ms after picture offset and removal to assess longer‐term recovery.Resting EEG right frontal asymmetry was collected prior to the IAPS presentation.Data was analyzed using SPSS 23.0. Linear mixed models were used to analyze the main effect of log‐transformed homeostasis model assessment of insulin resistance (HOMA‐IR) on EBR, as well as its interaction with IAPS picture valence (positive, neutral, negative). Higher log10 HOMA‐IR predicted greater EBR amplitude during negative versus positive pictures when paired with the startle stimulus (n=290, p&lt;.05, r2=0.127). Resting state EEG at frontal F3/F4 alpha 1 (8–13 Hz) showed that participants with hyperglycemia had more left than right alpha power (−0.0324 +/− 0.026 vs. 0.0126 +/− 0.028) indicating greater right EEG frontal asymmetry. This result is consistent with Jackson et al. (2003) that hyperglycemia individuals are predisposed to negative emotion/affect. In conclusion, higher IR and type 2 diabetes are related to biomarkers of psychological stress reactivity.Support or Funding InformationThis work is directly supported by the National Institute on Aging (AG047282). Data collection and sharing for this project was funded by the Alzheimer's Disease Neuroimaging Initiative (ADNI) (National Institutes of Health Grant U01 AG024904). The grantee organization is the Northern California Institute for Research and Education, and the study is coordinated by the Alzheimer's Disease Cooperative Study at the University of California, San Diego. ADNI data are disseminated by the Laboratory for Neuro Imaging at the University Southern California. This research was also supported by NIH grants P30 AG010129 and K01 AG030514.

Exploring miniaturized EEG electrodes for brain-computer interfaces. An EEG you do not see?

Electroencephalography (EEG) allows the study of the brain–behavior relationship in humans. Most of what we have learned with EEG was through observing the brain–behavior relationship under well-controlled laboratory conditions. However, by reducing “normal” behavior to a minimum the ecological validity of the results can be limited. Recent developments toward mobile EEG solutions allow to study the brain–behavior relationship outside the laboratory in more natural situations. Besides mobility and robustness with respect to motion, mobile EEG systems should also interfere as little as possible with the participant's behavior. For example, natural interaction with other people could be hindered when it is obvious that a participant wears an EEG cap. This study evaluates the signal quality obtained with an unobtrusive solution for EEG monitoring through the integration of miniaturized EEG ton-electrodes into both a discreet baseball cap and an individualized ear piece. We show that such mini electrodes located at scalp and ear locations can reliably record event related potentials in a P300 brain–computer–interface application.

Maximal electrogram attenuation recorded from mini electrodes embedded on 4.5-mm irrigated and 8-mm nonirrigated catheters signifies lesion maturation.

The electrograms (EGMs) recorded from mini electrodes (ME) placed on the tip of the ablation electrode allow more precise EGM monitoring during lesion formation. Our objective was to define the lesion boundaries and extracardiac injuries resulting from 60-second RF application versus RF application time titrated to maximal attenuation of the ME EGM in the atria and ventricles using 4.5-mm irrigated and 8-mm catheters. RF lesions were placed in both atria and ventricles in 13 (30-35 kg) canines; 6 (4.5-mm OI) and 7 (8 mm). The RF application time was fixed at 60 seconds or terminated at maximal ME EGM amplitude attenuation. Pre/postablation pacing thresholds, EGM amplitudes, and lesion dimensions were not significantly different between maximal EGM attenuation and 60-second RF application using either catheter. Atrial lesion transmurality was also similar for both catheters and groups 91.2% (4.5 mm) and 96% (8 mm) when the RF was titrated to the maximal EGM attenuation and 94.2% (4.5 mm) and 95% (8 mm) with 60-second RF. The 60-second RF ablation, however, presented with significant extracardiac injuries to the lungs and esophagus, along with char formation. Deep ventricular lesions were noted with maximal EGM attenuation that were not different from the 60-second RF ablation. Titration of the RF application time to the maximal EGM attenuation based on the ME recordings represents atrial lesion maturation and deep ventricular lesions. Prolonging the RF application results in greater extracardiac injury and char formation without increasing lesion size.