Late Potentials Research Articles

Clinic-Electrophysiologic Correlations in Rehabilitation of Adult Patients with Traumatic Brachial Plexus Lesions

Nerve-transfer surgery is the treatment of choice for traumatic brachial plexus injuries (tBPIs). Combined electromyography (EMG) follow-ups and results obtained by transcranial magnetic stimulation (TMS) may provide useful follow-up of rehabilitation outcomes of elbow flexion in C5-C7 tBPIs. A total of 11 patients with complex tBPIs, operated by the Oberlin surgical technique, were assessed clinically (British Medical Research Council’s score—MRC) and by EMG + TMS after undergoing neuromuscular electrical stimulation and proprioceptive neuromuscular facilitation. Dynamometer quantitative muscle strength (DQMS) was also assessed for overall grip strength evaluation. Six patients continued rehabilitation three times a week, whereas five patients did not follow recommendations for continuous physical therapy (PT). All patients were assessed after 6 months as planned. Following a 6-month PT protocol, clinical improvements correlated with decreases of the Motor Evoked Potential (MEP) latency recorded at the first dorsal interosseous muscle, biceps brachii, and cortical level in the sublot group with continuous PT protocol compliance. We obtained significant amelioration of MEP latency and needle EMG signs of amelioration in these six patients. These cases also correlated to the MRC improvement in elbow flexion, as well as DQMS parameters. TMS parameters also mildly and inconstantly improved in the other five patients who limited themselves just to PT after surgery; however, there was no correlation with the EMG findings or MRC scaling. PT influences the cortical representation within the motor area of the upper limb when performed continuously. The electrical signals within the motor cortex promote the utility adherence to long-term PT protocols.

Communicative intentions automatically hold attention – evidence from event-related potentials

ABSTRACT Numerous studies show that social cues are processed preferentially by the human visual system and that perception of communicative intentions, particularly those self-directed, attracts and biases attention. However, it is still unclear when in the temporal hierarchy of visual processing communicative cues exert impact on perception and whether their effects are automatic or volitional. Therefore, in the present study, we used electroencephalography (EEG) to investigate the pattern of neural activity associated with processing communicative and individual gestures. Participants (N = 24) were shown animations depicting either biological (BM) or scrambled motion (SM) and were asked to categorize them accordingly. Additionally, BM depicted either communicative or individual actions. The results showed that while early components (N1, N2) are sensitive to differences between BM and SM, the differentiation of neural activity related to the type of action performed by point-light agent (individuals vs. communicative) is observed only for late components such as posterior late positive potential (>500 ms). The findings of the current study show that even in the absence of any top-down effects, social intentions produce long-lasting attentional effects at the later stages of stimuli processing.

Contrasting effects of experiencing temporally heterogeneous light availability versus homogenous shading on plant subsequent responses to light conditions

Temporally heterogeneous environments is hypothesized to correlate with greater plasticity of plants, which has rarely been supported by direct evidence. To address this issue, we subjected three species from different ranges of habitats to a first round of alternating full light and heavy shading (temporally heterogeneous light experience), constant moderate shading and full light conditions (temporally homogeneous light experiences, control) and a second round of light-gradient treatments. We measured plant performance in a series of morphological, biomass, physiological and biochemical traits at the end of each round. Compared to constant full light experience, temporally heterogeneous light conditions induced immediate active biochemical responses (in the first round) with improved late growth in biomass (during the second round); constant moderate shading experience increased photosynthetic physiological and biomass performances of plants in early response, and decreased their late growth in biomass. The karst endemic species of Kmeria septentrionalis showed greater improvement in late growth of biomass and lower decrease in biochemical performance, due to early heterogeneous experience, compared to the non-karst species of Lithocarpus glaber and the karst adaptable species of Celtis sinensis. Results suggested plants will prefer to produce morphological and physiological responses that are less reversible and more costly in the face of more reliable environmental cues at early stage in spite of decreased future growth potential, but to produce immediate biochemical responses for higher late growth potential when early environmental cues are less reliable, to avoid the loss of high costs and low profits. Typical karst species should be more able to benefit from early temporally heterogeneous experience, due to long-term adaptation to karst habitats of high environmental heterogeneity and low resource availability.

PO-05-135 SIGNAL-AVERAGED ECG IN THE NORDIC ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY REGISTRY: ASSOCIATION WITH PREVALENT LIFE-THREATENING ARRHYTHMIAS AND ASCERTAINMENT OF CLINICAL DIAGNOSIS.

In arrhythmogenic right ventricular cardiomyopathy (ARVC), minor depolarization criteria by TFC2010 include ventricular late potentials (LP) assessed using signal-averaged ECG (SAECG) and terminal activation duration (TAD). TAD is measured from a standard V1 lead, which favors its use in clinical practice, however its ability to fully replace LP in ARVC workup is not clear. 1. To assess the association between TAD and LP and the prevalence of life-threatening ventricular arrhythmias in patients with ARVC. 2. To assess diagnostic impact of SAECG by characterizing the subgroup of patients, who would not have received definite ARVC diagnosis if LP were not considered. Patients with definite ARVC or genotype-positive family members who underwent SAECG were included (n=358, 47% women, age 41±16 years, 43% probands, 67% definite ARVC). LP and TAD were defined according to TFC2010 criteria. TFC score was calculated by assigning 2 points for major and 1 for minor criterium. Ventricular tachycardia (VT) was defined as sustained VT, aborted cardiac arrest or appropriate ICD shock. Logistic regression adjusted for clinical covariates was used to test association of TAD and LP with prevalent VT. In a subgroup of patients with TFC score 4, i.e. minimally required for diagnosis, patients who would be reclassified into borderline category if LP not considered (LP-dependent, n=38) were compared with those who had TFC score 4 regardless of LP (LP-independent, n=30) in terms of proband status, prevalence of imaging criteria and VT. LP were found in 209 patients (58%); TAD in 65 (18%); 90 patients had prevalent VT (25%). LP was associated with prevalent VT (OR=2.5 95%CI 1.2-5.3; Sensitivity 84%, Specificity 50%) while TAD was not (OR=1.6 95%CI 0.7-3.6; Sensitivity 32%, Specificity 87%). In the LP-dependent group, 9 of 14 (64 %) probands had prevalent VT, 7 (50%) survived cardiac arrest and 4 (29%) were genotype-positive. Clinical characteristics did not demonstrate significant differences between LP-dependent and LP-independent subgroups. LP is independently associated with VT and is more sensitive than TAD in identification of patients with prevalent VT. LP were critical for ascertainment of ARVC diagnosis required for initiation of family screening in 9% probands. Although the diagnostic impact of LP varies depending on SAECG availability, our data support its use as a sensitive non-invasive diagnostic tool.

PO-04-036 PERFORMANCE OF A NOVEL AUTOMATIC LATE POTENTIAL ANNOTATION ALGORITHM IN PATIENTS WITH SCAR-RELATED VENTRICULAR TACHYCARDIA

In patients with scar-related ventricular tachycardia (VT), mapping studies have documented a high prevalence of low amplitude, fragmented, and late potentials (LPs) during sinus or paced rhythm, whose relation to the VT reentry circuit has been extensively demonstrated. In these patients, a rapid and accurate identification of LPs is desirable. We investigated the performance of a novel LPs annotation algorithm in patients with scar-related VT. In 6 patients with scar-related VT (4 ischemic and 2 non-ischemic cardiomyopathy, LVEF 31±17%) high density (median 3,883 points, interquartile range – IQR: 2,177-5,510 points) LV endocardial (n=5) and epicardial (n=1) substrate maps in sinus or RV paced rhythm were created using a 48-electrode array catheter (Optrell, Biosense Webster). The performance of a novel automatic LPs annotation algorithm (LAM, Biosense Webster) that prioritizes annotation of low amplitude LPs within a set window of interest was tested against manually annotated LPs maps, and compared to conventional automatic annotation based on the unipolar/bipolar electrograms utilizing the maximum negative slope (-dV/dT) for local activation time (Wavefront, Biosense Webster). Distinct areas of LPs were identified in all patients and were located in the LV endocardium in 5 and in the RV epicardium in 1 patient. Following manual electrograms annotation, the median surface area subtending LPs was of 16.3 (10-21.3) cm2, corresponding 5.7% (3.5-9.9%) of the total LV/epicardial surface area. Conventional Wavefront annotation correctly identified only 26% (IQR 0% to 21%) of the manually annotated LPs areas due to preferential annotation of large amplitude far-field electrograms. The new LAM algorithm substantially improved identification of LPs compared to Wavefront annotation, correctly identifying 64% (IQR 39% to 78%) of the manually annotated LPs areas (P=0.035 for comparison) (Figure). However, the surface area subtending LPs with LAM was smaller than the area identified with manual annotation in 83% of cases typically due to lack of recognition of very low-amplitude LPs. The novel LAM algorithm significantly improves automatic identification of LPs compared to Wavefront annotation. However, the LPs area identified by LAM is smaller than that detected by manual annotation in the majority of cases.

PO-05-100 DETECTION OF THE CRITICAL SUBSTRATE FOR VENTRICULAR TACHYCARDIA ABLATION WITH THE COMBINED IMAGE OF TC-99M SCINTIGRAM AND LATE IODINE ENHANCEMENT CT

Late potentials (LPs) are the important target for ventricular tachycardia(VT) abltion. However, LPs sometimes cannot be observed sufficiently because of intramural localization of VT substrates. Efficacy of CT for prediction of VT substrates even in intramural layer has been reported. On the other hand, Tc-99m scintigram has been reported to determine the viability of myocardium. The uptake of Tc-99m scintigram could quantify the viability of VT substrates and predict the localization of critical VT substrates such as LPs. Moreover, combination of CT and Tc-99m scintigram could show intramural VT substrates. We evaluated the relationship between the localization of LPs and uptake rate of Tc-99m scintigram. Moreover, we evaluated VT substrates with combined image of scintigram and CT. In eight patients (age, 67.5±8.6 years ; left ventricular(LV) ejection fraction, 26.0±8.7%) with ischemic cardiomyopathy and VT, electroanatomical map (EAM) and Tc-99m scintigrafic image of LV were obtained and were divided into twenty segments. LPs were determined as isolated potentials after QRS and were evaluated in EAM. The relationship between LPs and scintigrafic characteristics was evaluated in total of 160 segments. Electrocardiogram gated CT was performed and late iodine enhancement(LIE) was recorded 8 minutes after administration of contrast media. LPs were recorded in 59 segments. According to the Tc-99m uptake rate, cut off value 35% was set for the prediction of the location of LPs with ROC curve. LPs were observed in the lower scintigram perfusion segments with ≤35% uptake rate (n=61) more than the segments with >35% uptake rate (n=99) with statistical significance (78.6% vs 11.1% p<0.0001). With this cutoff value, we performed another VT ablation with intramural substrate. EAM revealed the exit site of VT circuit from endocardium and the existence of intramural substrate (Fig.A). Low Tc-99m uptake area observed around the apical aneurysm and made the borderline between the basal normal voltage area (Fig.B). LIE showed the transmural damaged tissue on the apical aneurysm and the intramural damaged tissue of mid anterior wall(Fig.C). This border zone of Tc-99m uptake and intramural LIE was similar to the exit site of VT circuit. Long cauterization on this area terminated VT. Lower perfusion area of Tc-99m scintigram could be utilized to predict VT substrates in ICM patients and combination of LIE of CT could add the information of the depth of the VT substrate.

PO-02-228 ASSOCIATION BETWEEN SIGNAL-AVERAGED ECG INDICES AND RV STRUCTURAL ABNORMALITIES IN PATIENTS WITH ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY: INSIGHTS FROM NORDIC ARVC REGISTER

The value of signal-averaged ECG (SAECG) derived ventricular late potentials (LP) as a minor depolarization criterion of arrhythmogenic right ventricular cardiomyopathy (ARVC) has been debated. Another criterion from the same category, terminal activation duration (TAD>55 ms), is obtained from standard V1 ECG lead, which makes it easier for use. However little data exist regarding the relationship between structural right ventricular (RV) ARVC substrate, LP and TAD. We aimed to explore the association between structural and functional RV abnormalities assessed using cardiac magnetic resonance (CMR), SAECG parameters, and abnormal TAD. Patients with definite ARVC diagnosis or genotype-positive family members who were recruited in the Nordic ARVC Registry with SAECG and CMR were included (n=268, mean age 42±16 years, female 46%, probands 49%). RV end-diastolic volume index (RVEDVI), RV ejection fraction (RVEF), and late gadolinium enhancement (LGE) presence were assessed. RV was defined as enlarged if RVEDVI > 100 ml/m2 for men and 90 ml/m2 for women. RVEF was considered reduced if lower than 45%. SAECG components were assessed using TFC2010 definitions: filtered QRS duration (fQRSd)>114 ms, duration of terminal low-amplitude QRS signal below 40 μV (LAS40)> 38 ms and root-mean-square voltage of the terminal 40 ms (RMS40)< 20 μV. An abnormal value of any one or more of these indexes was considered as the presence of LP. We assessed sensitivity and specificity of the SAECG indexes and TAD for association with abnormal RVEF, LGE and/or RVEDVI. C-statistics was used to assess the association between each of SAECG parameters as continuous variables and RV abnormalities. All 3 SAECG indexes were significantly associated with RV structural abnormalities using c-statistics (Table), each of them characterized by higher specificity and lower sensitivity than LP. TAD demonstrated high specificity but poor sensitivity in prediction of RV structural abnormalities. LP had lower specificity, but much higher sensitivity for association with RV structural and functional abnormalities than TAD. In a large cohort of patients with definite ARVC or genotype-positive family members SAECG indexes appear to have lower specificity for detection of structural and functional RV abnormalities compared to TAD, however its sensitivity far exceeds the one of the TAD and supports SAECG value as an ECG indicator of RV substrate.

PO-04-230 IMPROVED VISUALIZATION OF LOW AMPLITUDE LATE POTENTIALS WITH VT SUBSTRATE MAPPING USING A NOVEL EP RECORDING SYSTEM

Accurate identification of low-voltage electrograms (EGMs) suffer from artifacts that often interfere with physiological signals in the <0.1-0.5mV range. For substrate based ablation of ventricular tachycardia (VT), dense scar is defined as regions of myocardium with EGM amplitudes below 0.5 mV. Within these regions, current EP recording systems can fail at identifying low-voltage late potentials that are effective targets of ablation therapy. More recently, new EP amplifiers designed specifically to reduce the impact of interference on the fidelity of signals have been introduced. This study used a novel EP recording system (ECGenius System, CathVision, Copenhagen, DK) to identify low amplitude (<0.5mV) late potentials in regions of scar, and quantify their characteristics in a head-head comparison to a standard recording system (LabSystem Pro, Boston Scientific, MA). We collected recordings in parallel from four patients (30-250 Hz bipolar recording bandwidth) referred to our center for an EP study and ablation for VT. We performed substrate mapping during sinus rhythm with a standard 4mm irrigated ablation catheter (SmartTouch, Biosense Webster, Diamond Bar, CA) and a multi-spline mapping catheter (PentaRay, Biosense Webster). In regions of dense scar (< 0.5 mV, delineated with 3-D electroanatomical mapping) we identified late potentials that were above the baseline noise level of the CathVision system that were otherwise not clearly visible with the LabSystem Pro system. In four patients we identified fourteen sites with late potentials (110 beats) that were only identified with the CathVision System (see figure). The average amplitude of the late signals was 0.079 +/- 0.063 mV, which was above the baseline mean noise of 0.008 mV (range 0.006 to 0.015 mV). In contrast, the baseline mean noise of the LabSystem Pro was 0.060 mV (range 0.040 to 0.090 mV). The mean delay of the late potentials (after the start of the surface ECG QRS) was 377ms (range 198 to 470ms). Improved visualization of low voltage EGMs and late potentials can improve upon substrate-based ablation of ischemic VT. With a novel, and state-of-the art recording amplifier, we demonstrate an improved ability to detect clinically relevant sites for ablation that were not visible with a standard recording system. This technology could improve upon current ablation strategies, and may be particularly useful in the current era of micro-electrodes and relatively smaller recording voltages.

PO-04-054 FIRST REPORTED HUMAN CASE OF ELECTRICAL STORM TREATED WITH THE NEW HIGH-POWER-SHORT-DURATION TACTIFLEXTMABLATION CATHETER.

In the last decade, standard-power-long-duration radiofrequency delivery systems were the standard care to treat ventricular arrhythmias. Recently, high-power-short-duration radiofrequency delivery systems are available and TactiFlexTM Ablation Catheter is the most recent one. we present the first worldwide case of electrical storm catheter ablation using the new TactiFlexTM. N/A A 78 years old female was admitted to the emergency department because of arrhythmic storm. Thirty days earlier she had been hospitalized for acute coronary syndrome. On initial assessment, she appeared soporous, arterial blood pressure was 80/50 mmHg and ECG revealed sustained monomorphic ventricular tachycardia, regular cycle length, left bundle branch morphology, negative concordance in precordial lead. Patient therapy included metoprolol, mexiletine and cordarone; intravenous lidocaine and procainamide were added, with poor results in controlling arrhythmia; then, we decide to perform VT catheter ablation. Left ventricle mapping was performed with TactiFlexTM and AdvisorTM HDGrid Mapping Catether supported by the new EnsiteX V2 electro-anatomical mapping system and Omnipolar Technology. During voltage substrate mapping we found a central necrotic core area surrounded by a low voltage area in the mild-apical posterior-lateral wall. During late potential mapping the same area showed late and multi-fragmented potentials. Clinical tachycardia was easily induced during programmed ventricular pacing. VT activation map was performed and no meso-diastolic potentials or "early meets late" areas were found, probably signifying a possible epicardial regions involvement in the VT circuitry: it was not possible to reconstruct the entire arrhythmia circuit. Activation velocity map was performed and VT slowed in the same regions of low voltage and fragmented potentials. High-power radiofrequency energy (35W-25seconds or 40W-20seconds pulses) was delivered in the mid-basal posterior-septal wall obtaining VT termination. Subsequently, substrate homogenization, which include late and fragmented potentials elimination, was performed. No ventricle arrhythmias were inducible during programmed ventricular pacing. No procedure-related complications occurred. TactiFlexTM appears safe and effective to control left VT. Further reports and studies are needed to evaluate the most appropriate Watts and seconds to perform effective and safe human left ventricle injuries.

PO-02-021 DIRECTION OF REPOLARIZATION IN BASELINE ECG IS PREDICTIVE OF RESPONSE TO CARDIAC RESYNCHRONIZATION THERAPY

Cardiac resynchronization therapy (CRT) is a cornerstone of treatment for advanced heart failure, but not all patients derive equal benefit from this intervention. Current approaches of using electrocardiographic and echocardiographic parameters to identify likely CRT responders demonstrate poor predictive ability. We seek to identify electrocardiographic parameters that can improve prediction of benefit with CRT This was a retrospective analysis of patients who underwent CRT-D placement at University of Pittsburgh Medical Center from 2014-2020. Patients were excluded if pre-implantation EKG or pre- and post-implantation echocardiograms were not available. Each patient’s immediate pre-implantation ECG was processed using the CineECG software (EKG Excellence) to obtain the mean temporospatial isochrone of ventricular activation. 192 features quantifying the activation and recovery pathways were computed for each patient. Response to CRT was defined as an improvement in ejection fraction (EF) of 5% on follow-up transthoracic echocardiogram 3-12 months after CRT implantation. Forward sequential feature selection was used to identify the features of highest importance based on negative logistic loss. 276 patients were included in this analysis (36% female, mean age 69 years, mean pre-procedural EF 27%). The 10 most important CineECG features were identified. When these features were used in a multivariate logistic regression, three features were independently predictive of CRT response: left bundle branch block (LBBB); leftward direction of late repolarization potentials (i.e., Tpeak - Tend rotated toward LV in the horizontal plane); and location of center-of-mass of terminal cardiac activation. Compared to CRT responders (n=169, 62%), non-responders were more likely to have abnormal direction of late repolarization potentials in both LBBB group (-0.34±0.30 vs. -0.45±0.30 vs, p=0.027) and RBBB group (0.25±0.51 vs. 0.61±0.27, p=0.031). In the latter group, direction of later repolarization potentials correlated with magnitude of change in post-procedural EF (r=0.23, p=0.016). Our findings confirm that the presence of LBBB is predictive of response to CRT. In addition, our data suggests that in patients with RBBB, a more leftward direction of late repolarization potentials is independently predictive of CRT response. Further studies into repolarization dynamics as a predictor of CRT response in RBBB are warranted.

PO-05-002 ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY WITH EXTENSIVE ABNORMAL SUBSTRATE: IS ISOLATION POSSIBLE?

In arrhythmogenic right ventricular cardiomyopathy (ARVC) patients with extensive right ventricular free wall (RVFW) abnormal substrate, large area homogenization with combined epicardial and endocardial approach is time consuming and often inadequate for modification. We aim to explore the feasibility and efficacy of RVFW abnormal substrate isolation in such patients to control ventricular tachycardia (VT). Eight consecutive ARVC patients with VT who had extensive abnormal RVFW substrate were included. VT induction was performed before substrate mapping and modification. Detailed voltage mapping was done during sinus rhythm. A circumferential linear lesion was deployed along the border zone of low-voltage-area on the RVFW to achieve electrical isolation. Other small areas with fractionated or late potentials were further homogenized. All eight patients had extensive RV endocardial low-voltage-area (113.8 ± 84.1 cm2, 49.6 ± 29.8%) and dense scar (59.6 ± 39.8 cm2, 25.0 ± 14.1%). Electrical isolation of abnormal substrate was achieved in 5/8 (62.5%) patients via endocardial approach alone and 3/8 (37.5%) patients via a combination of endocardial and epicardial approach. Electrical isolation was verified by slow automaticity (5/8, 62.5%) or RV non-capture (3/8, 37.5%) during high output pacing inside the encircled area. VTs were induced in 6 patients before ablation and all patients rendered non-inducible after ablation. During a median follow-up of 43 months (range 24-53), 7/8 (87. 5%) patients remained free of sustained VT. Electrical isolation of RVFW is feasible and effective in ARVC patients with extensive abnormal substrate and is associated with excellent long-term rhythm control.

EN-452414-1 IMPACT OF MULTI-DIRECTIONAL PACING ON LATE SIGNAL ACTIVATION, ACTIVATION SLOWING AND REPOLARIZATION GRADIENTS TO LOCALIZE RE-ENTRANT VENTRICULAR TACHYCARDIA CIRCUITS IN A PORCINE INFARCT MODEL.

Optimal signal parameters and substrate mapping strategies for identifying key arrhythmogenic sites in ventricular tachycardia (VT) ablation are not established. To evaluate multi-directional pacing on the distribution of late signal activation, activation slowing and repolarization gradients in relation to critical sites of re-entrant VT, in a porcine infarct model. Electrophysiology studies were performed 4 weeks post-infarction in 13 pigs using the EnSite Precision system (Abbott, IL, USA), and the Advisor HD Grid (Abbott) multi-electrode catheter. Substrate maps were created during right ventricular (RV), left ventricular (LV), and biventricular pacing (BIV), and sinus rhythm (SR). Sites of early, mid-, and late-diastolic signals of induced VT’s were delineated. Off-line analysis compared these critical VT sites to algorithmically identified 20 most vulnerable sites of latest activation timing within and post-QRS, and the largest activation (GradAT) and activation recovery interval gradients (GradARI). 34 VTs were mapped with at least one diastolic recorded component, with a mean tachycardia cycle length of 236.5 ± 32.4 ms. 48 sinus rhythm and pacing maps were obtained, 10 using BIV pacing (mean points 375 ± 263), 13 using LV pacing (mean points 610 ± 334), 13 from RV pacing (mean points 603 ± 263) and 12 in sinus rhythm (mean points 1078 ± 654). Late potential (LP) mapping in sinus rhythm was taken as the established clinical standard for statistical comparison with all other protocols, displayed in Figure 1. GradARI using RV pacing provided the closest localization for VT exit and entrance, with a median distance of 10.6mm (IQR 5.0mm, p <0.05) and median 9.4mm (IQR 8.0mm, p <0.05) compared to LP in sinus rhythm, respectively. LAT with BIV pacing provided closest VT isthmus localization for VT isthmus, with a median of 5.5mm (IQR 7.15mm, p <0.05) compared to LP in sinus rhythm (Figure 1). A global sensitivity and specificity analysis was performed on all points. GradARI mapping in SR reported the highest AUC (area – under curve) for early diastolic VT signals (AUC 0.96, sensitivity 93%, specificity 91%), mid-diastolic signals (AUC 0.92, sensitivity 84%, specificity 88%) and late diastolic signals (AUC 0.92, sensitivity 88%, specificity 84%). Sites with the largest ARI gradients in sinus rhythm best predict critical sites of VT in this model, with the most effective protocol being RV pacing examining ARI gradients.

PO-04-137 SCAR TRANSMURALITY IN VENTRICULAR ENDOCARDIAL UNIPOLAR ELECTROGRAMS IS RELATED TO POWER OF PATIENT-SPECIFIC FREQUENCY BANDS

Characteristic endocardial electrogram (EGM) features such as fractionation and late potentials have been associated with ventricular tachycardia (VT) substrate. Our prior analyses show that EGM frequency content allows for more accurate identification of mid-myocardial fibrosis within a given patient, compared to traditional bipolar or unipolar voltage thresholds. A relationship between frequency information and endocardial scar transmurality has not been described. To explore the relationship of frequency spectra to ventricular scar transmurality in patients undergoing VT catheter ablation. Thirteen patients with non-ischemic cardiomyopathy (NICM) undergoing VT ablation with pre-procedural tissue characterization using cardiac computed tomography (CCT) imaging with late-iodine enhancement were assessed. From the CCT data, scar transmurality was calculated for every EGM recording location. With multitaper spectral estimation, average normalized frequency content was calculated for regions with different levels of scar transmurality and compared to average frequency content from tissue locations with no scar. K-nearest neighbors classifiers were trained within patients to predict scar transmurality, assuming presence of scar is known. Frequency content of regions without scar is similar among patients. A comparison of the average normalized frequency spectra of the non-fibrotic endocardial tissue for each patient is presented. Differences in scar transmurality led to changes in strength of certain frequency bands, which varied between patients. Observed responses included a peak at 10-15 Hz whose magnitude increased with scar transmurality (panel B) and a peak at 35-40 Hz in regions with higher scar transmurality. Normalized frequency content predicted transmural scar above chance with at least p < .05 for all 13 patients. Frequency content of endocardial unipolar EGMs is related to scar transmurality in those regions. This relationship changes patient to patient, potentially due to differences in morphology of fibrotic tissue. Deviation from the consistent spectra seen in non-fibrotic tissue may be a strategy to identify fibrosis and these insights can inform development of physiological models of VT. Because of low EGM sample sizes in higher scar transmurality regions, more data should be collected to further support this claim.

Active inhibition of the retro-cue effect in visual working memory: Evidence from event-related potential.

This study used the event-related potential (ERP) technique to investigate whether active inhibition exists in retro-cue Effect (RCE) in visual working memory using modified retro-cue tasks. In this modified task, the participants were first asked to memorize six color blocks and then presented with directed remembering or directed forgetting cues; finally, their working memory performance was tested. For behavioral results, due to the extension of the memory interval, this study did not find RCE in accuracy but reflected it in the total reaction time. For ERP results, the frontal late positive potential (LPP) followed by the directed forgetting condition was larger than that followed by directed remembering and baseline conditions, and there was no significant difference between directed remembering and baseline conditions. There was no significant difference in parietal P3 followed by both the directed remembering and directed forgetting conditions, which were significantly larger than the baseline condition. This result reveals that active inhibition plays an important role in directed forgetting RCE. There was a correlation between parietal P3 and frontal LPP with the same time window but different scalp regions in the directed forgetting condition, indicating a potential relationship between active inhibition and retelling in directed forgetting RCE.

Behavioral and ERP indices of self-schematic processing show differential associations with emerging symptoms of depression and social anxiety in late childhood: Evidence from a community-dwelling sample

Symptoms of depression and social anxiety elevate in late childhood. An identified cognitive risk to both depression and social anxiety is maladaptive self-schemas (or self-schematic processing). Beyond the behavioral indices of this construct, event-related potentials (ERPs) during self-schematic processing have also been observed to be associated with depression or depressive symptoms. However, no study has examined the ERPs underlying self-schematic processing in relation to social anxiety. More importantly, it was unclear to what extent behavioral and ERP indices of self-schematic processing were differentially associated with depression and social anxiety, especially in typical-risk youth with emerging symptoms. A hundred and fifteen community-dwelling children (66 girls; Mean age=10.91 years, SD=1.45) completed a self-referent encoding task (SRET) with EEG recorded. A Principal Component Analysis identified a late positive potential (LPP) component elicited in both the positive and negative SRET conditions. Multivariate multiple regression showed that in both conditions, behavioral SRET scores were associated with depressive symptoms while partialling out social anxiety symptoms, but not with social anxiety symptoms with depressive symptoms partialled out. The LPP amplitude elicited in both conditions showed marginally positive associations with social anxiety symptoms while partialling out depressive symptoms, but not with depressive symptoms while accounting for social anxiety. This study provides novel evidence concerning the ERP correlates of self-schematic processing in relation to social anxiety symptoms. More importantly, our findings for the first time speak to the differential associations between the behavioral SRET scores and SRET-elicited LPP and emerging symptoms of depression and social anxiety in late childhood.

Central alpha-2 adrenergic mechanisms affect human sympathetic neuronal discharge strategies

The central neural mechanisms affecting sympathetic neuronal discharge strategies supporting homeostatic adjustments in human muscle sympathetic nerve activity (MSNA) remain unclear. This study investigated the hypothesis that central alpha-2 adrenergic mechanisms affect sympathetic action potential (AP) discharge, recruitment, and latency patterns within human MSNA (peroneal nerve microneurography and continuous wavelet transform). An alpha-2 adrenergic agonist (dexmedetomidine) was infused in eight healthy male and female participants (5 females; 28 ± 7years). Data were recorded during a 5-minute resting control condition, a 10-minute intravenous dexmedetomidine loading dose (0.225 μg/kg), and a dexmedetomidine maintenance dose (~0.1 μg/kg/hr). Data are reported as mean (SD) for the 5-minute control condition and 2-minutes of the dexmedetomidine infusion when MSNA bursting activity was demonstrably reduced. Two-tailed paired t-tests were performed. Dexmedetomidine reduced mean pressure (92 ± 7 to 80 ± 8 mmHg; P &lt; 0.01) but did not affect heart rate (61 ± 13 to 60 ± 14 bpm; P = 0.75). Dexmedetomidine reduced integrated MSNA burst frequency (14 ± 6 to 4 ± 3 bursts/min; P &lt; 0.01), sympathetic AP frequency (75 ± 46 to 16 ± 14 AP/min; P &lt; 0.01), APs per burst (5 ± 1 to 4 ± 1 AP/burst; P = 0.01), AP clusters per burst (3.5 ± 0.7 to 3.0 ± 0.7 clusters/burst; P = 0.03), and de-recruited the largest AP clusters (12 ± 3 to 7 ± 2 AP clusters; P &lt; 0.01). Despite de-recruiting large AP clusters with short conduction times, dexmedetomidine elicited shorter sympathetic AP conduction times (1.18 ± 0.12 to 1.14 ± 0.13 s; P = 0.03). Six participants performed a Valsalva Maneuver (20 s, 40 mmHg mouth pressure) during the control condition and during the dexmedetomidine maintenance dose. Data are reported as mean (SD) change (Δ) from the 2-minute period preceding the Valsalva Maneuver to the Valsalva Maneuver for each condition. During the control condition, Valsalva Maneuver increased AP frequency (Δ 311 ± 317 AP/min; P = 0.048), recruited larger previously silent AP clusters (Δ 2 ± 1 AP clusters; P &lt; 0.01), and elicited shorter AP conduction times (Δ ‑0.09 ± 0.07 s; P = 0.02). Compared to the control condition, Valsalva Maneuver performed during the dexmedetomidine maintenance dose condition elicited lesser increases in AP frequency (Δ 116 ± 189 AP/min; P vs. control = 0.02) and lesser recruitment of larger previously silent AP clusters (Δ 0 ± 1 AP clusters; P vs. control = 0.02). Dexmedetomidine did not affect the latency reduction elicited by Valsalva Maneuver (Δ ‑0.07 ± 0.14 s; P vs. control = 0.61). These data suggest that human central alpha-2 adrenergic mechanisms affect: i) sympathetic postganglionic neuronal discharge and recruitment patterns, and ii) synaptic delays within the sympathetic neurocircuitry influencing AP latency. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the National Institutes of Health (NIH). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Diagnosis and Treatment of Cauda Equina Arachnoiditis, a Rare Manifestation of Tuberculosis Meningoencephalitis: A Case Report

Tuberculous meningoencephalitis (TM) is an acute, progressive form of tuberculosis (TB). The epidemiology, clinical signs, and diagnosis of TB are well established, but several atypical forms of tuberculous spinal arachnoiditis can be easily misdiagnosed. We report a rare case of TM with cauda equina arachnoiditis diagnosed by magnetic resonance imaging and an electrodiagnostic study. A 26-year-old otherwise healthy male patient experienced fever, headache, gait disturbance, and bladder and bowel incontinence. Needle electromyography (EMG) recordings were suggestive of bilateral diffuse lumbar and lumbosacral polyradiculopathy, and the pudendal sensory-evoked potential and bulbocavernosus reflex latencies were prolonged. Lumbar arachnoiditis is a rare clinical condition that warrants a heightened index of suspicion. It has diverse etiologies and symptoms, and it can lead to potentially serious and irreversible disorders. This case illustrates the usefulness of nerve conduction, EMG, and pudendal sensory-evoked potential and bulbocavernosus reflex latency studies in the diagnosis of cauda equina syndrome induced by TB arachnoiditis.

Effects of the self-perceived sensorimotor demand and immersion during video gaming on visual-attention skills.

Playing specific genres of video games (e.g., action video games) has been linked to improvements in cognitive skills mostly related to attentional phenomena. Nonetheless, do video games have features or dimensions in common that impact cognitive improvements beyond the game genre? Here, we argue that the sensorimotor demand-the amount of demand for precise coordination between movement and perception-is a key element in the improvements associated with playing video games. We conducted a two-part study to test this hypothesis: a self-report online gaming instrument development and validation and an in-lab behavioural and electrophysiological study. In the first study, data from 209 participants were used to devise the sensorimotor demand instrument (SMDI). The SMDI was split into three dimensions of video game playing: sensorimotor contingency, immersion and unfocused gaming. Criterion validity related to video gamers' characteristics supported that the SMDI is sensitive to the input device (e.g., keyboard or touchscreens), and the most recent experience gained during gaming sessions while not being sensitive to the game genre. In the second study, data from 20 participants who performed four visual-attentional tasks previously reported in the literature showed that the SMDI's dimensions were associated with behavioural performance measures and the latency and amplitude of event-related potentials (N1, P2 and P3). Despite the challenge of studying the video gamer population, our study remarks on the relevance of sensorimotor demands in the performance of attentional tasks and its potential use as a dimension to characterize the experience of playing video games beyond the game genre.

Correlation between Elbow Flexor Muscle Strength and Needle Electromyography Parameters after Musculocutaneous Nerve Injury.

To explore the changes of elbow flexor muscle strength after musculocutaneous nerve injury and its correlation with needle electromyography (nEMG) parameters. Thirty cases of elbow flexor weakness caused by unilateral brachial plexus injury (involving musculocutaneous nerve) were collected. The elbow flexor muscle strength was evaluated by manual muscle test (MMT) based on Lovett Scale. All subjects were divided into Group A (grade 1 and grade 2, 16 cases) and Group B (grade 3 and grade 4, 14 cases) according to their elbow flexor muscle strength of injured side. The biceps brachii of the injured side and the healthy side were examined by nEMG. The latency and amplitude of the compound muscle action potential (CMAP) were recorded. The type of recruitment response, the mean number of turns and the mean amplitude of recruitment potential were recorded when the subjects performed maximal voluntary contraction. The quantitative elbow flexor muscle strength was measured by portable microFET 2 Manual Muscle Tester. The percentage of residual elbow flexor muscle strength (the ratio of quantitative muscle strength of the injured side to the healthy side) was calculated. The differences of nEMG parameters, quantitative muscle strength and residual elbow flexor muscle strength between the two groups and between the injured side and the healthy side were compared. The correlation between elbow flexor manual muscle strength classification, quantitative muscle strength and nEMG parameters was analyzed. After musculocutaneous nerve injury, the percentage of residual elbow flexor muscle strength in Group B was 23.43% and that in Group A was 4.13%. Elbow flexor manual muscle strength classification was significantly correlated with the type of recruitment response, and the correlation coefficient was 0.886 (P<0.05). The quantitative elbow flexor muscle strength was correlated with the latency and amplitude of CMAP, the mean number of turns and the mean amplitude of recruitment potential, and the correlation coefficients were -0.528, 0.588, 0.465 and 0.426 (P<0.05), respectively. The percentage of residual elbow flexor muscle strength can be used as the basis of muscle strength classification, and the comprehensive application of nEMG parameters can be used to infer quantitative elbow flexor muscle strength.

Botulinum Toxin-A Treatment of Post-Stroke Spasticity Is Associated with Changes in Interhemispheric Parietal Cortex Connectivity (P12-8.001)

<h3>Objective:</h3> To assess resting-state functional connectivity (rsFC) of the ipsilesional superior parietal lobule (SPL) and intraparietal sulcus (IPS) using functional magnetic resonance imaging (fMRI) in chronic stroke patients with hemiparesis both with and without post-stroke spasticity (PSS) and to explore the relationship between SPL/IPS resting-state functional connectivity (rsFC) and PSS severity. <h3>Background:</h3> Posts-stroke spasticity hampers effective rehabilitation of the paretic arm and lowers the quality of life. Effective PSS treatment with botulinum neurotoxin (BoNT) is associated with transient decrease in task-related fMRI activation of the ipsilesional SPL and IPS. We hypothesized that this would be reflected in changes in rsFC of the SPL/IPS. <h3>Design/Methods:</h3> Fourteen chronic stroke patients with upper limb weakness and PSS (the PSS group) and 8 patients with comparable weakness but no PSS (the control group) underwent clinical and spasticity evaluation and 3 fMRI examinations, at baseline (W0) and 4 and 11 weeks after BoNT (W4 and W11, respectively). Seed-based rsFC of the atlas-based SPL and IPS was evaluated using a group×time interaction analysis and the change in rsFC of SPL/IPS was correlated with change in PSS (modified Ashworth scale), integrity of the ipsilesional somatosensory afferent pathway (evoked potential N20 latency), and age. <h3>Results:</h3> In the PSS group, transient improvement in PSS was associated with increase in rsFC between the ipsilesional IPS and the contralesional SPL at W4. The interhemispheric connectivity was negatively correlated with PSS severity at baseline and with PSS improvement at W4. These changes in the posterior parietal interhemispheric rsFC suggest that previously observed task-related changes in SPL/IPS were independent of actual task performance. <h3>Conclusions:</h3> We propose adaptation of the internal forward model as the possible underlying mechanism and discuss its potential association with increased limb use or improved motor performance, as well as its potential contribution to the clinical effects of BoNT. <b>Disclosure:</b> The institution of Prof. Hlustik has received research support from Czech Health Research Council (AZV CR). Dr. Hok has nothing to disclose. Tomas Veverka has nothing to disclose. Markéta Trnecková has nothing to disclose. Pavel Otruba has nothing to disclose. Jana Zapletalova has nothing to disclose. Zbynek Tudos has nothing to disclose. Prof. Lotze has received publishing royalties from a publication relating to health care. Dr. Kanovsky has nothing to disclose.