Local Electrical Activity Research Articles

Fractal Neurodynamics.

The neuronal ongoing electrical activity in the brain network, the neurodynamics, reflects the structure and functionality of generating neuronal pools. The activity of neurons due to their excitatory and inhibitory projections is associated with specific brain functions. Here, the purpose was to investigate if the local ongoing electrical activity exhibits its characteristic spectral and fractal features in wakefulness and sleep across and within subjects. Moreover, we aimed to show that measures typical of complex systems catch physiological features missed by linear spectral analyses. For this study, we concentrated on the evaluation of the power spectral density (PSD) and Higuchi fractal dimension (HFD) measures. Relevant clinical impact of the specific features of neurodynamics identification stands primarily in the potential of classifying cortical parcels according to their neurodynamics as well as enhancing the effectiveness of neuromodulation interventions to cure symptoms secondary to neuronal activity unbalances.

The coupling between the spatial and temporal scales of neural processes revealed by a joint time-vertex connectome spectral analysis

Brain oscillations are produced by the coordinated activity of large groups of neurons and different rhythms are thought to reflect different modes of information processing. These modes, in turn, are known to occur at different spatial scales. Nevertheless, how these rhythms support different spatial modes of information processing at the brain scale is not yet fully understood. Here we use "Joint Time-Vertex Spectral Analysis" to characterize the joint spectral content of brain activity both in time (temporal frequencies) and in space over the connectivity graph (spatial connectome harmonics). This method allows us to characterize the relationship between spatially localized or distributed neural processes on one side and their respective temporal frequency bands in source-reconstructed M/EEG signals. We explore this approach on two different datasets, an auditory steady-state response (ASSR) and a visual grating task. Our results suggest that different information processing mechanisms are carried out at different frequency bands: while spatially distributed activity (which may also be interpreted as integration) specifically occurs at low temporal frequencies (alpha and theta) and low graph spatial frequencies, localized electrical activity (i.e., segregation) is observed at high temporal frequencies (high and low gamma) over restricted high spatial graph frequencies. Crucially, the estimated contribution of the distributed and localized neural activity predicts performance in a behavioral task, demonstrating the neurophysiological relevance of the joint time-vertex spectral representation.

BurstDR spinal cord stimulation rebalances pain input and pain suppression in the brain in chronic neuropathic pain

ObjectiveChronic pain is processed by at least three well-known pathways, two pain provoking pathways including a medial ‘suffering’ and lateral ‘painfulness’ pathway. A third descending pain pathway modulates pain but is predominantly inhibitory. Chronic pain can be seen as an imbalance between the two pain-provoking and the pain inhibitory pathways. If this assumption is correct, then the imbalance between pain input and pain suppression should reverse and normalize in response to successful, i.e., pain reducing burstDR spinal cord stimulation, one of the current treatment options for neuropathic pain. Materials and methodsFifteen patients, who received spinal cord stimulation for failed back surgery were included in this study, using source localized electrical brain activity and connectivity recording via EEG to identify the purported imbalance. ResultsBurstDR spinal cord stimulation induces a significant change in EEG activity in both the left and right somatosensory cortex (SSC) for both θ and γ oscillations. In the dorsal anterior cingulate cortex (dACC), we observed a significant drop in both α and β oscillations. This reduction is accompanied by a change in pain intensity and suffering. BurstDR spinal cord stimulation is also associated with a reduction in θ at the pregenual anterior cingulate cortex (pgACC). Analyzing effective connectivity indicates that for the θ band, more information is sent from the pgACC to the left and right SSC. For α, increased information is sent from the pgACC to the dACC and both the left and right SSC. This is associated with a reduced θ-γ coupling in the SSC and reduced α-β coupling in dACC. ConclusionThis study suggests that chronic pain is indeed an imbalance between the ascending and descending pathways in the brain and that burst spinal cord stimulation can normalize this imbalance in the brain.

Dynamics of local unipolar electrograms during epicardial pulsed field ablation (PFA)

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Instituto de Salud Carlos III Background The use of irreversible electroporation (IRE) as a method for cardiac ablation in the treatment of cardiac arrhythmias, known as Pulsed Field Ablation (PFA), has rapidly moved from preclinical studies to clinic. The reference indicator of acute lesion formation during cardiac ablation with thermal techniques consists in recording the local electrical activity changes. In the case of PFA, modifications in the electrical activity have been observed in areas that are not permanently damaged (reversible electroporation) but this is still poorly characterized. Of particular interest from a clinical perspective is to determine how and when the electrical activity of the reversible electroporation areas recovers after PFA. Purpose The purpose of this work was to simultaneously characterize the dynamic evolution of local electrograms after PFA in areas exposed to different levels of tissue damage. Methods High-density local unipolar electrograms were acquired at baseline, and continuously and during 60 min after each PFA application. The measurements were performed in different points of the right and left ventricular epicardial surface of 5 swine weighing 57±8 kg using an open-chest approach following the Principles of laboratory animal care" (NIH Publication no. 85-23 revised 1985). Under general anesthesia, a median sternotomy was made to create a surgical window. Unipolar electrograms were recorded using a 128-channel electrode matrix attached to the epicardial surface. For PFA ablation, a standard 8F, 3.5 mm tip monopolar catheter was positioned in the region corresponding to the center of the electrode array and a return electrode patch was attached to the back of the animals (see Fig. 1). At least 3 hours after the last ablation point, animals were euthanized and tissue was processed and stained with Triphenyltetrazolium Chloride (TTC) to assess acute lesion morphology. Results Our results show an immediate change in the morphology of unipolar electrograms: from basal biphasic electrograms to monophasic electrograms displaying a sudden ST-segment elevation (from 0.0±0.3 mV to 5.9±1.7mv; p<0.01), reduction in the R-S amplitude (from 3.4±3.3 mV to 0.3±0.2 mV; p<0.01) and reduction in the maximum derivative of the QRS-complex (from 3051±2473 mV/s to 394±242 mV/s; p<0.01). Interestingly, the extent and dynamics of the observed changes clearly depended on the ablation level (distance from the ablation point) (see Fig 2.). Conclusions Our observations confirmed that the electrical activity of the reversible electroporation area was also acutely modified while the recovery dynamics were different from the irreversible damaged areas. Our preliminary analysis suggests that the different recovery dynamics observed could help in differentiating between reversible and irreversible electroporation areas.

Does targeted positioning of the left ventricular pacing lead towards the latest local electrical activation in cardiac resynchronization therapy reduce the incidence of death or hospitalization for heart failure?

Cardiac resynchronization therapy (CRT) improves symptoms, health-related quality of life and long-term survival in patients with systolic heart failure (HF) and shortens QRS duration. However, up to one third of patients attain no measurable clinical benefit from CRT. An important determinant of clinical response is optimal choice in left ventricular (LV) pacing site. Observational data have shown that achieving an LV lead position at a site of late electrical activation is associated with better clinical and echocardiographic outcomes compared to standard placement, but mapping-guided LV lead placement towards the site of latest electrical activation has never been investigated in a randomized controlled trial (RCT). The purpose of this study was to evaluate the effect of targeted positioning of the LV lead towards the latest electrically activated area. We hypothesize that this strategy is superior to standard LV lead placement. The DANISH-CRT trial is a national, double-blinded RCT (ClinicalTrials.gov NCT03280862). A total of 1,000 patients referred for a de novo CRT implantation or an upgrade to CRT from right ventricular pacing will be randomized 1:1 to receive conventional LV lead positioning preferably in a nonapical posterolateral branch of the coronary sinus (CS) (control group) or targeted positioning of the LV lead to the CS branch with the latest local electrical LV activation (intervention group). In the intervention group, late activation will be determined using electrical mapping of the CS. The primary endpoint is a composite of death and nonplanned HF hospitalization. Patients are followed for a minimum of 2 years and until 264 primary endpoints occurred. Analyses will be conducted according to the intention-to-treat principle. Enrollment for this trial began in March 2018, and per April 2023, a total of 823 patients have been included. Enrollment is expected to be complete by mid-2024. The DANISH-CRT trial will clarify whether mapping-guided positioning of the LV lead according to the latest local electrical activation in the CS is beneficial for patients in terms of reducing the composite endpoint of death or nonplanned hospitalization for heart failure. Results from this trial are expected to impact future guidelines on CRT. NCT03280862.

Right ventricular cardiac resynchronization therapy in patients with right ventricular conduction delay and heart failure

Right ventricular cardiac resynchronization therapy in patients with right ventricular conduction delay and heart failure

Effect of Acupoint Therapies on Postoperative Sleep Quality: A Narrative Review.

Several studies have reported that sleep quality often decreases in patients after surgery, especially in elderly patients, which seriously affects postoperative prognosis and outcomes, inducing diseases such as postoperative delirium, long-term chronic pain, and potentially fatal cardiovascular events. With the popularization of comfortable medicine, medical workers pay more attention to the postoperative sleep quality of patients. The causes underlying the decrease in postoperative sleep quality may include postoperative pain, the severity of surgical trauma and stress, perioperative anxiety and depression, and postoperative complications. Patients with insomnia often use acupoint therapies as a safe and effective alternative to drugs. Acupoint therapies are among the oldest medical therapies of Traditional Chinese Medicine and are gradually gaining recognition among medical workers worldwide. Various types of acupoint stimulation methods such as transcutaneous electrical acupoint simulation (TEAS), acupressure, acupuncture, and electroacupuncture can change the brain's local electrical activity, inhibit the central nervous system, and achieve deep sedation through stimulating the related acupoints, which provides a novel idea and basis for improvement in factors affecting postoperative sleep quality. This review explores the mechanism of acupoint therapies from several aspects of affecting the sleep quality of patients after surgery and its clinical results. We found that acupoint therapies effectively improve sleep quality and alleviate the postoperative complications of patients, and we emphasize the importance of acupoint therapies to guide future research and clinical practice. Large-scale, multicenter studies are needed to determine the optimal duration, frequency, and timing of acupoint stimulation for improving postoperative sleep quality.

376 CARDIAC CONTRACTILITY MODULATION: A NEW THERAPY FOR HEART FAILURE

Abstract Introduction Cardiac Contractility Modulation is a therapy for chronic Heart Failure patients with EF 25-45% in sinus rhythm with QRS < 130 ms clinically symptomatic (NYHA Class > II) despite optimised medical therapy. It is made possible by the implantation of the OPTIMIZER SMART® device. The CCM works by delivering a non-excitatory high-energy bipolar signal, synchronised with local electrical activity (or cooperating with another pre-existing CIED), in the absolute ventricular refractory period, by means of two actively fixating leads, positioned in the interventricular septum and spaced at least 1-2 cm apart. Purpose Assessment and feedback of the CCM therapy process in patients with dilated cardiomyopathy. Educational update for health professionals. Patient education. Method A Pubmed search correlated with clinical data and field experience was performed. Results Patients with severe Dilated Cardiomyopathy already on optimised medical therapy. The mechanism of action demonstrated a remodelling of the left ventricle with a so-called 'metabolic' therapy. In CCM therapy, electrical stimulation is delivered to the heart muscle during the absolute refractory period. In this phase, electrical signals activate the mobilisation of calcium ions in cardiomyocytes. CCM signals applied during the absolute refractory period cause an increase in cytosolic calcium during systole, resulting in improved cardiac contraction without an increase in oxygen consumption. Conclusions CCM therapy has shown to improve contractility and cardiac performance improving the quality of life of patients undergoing this treatment by reducing symptoms of fatigue and dyspnoea; it has reduced the number of hospitalisations for moderate to severe heart failure. Healthcare professionals recognise The typical ECG of a patient implanted with a CCM device shows a 'spike' in the absolute refractory period of the cardiac cycle: the 'R wave' of the QRS complex without being alarmed. The patient has been trained to be autonomous in charging. OPTIMIZER SMART® is recharged externally with a weekly rechargeable battery through a mini induction charger, rechargeable by itself.

Evaluation of left ventricular dyssynchrony by ultra-high-frequency ECG in patients with non-LBBB conduction disorder treated with cardiac resynchronization therapy

Abstract Funding Acknowledgements Type of funding sources: None. Introduction LBBB is a reliable left ventricular (LV) electrical dyssynchrony indicator. Patients with RBBB/IVCD are a heterogeneous group, where even with "larger" QRS complex expansion, LV dyssynchrony may not be present. Ultra-high-frequency (UHF) 14-lead ECG is a non-invasive method based on signal averaging that allows better assessment of local electrical activation of the ventricles than standard ECG. Our study aims to test the hypothesis of the usefulness of UHF ECG to select non-LBBB patients for cardiac resynchronization therapy (CRT) based on evidence of electrical dyssynchrony. Methods Using UHF ECG we analysed patients who underwent CRT implantation. The groups of patients with RBBB, IVCD, and LBBB were compared and the presence of electrical dyssynchrony (e-DYS) as a parameter of global ventricular activation, and delayed activation of the left ventricular lateral wall (LVLWd) as a marker of LV intravenricular dyssynchrony was assessed. Results UHF ECG was recorded in 49 patients treated with CRT. IVCD patients had lower e-DYS compared to LBBB patients (26±17 ms vs. 86±20 ms; p<0.0001) and lower LVLWd (26±16 ms vs. 83±22 ms; p<0.0001). In RBBB patients, e-DYS was -52±22 ms, corresponding to right ventricular delay. Delayed left ventricular free wall activation ("RBBB masking LBBB" activation pattern) was not found in any RBBB patient. Conclusion UHF ECG appears to be a promising tool to detect LV electrical dyssynchrony in non-LBBB candidates for cardiac resynchronization therapy. Delayed left ventricular free wall activation was not found in any RBBB patient. Our findings are consistent with the lack of effect of CRT in this group of patients.

Electrophysiological predictors of ventricular tachycardia recurrence in patients with structural heart disease after combined endo-epicardial substrate catheter ablation

Abstract Background Although there is a tremendous improvement in mapping and ablation techniques over the last decades, the recurrence rate of ventricular tachycardia (VT) in patients with structural heart diseases following endo-epicardial catheter ablation remains high. Purpose To determine predictors of VT recurrence in patients with structural heart disease after combined endo-epicardial radiofrequency (RF) VT ablation. Methods This prospective single-center study included 39 patients (34 men and 5 women, mean age 49.6±16.0 years), who underwent endo-epicardial mapping and ablation of the VT substrate. Etiology of structural heart diseases included: previous myocardial infarction (n=15); non-ischemic cardiomyopathy (n=24: 15 – arrhythmogenic right ventricular cardiomyopathy (ARVC), 6 – myocarditis, 3 – unspecified). First-line epicardial access was performed in 16 patients, as a second approach – in 23 subjects. We evaluated total ventricular myocardial areas, epi- and endocardial areas with bipolar low voltage (<1.5mV), scar area (bipolar <0.5mV), and unipolar low voltage (<5.0mV) and transient (<8.0mV) areas; areas of late potential registration were evaluated. Ratios of transient, low amplite and late-potential areas were calculated for endo- and epicardial surfaces, bipolar and unipolar maps. The following procedural electrophysiology characteristics were considered: inducibility of clinical VT, the number and morphology of induced VT, QRS width on sinus rhythm and VT, tachycardia cycle length, pseudo-delta wave extant and width, internal activation time, intrisicoud deflection time, and RS length. Clinical data such as echocardiography parameters, comorbidity and antiarrhythmic drug therapy were also taken into account. VT recurrences were documented using ICD/CRT-D interrogation, event ECG monitoring. Follow-up included mandatory visits at 6 and 12 months and unscheduled visits. Results Epicardial late potentials were registered in 69% of cases before ablation. Epicardial RF applications were delivered in 67% of patients; while only endocardial RF applications (including cases with intended epicardial substrate modification by endocardial ablation) were present in 28% cases. Non-inducibility of any VT plus abatement of local abnormal electrical activity was achieved in 32 (82%) of cases. The ratio epi/endo bipolar areas <0.5mV was much higher in patients with vs without VT recurrence at 6 months (4.3 (IQR: 2.5; 8.2) vs 0.75 (IQR:0.4; 1.6), P=0.001). A strong negative correlation was found between the induced VT cycle length and the ratio epi/endo bipolar areas <0.5mV: the shorter induced VT cycle length -the larger the area of the epicardial low voltage area (r=−0,52). Conclusion Regardless of epicardial substrate modification, patients with a larger epicardial low voltage area are more likely to have VT recurrence at 6 months after index ablation. A shorter induced VT cycle length is associated with a larger epicardial low-voltage area. Funding Acknowledgement Type of funding sources: None.

Separating atrial near fields and atrial far fields in simulated intra-atrial electrograms

Abstract The detailed characterization of complex forms of atrial flutter relies on the correct interpretation of intra-atrial electrograms. For this, the near field components, which represent the local electrical activity, are decisive. However, far field components arising from distant electrical sources in the atria can obscure the diagnosis. We developed a method to separate and characterize atrial near field and atrial far field components from bipolar intra-atrial electrograms. First, a set of bipolar electrograms was created by simulating different propagation scenarios representing common clinical depolarization patterns. Second, near and far fields were detected as active segments using a non-linear energy operator-based approach. Third, the maximum slope and the spectral power were extracted as features for all active segments. Active segments were grouped accounting for both the timing and the location of their occurrence. In a last step, the active segments were classified in near and far fields by comparing their feature values to a threshold. All active segments were detected correctly. On average, near fields showed 15.1x larger maximum slopes and 40.4x larger spectral powers above 100 Hz than far fields. For 135 active segments detected in 72 bipolar electrograms, 5.2% and 6.7% were misclassified using the maximum slope and the spectral power, respectively. All active segments were classified correctly if only one near field segment was assumed to occur per electrogram. The separation of atrial near and atrial far fields was successfully developed and applied to in silico electrograms. These investigations provide a promising basis for a future clinical study to ultimately facilitate the precise clinical diagnosis of atrial flutter.

Recording Intrinsic Nerve Activity at the Sinoatrial Node in Normal Dogs With High-Density Mapping.

It is known that autonomic nerve activity controls the sinus rate. However, the coupling between local nerve activity and electrical activation at the sinoatrial node (SAN) remains unclear. We hypothesized that we would be able to record nerve activity at the SAN to investigate if right stellate ganglion (RSG) activation can increase the local intrinsic nerve activity, accelerate sinus rate, and change the earliest activation sites. High-density mapping of the epicardial surface of the right atrium including the SAN was performed in 6 dogs during stimulation of the RSG and after RSG stellectomy. A radio transmitter was implanted into 3 additional dogs to record RSG and local nerve activity at the SAN. Heart rate accelerated from 108±4 bpm at baseline to 125±7 bpm after RSG stimulation (P=0.001), and to 132±7 bpm after apamin injection (P<0.001). Both electrical RSG stimulation and apamin injection induced local nerve activity at the SAN with the average amplitudes of 3.60±0.72 and 3.86±0.56 μV, respectively. RSG stellectomy eliminated the local nerve activity and decreased the heart rate. In ambulatory dogs, local nerve activity at the SAN had a significantly higher average Pearson correlation to heart rate (0.72±0.02, P=0.001) than RSG nerve activity to HR (0.45±0.04, P=0.001). Local intrinsic nerve activity can be recorded at the SAN. Short bursts of these local nerve activities are present before each atrial activation during heart rate acceleration induced by stimulation of the RSG.

A stage-structured population model for activity-dependent dendritic spines

ABSTRACT Here we present a novel application of stage-structured population modelling to explore the properties of neuronal dendrites with spines. Dendritic spines are small protrusions that emanate from the dendritic shaft of several functionally important neurons in the cerebral cortex. They are the postsynaptic sites of over 90% of excitatory synapses in the mammalian brain. Here, we formulate a stage-structured population model of a passive dendrite with activity-dependent spines using a continuum approach. This computational study models three dynamic populations of activity-dependent spine types, corresponding to the anatomical categories of stubby, mushroom, and thin spines. In this stage-structured population model, transitions between spine type populations are driven by calcium levels that depend on local electrical activity. We explore the influence of the changing spine populations and spine types on the development of electrical propagation pathways in response to repetitive synaptic input, and which input frequencies are best for facilitating these pathways.

Endocardial vs endo-epicardial ablation of ventricular arrhythmia in arrhythmogenic right ventricular cardiomyopathy: a single center experience

Abstract Background The majority of patients have a sub-epicardial scar as a substrate for VT episodes. Purpose We sought to compare the efficacy of endocardial (ENDO) and epicardial (EPI) substrate modification in patients with ARVC. Methods 20 consecutive ARVC patients (mean age 41,4±13,8, 70% males; ICD previously implanted in 10 patients) with indications to ventricular arrhythmia ablation (RFA) were included into a prospective observational study. The EPI group consisted of 10 patients with sustained ventricular tachycardia (VT) (definite diagnosis ARVC – 8 patients; borderline – 1, possible – 1) who signed an informed consent to epicardial access. The ENDO group included 10 patients (definite diagnosis ARVC – 9 patients), five of them demonstrated sustained VT and 5 patients had frequent symptomatic premature ventricular contractions (PVC). Epicardial access in the EPI group was obtained through subxyphoid puncture. Bi- and unipolar voltage mapping of endocardial and epicardial surfaces was performed. Maps were evaluated for the presence of local abnormal ventricular electrical activity (LAVA, low-voltage areas and sites with highly fractionated or late activity). Ablation was performed at sites of LAVA on either side of the ventricular wall. In the ENDO group endocardial only ablation at LAVA sites was performed. RF energy ablation was 40W at the epicardial surface and 40–50W at the endocardial surface. Results In the EPI group endocardially mapped area of unipolar endocardial low voltage zone (LVZ) significantly prevailed over bipolar endocardial area of LVZ: 75.4 cm2 [IQR: 23.2; 211.9] vs 6.7 cm2 [IQR: 4.4; 35.5](P=0.009). Epicardial bipolar LVZ area prevailed over unipolar epicardial LVZ area: 65.3 cm2 [IQR: 55.6; 91.3] vs 6.7 cm2 [IQR: 4.4; 35.3] (P=0.005). Endocardial unipolar LVZ area in the EPI group was larger than in the ENDO group (P&amp;gt;0,05). After ablation non-inducibility of any ventricular arrhythmia was achieved in 90% of patients in the EPI group and in 80% of cases in the ENDO group. During a mean follow-up period of 22.3±10.5 months freedom of ventricular arrhythmia recurrence was 70% in the EPI group and 100% in the control group. Conclusions Although epicardial area of abnormal potentials significantly prevails over endocardial area, endocardial unipolar mapping and higher RF ablation power allow performing successful ventricular arrhythmia treatment in the majority of ARVC patients. Funding Acknowledgement Type of funding source: None

P357Epicardial abnormal electrical activity in unselected patients with ischemic ventricular tachycardia: a pilot mapping study

Abstract Background radiofrequency catheter ablation (RFA) on the endocardial ventricular surface is widely used for post-myocardial infarction (post-MI) ventricular tachycardia (VT) treatment. It has been described that about 10% of patients with post-MI require additional epicardial ablation for successful VT termination. However, there is still lack of data regarding the extent of scarring and the presence of local abnormal ventricular electrical activity (LAVA, low-voltage and/or fractionated signals) on the epicardial surface in patients with ischemic VT. Purpose to assess the extent of epicardial electrophysiological substrate in patients with remote myocardial infarction and indications for VT ablation. Methods thirteen out of 59 patients with sustained ischemic VT (12 men; mean age 59,9 ± 9,5) and without previous cardiac surgery signed an informed consent to undergo epicardial mapping and comprized the study population. Endocardial access was used previously as primary method in 4 patients ICD/ CRT-D had been previously implanted in 11 patients: mean left ventricle ejection fraction was 38,8 ± 10,6 %: hemodynamically unstable VT was present in 10 patients; the most frequent scar localization by ECG and transthoracic echocardiography – left ventricle (LV) inferior wall (10 patients), LV lateral wall – (7 patients). All patients underwent full clinical evaluation. Electrophysiological procedure and catheter ablation was performed under general anesthesia. Epicardial access was obtained through percutaneous subxyphoid puncture. Voltage mapping of endocardial and epicardial surfaces was performed. Maps were evaluated for the presence of LAVA. Ablation was performed at sites of LAVA on either side of the ventricular wall. Results epicardial access was successful in 12 patients. Bi- and unipolar mapping was successfully performed and analyzed in 11 subjects. LAVA was present in all but one patient on endocardial surface and in 9 (82%) out of 12 patients on epicardial surface. Localization of endocardial and epicardial LAVA coincided in 8 (67%) patients suggesting transmural ischemic scar. One patient had only epicardial scar, 1 patient had septal endocardial scar without LAVA on the epicardial surface. In one patient LAVA sites were localized on different left ventricle walls. More extensive unipolar than bipolar endocardial scar area was found (11,8 (IQR:2,0;31,6) vs 45,8 (IQR:17,1;86,5) сm2; р=0,03). Epicardial unipolar scar area prevailed over bipolar scar area: median 46.0 cm2 (IQR: 15.9;55.5) vs 107.7 cm2 (IQR: 84.3;168.9) р=0,04. LAVA epicardial area was wider than endocardial: 19.7 cm2 (IQR: 2.3; 29.7) vs 4.1 cm2 (IQR: 0.4; 23.8) р=0.03. Conclusion according to the results of our pilot study in unselected patients with ischemic VT, epicardial arrhythmogenic substrate was detected in 82% of cases. Epicardial LAVA area significantly prevailed over endocardial LAVA area.

P1449Anti-thrombotic management for electrophysiological procedures: results of the European Heart Rhythm Association (EHRA) young investigators survey

Abstract Funding Acknowledgements none Background Electrophysiological studies (EPS), with or without ablation, require percutaneous introduction of catheters into the heart to record local electrical activity. Instrumentation of catheters within the blood causes activation of the clotting cascade, increasing the risk of thrombus formation. To date, the electrophysiological community lacks international guidelines on the use of anti-thrombotic therapies before, during and after EPS. Purpose To survey the current practice regarding the use of anti-thrombotic therapies across member countries of the European Heart Rhythm Association (EHRA). Methods The survey was conducted in February 2019. Electrophysiologists from EHRA member countries were contacted to complete the survey by e-mail, utilizing the EHRA Young EP network. They were asked to answer a questionnaire containing information on anti-thrombotic and anticoagulation management before, during and after left-sided EPS and ablation: atrial tachycardia (AT), accessory pathway (AP) and ventricular tachycardia (VT). Results We obtained 41 answers responses from 40 centers in 15 European EHRA member countries. Regarding of antiaggregation, the most used antiplatelet is aspirin (100% before, during and after ablation). The most used anticoagulant was novel oral anticoagulants (NOAC) before ablation (47.1%), during hospitalization (85.2%) and at discharge (70.3%). The administration of anti-thrombotic therapy depended on the procedure time only in 10 cases (24.4%). For AP, before ablation, only 4 centers (9.7%) administered anti-platelets and 2 (4.9%) anticoagulants. During ablation, heparin was used by 85.4% of respondents maintaining ACT target 300-350 s in 36.6% of cases. At discharge, antiaggregation therapy was prescribed by 22 colleagues (53.7%) and anticoagulation only by one (2.4%). In patients with AT, before ablation, antiaggregation prophylaxis was prescribed by only 4 centers (19.5%) and anticoagulation by 11 (26.8%). During procedure, almost all centers (40, 97.6%) used heparin with ACT target 300-350 s in 58.5% of cases. At discharge, antiplatelet therapy was recommended by 12 colleagues (29.3%) and anticoagulation by 24 (58.5%). Regarding VT, before procedure, 8 centers (19.5%) prescribed antiaggregation and 5 (12.2%) anticoagulation prophylaxis. During ablation, all centers used heparin, maintaining ACT target 300-350 s in 58% of cases. The use of antiaggregation or anticoagulation depended on the left ventricle (LV) access in 15 centers (37.5%) and on LV ejection fraction in 11 (26.8%). At discharge, anti-thrombotic therapy was recommended by 16 colleagues (39%) and anticoagulation by 13 (31.7%). Conclusion Our survey showed that there is considerable variation in the management of anti-thrombotic therapy surrounding left-sided EPS and ablation. Further studies are necessary to evaluate the right approach to these procedures.

Relationship between muscle spindles and myofascial trigger spots according to Hoffmann reflex pathway and tissue morphology characteristics in a rat model.

To determine how muscle spindles are involved in the pathophysiology of chronic myofascial trigger spots (MTrSs, similar to myofascial trigger points) in a rat injury model according to the characteristics of the Hoffmann reflex (H-reflex) and the anatomical relationship between muscle spindles and MTrSs. 16 male Sprague-Dawley rats (7 weeks old) were randomly divided into experimental and control groups. A blunt strike injury and eccentric exercise were applied to the gastrocnemius muscle of rats in the experimental group once a week for 8 weeks as a MTrS modelling intervention. Subsequently, the rats were reared normally and rested for 4 weeks. At the end of the 12th week, the rats were examined for the presence of MTrSs defined by the detection of a palpable taut band exhibiting both a local twitch response and spontaneous electrical activity. After modelling, evocation of the H-reflex and morphological examination of muscle spindles and MTrSs were conducted. The threshold (0.35±0.04 mA) of the H-reflex and latency (1.24±0.18 ms) of the M wave recorded at MTrSs were not significantly different to those at non-MTrSs (P>0.05). Compared with non-MTrSs, a lower Mmax (4.28±1.27 mV), higher Hmax (median (IQR) 0.95 (0.80-1.08) mV) and Hmax/Mmax (median (IQR) 0.21 (0.16-0.40)), and shorter H wave latency (4.60±0.89 ms) were recorded at MTrSs (P<0.05). Morphologically, there was a close anatomical relationship between the MTrS cells and the muscle spindles. Compared with normal muscles, the H-reflex myoelectrical activity was enhanced and some muscle spindles might have been influenced by active MTrSs. Thus, muscle spindles may play an important role in the pathological mechanism underlying myofascial trigger points.

Kolmogorov Complexity of Coronary Sinus Atrial Electrograms before Ablation Predicts Termination of Atrial Fibrillation after Pulmonary Vein Isolation

Atrial fibrillation (AF) is related to a very complex local electrical activity reflected in the rich morphology of intracardiac electrograms. The link between electrogram complexity and efficacy of the catheter ablation is unclear. We test the hypothesis that the Kolmogorov complexity of a single atrial bipolar electrogram recorded during AF within the coronary sinus (CS) at the beginning of the catheter ablation may predict AF termination directly after pulmonary vein isolation (PVI). The study population consisted of 26 patients for whom 30 s baseline electrograms were recorded. In all cases PVI was performed. If AF persisted after PVI, ablation was extended beyond PVs. Kolmogorov complexity estimated by Lempel–Ziv complexity and the block decomposition method was calculated and compared with other measures: Shannon entropy, AF cycle length, dominant frequency, regularity, organization index, electrogram fractionation, sample entropy and wave morphology similarity index. A 5 s window length was chosen as optimal in calculations. There was a significant difference in Kolmogorov complexity between patients with AF termination directly after PVI compared to patients undergoing additional ablation (p < 0.01). No such difference was seen for remaining complexity parameters. Kolmogorov complexity of CS electrograms measured at baseline before PVI can predict self-termination of AF directly after PVI.

P1598Electrophysiological and structural characterization of acute atrial myocardial infarction

Abstract Background Atrial myocardial infarction may be a risk for atrial fibrillation. However, the electrophysiological and structural characteristics of the infarcted atrial myocardium are not well known. This study aimed to analyse the changes in local atrial electrograms and myocardial structure in an experimental model of isolated atrial myocardial infarction. Methods Five anesthetized, open-chest pigs were submitted to 4 hours of acute atrial myocardial ischemia induced by direct surgical clamping of atrial coronary branches originating from the right coronary artery. In all cases, we recorded simultaneously the 12-lead surface electrocardiogram (ECG) and the epicardial mapping of local atrial electrograms (17 x 12.5 mm patches containing 128 electrodes, with 1 mm inter-electrode distance) in a region close to the occluded branches and in control non-treated atria. The changes in local atrial QRS-ST segment and the amplitude of the P-wave of the ECG were sequentially analysed (Figure). The hearts were removed and processed for anatomopathological examination. Results Selective atrial coronary branch occlusion induced a patchy atrial myocardial necrosis with an irregular and abrupt border zone (circled areas in the Figure). During the first 15 min of ischemia, the local atrial electrograms showed increasing R waves, widening of QRS complex, and ST segment elevation leading to monophasic potentials (maximal ST segment at 30 min: from 0.2±0.7 mV to 1.9±1.4 mV, ANOVA p&lt;0.01). This period was followed by a phase of transient electrical recovery characterized by disappearance of monophasic potentials, reduction of ST segment elevation, and recovery of local electrical activation. After 60 min of occlusion, monophasic potentials reappeared and the magnitude of ST segment elevation decreased progressively during the ensuing 3 hours. The spatial transition from areas with monophasic potentials to normal electrograms encompassed 1 or 2 electrodes. The surface ECG showed increased duration of the P-wave (lead II at 3h occlusion: from 73.2±4.5 ms to 88.9±15.5 ms, ANOVA p&lt;0.05) with absence of ST segment changes. Atrial arrhythmias were not observed. Structural and electrical atrial changes Conclusion Selective occlusion of atrial coronary branches induced patchy atrial myocardial necrosis with abrupt anatomical and electrical border zone. The overt QRS and ST segment changes in local atrial electrograms resembled those described in acute ventricular myocardial ischemia, and were associated with widening of the P-wave on the surface ECG. Although acute ischemic arrhythmias were not observed, the atrial structural alterations might set the substrate for re-entrant arrhythmias late after the healing over process. Acknowledgement/Funding Supported by grants from ISCI-MINECO (FISPI17/00069), CIBERCV (CB16/11/00276), FEDER and Fundaciό “La Maratό” TV3 (20150830).

Unmixing Oscillatory Brain Activity by EEG Source Localization and Empirical Mode Decomposition.

Neuronal activity is composed of synchronous and asynchronous oscillatory activity at different frequencies. The neuronal oscillations occur at time scales well matched to the temporal resolution of electroencephalography (EEG); however, to derive meaning from the electrical brain activity as measured from the scalp, it is useful to decompose the EEG signal in space and time. In this study, we elaborate on the investigations into source-based signal decomposition of EEG. Using source localization, the electrical brain signal is spatially unmixed and the neuronal dynamics from a region of interest are analyzed using empirical mode decomposition (EMD), a technique aimed at detecting periodic signals. We demonstrate, first in simulations, that the EMD is more accurate when applied to the spatially unmixed signal compared to the scalp-level signal. Furthermore, on EEG data recorded simultaneously with transcranial magnetic stimulation (TMS) over the hand area of the primary motor cortex, we observe a link between the peak to peak amplitude of the motor-evoked potential (MEP) and the phase of the decomposed localized electrical activity before TMS onset. The results thus encourage combination of source localization and EMD in the pursuit of further insight into the mechanisms of the brain with respect to the phase and frequency of the electrical oscillations and their cortical origin.