Deceleration Zone Research Articles

Driving Safety and Comfort Enhancement in Urban Underground Interchanges via Driving Simulation and Machine Learning

Urban transportation systems, particularly underground interchanges, present significant challenges for sustainable and resilient urban design due to their complex road geometries and dense traffic signage. These challenges are further compounded by the interaction of diverse road users, which heightens the risk of accidents. To enhance both safety and sustainability, this study integrates advanced driving simulation techniques with machine learning models to improve driving safety and comfort in underground interchanges. By utilizing a driving simulator and 3D modeling, real-world conditions were replicated to design key traffic safety features with an emphasis on sustainability and driver well-being. Critical safety parameters, including speed, acceleration, and pedal use, were analyzed alongside comfort metrics such as lateral acceleration and steering torque. The LightGBM machine learning model was used to classify safety and comfort grades with an accuracy of 97.06%. An important ranking identified entrance signage and deceleration zones as having the greatest impact on safety and comfort, while basic road sections were less influential. These findings underscore the importance of considering visual cues, such as markings and wall color, in creating safer and more comfortable underground road systems. This study’s methodology and results offer valuable insights for urban planners and engineers aiming to design transportation systems that are both safe and aligned with sustainable urban mobility objectives.

Spatial relationship between evoked delayed potentials and deceleration zones of an isochronal late activation map in a patient with sarcoid-related ventricular tachycardia

Spatial relationship between evoked delayed potentials and deceleration zones of an isochronal late activation map in a patient with sarcoid-related ventricular tachycardia

Whole-Heart Histological and Electroanatomic Assessment of Postinfarction Cardiac Magnetic Resonance Imaging Scar and Conducting Channels.

Cardiac magnetic resonance imaging (CMR)-defined ventricular scar and anatomic conduction channels (CMR-CCs) offer promise in delineating ventricular tachycardia substrate. No studies have validated channels with coregistered histology, nor have they ascertained the histological characteristics of deceleration zones (DZs) within these channels. We aimed to validate CMR scar and CMR-CCs with whole-heart histology and electroanatomic mapping in a postinfarction model. Five sheep underwent anteroseptal infarction. CMR (116±20 days post infarct) was postprocessed using ADAS-3D, varying pixel intensity thresholds (5545, 6040, 6535, and 7030). DZs were identified by electroanatomic mapping (129±12 days post infarct). Explanted hearts were sectioned and stained with Picrosirius red, and whole-heart histopathologic shells were generated. Scar topography as well as percentage fibrosis, adiposity, and remaining viable myocardium within 3 mm histological biopsies and within CMR-CCs were determined. Using the standard 6040 thresholding, CMR had 83.8% accuracy for identifying histological scar in the endocardium (κ, 0.666) and 61.4% in the epicardium (κ, 0.276). Thirty-seven CMR-CCs were identified by varying thresholding; 23 (62%) were unique. DZs colocalized to 19 of 23 (83%) CMR-CCs. Twenty (87%) CMR-CCs were histologically confirmed. Within-channel histological fibrosis did not differ by the presence of DZs (P=0.242). Within-channel histological adiposity was significantly higher at sites with versus without DZs (24.1% versus 8.3%; P<0.001). Postprocessed CMR-derived scars and channels were validated by histology and electroanatomic mapping. Regions of CMR-CCs at sites of DZs had higher adiposity but similar fibrosis than regions without DZs, suggesting that lipomatous metaplasia may contribute to arrhythmogenicity of postinfarction scar.

Self-adaptive numerical dispersion suppressed method for shallow seismic simulation

Near-surface in seismic exploration generally refers to the low deceleration zone and a section of stratum below it, which can be described in geophysical language as “low velocity”, “low Q”, and “Free surface”, etc. Due to the presence of low-velocity layers in near-surface, shallow seismic simulation is plagued by numerical dispersion. Numerical dispersion affects the accuracy of seismic wave simulation, especially severe in shallow areas containing low-velocity layers. To improve the simulated quality, denser grids or higher-order difference schemes are used, but both of which would seriously reduce computational efficiency, especially for frequency-domain numerical modeling. Differentiation is replaced by difference in wave field simulation, which would inevitably result in numerical errors. These numerical errors are manifested as the difference between the phase velocity of the discretized wave field and the medium velocity. The waves with different wavenumber components have different phase velocities, and the larger the wavenumber, the more that its phase velocity lags the group velocity. Based on this theoretical analysis, a regularization factor is added to the frequency-domain acoustic wave equation to correct the phase velocity of high wavenumber components. According to the Von Neumann stability requirements, a regularization factor that adaptively changes with simulation parameters is derived. Compared to the fixed regularization factor, adaptive regularization factor can better match the velocity field and protect the effective wave field to the maximum extent while suppressing numerical dispersion. The improved acoustic wave equation can effectively suppress numerical dispersion without increasing the number of grids. Different numerical models demonstrate the effectiveness and efficiency of the improved acoustic equation with the adaptive regularization factor for suppressing numerical dispersion.

Near-field detection and peak frequency metric for substrate and activation mapping of ventricular tachycardias in two- and three-dimensional circuits.

Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the electrogram (EGM) may improve correct near-field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of NF and far-field (FF) EGMs may delineate the three-dimensional path of a ventricular tachycardia (VT) circuit. A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared with manually reviewed maps employing first deflection (FDcorr) for VT activation maps and last deflection (LD) for substrate maps. Ventricular tachycardia isthmus location and characteristics mapped with FDcorr vs. NF were compared. Omnipolar low-voltage areas, late activating areas, and deceleration zones (DZ) in LD vs. NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander sites. Activation mapping with entrainment and/or VT termination with radiofrequency (RF) ablation confirmed critical sites. Eighteen patients with high-density VT activation and substrate maps (55.6% ischaemic) were included. Near-field detection correctly located critical parts of the circuit in 77.7% of the cases compared with manually reviewed VT maps as reference. In substrate maps, NF detection identified deceleration zones in 88.8% of cases, which overlapped with FDcorr VT isthmus in 72.2% compared with 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus sites from low-voltage bystander sites. Omnipolar voltage was significantly higher at isthmus sites with longer EGM durations compared with low-voltage bystander sites. The NF algorithm may enable rapid high-density activation mapping of VT circuits in the NF of the mapped surface. Integrated assessment and combined analysis of NF and FF EGM-components could support characterization of three-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low-voltage bystander sites in this cohort.

Identification of deceleration zones during sinus rhythm for locating critical isthmuses in left atrial macroreentrant tachycardias

Abstract Introduction Ablation of left atrial (LA) macroreentrant tachycardias (LAMT) poses considerable challenges, with issues such as tachycardia cycle length variations, multiple reentrant circuits, and tachycardia termination during entrainment maneuvers. Evaluating deceleration zones (DZ) through atrial pacing during sinus rhythm, and their correlation with potential critical conduction isthmuses (CI) in LAMT, remains unexplored. This approach may facilitate LAMT ablation. Objective To investigate the presence of DZ through atrial pacing during sinus rhythm and their association with LAMT critical conduction isthmuses (CI). Methods Patients who underwent LAMT high-density activation mapping with a 16-pole grid catheter were included. Conventional mapping (activation, voltage and entrainment mapping during tachycardia) was performed to localize the CI. Atrial pacing with three atrial extrastimuli (S2/S3/S4 with 500/500/300 ms coupling interval) was performed during sinus rhythm from the distal coronary sinus (CS). Isochronal late activation mapping (ILAM) of the S3 and S4 cycles was compared. Deceleration zones (DZ) were defined as an offset in the color scale of the activation map in an area with at least a radius of 10 mm. ILAMs were evaluated blindly, and DZs were compared with CIs defined by conventional mapping during tachycardia and validated by radiofrequency application termination. Results 18 p (60.50 ± 11.63 yo, 11 male) and 21 procedures were included. LAMT termination was successful in 18 out of 21 procedures (85.71%) and failed in 3 due to the epicardial component of the reentrant circuit. ILAM during CS pacing was achieved in 13 patients and was not possible in 5 p due to multiple LAMTs leading to empiric linear ablation in 1 and to recurrent induction of LAMT or AF during the pacing protocol. A DZ was identified in 13 out of 16 maps (81.25%) in the S3 map, which was more pronounced in the S4 map. In all these 13 maps, the final ablation site was within the DZ in the S4 map, terminating the tachycardia with focal RF applications in 11 and with extended in 2. Conclusions Deceleration zones identified through atrial pacing during sinus rhythm are prevalent in LAMT patients. These zones generally correspond to the critical conduction isthmus and offer a valuable method for mapping the reentrant circuit when mapping during stable LAMT is not feasible.

Clinical validation of a novel digital twin framework for ventricular functional substrate simulation in post-infarction patients

Abstract Background Catheter ablation is a cornerstone treatment for scar related post-infarction ventricular arrhythmias. Functional substrate driven ablation strategies guided by local activation time (LAT) mapping have been proven as efficient and effective approaches, especially when dealing with large scar areas. In-silico electrophysiological modeling is emerging as a potential tool for procedural planning and guidance. Purpose To clinically validate the feasibility, diagnostic performance, and accuracy of a novel late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) based digital twin framework for simulated LAT map generation in post-infarction patients and their integration with CARTO3 EAM suite. Methods Five ischemic subjects who underwent CMR-aided scar-related ventricular tachycardia ablation at our referral center were retrospectively enrolled. Their CMR derived 3D pixel-signal-intensity (PSI) maps generated with ADAS3D were processed with novel in-house software to obtain patient-specific ventricular geometry, tissue characterization, and to generate a model of Purkinje system and myocyte fiber orientation. According to local normalized pixel intensity (NPI) values, myocardial regions were marked as healthy, scar, or border-zone. Electrophysiological properties of border-zone (BZ) were modulated according to local NPI. Continuous and 8-steps isochronal endo-epicardial LAT maps were generated and imported in CARTO3 system, aligned with electroanatomical mapping (EAM), and compared at an ASE 17-segments level, in terms of sensitivity, specificity, predictive values, and accuracy to actual high-density LAT maps obtained with a multipolar catheter. Deceleration Zones (DZ) were defined as previously described (&amp;gt;3 isochrones within 1 cm radius). Results A total of 85 ASE segments (34 epicardial) were analyzed. 24 EAM segments (28%) held DZs, 40 (47%) segments harbored bipolar scar or BZ. Thirty-seven (44%) CMR segments held scar core/BZ. Thirty (35%) digital model segments harbored DZs. Generated LAT maps were successfully imported and aligned with CARTO3 EAM suite for validation. In terms of DZ localization prediction, our LAT model showed 83% sensitivity (95% CI 63%-95%), 90% specificity (95% CI 80%-96%), 77% positive predictive value (PPV) (95% CI 56%-91%), 93% negative predictive value (NPV) (95% CI 83%-98%), 88% accuracy (95% CI 79%-94%). Conclusion Our newly developed framework for LGE-CMR derived functional substrate simulation in post-infarction patients holds high sensitivity, specificity, predictive values, and accuracy for DZ localization. Further validation, with a larger sample size, is required for evaluating potential implications in clinical practice.

The evaluation of the efficacy of automated peak frequency annotation algorithm for the identification of critical isthmus of ventricular tachycardia and deceleration zones

Abstract Background Substrate modification techniques have widely been adopted due to hemodynamic instability and non-inducibility of clinical ventricular tachycardia (VT). Accurate annotation of local near field EGMs is paramount to better evaluate the ventricular substrate. Furthermore, annotation of late potentials (LP) necessitates substantial manual input and isochronal late activation mapping (ILAM) involves constant sensitivity adjustments, potentially affecting the accuracy of local ventricular signal representation. Objective This study aims to assess the utility of novel automated peak frequency (PF), which aims to determine near field local activity in low voltage regions in the prediction of the CI of scar related reentrant VTs. Furthermore, the effectiveness of automated PF annotation of near field EGMs to identify deceleration zone (DZ) during ILAM was also evaluated. Methods A total of 18 patients with scar-related VT were analyzed. In all patients, VT isthmuses were identified based on activation maps and acute termination achieved during radiofrequency ablation. Automated PF annotation using Ensite X system (Abbott) was retrospectively performed in all cases specifically in areas of low voltage with fractioned signals. The accuracy of applying the PF value and automated ILAM map for detecting VT isthmus was also assessed. Results Among the study group, 12 (66.7%) had ischemic cardiomyopathy, while 6 (33.3%) had nonischemic cardiomyopathy [3 (16.7%) with arrhythmogenic right ventricular cardiomyopathy, 2 (11.1%) with idiopathic dilated cardiomyopathy, and 1 (5.6%) with hypertrophic cardiomyopathy]. All identified isthmuses were located in areas exhibiting bipolar voltage below 0.5 mV and a PF of 250 Hz with fractionated EGMs Automated NF DZ annotation predicted the VT isthmus in 16/18 (88.9%) of the cases similar to the conventional ILAM with manual adjustment (88.9%). Conclusion Using high-density electroanatomical mapping with near field algorithm, a PF cutoff of 250 Hz accurately identified the low voltage regions to predict the CI of VT. In addition, automated annotation of EGMs during ILAM similarly identified the DZs compared with conventional last deflection algorithm with manual adjustments, which were colocalized with CI of VTs.

Manifestation of conduction block zones by substrate mapping evaluated under multidirectional pacing during ventricular tachycardia ablation

Abstract Introduction Catheter ablation (CA) has proven to be effective therapy for ventricular tachycardia (VT) in patients with structural heart disease. However, activation mapping during VT is often limited in case of non-inducible, non-sustained or hemodynamically tolerable. It has been reported that a substrate-based approach for identifying conduction block and slow-conducting sites during sinus rhythm and ventricular pacing is promising strategies for CA. However, detailed analysis on the effectiveness of substrate mapping with multidirectional pacing to identify critical isthmus in unmappable VT have been lacking. Purpose The purpose of the present study was to evaluate the effectiveness of substrate mapping with multidirectional pacing in VT ablation. Methods From April 2022 to July 2023, 7 consecutive patients (4 men, age 62±9years) who underwent CA of VTs at our institute were enrolled. Isochronal late activation mapping (ILAM) was performed during sinus rhythm, right ventricular (RV) and left ventricular (LV) pacing. Cardiovascular magnetic resonance were performed in 3 of 7 cases to assess the distribution of myocardial late gadolinium enhancement. For catheter ablation, 2Fr electrode catheter was inserted into the anterior interventricular vein (AIV) at the distal site of the coronary sinus. LV pacing was performed using an electrode catheter placed in the AIV. ILAM were constructed by annotating the last deflection of each electrogram. Results In the 7 patients, 5 had ischemic cardiomyopathy and 2 had non-ischemic cardiomyopathy (Figure 1). During sinus rhythm, a deceleration zone (DZ) was identified in only 1 of 7 cases, consistent with linear conduction block. RV pacing demonstrated DZ in 3 of 7 cases. LV pacing revealed DZ in 6 of 7 cases, all of which had conduction blocks. U-shaped conduction blocks, which was not detectable in activation mapping during sinus rhythm, was newly identified in 29% of RV pacing, 71% of LV pacing. Combined RV and LV pacing unmasked the U-shaped conduction block in 86% of the cases. Only in case 7, activation mapping of VT with a cycle length of 470ms could be performed, and VT isthmus activation was observed in the area surrounded by the U-shaped conduction block (Figure 2). In other cases, the clinical VTs were unmappable because of the hemodynamic instability with tachycardia cycle length of approximately 300 milliseconds. Eventually, VTs became non-inducible in 3 of 5 cases in which induction was performed after the CA. During the follow-up period of 7±5 months, 6 of 7 cases remained free from any VT episodes. One patient showed small amount of pericardial effusion after CA. However, there were no life-threatening complications in any patients. Conclusion Substrate mapping using several different wavefront vectors in unstable VTs unveiled conduction block zones that might be potential ablation target sites for VT.Figure 1Figure 2

Improving functional substrate delineation for ablation of ventricular tachycardia using high-density electroanatomic mapping and double ventricular extra stimuli protocol

Abstract Background A partial delineation of targets for ventricular tachycardia (VT) ablation may contribute to a suboptimal success rate. Abnormal electrograms (EGMs) with low-voltage near-field components might be concealed within high-amplitude far-field signals. Our hypothesis posited that acquiring functional mapping after double ventricular extrastimuli (S3 protocol) could reveal relevant areas of functional substrate overlooked during sinus or S1 mapping. Purpose To assess the benefit and feasibility of functional substrate mapping using a full ventricle S3 protocol and to evaluate its colocalization with conducting channels (CCs) identified in late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). Methods (Figure 1) - An S3 mapping protocol with a drive train of S1 followed by S2 (effective refractory period (ERP) +30ms) and S3 (ERP+50ms) from the RV apex was conducted in 40 consecutive patients undergoing scar-related VT ablation. Deceleration zones (DZs) and areas of late potentials (LPs) were identified for all maps (S1, S2, and S3). Pre-procedural non-invasive substrate assessment was performed with LGE-CMR and post-processing using a commercially available system with automated CC identification. Results The S3 protocol was completed in 34 of the 40 procedures (85.0%). Repeated induction of ventricular arrhythmias prevented the full S3 protocol in 5 patients (15.0%). Functional substrate identified during S3 activation mapping was significantly more extensive than that identified using S2 and S1, including a higher number of DZs (2.94, 2.47, and 1.82, respectively; p&amp;lt;0.01) and a wider area of LPs (44.1cm2, 38.2cm2, and 29.4cm2, respectively; p&amp;lt;0.001). The percentage of CCs unmasked by DZs and LPs using S3 maps was significantly higher than the ones using S2 and S1 maps(78%, 65%, and 48%; p&amp;lt;0.001, and 88%, 81%, and 68%; p&amp;lt;0.01, repectively). After VT ablation based on an S3 protocol, 77.9% of patients have been VT free during a median follow-up of 13.6 months. Conclusions (Graphical abstract -Figure 2) - This novel substrate-based protocol for assessing functional substrate is feasible in most patients, enables better identification of ablation targets, and has the potential to improve patient prognosis post-ablation.Methods - The S3 protocolConclusion - Graphical abstract

Modification of deceleration zones and late potentials after ventricular tachycardias substrate ablation

Abstract Introduction Characterization of ventricular substrate is crucial during ventricular tachycardias (VT) ablation. Isochronal Late Activation Mapping (ILAM) is a recently introduced visualization tool that permit to identify areas of slow conduction (deceleration zones, DZs), these seems to well correlate with VT isthmuses. However, there are limited data about changes in this substrate after catheter ablations. Purpose To evaluate changes that occur to DZs and late potentials (LPs) after repeated ablative lesion sets. Methods High density voltage map and ILAM of the left ventricles (LV) during paced rhythm were performed in all cases. LV activation map was divided into 8 isochrones and DZ was defined as the presence of 3 isochrones within 1 cm-radius. LPs were defined as EGMs with late and fragmented components after the QRS. PES was performed at the beginning and at the end of the procedure. Each RF lesion set were applied with force-sensing irrigation catheter (target LSI 6-6.5) to abolish all the DZs and LPs discovered at baseline. After the first lesion set a re-map was performed looking for persistent DZs or LPs in the same LV segment (residual) or the appearance in a new ones (shift) in a 17-segment LV model; additional RF lesions and maps were performed only if DZs or LPs were still present in the last map. Results Of 28 VT cases considered, 9 patients with detailed LV maps and subsequent remaps were analyzed. Median age was 66 yo, 8 males, 7/9 with ischemic heart disease. In 7/9 patients clinical VTs were also induced and mapped. At baseline ILAM maps identified 24 DZs; after the first lesion set, 9 DZs were still appreciable at the same localization and 9 shifts to another LV segment (e.g. fig1). In 100% of patients at least one DZ was still appreciable at the first remap, while in 78% of patients a shift of the previous one was noted. At remap after a second lesion set 9 DZs were still present (3 residual, 6 shifts) in 33% of pts. Finally after a third lesion set only 2 DZs were still present in the same segment and then abolished. Furthermore, at baseline LPs were present in 28 LV segments, and after the first lesion set LPs were still present in 15 segments (9 residual, 6 new LPs). At first remap 78% of patients still showed LPs. After a second lesion set LPs were still visible in 6 segments (3 residual, 3 shift) in 22% of patients. In the third remap only in 2 segments could still be appreciated (1 residual, 1 shift) and finally were all abolished (summary in fig2). In 5/7 patients the clinical VT isthmus were identified in a DZ at baseline. At median FU of 6 months 7/9 patients has no VT recurrences, while there was one non-cardiovascular death. Conclusions Frequently DZs and LPs persistence is observed after first sets of lesions and additional RF deliveries are required for complete abolition. Remapping often demonstrates that both DZs and LPs move to other adjacent LV segments, likely where they were previously masked.Fig1Fig2

Evaluating left atrial wall thickness: a new frontier in predicting atrial scar and reentrant tachycardia

Abstract Background and Objective Reentrant atrial tachycardias (AT) are commonly observed in patients with atrial scar. These scars form a substrate in the atrium, characterized by areas of slow conduction, crucial for initiating reentrant cycles. During these cycles, zones of slow conduction often act as critical isthmuses (CI), becoming prime targets for ablation. Late potential mapping is a technique used to identify these slow conduction zones. Moreover, recent advancements in imaging software now allow for the precise measurement of myocardial wall thickness, aiding in the identification of thin myocardial areas that could potentially have the CI of AT. Methods We conducted a retrospective study of patients who underwent catheter ablation for AT. The study focused on patients who either presented with AT or in whom it was induced and who had undergone late potential mapping of the left atrium. To identify deceleration zones (DZ), we created voltage maps and isochronal late activation maps (ILAM) during sinus or paced rhythm. Electrograms exhibiting a continuous-fragmented morphology were explicitly marked. Upon induction of AT, activation mapping was employed to pinpoint the CI of the tachycardia circuit. Additionally, the thickness of the left atrial (LA) wall and LA volume were measured using ADAS3D software. Results A total of 39 patients, with 25 (65.1%) being female, were enrolled in the study. The mean age of the participants was 62.5 ± 9.5 years. The average volume of the left atrium was measured at 124.8 ± 35.5 mL, and the mean thickness of the LA wall was 1.58 ± 0.2 mm. In most patients (16, 41.0%), the septal wall was the thinnest part of the left atrium. However, significant thinning of the LA wall was observed predominantly on the anterior wall in 29 patients (74.2%) and on the LA roof in 18 patients (46.2%). The sensitivity and positive predictive value (PPV) of thinning in the LA anterior wall in detecting late potentials were 74.1% and 68.9%, respectively. For detecting critical isthmuses, these values were 76.9% (sensitivity) and 66.7% (PPV). Regarding the LA roof, the diagnostic value for thinning in detecting late potentials and critical isthmuses showed a sensitivity of 57.1% and 57.9%, respectively, and a PPV of 57.1% and 52.4%, respectively. Conclusion Evaluating LA thickness represents a novel approach that can potentially identify LA scars and late potentials before the procedure, particularly in the LA anterior wall. While the observed positive predictive values are acceptable, the negative predictive values and specificity are relatively low. Future advancements in imaging software, along with the development of standardized cardiac computed tomography protocols, can potentially enhance these outcomes. Consequently, preprocedural computed tomography could become increasingly significant in managing and treating AF and AT beyond LA anatomy evaluation.TablesLeft Atrial Wall Thickness

A novel method to identify critical isthmus of right atrial reentrant tachycardia; Functional substrate mapping characteristics during sinus rhythm

Abstract Background Right atrial tachycardia (AT) is a frequent rhythm disorder in patients with atrial scar mainly due to surgical incisions or congenital heart diseases. Despite the mounting evidence about AT mechanisms and types, data is scarce regarding the conduction properties as well as functional characteristics of atrial substrate during sinus rhythm that has role in the maintenance of the tachycardia. Purpose We sought to evaluate the relationship between the functional substrate mapping (FSM) characteristics of right atrium and the critical isthmus (CI) of re-entrant ATs in patients with underlying atrial scar. Methods Among patients with the history of right AT who underwent catheter ablation with 3-D mapping were retrospectively enrolled. Voltage map and isochronal late activation mapping (ILAM) were created during sinus / paced rhythm using multielectrode catheters to detect deceleration zones (DZ). Subsequently AT was induced with programmed stimulation and activation mapping was performed to detect CI of the tachycardia. Atrial tachyarrhythmia (ATa) recurrence was defined as detection of atrial fibrillation or AT (≥ 30 s) during the follow-up. Results A total of 24 patients [mean age: 46 ±15, gender: 13 (54 %) female] with right AT were included. A total of 37 ATs were mapped [16 (43.2%); localized reentry, 21 (56.7%), macroreentry]. Atrial low voltage zones comprised 23.3 ± 13.0 % of total right atrium. The mean value of bipolar voltage, EGM duration and conduction velocity during sinus rhythm corresponding to CI of ATs were 0.18 ± 0.10 mV, 121.7 ± 29.4 ms, 0.06 ± 0.04 m/s and, respectively. Total number of DZs per chamber was 1.1 ± 0.3, which were all located in the low-voltage zone (&amp;lt;0.5 mV) detected by high density mapping. All CIs of non- cavo-tricuspid-isthmus (CTI) dependent reentry were colocalized with DZs detected during FSM. The positive predictive value of DZs to detect CI of inducible ATs is 80.8%. During the mean follow-up of 11.7 ± 8.1 months, freedom from ATa was 87.5%. Conclusion Although, CTI-dependent macroreentry is the most common mechanism in patients with RA scar, our findings demonstrated the relevance of FSM to predict non-CTI dependent ATs. Conduction slowing manifested as DZs with continuous-fragmented signal morphology may guide to tailor ablation strategy in case of underlying RA scar.

Significance of Coherent Mapping in unveiling slow conduction zones of ventricular tachycardia substrate in ischemic cardiomyopathy

Abstract Introduction Ventricular tachycardia (VT) presents a formidable challenge, particularly in cases with extensive myocardial scar tissue, complicating critical ablation site identification. Prolonged interventions not only extend procedural durations but also heighten the risk of complications. This study aimed to assess the efficacy of coherent mapping techniques in precisely locating regions of slow conduction within scar tissue and explored potential correlations with electrophysiological markers in scar-related VT. Methods Seventeen patients (mean age: 61.6 ± 9.2 years, mean EF: 28 ± 9%) with ischemic cardiomyopathy (ICM) and frequent implantable cardioverter-defibrillator (ICD) shocks underwent high-density (&amp;gt;2000 points) left ventricular (LV) substrate mapping (15 endo, 2 epicardial) during sinus or right ventricular (RV) pacing and ablation. Coherent mapping tool was utilized for the identification of slow conduction, demonstrated by vector thickening. Bipolar low voltage areas (LVAs) below 0.5 mV were defined as dense scar, and bipolar voltage between 0.5 and 1.5 mV was defined as the border zone (Figure, panel A). Late potentials (LPs) and local abnormal ventricular activities (LAVA) were manually identified and tagged. Isochronal late activation mapping (ILAM) was also performed to elucidate the functional properties of the substrate (Figure, Panel B). Results LPs and LAVA were identified in all cases, with a mean number of LPs being 10.0 ± 7.1. Of these, 14/17 cases had LPs located in dense scar, while 4/17 cases had LPs in the border zone. The mean area of LAVA was 9.9 ± 7.7 mm², located in dense scar in 6/17 cases and in the border zone in 15/17 cases. Average deceleration zones (DZ, &amp;gt;3 isochrones in 1 cm radius) identified by ILAM was 2 ± 1. Coherent mapping consistently identified slow conduction zones adjacent to LVA in all cases, with these coherent map-based slow conduction zones (CM-SCZ) located in dense scar in 3/17 cases and in the border zone in 14/17 cases. The distance of CM-SCZ to LPs was 12.6 ± 13.9 mm (in 4 cases, LPs were recorded on the spot), and the distance to LAVAs was 18.8 ± 13.7 mm (in 2 cases, LAVAs were recorded on the spot). CM-SCZ was colocalized with DZ in 14/17 of the patients. Ablation lesions covered CM-SCZ in 10/17 cases. Over a mean follow-up duration of 11 ± 6.5 months, 4 patients experienced VT recurrence, with 3 having no ablation lesions covering CM-SCZ, and 2 patients died due to pump failure. Conclusion This study underscores the significance of coherent mapping in refining the understanding of VT substrate in ICM. Identifying and ablating CM-SCZ during substrate-based mapping may provide a potential additional benefit for VT ablation. Nevertheless, larger studies are needed to clarify the prognostic significance and validate the clinical benefits of this approach.Figure 1

Functional substrate mapping characteristics during sinus rhythm predicts critical isthmus of scar related atrial tachycardia

Abstract Background Atrial tachycardia (AT) is a common rhythm disorder in patients with underlying atrial scar due to previous atrial surgery or valvular heart disease. Data is scarce about the role of functional characteristics or conduction properties during sinus rhythm that may have role in the critical isthmus (CI) of re-entry. Purpose We aimed to evaluate the relationship between the functional substrate mapping (FSM) characteristics of right and left atrium and the CI of re-entrant ATs in patients with atrial low-voltage areas. Methods A total of 95 [mean age: 57 ± 13, gender: 57 (60%) female] symptomatic patients with history of left and right AT who underwent catheter ablation with 3-D high-density mapping were enrolled. Isochronal late activation mapping were created during sinus/paced rhythm to detect deceleration zones (DZ). After induction of AT, activation mapping was performed in all patients. Results In 95 patients, 96 left-ATs [49 (51%) ATs were macroreentry and 47 (49%) ATs were localized reentry] and 40 right-ATs [24 (60%) ATs were macroreentry and 16 (40%) ATs were localized reentry] were mapped. Atrial low voltage zones comprised 23.3 ± 13.0 % of total right atrium and 33.3 ± 21.2 % of total left atrium. The mean value of bipolar voltage, EGM duration, and conduction velocity during sinus rhythm corresponding to CI of ATs were 0.17 ± 0.10 mV, 121 ± 39 ms, and 0.09 ± 0.06 m/s, respectively. Total number of DZs were 125 and all CIs of reentry were colocalized with DZs detected during FSM. The positive predictive value of DZs to detect CI of inducible ATs is 87.2%. Freedom from ATa was 76.8% at 12 months follow-up. Conclusion Our findings demonstrated the utility of FSM during sinus rhythm to predict the successful termination sites for ATs. These areas displayed continuous-fragmented signal morphology in correlation with the CI of AT detected during activation mapping.

Substrate Mapping for Ventricular Tachycardia Ablation Through High-Density Whole-Chamber Double Extra Stimuli: The S3 Protocol

BackgroundA partial delineation of targets for ablation of ventricular tachycardia (VT) during a stable rhythm is likely responsible for a suboptimal success rate. The abnormal low-voltage near-field functional components may be hidden within the high-amplitude far-field signal. ObjectivesThe aim of this study was to evaluate the benefit and feasibility of functional substrate mapping using a full-ventricle S3 protocol and to assess its colocalization with arrhythmogenic conducting channels (CCs) on late gadolinium enhancement cardiac magnetic resonance. MethodsAn S3 mapping protocol with a drive train of S1 followed by S2 (effective refractory period + 30 ms) and S3 (effective refractory period + 50 ms) from the right ventricular apex was performed in 40 consecutive patients undergoing scar-related VT ablation. Deceleration zones (DZs) and areas of late potentials (LPs) were identified for all maps. A preprocedural noninvasive substrate assessment was done using late gadolinium enhancement cardiac magnetic resonance and postprocessing with automated CC identification. ResultsThe S3 protocol was completed in 34 of the 40 procedures (85.0%). The S3 protocol enhanced the identification of VT isthmus on the basis of DZ (89% vs 62%; P < 0.01) and LP (93% vs 78%; P = 0.04) assessment. The percentage of CCs unmasked by DZs and LPs using S3 maps was significantly higher than the ones using S2 and S1 maps (78%, 65%, and 48% [P < 0.001] and 88%, 81%, and 68% [P < 0.01], respectively). The functional substrate identified during S3 activation mapping was significantly more extensive than the one identified using S2 and S1, including a greater number of DZs (2.94, 2.47, and 1.82, respectively; P < 0.001) and a wider area of LPs (44.1, 38.2, and 29.4 cm2, respectively; P < 0.001). After VT ablation, 77.9% of patients have been VT free during a median follow-up period of 13.6 months. ConclusionsThe S3 protocol was feasible in 85% of patients, allows a better identification of targets for ablation, and might improve VT ablation results.

Antiarrhythmic and Anti-Inflammatory Effects of Sacubitril/Valsartan on Post-Myocardial Infarction Scar.

Sacubitril/valsartan (Sac/Val) is superior to angiotensin-converting enzyme inhibitors in reducing the risk of heart failure hospitalization and cardiovascular death, but its mechanistic data on myocardial scar after myocardial infarction (MI) are lacking. The objective of this work was to assess the effects of Sac/Val on inflammation, fibrosis, electrophysiological properties, and ventricular tachycardia inducibility in post-MI scar remodeling in swine. After MI, 22 pigs were randomized to receive β-blocker (BB; control, n=8) or BB+Sac/Val (Sac/Val, n=9). The systemic immune response was monitored. Cardiac magnetic resonance data were acquired at 2-day and 29-day post MI to assess ventricular remodeling. Programmed electrical stimulation and high-density mapping were performed at 30-day post MI to assess ventricular tachycardia inducibility. Myocardial samples were collected for histological analysis. Compared with BB, BB+Sac/Val reduced acute circulating leukocytes (P=0.009) and interleukin-12 levels (P=0.024) at 2-day post MI, decreased C-C chemokine receptor type 2 expression in monocytes (P=0.047) at 15-day post MI, and reduced scar mass (P=0.046) and border zone mass (P=0.043). It also lowered the number and mass of border zone corridors (P=0.009 and P=0.026, respectively), scar collagen I content (P=0.049), and collagen I/III ratio (P=0.040). Sac/Val reduced ventricular tachycardia inducibility (P=0.034) and the number of deceleration zones (P=0.016). After MI, compared with BB, BB+Sac/Val was associated with reduced acute systemic inflammatory markers, reduced total scar and border zone mass on late gadolinium-enhanced magnetic resonance imaging, and lower ventricular tachycardia inducibility.

Personalized voltage maps guided by cardiac magnetic resonance in the era of high-density mapping

BackgroundVoltage mapping could identify the conducting channels potentially responsible for ventricular tachycardia (VT). Standard thresholds (0.5–1.5 mV) were established using bipolar catheters. No thresholds have been analyzed with high-density mapping catheters. In addition, channels identified by cardiac magnetic resonance (CMR) has been proven to be related with VT. ObjectiveThe purpose of this study was to analyze the diagnostic yield of a personalized voltage map using CMR to guide the adjustment of voltage thresholds. MethodsAll consecutive patients with scar-related VT undergoing ablation after CMR (from October 2018 to December 2020) were included. First, personalized CMR-guided voltage thresholds were defined systematically according to the distribution of the scar and channels. Second, to validate these new thresholds, a comparison with standard thresholds (0.5–1.5 mV) was performed. Tissue characteristics of areas identified as deceleration zones (DZs) were recorded for each pair of thresholds. In addition, the relation of VT circuits with voltage channels was analyzed for both maps. ResultsThirty-two patients were included [mean age 66.6 ± 11.2 years; 25 (78.1%) ischemic cardiomyopathy]. Overall, 52 DZs were observed: 44.2% were identified as border zone tissue with standard cutoffs vs 75.0% using personalized voltage thresholds (P = .003). Of the 31 VT isthmuses detected, only 35.5% correlated with a voltage channel with standard thresholds vs 74.2% using adjusted thresholds (P = .005). Adjusted cutoff bipolar voltages that better matched CMR images were 0.51 ± 0.32 and 1.79 ± 0.71 mV with high interindividual variability (from 0.14–1.68 to 0.7–3.21 mV). ConclusionPersonalized voltage CMR-guided personalized voltage maps enable a better identification of the substrate with a higher correlation with both DZs and VT isthmuses than do conventional voltage maps using fixed thresholds.

Phenomena-based optimization of load function during nanoindentation experiments for estimating elastic aspect of viscous materials

We propose an optimized load function designed to acquire the elastic aspect during nanoindentation for two viscous polymers, i.e., polycarbonate (PC) and poly (methyl methacrylate) (PMMA). To do so, various load functions are followed where constant strain rate (P˙/P) varies from 0.05 /s to 50.0 /s, maximum load (Pm) from 1000 μN to 9000 μN and unloading rate (P˙UL) from 9.0 × 102 μN/s to 107 μN/s. Depending upon the P˙/P, extent of viscous deformation varies during loading, e.g., slow P˙/P shows more viscous deformation due to sufficient loading time and vice-versa. However, for fast P˙/P, a large amount of viscous deformation is observed only when the tip decelerates at the end of loading since the deceleration zone is the favor of viscous deformation. During holding, it is seen that a large amount of viscous deformation takes place for fast P˙/P at any Pm. Because viscous deformation could not take place during loading due to insufficient time that is why it takes place during holding. In addition, at high Pm large amount of viscous deformation takes place than low Pm. Since it is observed that different time is required for various P˙/P and Pm to saturate the viscous deformation during holding; hence, a novel method is suggested to estimate the required time for any P˙/P and Pm indentation. During unloading, it is noticed that for fast P˙UL less amount of viscoelastic recovery takes place towards Pm, hence, it is recommended that 95%–40% and 95%–60% unloading range should be considered to evaluate the elastic aspect for PC and PMMA, respectively.

Functional substrate mapping of atrium in patients with atrial scar: A novel method to predict critical isthmus of atrial tachycardia.

Atrial tachycardia (AT) is a common rhythm disorder, especially in patients with atrial structural abnormalities. Although voltage mapping can provide a general picture of structural alterations which are mainly secondary to prior ablations, surgery or pressure/volume overload, data is scarce regarding the functional characteristics of low voltage regions in the atrium to predict critical isthmus of ATs. Recently, functional substrate mapping (FSM) emerged as a potential tool to evaluate the functionality of structurally altered regions in the atrium to predict critical sites of reentry. Current evidence suggested a clear association between deceleration zones of isochronal late activation mapping (ILAM) during sinus/paced rhythm and critical isthmus of reentry in patients with left AT. Therefore, these areas seem to be potential ablation targets even not detected during AT. Furthermore, abnormal conduction detected by ILAM may also have a role to identify the potential substrate and predict atrial fibrillation outcome after pulmonary vein isolation. Despite these promising findings, the utility of such an approach needs to be evaluated in large-scale comparative studies. In this review, we aimed to share our experience and review the current literature regarding the use of FSM during sinus/paced rhythm in the prediction of re-entrant ATs and discuss future implications and potential use in patients with atrial low-voltage areas.