Extra Stimulus Research Articles

Spontaneous termination of ventricular tachycardia in the human heart.

Understanding the spatiotemporal location of the spontaneous termination of ventricular tachycardia (VT) may provide new insights for ablation. To test the hypothesis that spontaneous VT termination most frequently occurs at the VT exit due to source-sink mismatch and to characterize electrophysiological properties of the sites termination during VT and with extra-stimulus technique. Retrospective analysis of intraoperative mapping studies of nine patients with ischemic cardiopathy or repaired tetralogy of Fallot. Simultaneous endocardial and epicardial mapping was performed in both ventricles using a custom mapping array during VT. Electrogram (EGM) characteristics before and at the moment of termination were analyzed including: cycle length oscillations, EGM heterogeneity and a variation in the systolic/diastolic path. The decrements to extra stimulus were analysed for termination sites and other diastolic sites. Nine VTs in seven patients demonstrated spontaneous VT termination. Seven VTs (77.8%) spontaneously terminated in the final third of the systolic interval, one (11.1%) in early diastole and one (11.1%) in mid diastole. Cycle length oscillations (prolongation, shortening, and no change) were seen in equal frequency. Four VTs (44.4%) showed alternans in the local EGM at the site of termination and this was more prevalent than alternans at other sites in the diastolic pathway (p < .001). Only one-third of VTs showed a change in activation pattern before termination. There was no difference based on etiology. During substrate characterization with extra-stimulus pacing, sites of spontaneous termination showed greater decrement than other sites of the VT circuit during pacing (43.5 ± 14.5 ms vs. 31.2 ± 31.2 ms; p = .003). The entrance zone rather than the exit is the commonest site for the spontaneous termination of VT in the human heart. These sites tend to demonstrate EGM alternans during VT and greater decrement during extrastimulus pacing. These findings may help guide future studies into improving the success of VT ablation.

Comparison of using Words with Pictures and Words alone with Simultaneous Prompting to Teach Sight-Word Reading to Students with Mild Intellectual Disability

This study compares the effectiveness and efficiency of using words with pictures and words alone with simultaneous prompting (SP) to teach sight word reading to four students, 8 to 11 years of age, with mild intellectual disabilities (ID). An adapted alternating treatment design was used to assess the two methods. The results suggest that both procedures were equally effective. Maintenance data showed that all students were able to maintain the acquired skills through the two teaching procedures, although words with picture resulted in a slightly higher maintenance level. words with pictures were more efficient according to four efficiency measures. All participants learned the words in fewer sessions and trials, made less errors, and needed less instructional time when they were presented with pictures rather than alone. Although pictures do assist in sight word acquisition, participant were unable to read all words in the absence of the picture. This finding is consistent with the phenomenon of overshadowing (pictures can be extra stimulus prompt where it distracts the learner's attention from the word) and blocking effect where the learner associates the spoken word with the picture and not with the written word.

Prevalence and characteristics of atrioventricular nodal reentrant tachycardia with a bystander concealed nodoventricular/nodofascicular pathway

BackgroundThe concealed nodoventricular/nodofascicular (NV/NF) pathway is mostly a bystander, retrograde bypass tract connecting the right ventricle/right bundle branch (RBB) and slow pathway that is observed in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its prevalence and characteristics in response to pacing maneuvers have not been fully evaluated. ObjectiveThis study investigated the prevalence and characteristics of AVNRT with a bystander NV/NF pathway. MethodsWe retrospectively reviewed 153 consecutive patients undergoing catheter ablation of AVNRT. After exclusion of 52 patients with inadequate electrophysiologic data, 101 patients composed the study population. ResultsThree patients (3.0%) had bystander concealed NV/NF pathways, all of which were connected to the slow pathway. The tachycardia was typical slow pathway/fast pathway AVNRT in 2 patients and atypical fast pathway/slow pathway AVNRT in 1 patient. In all cases, His-refractory ventricular extra-stimuli (VES) reset the AVNRTs with delay through the NV/NF pathways. Ventricular overdrive pacing (VOP) in the early phase also reset the AVNRT with delay. Earlier VES and middle phase of VOP did not reset the tachycardia, and further earlier VES and late phase of VOP reset the tachycardia with advance through the RBB-His conduction. ConclusionA bystander NV/NF pathway was not rare in patients with AVNRT. The VES and VOP for the AVNRTs with the bystander NV/NF pathways were characterized by the 2-phase resetting phenomenon: initial transient resetting with delay through the NV/NF pathway, and late resetting with advance through the RBB-His conduction.

TRANSOESOPHAGEAL ELECTROPHYSIOLOGICAL STUDY IN PEDIATRIC PATIENTS WITH VENTRICULAR PRE–EXCITATION

Abstract Introduction The transoesophageal electrophysiological study (SETE) is a simple, semi–invasive and highly reliable test for risk stratification in patients with ventricular pre–excitation. In paediatric subjects, symptoms may be nonspecific or poorly reported; hence the usefulness of the study in guiding the therapeutic strategy. The guidelines also suggest performing it in all asymptomatic patients with ventricular preexcitation above 8 years of age.Purpose of the study: to evaluate the inducibility of re–entry tachycardia at SETE in paediatric patients with ventricular pre–excitation. Materials and Methods We observed 21 patients aged between a few days of life and 12 years (average age 11 years); 14 of them had constant and 7 intermittent pre–excitations. The latter were subjected to the study as they reported dubious symptoms either due to sports activities or due to a previous diagnosis of neonatal TPS. The study was performed by carrying out the protocols of continuous atrial stimulation at increasing frequencies, programmed atrial stimulation with single, double, and triple extra stimulus and atrial stimulation with burst. Results Of the 21 patients, 8 (38.1%) were inducible. Of the 14 patients with constant ventricular pre–excitation, 5 had tachycardia upon return to the study (35.7%), 4 of which were symptomatic due to previous TPS. Therefore, only one patient with constant and asymptomatic ventricular pre–excitation was inducible. Of the 7 patients with intermittent ventricular preexcitation (documented by Holter or exercise test), 3 developed TPS at SETE (42.8%): all these patients complained of heart palpitations but did not have a documented arrhythmia. On the contrary, all patients with intermittent ventricular preexcitation and asymptomatic were found to be non–inducible. In patients in whom it was possible to calculate the effective antegrade refractory period of the anomalous pathway, shorter refractory period showed greater inducibility. Non–sustained atrial fibrillation was induced in only two patients. Conclusions SETE demonstrates a good correlation between symptoms and inducibility especially in patients with intermittent ventricular pre–excitation. In fact, if the manifest pre–excitation disappears with growth in about a third of patients, the retrograde conduction capacity of the pathway often persists. The study also allows us to identify patients with constant pre–excitation but pathway at low risk.

Hot-spots of epiphytic and epixylic lichens in fragmented temperate forests are underpinned by microhabitat heterogeneity and spatiotemporal habitat continuity

Habitat loss, fragmentation and degradation are major causes of the ongoing decline of epiphytic and epixylic lichen species in temperate forests throughout Europe. We investigated how extant species richness and composition of epiphytic and epixylic lichen communities in ten hot-spots of lichen diversity in the Czech Republic reflected the occurrence and properties of potentially suitable microhabitats and habitats. At each hot-spot, we surveyed a pair of 1-ha square plots, one in (over-)mature managed and the second in unmanaged forest. In total, we recorded 513 epiphytic and epixylic lichen species which represent a substantial part of lichen biota in Central Europe. Species richness and composition of lichen communities were explained by microhabitat heterogeneity, and also by the area of near-natural forest habitats (habitat extent) at the landscape scale. In addition, lichen species richness and number of red-listed species were explained by a categorial variable distinguishing mature managed and unmanaged plots, used as a proxy of temporal continuity of natural succession. This finding illustrates that temporal continuity of natural succession in unmanaged forests likely had an extra stimulus for lichen communities that may not be reflected by observed aspects of forest habitats. Hence, we confirmed indispensable positive effects of (micro)habitat heterogeneity, and spatial and temporal continuity for preserved hot-spots of lichen diversity in Central Europe. Due to generally slow colonization-extinction dynamics of epiphytic and epixylic lichens we call for strengthening microhabitat heterogeneity, and the spatial and temporal continuity of European temperate forests at the landscape scale.

Multiplexed terahertz multifocal metalens based on stretchable single-, dual-, and quad-axis synthetic rectangular optical sparse aperture

As ultrathin optical elements with subwavelength structures densely arranged, planar lens or called metalens can effectively focus incident wave. Due to the compact design and wide operating frequency of metalens, it becomes promising in applications like information encryption, imaging, and wireless communication fields. However, the fabrication of large-aperture metalens is still time-consuming and costly while the focusing performances are commonly tuned by introducing active materials requiring extra stimuli, such as laser and electrical pulses. In this study, five designs of metalenses with synthetic rectangular aperture are proposed and demonstrated with excellent focusing performances. By reconfiguring the synthetic aperture, focusing properties like focusing lengths, full width at half maximum values, and modulation transfer function can be tuned with great flexibility. With a polarization-dependent phase-shifting structure, the proposed metalens shows different focusing performances with incident wave under transverse magnetic field and transverse electric field modes. By utilizing spatial multiplexing, terahertz variable foci metalenses based on a stretchable single-, dual- and quad-axis synthetic rectangular optical sparse aperture are investigated to achieve tunable multifocal performances. These designs provide a novel strategy that can reconfigure the synthetic aperture with stretchable substrate to make metalens with multifunction and active tunability, which show promising applications in imaging, information encryption, and space telescope areas.

Hidroxiapatita sustituida con estroncio: plataforma para regeneración ósea con actividad antimicrobiana

Hydroxyapatite (HA) is a calcium phosphate with great analogy to biological apatite. Because of that it has demonstrated excellent results in clinical applications for bone tissue replacement. However, there are certain pathologies such as osteopenia or osteoporosis where the natural bone formation capacity is diminished and which may require an extra stimulus to accelerate and guarantee the osseointegration processes. In these cases, doping hydroxyapatite with strontium ions (Sr-HA) has given excellent results. This ion participates in bone metabolism in various ways and, while stimulating osteosynthesis, it inhibits osteoclast to a certain extent, which as a whole promotes the formation of new bone more quickly. Thus, the development of Sr-HA implants has evolved to not only consider substitutes for bone tissue with greater speed of osseointegration, but also to become platforms for the release of other active ingredients that can also counteract different medical conditions. This work delves into the complexity of septic processes associated with prostheses, which justifies the diversity of approaches to this clinical problem from biomedical engineering. In addition, review different formulations based on Sr-HA reported to eradicate septic processes. In particular, it explores new devices carrying antibiotics (Antb/Sr-HA) and new platforms that have been formed from the double ion doping of the HA where one of those ions is strontium and the other is some metallic element with demonstrated antibacterial activity (M/Sr-HA).

The benefit of a double ventricular extra stimuli protocol to improve functional substrate mapping during ablation of ventricular tachycardia. – The S3-VT-FREE project

The benefit of a double ventricular extra stimuli protocol to improve functional substrate mapping during ablation of ventricular tachycardia. – The S3-VT-FREE project

The benefit of a double ventricular extra stimuli protocol to improve functional substrate mapping during ablation of ventricular tachycardia. - The S3-VT-FREE project

Abstract Introduction Ablation of ventricular tachycardia (VT) based on substrate-based mapping has been proposed to itemize areas of interest identifying areas of low-voltage, late potentials (LPs), and deceleration zones (DZs). However, partial delineation of targets for ablation is likely responsible for a suboptimal long-term success rate. The abnormal electrograms (EGMs), featuring low-voltage near-field components may be hidden within the high-amplitude far-field signal. We hypothesized that the acquisition of functional mapping after double ventricular extrastimuli (S3 protocol) would uncover relevant areas of functional substrate that could be missed during sinus or S1 map. We aim to evaluate the potential benefit and the feasibility of functional substrate mapping using an S3 protocol for VT ablation and to assess its colocalization with detected corridors using late gadolinium enhancement magnetic resonance imaging (LGE-MRI). Methods We included consecutively 29 patients with structural cardiomypathy who underwent a VT ablation. The S3 protocol included: (1) assessment of the ventricular effective refractory period (ERP), (2) pacing protocol from the apex of the right ventricle with S1 x 6 (cycle length: 600ms) followed by S2 (ERP+30ms) and S3 (ERP+50ms). Electroanatomical mapping was acquired with the EnsiteX system (Abbott, IL) using HD Grid catheter and omnipolar signals. ILAMs were used to identify deceleration zones and areas of late potentials were identified for all maps. A non-invasive substrate assessment was done with LGE-MRI and post-processing with a commercially available system (ADAS3D, Spain) with automated identification of corridors. Results The S3 protocol was completed in 25 of the 29 procedures (86.2%). The repeated induction of ventricular arrhythmias did not allow for full protocol of the S3 protocol in 4 patients (13.8%). The functional substrate identified during the S3 activation mapping was significantly more extensive than the one identified using S1 and S2 activation mappings (p&amp;lt;0.05) (Table). The S3 protocol unmasked a higher number of DZs (p&amp;lt;0.01), a wider area of LPs (p&amp;lt;0.01), and a longer duration of the DZs (p=0.01). All DZ maps were compared with preprocedural cardiac magnetic resonance. The number of DZs matching with conduction corridors identified by LGE-MRI was higher in the activation mapping of S3 compared with the S1 and S2 ones (p=0.02). After VT ablation based on an S3 protocol, 88% of patients have been VT free during a median follow-up of 9 months. Conclusions This novel substrate-based protocol to assess the ventricular functional substrate is feasible in the majority of patients (86.2%) and allows for a better identification of targets for ablation and could facilitate VT ablation, and improve the prognosis of the patients after ablation.

Incidentally induced atrial fibrillation during programmed electrical stimulation in patients with depressed left ventricular systolic function after an acute myocardial infarction: a CARISMA substudy

Abstract Background The aim of this study was to investigate the clinically significant value of incidentally induced atrial fibrillation (AF) during programmed electrical stimulation (PES) in patients with left ventricular systolic dysfunction (≤40%) after an acute myocardial infarction (MI). Methods In this study we included 231 patients from the Cardiac Arrhythmias and RIsk Stratification after Myocardial InfArction (CARISMA) study. These patients were identified 3-21 days after being diagnosed with an MI, had left ventricular ejection fraction ≤40% and had no prior history of AF. They all received an implantable cardiac monitor (ICM) and were continuously monitored for cardiac arrhythmias for 2 years. A PES was performed 6 weeks post-MI with pacing from the right atrium and coronary sinus for induction of SVT and from the ventricular apex and outflow tract with up to three extra stimuli for induction of VT. Induction of AF was unwanted but reported if this incidentally occurred. Results AF was induced in 34 patients (15%) during the PES of which 10 (29%) later developed AF. A total of 61 patients (26%) developed AF within 2-years follow-up and the overall risk of AF was not significantly increased in patients with PES induced AF compared to patients without inducible AF (HR 1.6, P=0.14), however, the risk of AF ≤188 days post-MI was slightly increased (HR 3.0, P=0.01). The risk of bradyarrhythmia (HR=0.2, P=0.07), ventricular arrhythmias (HR=0.7, P=0.77) and MACE (HR 0.5, P=0.28) was reduced in patients with inducible AF compared to patients without inducible AF. Conclusions Incidentally induced AF during an electrophysiological study in post-MI patients was relatively frequent (15%) but was not associated with a higher risk of atrial fibrillation, other cardiac brady- or tachy-arrhythmias or major cardiac events. Even though the short-term risk for AF slightly increased, this does not seem to justify anticoagulation treatment or intensified follow-up in these patients.

Abstract 14364: Atrial Fibrillation With Rapid Ventricular Response Induced Ventricular Tachycardia Terminated by Intrinsic Anti-Tachycardia Pacing - A First in Literature Case Report

Background: Intrinsic anti-tachycardia pacing (iATP) is a novel tailored algorithm that has shown increased efficacy against ventricular tachycardia (VT), including fast VT. We describe a case of atrial fibrillation (AF) with rapid ventricular response (RVR) induced VT terminated by iATP. Case description: A 71-year-old male with coronary artery disease, heart failure (EF 30-35%), atrial fibrillation, VT status post biventricular implantable cardioverter defibrillator and failed renal transplant presented with syncope during dialysis. His home medications included amiodarone, metoprolol, apixaban. He was hemodynamically stable on presentation. He had bilateral pitting edema with a systolic murmur and bilateral basilar crackles on exam. His labs were consistent with anemia and end stage renal disease. His device interrogation (Figure) showed AFRVR which degenerated to VT with final cycle length (CL) of 290 msec. First round of ATP with S1x10 burst pulses (88%, CL 250msec) and S2 extra stimuli (CL 230 msec) failed to terminate the VT. Post pacing interval (PPI) was 450 msec. Given calculated remote distance, another five rounds of adaptive iATP with similar S1 pulses but faster S2 and addition of S3 extra stimuli were delivered but were unsuccessful in terminating VT. Finally, the seventh round of iATP (S1x10 at CL 260 msec, S2 at 240 msec) was successful at conversion to sinus rhythm briefly before reverting to AF with controlled ventricular pacing. Discussion: ATP decreases ICD shocks but is programmed empirically and there is less success with fast VT. iATP analyses the PPI of the prior failed sequence to adjust the subsequent ATP therapy by altering the number of burst pulses (S1) and addition of ramp extra stimuli. Computational models and early clinical experience have shown increased efficacy of iATP in terminating fast VT without concomitant increase in VT acceleration. To the best of our knowledge, this is first case report of AFRVR induced VT terminated by iATP.

Clean energy transitions and health

Clean energy can lead to significant health benefits. Making it accessible throughout the world can address many ills. We delve deeply into one example—the transition toward clean residential heating and its relationship to health benefits—in China. We find that the health benefits can outweigh costs from energy expenses in northern provinces. Low-income households enjoy larger health benefits but also experience a higher expense increase, suggesting that extra subsidies or stimuli are needed to help them benefit from clean energy. Our findings suggest that clean energy transitions should be promoted in developing economies due to improved social health, lessened medical costs, and significant environmental improvements.

Decrement Evoked Potential (DEEP) Mapping of the Atria: Unmasking Atrial Fibrillation Substrate.

Atrial myopathy may underlie the progression of atrial fibrillation (AF) from a treatable disease to an irreversible condition with poor ablation outcomes. Electrophysiological methods to unmask areas prone to re-entry initiation could be key to defining latent atrial myopathy. Consecutive patients referred for AF ablation were prospectively included at four institutions. Decrement evoked potential mapping (DEEP) was performed in eight left atrial sites and five right atrial sites, from two different pacing locations (endocardially from the left atrial appendage, epicardially from the proximal coronary sinus). The electrograms (EGMs) during S1 600 ms drive and after an extra stimulus (S2 at+30 ms above atrial refractoriness) were studied at each location and assessed for decremental properties. Follow-up was 12 months. Seventy-four patients were included and 85% had persistent AF. A total of 17,614 EGMs were individually analysed and measured. Nine percent of the EGMs showed DEEP properties (local delay of >10 ms after S2) with a mean decrement of 33±26 ms. DEEPs were more frequent in the left atrium than the right atrium (9.4% vs 8.0%; p<0.001) and more prevalent in persistent AF patients than paroxysmal AF patients (9.8% vs 4.6% p=0.001). Atrial DEEPs were more frequently unmasked in normal bipolar voltage areas and by epicardial pacing than endocardial pacing (9.6% vs 8.4%, respectively; p=0.004). Within the left atrium, the roof had the highest prevalence of DEEP EGMs. DEEP mapping of both atria is useful for highlighting areas with a tendency for unidirectional block and re-entry initiation. Those areas are more easily unmasked by epicardial pacing from the coronary sinus and more prevalent in persistent AF patients than in paroxysmal AF patients.

An annotation-independent algorithm based on electrogram characteristics to guide the identification of ventricular tachycardia isthmuses in patients with structural heart disease.

Criteria such as electrograms voltage or late potentials have been largely utilized in the past to help identify areas of substrate maps that are within the ventricular tachycardia (VT) isthmus; yet their specificity and positive predictive value are quite low. The Lumipoint fractionation tool of the Rhythmia system illuminates regions with fractionated electrograms irrespective of their timing and annotation. We aimed to ascertain whether the use of this tool can rapidly identify areas within VT isthmuses from substrate maps. Thirty patients with structural cardiomyopathy in whom a complete right ventricular-paced substrate map and a full reconstruction of the diastolic isthmus during VT could be obtained were enrolled. The VT isthmus border was projected on each substrate map to verify whether the areas illuminated by Lumipoint fell within those borders. The behavior of the electrograms detected at the illuminated areas of the substrate maps was studied during a right ventricular drive train and extra stimulus protocol: if the near field potentials showed a delayed conduction after a single extra stimulus, defined as a minimum of 10 ms increase of the time interval between the far field and the near field activation measured during the drive train, the electrogram was said to have a "decremental" behavior. The logistic analysis showed that areas with fractionated electrograms illuminated by the Lumipoint software and showing the greatest decremental behavior fell within the VT isthmus borders (OR = 1.66, CI: 1.41-1.75, p<0.001; OR=1.57 CI: 1.32-1.72, p<0.001, respectively) with a sensitivity, specificity, and positive predictive value of 87%, 96%, and 97%, respectively. Fractionated electrograms illuminated by the automated Lumipoint software on right ventricular-paced substrate maps showing the greatest decremental behavior fall within the VT isthmus borders with a probability of 0.97, irrespective of their timing, annotation, or voltage, without any need for subjective assessment of their involvement in slow conduction areas.

Effect of Internal Mechanical Environment of Porous Scaffolds On Mechano-driven Bone Ingrowth: a Numerical Study.

Porous cages with lower global stiffness induce more bone ingrowth and enhance bone-implant anchorage. However, for spinal fusion cages, which usually act as stabilizers, it's dangerous to sacrifice global stiffness for bone ingrowth. Intentional design on internal mechanical environment might be a promising approach to promote osseointegration without undermining global stiffness excessively. In this study, three porous cages with different architectures were designed to provide distinct internal mechanical environments for bone remodeling during spinal fusion process. A design space optimization-topology optimization based algorithm was utilized to numerically reproduce the mechano-driven bone ingrowth process under three daily load cases, and the fusion outcomes were analyzed in terms of bone morphological parameters and bone-cage stability. Simulation results show that the uniform cage with higher compliance induces deeper bone ingrowth than the optimized graded cage. Whereas, the optimized graded cage with the lowest compliance exhibits the lowest stress at the bone-cage interface and better mechanical stability. Combining the advantages of both, the strain-enhanced cage offers extra mechanical stimulus while keeping relatively low compliance, leading to more bone formation and the best mechanical stability. Thus, the internal mechanical environment can be well-designed via tailoring architectures to promote bone ingrowth and achieve a long-term bone-scaffold stability.

Retrograde ventriculoatrial jump-What is the mechanism?

During ventricular extra stimuli(VES) protocol a VA jump was noted. In upper panel with VES @ 500/270 ms (Fig A) the His signal appeared after the A-EGM, ruling out pure nodal VA conduction and confirming presence of an accessory pathway (AP). The H signal was delayed due to probable retrograde RBBB. The atrium was already depolarised via AP and the VA traversing via left bundle-His-node got blocked with a H signal. In the lower panel with VES of 500/260 ms the retrograde AP conduction reached the effective refractory period and pure nodal VA conduction took place along with retrograde RBBB. The retrograde VA jump was hence due to a jump from AP to AV node.

Determining physiological VT ablation targets in the era of early VT ablation

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Professor Nanthakumar is a recipient of the Mid-career Investigator Award from the Heart &amp; Stroke Foundation of Ontario. Background Ablation targets in the era of early ventricular tachycardia (VT) ablation will likely be driven by substrate-based physiological target approaches rather than activation mapping. Decrement evoked potentials (DeEP) have been co-localized to the diastolic VT circuit and are used as a method to perform VT ablation when VT cannot or should not be induced.1 Traditionally these potentials are evoked by a single extrastimulus. The incremental utility of a second extrastimulus in detecting these potentials has not been evaluated. Purpose We studied the utility of the second extra stimulus (S3) in detecting substrate ablation over the first extra stimulus (S2) following a drivetrain (S1) of 8 beats at 600ms. Methods DeEP was measured as the time difference between the pacing stimulus and the nearfield local activation delay on the bipolar electrogram during the S1 drivetrain and after the S2 or S3 respectively. Decrement of ≥10ms was considered a positive DeEP site. A total of 157 sites from 6 patients with VT were analysed. The incremental value of S3-induced DeEP was compared to the S2-induced DeEP. Results The mean decrement was significantly greater on the S3 compared to the S2 (41.8±35.6ms for S3 vs 25.8±20.4ms for S2, P &amp;lt;0.0001). The mean incremental value of the S3 was 15.9ms (95% CI, 11.5-20.3ms). From the 157 intracardiac electrograms studied, 79.1% had a positive DeEP with S2 alone. At the same electrode locations, an additional S3 evoked DeEP in 82.2% of sites. Conclusion When physiological substrate is present on the first extra stimulus, the second extra stimulus magnifies the identification of the target. However, we found in our study that the second extrastimulus uncovered a hidden arrhythmogenic substrate in only 3.1% additional mapped sites. Consequently, the utility of the second extrastimulus in identification of hidden substrate needs to be balanced with the risk of induction of potentially unstable rhythms.

A method to identify which patients will have VT substrate ablation targets prior to ablation procedure

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Dr Nanthakumar is a recipient of the Mid-career Investigator Award from the Heart &amp; Stroke Foundation of Ontario Background Recent trials in ventricular tachycardia (VT) ablation suggest that early ablation could reduce VT burden. A method to predict which patients will have substrate ablation targets based on non-invasive testing prior to the procedure does not exist and could be of value in selecting ideal patients for early VT substrate ablation. Decrement-evoked potential (DeEP) mapping is used to identify VT substrate ablation targets.1 A method for predicting which patients would have DeEP targets on a pre-ablation 12-lead ECG has not yet been developed. Objective To develop a metric to predict the presence of physiological substrate VT ablation targets from the 12-lead ECG. Method 22 electrophysiology (EP) lab VT cases that had undergone DeEP mapping were extracted from the CARTO® 3 system and were analysed retrospectively. For each case, DeEP was calculated by subtracting last component of the nearfield evoked response in the pacing train (S1) from the latest component of the nearfield evoked decremented response of the extra stimulus (S2). By inference, 12-lead ECG prediction was calculated by subtracting the width of the 12-lead surface ECG envelope of S1 from the width of the 12-lead ECG envelope of S2. Cases were divided into three categories: - Cases displaying intracardiac DeEP between 0-10ms – no ablation targets - Cases displaying intracardiac DeEP between 10-50ms – DeEP positive - Cases displaying intracardiac DeEP &amp;gt;50ms – prominent DeEP present Results Out of the 22 cases, 8 were characterised as no ablation targets, 12 as DeEP positive, and 2 as prominent DeEP present. The 12-lead surface ECG measurement means were 3.5±4.6ms for the no ablation target group, 23.2±9.1ms for positive DeEP group, and 80.9±8.1ms for prominent DeEP group. The surface ECG decrement was significantly different P&amp;lt;0.0001 between the three groups. Consequently, we propose that ECG QRS widening of envelope width of 20ms or more may indicate the presence of DeEP targets during invasive mapping. Conclusion It may be possible to detect which patients will have substrate ablation targets based on 12-lead ECG, prior to the VT ablation procedure. Additionally, this prediction rule, based on its association with arrhythmogenic potentials, may be able to predict which ambulatory patients who have not had manifest VT, may be prone to develop VT thus help identify early VT ablation candidates. This concept should be validated in larger data sets and is ideal for training and testing using surface ECG envelopes with artificial intelligence algorithms.

P403 MITRAL VALVE PROLAPSE AND RISK OF SUDDEN CARDIAC DEATH IN A PATIENT WITH VENTRICULAR ARRHYTHMIAS: THE PROGNOSTIC ROLE OF CARDIAC MAGNETIC RESONANCE IMAGING

Abstract Introduction in most cases mitral valve prolapse is a benign condition, however in 2% of cases it has been associated with the risk of sudden cardiac death (SCD). Basso et al have demonstrated papillary muscle’s and left ventricle’s inferolateral wall fibrosis on cardiac magnetic resonance imaging (MRI), in patients who died from SCD with mitral valve prolapse. Clinical case A 59–year–old patient was admitted to the Cardiology Department of Pertini Hospital (Rome, Italy) for episodes of vertigo and not sustained ventricular tachycardia in two morphologies at 24–hour ECG monitoring. The patient had negative history for cardiovascular risk factors, but an echocardiogram had demonstrated a moderate mitral valve regurgitation, secondary to valve prolapse with mitral annular disjunction (MAD) (Fig.1). Considering patient‘s age associated with low pre–test probability of coronary artery disease, the patient underwent coronary CT that showed a coronary artery tree free from injury. Cardiac MRI showed increased volumes in the left ventricle and slightly reduced systolic function and valve prolapse of both mitral leaflets determining moderate regurgitation. In addition, intra–myocardial Late Gadolinium Enhancement (LGE) showed fibrosis of the inferior and inferolateral wall with extension to the proximal portion of the inferior papillary muscle (Fig.2). Considering such findings, an intracavitary electrophysiological study (EPS) was performed for an evaluation of the arhythmic burden, by administrating the patient a double extra stimulus from the outflow tract of the right ventricle; the treatment induced a polymorphic ventricular tachycardia, starting from the inferior papillary muscle and degenerating into ventricular fibrillation (Fig.3). Discussion considering all the above findings, a mitral valve prolapse at high risk of malignant arrhythmias has been diagnosed and a subcutaneous cardiac defibrillator was implanted. Conclusions in mitral valve prolapse associated with complex ventricular arrhythmias, evaluation with cardiac MRI increasingly plays a crucial role in prognostic stratification for defibrillator implantation in primary prevention.

PO-01-163 CHARACTERIZATION OF ATRIAL SUBSTRATE USING CLOSE-COUPLED PACED ELECTROGRAM FEATURE ANALYSIS (PEFA) IN PATIENTS WITH NON-VALVULAR ATRIAL FIBRILLATION

Mapping strategies that lead to a better understanding and therapy for persistent atrial fibrillation (AF) are urged. Paced electrogram feature analysis (PEFA) exposes slow conduction zones as substrate for ventricular arrhythmias and previous studies support its efficacy for guiding ablation. PEFA has not been studied in the left atrium (LA). Our goal was to demonstrate that PEFA exposes slow conduction areas in the LA that may trigger and perpetuate AF. Prospective exploratory cohort study. The intervention group was formed by patients with paroxysmal AF undergoing catheter ablation (Group A), compared to a control group of patients without AF and structurally normal heart presenting for left-sided electrophysiological procedures (Group B). Antiarrhythmic drugs were discontinued at least five half-lives before the study and amiodarone, at least 3 months LA effective refractory period (AERP) was defined while pacing from the LA appendage (LAA). PEFA protocol consisted of a paced (S1) at 600 ms with an extra stimulus (S2) at a fixed coupling interval of AERP+30ms. EGM conduction time (time from pacing artifact to first deflection), EGM latency (conduction time from pacing artefact to local activation time of the S2 less same value for S1), EGM duration (first deflection to last deflection), EGM propagation time (latency + EGM duration), and last deflection (sum of CT + EGM duration) were defined (Figure 1). Group B data was used as the reference values, the percentage of abnormal EGM features in group A compared to group B were calculated. Twenty-four AF and 8 control patients were included. EGM features were evaluated in 13 different locations of the LA with a total of 12,291 EGMs to analyze (Table 1). Compared to non-AF controls, AF patients had a higher percentage of abnormal latency (10.43%, p<0.001), propagation time (12.04%, p<0.001), and last deflection (10.49%, p<0.001) for all locations evaluated together, however, the LA roof expressed more remarkable abnormal EGM properties than other areas (Table 1). There was no statistically significant difference in EGM duration between groups (p=0.83). PEFA exhibits abnormal conduction properties (latency, propagation time and last deflection) in certain areas of the LA. This may be used in the future to characterize AF substrate; objective assessment of these responses may inform ablation sites in patients with atrial fibrillation and warrants further study.Tabled 1Paced electrogram fractionation characteristics in patients with AF (Group A) and controls (Group B)EGM characteristicLatency (CT in S2 less CT in S1)Propagation (latency + EGM duration)Last deflection (sum of CT + EGM duration)Group A (N=9823)Time in ms (SD)Group B (N=2464)Time in ms (SD)% Abnormalp-valueGroup A (N=9823)Time in ms (SD)Group B (N=2464)Time in ms (SD)% Abnormalp-valueGroup A (N=9359)Time in ms (SD)Group B (N=2468)Time in ms (SD)% Abnormalp-valueAll54.7 (27.7)45.4 (21.9)10.43%<0.001*111.1 (35.9)101.6 (25.7)12.04%<0.001*172.0 (43.0)157.7 (31.5)10.49%<0.001*Anterior wall51.3 (28.4)45.1 (18.1)11.17%<0.001*113.2 (35.7)98.1 (22.3)19.39%<0.001*158.9 (34.7)154.5 (33.3)6.195%0.057Floor52.9 (27.2)36.6 (22.3)18.06%<0.001*109.2 (35.5)96.6 (28.3)10.31%<0.001*168.2 (44.7)149.8 (32.8)11.30%<0.001*LAA43.6 (40.5)32.7 (24.6)2.80%0.001*106.7 (48.2)100.4 (32.5)6.54%0.1192138.8 (48.2)131.0 (28.3)9.91%0.047*Left anterior wall55.0 (22.6)45.3 (18.0)14.34%<0.001*109.5 (29.5)104.4 (23.6)7.46%0.005*175.4 (38.4)153.6 (22.6)14.14%<0.001*LIPV33.8 (30.3)52.8 (14.4)6.94%<0.001*79.3 (36.7)96.9 (18.8)7.67%0.009*151.7 (34.5)161.0 (17.8)6.99%0.1470LSPV44.6 (34.7)54.4 (17.3)9.38%0.011*101.7 (44.3)102.7 (24.2)13.13%0.8265173.9 (33.8)169.0 (23.3)6.25%0.2189Mitral isthmus46.0 (26.0)43.6 (26.1)0.94%0.3334105.5 (35.0)101.3 (29.8)5.82%0.19137.5 (38.7)128.0 (29.2)7.36%0.006*Posterior wall53.9 (23.6)41.7 (16.7)19.26%<0.001*108.8 (33.2)92.5 (16.8)25.64%<0.001*178.6 (38.0)151.8 (21.4)27.61%<0.001*Right anterior wall62.1 (26.4)55.5 (15.8)17.47%<0.001*112.6 (33.7)109.3 (24.9)11.43%0.01191.6 (46.5)179.4 (24.7)14.08%<0.001*RIPV53.8 (13.1)60.3 (12.3)4.00%<0.001*97.1 (33.2)98.4 (18.1)6.4%0.01182.8 (32.8)184.5 (16.2)3.01%0.0682Roof57.1 (22.5)46.9 (17.3)26.63%<0.001*117.3 (30.3)100.2 (28.3)39.95%<0.001*175.5 (34.3)154.0 (49.5)36.96%<0.001*RSPV72.6 (27.0)63.5 (15.1)18.47%0.003*128.8 (46.3)113.4 (28.6)16.30%0.003*199.3 (29.5)200.4 (23.1)4.324%0.7597Septum61.7 (27.7)44.4 (28.0)10.64%<0.001*118.3 (37.7)106.4 (28.2)15.51%<0.001*184.6 (37.6)161.7 (30.2)12.61%<0.001**Statistically significant, CT: Conduction time, EGM: Electrogram, LAA: Left atrium appendage, LIPV: Left inferior pulmonary vein, LSPV: Left superior pulmonary vein, RIPV: Right inferior pulmonary vein, LIPV: Left inferior pulmonary vein. Open table in a new tab