Automatic Recognition of Ventricular Abnormal Potentials in Intracardiac Electrograms

Discrete potentials (DPs) have been recorded and targeted as the site of ablation of the outflow tract arrhythmias. The aim of the present study was to investigate the significance of DPs with respect to mapping and ablation for idiopathic outflow tract premature ventricular contractions (PVCs) or ventricular tachycardias (VTs). Seventeen out of 24 consecutive patients with idiopathic right or left ventricular outflow tract PVCs/VTs who underwent radiofrequency catheter ablation between September 2012 and December 2013 in our department were included. Intracardiac electrograms during the mapping and ablation were analyzed. During sinus rhythm, sharp high-frequency DPs that displayed double or multiple components were recorded following or buried in the local ventricular electrograms in all of the 17 patients, peak amplitude was (0.51 ± 0.21) mV. The same potential was recorded prior to the local ventricular potential of the PVCs/VTs. Spontaneous reversal of the relationship of the DPs to the local ventricular electrogram was noted during the arrhythmias. The DPs were related to a region of low voltage showed by intracardiac high-density contact mapping. At the sites with DPs, unipolar and bipolar ventricular voltage of sinus beats were lower compared with the adjacent regions without DPs (unipolar: (6.1 ± 1.8) mV vs. (8.3 ± 2.3) mV, P < 0.05; bipolar: (0.62 ± 0.45) mV vs. (1.03 ± 0.60) mV, P < 0.05). The targeted DPs were still present in 12 patients after successful elimination of the ectopies. Discrete potentials were not present in seven controls. Discrete potentials and related low-voltage regions were common in idiopathic outflow tract ventricular arrhythmias. Discrete potential- and substrate-guided ablation strategy could help to reduce the recurrence of idiopathic outflow tract arrhythmias.

Objective To investigate the radiofrequency catheter ablation(RFCA) of idiopathic ventricular arrhythmias(VAs) originating from the distal great cardiac veins(DGCV). Methods The study included 50 patients underwent successful RFCA of premature ventricular contraction(PVC)/ventricular tachycardia(VT) originating from different portions of the DGCV in Department of Cardiology, Second Affiliated Hospital of Wenzhou Medical University from October 2006 to March 2016.The intracardiac electrogram feature, intraventricular ablation mapping features and announcements of ablating PVC/VT originating from different portions of DGCV were assessed. Results The patients were divided into four groups according to the mapping and ablation results, DGCV1(11 patients, man 7, age 52.18±15.81), DGCV2(13 patients, man 7, age 51.01±15.22), proximalanterior interventricular vein(PAIV)(17 patients, man 9, age 52.51±14.35)and extend DGCV(EDGCV)(9 patients, man 3, age 52.91±14.11)groups.All four groups shared similar intracardiac electrogram feature in efficient ablation site.Bipolar mapping showed multi-peak fractional potentials 82.00%(41/50), 26.00%(13/50)with reserve potentials.Pace-mapping can be achieved in 45 patients(90%). The QRS complex morphology of pacing were perfect match(12/12)with spontaneous PVC/VT in 22 patients, near-perfect match(11/12)in 18 patients(10/12)in 5 patients. The veins of this area were thin and near the left coronary artery, so both coronary arteriongraphy(CAG) and coronary venography(CVG) should be performed before the ablation to ensure the security. Conclusion RFCA via the coronary venous system was a relatively effective and safe approach for PVC/VTs when fail to achieve the successful ablation in and under the aortic sinus and RVOT. Key words: Radiofrequency catheter ablation; Ventricular arrhythmias; Great cardiac veins

ORAL PRESENTATION

Ventricular abnormal potentials (VAPs) identification is a challenging issue, since they constitute the ablation targets in substrate-guided mapping and ablation procedures for ventricular tachycardia (VT) treatment. In this work, two approaches for the supervised classification of VAPs in bipolar intracardiac electrograms are evaluated and compared. To this aim, 954 bipolar electrograms were retrospectively annotated by an expert cardiologist. All signals were acquired from six patients affected by post-ischemic VT by the CARTO3 system at the San Francesco Hospital (Nuoro, Italy) during routine procedures. The first classification approach was based on a support vector machine trained and tested on four different features, extracted from both the time and time-scale domain, to identify physiological and abnormal potentials. Conversely, in order to assess the significance of the first approach and its features, in the second approach all the samples constituting a time-domain segment of each bipolar electrogram were given as input to a feed-forward artificial neural network. In both cases, the accuracy in VAPs and physiological potentials identification exceeded 79%, suggesting their efficacy and the possibility of VAPs automatic recognition without identifying peculiar features.

Funding AcknowledgementsType of funding sources: Foundation. Main funding source(s): Dr Nanthakumar is a recipient of the Mid-career Investigator Award from the Heart & Stroke Foundation of OntarioBackgroundRecent 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.ObjectiveTo develop a metric to predict the presence of physiological substrate VT ablation targets from the 12-lead ECG.Method22 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 >50ms – prominent DeEP presentResultsOut 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<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.ConclusionIt 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.Figure 1

The recurrence rate of ventricular tachycardia (VT) after ablation remains high due to the difficulty in locating VT critical sites. This study proposes a machine learning approach for improved identification of ablation targets based on intracardiac electrograms (EGMs) features derived from standard substrate mapping in a chronic myocardial infarction (MI) porcine model. Thirteen pigs with chronic MI underwent invasive electrophysiological studies using multipolar catheters (Advisor™ HD grid, EnSite Precision™). Fifty-six substrate maps and 35 068 EGMs were collected during sinus rhythm and pacing from multiple sites, including left, right, and biventricular pacing. Ventricular tachycardia was induced in all pigs, and a total of 36 VTs were localized and mapped with early, mid-, and late diastolic components of the circuit. Mapping sites within 6 mm from these critical sites were considered as potential ablation targets. Forty-six signal features representing functional, spatial, spectral, and time-frequency properties were computed from each bipolar and unipolar EGM. Several machine learning models were developed to automatically localize ablation targets, and logistic regressions were used to investigate the association between signal features and VT critical sites. Random forest provided the best accuracy based on unipolar signals from sinus rhythm map, provided an area under the curve of 0.821 with sensitivity and specificity of 81.4% and 71.4%, respectively. This study demonstrates for the first time that machine learning approaches based on EGM features may support clinicians in localizing targets for VT ablation using substrate mapping. This could lead to the development of similar approaches in VT patients.

AimsExisting strategies that identify post-infarct ventricular tachycardia (VT) ablation target either employ invasive electrophysiological (EP) mapping or non-invasive modalities utilizing the electrocardiogram (ECG). Their success relies on localizing sites critical to the maintenance of the clinical arrhythmia, not always recorded on the 12-lead ECG. Targeting the clinical VT by utilizing electrograms (EGM) recordings stored in implanted devices may aid ablation planning, enhancing safety and speed and potentially reducing the need of VT induction. In this context, we aim to develop a non-invasive computational-deep learning (DL) platform to localize VT exit sites from surface ECGs and implanted device intracardiac EGMs.Methods and resultsA library of ECGs and EGMs from simulated paced beats and representative post-infarct VTs was generated across five torso models. Traces were used to train DL algorithms to localize VT sites of earliest systolic activation; first tested on simulated data and then on a clinically induced VT to show applicability of our platform in clinical settings. Localization performance was estimated via localization errors (LEs) against known VT exit sites from simulations or clinical ablation targets. Surface ECGs successfully localized post-infarct VTs from simulated data with mean LE = 9.61 ± 2.61 mm across torsos. VT localization was successfully achieved from implanted device intracardiac EGMs with mean LE = 13.10 ± 2.36 mm. Finally, the clinically induced VT localization was in agreement with the clinical ablation volume.ConclusionThe proposed framework may be utilized for direct localization of post-infarct VTs from surface ECGs and/or implanted device EGMs, or in conjunction with efficient, patient-specific modelling, enhancing safety and speed of ablation planning.

Catheter ablation is a major treatment for atrial tachycardias. Hereby, the precise monitoring of the lesion formation is an important success factor. This book presents computational, wet-lab, and clinical studies with the aim of evaluating the signal characteristics of the intracardiac electrograms (IEGMs) recorded around ablation lesions from different perspectives. The detailed analysis of the IEGMs can optimize the description of durable and complex lesions during the ablation procedure.

Objective To review the characteristics of intraoperative 12-lead intracardiac electrograms in successful ablation of ventricular arrhythmias originating from outflow tract, and to obtain a rapid and effective method for locating left and right ventricular outflow tracts, in order to effectively determine the target orientation and reduce the operation time. Methods Retrospective analysis was performed on the figures of 125 patients successfully ablated on the site of right ventricular outflow tract (RVOT) and 32 cases originating from left ventricular outflow tract (LVOT) , underwent ablation for premature ventricular contraction (PVC) or ventricular tachycardia (VT) in Sir Run Run Shaw Hospital between June, 2016 and April, 2018. The patients with ventricular arrhythmia whose V1 lead was rS or QS, and the main wave of inferior wall leads was upward electrocardiographic manifestation were selected as the research objects. We measured and analyzed the R wave amplitude and R-wave peak time (RWPT) , R-wave maximum deflection index (MDI) , R-wave amplitude index in lead V2, S-wave amplitude in lead V2 divided by R-wave amplitude in lead V3 (SV2/RV3) , S-wave amplitude in former lead of R-wave transition in precordial lead divided by R-wave amplitude in transition in precordial lead (TS/R) , transitional zone index (TZI) . Results rS or QS type in lead V1, the T S/R had the highest specificity (88%) and the R-wave maximum deflection index in lead V2 had the highest sensitivity (87.5%) whether the heart was transposed or not. The SV2/RV3 had a higher sensitivity but a lower specificity than TS/R index. Conclusion T S/R index≤1.0, indicatingLVOT ventricular arrhythmia could be used as a new high specificity index, and the R-wave maximum deflection index in lead V2≥0.3 indicated a high sensitivity of LVOT in outflow tract PVC/VT. Key words: Electrocardiography; Arrhythmias, cardiac; Catheter ablation

Objective Until now, whether left posterior fascicular block (LPFB) could predict the success of ablation for fascicular ventricular tachycardia (VT) is ongoing controversy.In this study, we investigated whether LPFB could be as the predictor of left posterior fascicle VT(LPF-VT) long term success after ablation. Methods From January 2010 to December 2012, consecutive patients (n=67) with LPF-VT underwent mapping and ablation by using three dimension mapping and ablation were enrolled in department of cardiology the First Affiliated Hospital of Nanjing Medical University.Burst and programmed stimulation at the right atrium and right ventricle apex were used for VT inducing.Activation mapping was performed to find the ablation target (earliest fascicular potential, PP) during VT.Pace mapping was used to locate the ablation target for patients in whom VT could not be induced.Ablation was performed by delivering radiofrequency energy in temperature-control mode.According to LPFB or not, patients were assigned to LPFB group (group A) and LPF not block group (group B), and with long-term follow-up. Results Among 67 patients (mean age 30.1±12.6, male 53) with LPF-VT, VT could not be induced in two cases, failed ablation in one case.Ablation target with earliest P potential was located by activation mapping during VT in 61 patients.Ablation target was disclosed by pace mapping in 3 patients.Altogether, ablation was succeeding in 64 cases without inducing of VT with isoproterenol infusion.After ablation, 46 patients were enrolled in group A, and 18 were in group B. During (55.8±10.4)months of follow-up, the long term success rate after a single procedure without anti-arrhythmic agents was 82.8%(53/64). VT reoccurred in 11 cases, 8 cases in group A, 3 cases in group B(P=0.94). The mean duration of reoccurred time was 1.4-54.9(9.2±16.1) months after the ablation.All reoccurred 11 cases and one failed case had repeated successful ablation.No complications were observed in these cases. Conclusions Activation mapping guided ablation is highly effective and associated with long term clinical outcomes in patients with LPF-VT.The reoccurred rate was not lower in LPFB group, indicating that LPFB could not predict long term success of ablation for LPF-VT. Key words: Fascicular ventricular tachycardia; Activation mapping; Left posterior fascicle block

POSTER PRESENTATIONS

Structure and function of the ventricular tachycardia isthmus.

Objective To investigate the electrocardiographic characteristics of the multi-channel conduction phenomennon in the ventricular outflow tract(VOT). Methods From October 2010 to June 2015, a total of 897 patients received catheter ablation for PVC/IVT in the cardiology department of the Second Affiliated Hospital of Wenzhou Medical University, among them, 5 patients with PVC/IVT had multi-pathway conduction between ventricular outflow tracts.Electrocardiographic morphology indicated that arrhythmias might originate from VOT in 5 patients(1 males, average age of 40.6±10.9 years old)undergoing radiofrequency catheter ablation(RFCA), intracardiac electrocardiographic characteristics and variations were analysed during the procedure of mapping and ablation. Results The premature ventricular contractions(PVC)were originating from left ventricular outflow tract(LVOT), conducted by multi-channel between LVOT and right ventricular outflow(RVOT), and were successfully ablated in LVOT in two patients.The PVC were originating from RVOT, conducted via multi-channel between RVOT and LVOT, and finally were ablated in RVOT in three patients. Conclusions The phenomenon of multi-channel conduction in the VOT was rare.However, if this phenomenon is sufficiently recognized, a higher success rate of ablation can be expected. Key words: Left ventricular outflow tract; Right ventricular outflow; Multi-channel conduction; Electrocardiography

Are intracardiac defibrillator electrogram recordings of triggering ectopy the key to successful ablation of polymorphic ventricular tachycardia/ventricular fibrillation?

Under persistent atrial fibrillation (peAF), cardiac tissue experiences electrophysiological and structural remodeling. Fibrosis in the atrial tissue has an important impact on the myocyte action potential and its propagation. The objective of this work is to explore the effect of heterogeneities present in the fibrotic tissue and their impact on the intracardiac electrogram (EGM). Human atrial myocyte and fibroblast electrophysiology was simulated using mathematical models proposed by Koivumaki et al. to represent electrical remodeling under peAF and the paracrine effect of the transforming grow factor βl (TGF-βl). 2D tissue simulations were computed varying the density of fibrosis (10%, 20% and 40%), myofibroblasts and collagen were randomly distributed with different ratios (0%-100%, 50%-50% and 100%- 0%). Results show that increasing the fibrosis density changes the re-entry dynamics from functional to anatomical due to a block in conduction in regions with high fibrosis density (40%). EGM morphology was affected by different ratios of myofibroblasts-collagen. For low myofibroblast densities (below 50%) the duration of active segments was shorter compared to higher myofibroblasts densities (above 50%). Our results show that fibrosis heterogeneities can alter the dynamics of the re-entry and the morphology of the EGM.