Characterization of conduction system activation in the postinfarct ventricle using ripple mapping.

BACKGROUND: Three-dimensional (3D) mapping of the ventricular conduction system is challenging. OBJECTIVE: The purpose of this study was to use ripple mapping to distinguish conduction system activation to that of adjacent myocardium in order to characterize the conduction system in the postinfarct left ventricle (LV). METHODS: High-density mapping (PentaRay, CARTO) was performed during normal rhythm in patients undergoing ventricular tachycardia ablation. Ripple maps were viewed from the end of the P wave to QRS onset in 1-ms increments. Clusters of >3 ripple bars were interrogated for the presence of Purkinje potentials, which were tagged on the 3D geometry. Repeating this process allowed conduction system delineation. RESULTS: Maps were reviewed in 24 patients (mean 3112 ± 613 points). There were 150.9 ± 24.5 Purkinje potentials per map, at the left posterior fascicle (LPF) in 22 patients (92%) and at the left anterior fascicle (LAF) in 15 patients (63%). The LAF was shorter (41.4 vs 68.8 mm; P = .0005) and activated for a shorter duration (40.6 vs 64.9 ms; P = .002) than the LPF. Fourteen of 24 patients had left bundle branch block (LBBB), with 11 of 14 (78%) having Purkinje potential-associated breakout. There were fewer breakouts from the conduction system during LBBB (1.8 vs 3.4; 1.6 ± 0.6; P = .039) and an inverse correlation between breakout sites and QRS duration (P = .0035). CONCLUSION: We applied ripple mapping to present a detailed electroanatomic characterization of the conduction system in the postinfarct LV. Patients with broader QRS had fewer LV breakout sites from the conduction system. However, there was 3D mapping evidence of LV breakout from an intact conduction system in the majority of patients with LBBB.

The Nottingham Ischaemic Cardiovascular Magnetic Resonance resource (NotIs CMR): a prospective paired clinical and imaging scar database-protocol.

INTRODUCTION: Research utilising artificial intelligence (AI) and cardiovascular magnetic resonance (CMR) is rapidly evolving with various objectives, however AI model development, generalisation and performance may be hindered by availability of robust training datasets including contrast enhanced images. METHODS: NotIs CMR is a large UK, prospective, multicentre, observational cohort study to guide the development of a biventricular AI scar model. Patients with ischaemic heart disease undergoing clinically indicated contrast-enhanced cardiac magnetic resonance imaging will be recruited at Nottingham University Hospitals NHS Trust and Mid-Yorkshire Hospital NHS Trust. Baseline assessment will include cardiac magnetic resonance imaging, demographic data, medical history, electrocardiographic and serum biomarkers. Participants will undergo monitoring for a minimum of 5 years to document any major cardiovascular adverse events. The main objectives include (1) AI training, validation and testing to improve the performance, applicability and adaptability of an AI biventricular scar segmentation model being developed by the authors and (2) develop a curated, disease-specific imaging database to support future research and collaborations and, (3) to explore associations in clinical outcome for future risk prediction modelling studies. CONCLUSION: NotIs CMR will collect and curate disease-specific, paired imaging and clinical datasets to develop an AI biventricular scar model whilst providing a database to support future research and collaboration in Artificial Intelligence and ischaemic heart disease.

Ripple AT Plus - isthmus-guided vs conventional ablation in the treatment of scar-related atrial tachycardia: study protocol for a randomised controlled trial.

BACKGROUND: Catheter ablation is routinely used to treat scar-related atrial tachycardia (s-AT). Conventional ablation often involves creating anatomical "lines" that transect myocardial tissue supporting reentry. This can be extensive, creating iatrogenic scar as a nidus for future reentry, and may account for arrhythmia recurrence. High-density mapping may identify "narrower isthmuses" requiring less ablation, with ripple mapping proven to be an effective approach in identifying. This trial explores whether ablation of narrower isthmuses in s-AT, defined using ripple mapping, results in greater freedom from arrhythmia recurrence compared to conventional ablation. METHODS: The Ripple-AT-Plus trial (registration ClinicalTrials.gov , NCT03915691) is a prospective, multicentre, single-blinded, randomised controlled trial with 12-month follow-up. Two hundred s-AT patients will be randomised in a 1:1 fashion to either "ripple mapping-guided isthmus ablation" vs conventional ablation on the CARTO3 ConfiDENSE system (Biosense Webster). The primary outcome will compare recurrence of any atrial arrhythmia. Multicentre data will be analysed over a secure web-based cloud-storage and analysis software (CARTONETTM). CONCLUSION: This is the first trial that considers long-term patient outcomes post s-AT ablation, and whether targeting narrower isthmuses in the era of high density is optimal.

Hybrid surgical epicardial cryoablation for ventricular tachycardia in the electrophysiology laboratory: a case report.

Background: Scar-related ventricular tachycardia (VT) is a challenging medical condition, with catheter ablation providing a valuable treatment option. Whilst most VTs can be ablated endocardially, epicardial ablation is often required in patients with non-ischaemic cardiomyopathy. The percutaneous subxiphoid technique has become instrumental for epicardial access. However, it is not feasible in up to 28% of cases for multiple reasons. Case summary: A 47-year-old patient was managed at our centre for VT storm and recurrent implantable cardioverter defibrillator shocks for monomorphic VT despite maximum drug therapy. No scar was noted during endocardial mapping, with confirmation of the localized epicardial scar on cardiac magnetic resonance imaging (CMR). Following failed percutaneous epicardial access, a successful hybrid surgical epicardial VT cryoablation via median sternotomy was performed in the electrophysiology (EP) laboratory utilizing data from CMR, prior endocardial ablation, and conventional EP mapping. The patient has remained arrhythmia-free for 30 months post-ablation without antiarrhythmic therapy. Discussion: This case describes a practical multidisciplinary approach to managing a challenging clinical problem. Whilst the described technique is not entirely novel, this is the first case report that describes the practicalities and demonstrates the safety and feasibility of hybrid epicardial cryoablation via median sternotomy performed in the cardiac EP laboratory for the sole treatment of VT.

Deep Vein Thrombosis is Common After Cardiac Ablation and Pre-Procedural D-Dimer Could Predict Risk.

PURPOSE: Cardiac catheter ablations are an established treatment for supraventricular tachycardia (SVT) involving prolonged cannulation of the common femoral vein with multiple catheters. This study aimed to identify the risk of deep vein thrombosis (DVT) by studying the frequency of this complication after catheter ablation. METHODS: This was a prospective multi-centre cohort study of patients undergoing cardiac ablation for atrioventricular nodal re-entry tachycardia or right-sided accessory atrioventricular connection. Those taking anticoagulation or antiplatelet therapy prior to the procedure were excluded. Following the procedure, bilateral venous duplex ultrasonography from the popliteal vein to the inferior vena cava for DVT was undertaken at 24 hours and between 10 to 14 days. RESULTS: Eighty (80) patients (mean age 47.6 yrs [SD 13.4] with 67% female) underwent cardiac ablation (median duration 70 mins). Seven (7) patients developed acute DVT in either the femoral or external iliac vein of the intervention leg, giving a frequency of 8.8% (95% CI 3.6-17.2%). No thrombus was seen in the contralateral leg (p=0.023). An elevated D-dimer prior to the procedure was significantly more frequent in patients developing DVT (42.9% vs 4.1%, p=0.0081; OR 17.0). No other patient or procedural characteristics significantly influenced the risk of DVT. CONCLUSION: In patients without peri-procedural anticoagulation catheter ablation precipitated DVT in the catheterised femoral or iliac veins in 8.8% of patients. Peri-procedure prophylactic anticoagulation may be considered for all patients undergoing catheter ablation for SVT. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT03877770.

Real-world performance and accuracy of stress echocardiography: the EVAREST observational multi-centre study.

AIMS: Stress echocardiography is widely used to identify obstructive coronary artery disease (CAD). High accuracy is reported in expert hands but is dependent on operator training and image quality. The EVAREST study provides UK-wide data to evaluate real-world performance and accuracy of stress echocardiography. METHODS AND RESULTS: Participants undergoing stress echocardiography for CAD were recruited from 31 hospitals. Participants were followed up through health records which underwent expert adjudication. Cardiac outcome was defined as anatomically or functionally significant stenosis on angiography, revascularization, medical management of ischaemia, acute coronary syndrome, or cardiac-related death within 6 months. A total of 5131 patients (55% male) participated with a median age of 65 years (interquartile range 57-74). 72.9% of studies used dobutamine and 68.5% were contrast studies. Inducible ischaemia was present in 19.3% of scans. Sensitivity and specificity for prediction of a cardiac outcome were 95.4% and 96.0%, respectively, with an accuracy of 95.9%. Sub-group analysis revealed high levels of predictive accuracy across a wide range of patient and protocol sub-groups, with the presence of a resting regional wall motion abnormalitiy significantly reducing the performance of both dobutamine (P < 0.01) and exercise (P < 0.05) stress echocardiography. Overall accuracy remained consistently high across all participating hospitals. CONCLUSION: Stress echocardiography has high accuracy across UK-based hospitals and thus indicates stress echocardiography is being delivered effectively in real-world practice, reinforcing its role as a first-line investigation in the assessment of patients with stable chest pain.

Postinfarct ventricular tachycardia substrate: Characterization and ablation of conduction channels using ripple mapping.

BACKGROUND: Conduction channels have been demonstrated within the postinfarct scar and seem to be co-located with the isthmus of ventricular tachycardia (VT). Mapping the local scar potentials (SPs) that define the conduction channels is often hindered by large far-field electrograms generated by healthy myocardium. OBJECTIVE: The purpose of this study was to map conduction channel using ripple mapping to categorize SPs temporally and anatomically. We tested the hypothesis that ablation of early SPs would eliminate the latest SPs without direct ablation. METHODS: Ripple maps of postinfarct scar were collected using the PentaRay (Biosense Webster) during normal rhythm. Maps were reviewed in reverse, and clusters of SPs were color-coded on the geometry, by timing, into early, intermediate, late, and terminal. Ablation was delivered sequentially from clusters of early SPs, checking for loss of terminal SPs as the endpoint. RESULTS: The protocol was performed in 11 patients. Mean mapping time was 65 ± 23 minutes, and a mean 3050 ± 1839 points was collected. SP timing ranged from 98.1 ± 60.5 ms to 214.8 ± 89.8 ms post QRS peak. Earliest SPs were present at the border, occupying 16.4% of scar, whereas latest SPs occupied 4.8% at the opposing border or core. Analysis took 15 ± 10 minutes to locate channels and identify ablation targets. It was possible to eliminate latest SPs in all patients without direct ablation (mean ablation time 16.3 ± 11.1 minutes). No VT recurrence was recorded (mean follow-up 10.1 ± 7.4 months). CONCLUSION: Conduction channels can be located using ripple mapping to analyze SPs. Ablation at channel entrances can eliminate the latest SPs and is associated with good medium-term results.

Electroanatomic Characterization and Ablation of Scar-Related Isthmus Sites Supporting Perimitral Flutter.

OBJECTIVES: The authors reviewed 3-dimensional electroanatomic maps of perimitral flutter to identify scar-related isthmuses and determine their effectiveness as ablation sites. BACKGROUND: Perimitral flutter is usually treated by linear ablation between the left lower pulmonary vein and mitral annulus. Conduction block can be difficult to achieve, and recurrences are common. METHODS: Patients undergoing atrial tachycardia ablation using CARTO3 (Biosense Webster Inc., Irvine, California) were screened from 4 centers. Patients with confirmed perimitral flutter were reviewed for the presence of scar-related isthmuses by using CARTO3 with the ConfiDense and Ripple Mapping modules. RESULTS: Confirmed perimitral flutter was identified in 28 patients (age 65.2 ± 8.1 years), of whom 26 patients had prior atrial fibrillation ablation. Scar-related isthmus ablation was performed in 12 of 28 patients. Perimitral flutter was terminated in all following correct identification of a scar-related isthmus using ripple mapping. The mean scar voltage threshold was 0.11 ± 0.05 mV. The mean width of scar-related isthmuses was 8.9 ± 3.5 mm with a conduction speed of 31.8 ± 5.5 cm/s compared to that of normal left atrium of 71.2 ± 21.5 cm/s (p < 0.0001). Empirical, anatomic ablation was performed in 16 of 28, with termination in 10 of 16 (63%; p = 0.027). Significantly less ablation was required for critical isthmus ablation compared to empirical linear lesions (11.4 ± 5.3 min vs. 26.2 ± 17.1 min; p = 0.0004). All 16 cases of anatomic ablation were reviewed with ripple mapping, and 63% had scar-related isthmus. CONCLUSIONS: Perimitral flutter is usually easy to diagnose but can be difficult to ablate. Ripple mapping is highly effective at locating the critical isthmus maintaining the tachycardia and avoiding anatomic ablation lines. This approach has a higher termination rate with less radiofrequency ablation required.

Diagnostic utility of artificial intelligence for left ventricular scar identification using cardiac magnetic resonance imaging-A systematic review.

Background: Accurate, rapid quantification of ventricular scar using cardiac magnetic resonance imaging (CMR) carries importance in arrhythmia management and patient prognosis. Artificial intelligence (AI) has been applied to other radiological challenges with success. Objective: We aimed to assess AI methodologies used for left ventricular scar identification in CMR, imaging sequences used for training, and its diagnostic evaluation. Methods: Following PRISMA recommendations, a systematic search of PubMed, Embase, Web of Science, CINAHL, OpenDissertations, arXiv, and IEEE Xplore was undertaken to June 2021 for full-text publications assessing left ventricular scar identification algorithms. No pre-registration was undertaken. Random-effect meta-analysis was performed to assess Dice Coefficient (DSC) overlap of learning vs predefined thresholding methods. Results: Thirty-five articles were included for final review. Supervised and unsupervised learning models had similar DSC compared to predefined threshold models (0.616 vs 0.633, P = .14) but had higher sensitivity, specificity, and accuracy. Meta-analysis of 4 studies revealed standardized mean difference of 1.11; 95% confidence interval -0.16 to 2.38, P = .09, I2 = 98% favoring learning methods. Conclusion: Feasibility of applying AI to the task of scar detection in CMR has been demonstrated, but model evaluation remains heterogenous. Progression toward clinical application requires detailed, transparent, standardized model comparison and increased model generalizability.

Ripple-AT Study: A Multicenter and Randomized Study Comparing 3D Mapping Techniques During Atrial Tachycardia Ablations.

BACKGROUND: Ripple mapping (RM) is an alternative approach to activation mapping of atrial tachycardia (AT) that avoids electrogram annotation. We tested whether RM is superior to conventional annotation based local activation time (LAT) mapping for AT diagnosis in a randomized and multicenter study. METHODS: Patients with AT were randomized to either RM or LAT mapping using the CARTO3v4 CONFIDENSE system. Operators determined the diagnosis using the assigned 3D mapping arm alone, before being permitted a single confirmatory entrainment manuever if needed. A planned ablation lesion set was defined. The primary end point was AT termination with delivery of the planned ablation lesion set. The inability to terminate AT with this first lesion set, the use of more than one entrainment manuever, or the need to crossover to the other mapping arm was defined as failure to achieve the primary end point. RESULTS: One hundred five patients from 7 centers were recruited with 22 patients excluded due to premature AT termination, noninducibility or left atrial appendage thrombus. Eighty-three patients (pts; RM=42, LAT=41) completed mapping and ablation within the 2 groups of similar characteristics (RM versus LAT: prior ablation or cardiac surgery n=35 [83%] versus n=35 [85%], P=0.80). The primary end point occurred in 38/42 pts (90%) in the RM group and 29/41pts (71%) in the LAT group (P=0.045). This was achieved without any entrainment in 31/42 pts (74%) with RM and 18/41 pts (44%) with LAT (P=0.01). Of those patients who failed to achieve the primary end point, AT termination was achieved in 9/12 pts (75%) in the LAT group following crossover to RM with entrainment, but 0/4 pts (0%) in the RM group crossing over to LAT mapping with entrainment (P=0.04). CONCLUSIONS: RM is superior to LAT mapping on the CARTO3v4 CONFIDENSE system in guiding ablation to terminate AT with the first lesion set and with reduced entrainment to assist diagnosis. CLINICAL TRIALS REGISTRATION: https://www.clinicaltrials.gov. Unique identifier: NCT02451995.

Isthmus sites identified by Ripple Mapping are usually anatomically stable: A novel method to guide atrial substrate ablation?

BACKGROUND: Postablation reentrant ATs depend upon conducting isthmuses bordered by scar. Bipolar voltage maps highlight scar as sites of low voltage, but the voltage amplitude of an electrogram depends upon the myocardial activation sequence. Furthermore, a voltage threshold that defines atrial scar is unknown. We used Ripple Mapping (RM) to test whether these isthmuses were anatomically fixed between different activation vectors and atrial rates. METHODS: We studied post-AF ablation ATs where >1 rhythm was mapped. Multipolar catheters were used with CARTO Confidense for high-density mapping. RM visualized the pattern of activation, and the voltage threshold below which no activation was seen. Isthmuses were characterized at this threshold between maps for each patient. RESULTS: Ten patients were studied (Map 1 was AT1; Map 2: sinus 1/10, LA paced 2/10, AT2 with reverse CS activation 3/10; AT2 CL difference 50 ± 30 ms). Point density was similar between maps (Map 1: 2,589 ± 1,330; Map 2: 2,214 ± 1,384; P  =  0.31). RM activation threshold was 0.16 ± 0.08 mV. Thirty-one isthmuses were identified in Map 1 (median 3 per map; width 27 ± 15 mm; 7 anterior; 6 roof; 8 mitral; 9 septal; 1 posterior). Importantly, 7 of 31 (23%) isthmuses were unexpectedly identified within regions without prior ablation. AT1 was treated following ablation of 11/31 (35%) isthmuses. Of the remaining 20 isthmuses, 14 of 16 isthmuses (88%) were consistent between the two maps (four were inadequately mapped). Wavefront collision caused variation in low voltage distribution in 2 of 16 (12%). CONCLUSIONS: The distribution of isthmuses and nonconducting tissue within the ablated left atrium, as defined by RM, appear concordant between rhythms. This could guide a substrate ablative approach.

A Prospective Study of Ripple Mapping the Post-Infarct Ventricular Scar to Guide Substrate Ablation for Ventricular Tachycardia.

BACKGROUND: Post-infarct ventricular tachycardia is associated with channels of surviving myocardium within scar characterized by fractionated and low-amplitude signals usually occurring late during sinus rhythm. Conventional automated algorithms for 3-dimensional electro-anatomic mapping cannot differentiate the delayed local signal of conduction within the scar from the initial far-field signal generated by surrounding healthy tissue. Ripple mapping displays every deflection of an electrogram, thereby providing fully informative activation sequences. We prospectively used CARTO-based ripple maps to identify conducting channels as a target for ablation. METHODS AND RESULTS: High-density bipolar left ventricular endocardial electrograms were collected using CARTO3v4 in sinus rhythm or ventricular pacing and reviewed for ripple mapping conducting channel identification. Fifteen consecutive patients (median age 68 years, left ventricular ejection fraction 30%) were studied (6 month preprocedural implantable cardioverter defibrillator therapies: median 19 ATP events [Q1-Q3=4-93] and 1 shock [Q1-Q3=0-3]). Scar (<1.5 mV) occupied a median 29% of the total surface area (median 540 points collected within scar). A median of 2 ripple mapping conducting channels were seen within each scar (length 60 mm; initial component 0.44 mV; delayed component 0.20 mV; conduction 55 cm/s). Ablation was performed along all identified ripple mapping conducting channels (median 18 lesions) and any presumed interconnected late-activating sites (median 6 lesions; Q1-Q3=2-12). The diastolic isthmus in ventricular tachycardia was mapped in 3 patients and colocated within the ripple mapping conducting channels identified. Ventricular tachycardia was noninducible in 85% of patients post ablation, and 71% remain free of ventricular tachycardia recurrence at 6-month median follow-up. CONCLUSIONS: Ripple mapping can be used to identify conduction channels within scar to guide functional substrate ablation.

A Prospective Study of Ripple Mapping in Atrial Tachycardias: A Novel Approach to Interpreting Activation in Low-Voltage Areas.

BACKGROUND: Post ablation atrial tachycardias are characterized by low-voltage signals that challenge current mapping methods. Ripple mapping (RM) displays every electrogram deflection as a bar moving from the cardiac surface, resulting in the impression of propagating wavefronts when a series of bars move consecutively. RM displays fractionated signals in their entirety thereby helping to identify propagating activation in low-voltage areas from nonconducting tissue. We prospectively used RM to study tachycardia activation in the previously ablated left atrium. METHODS AND RESULTS: Patients referred for atrial tachycardia ablation underwent dense electroanatomic point collection using CARTO3v4. RM was played over a bipolar voltage map and used to determine the voltage "activation threshold" that differentiated functional low voltage from nonconducting areas for each map. Ablation was guided by RM, but operators could perform entrainment or review the isochronal activation map for diagnostic uncertainty. Twenty patients were studied. Median RM determined activation threshold was 0.3 mV (0.19-0.33), with nonconducting tissue covering 33±9% of the mapped surface. All tachycardias crossed an isthmus (median, 0.52 mV, 13 mm) bordered by nonconducting tissue (70%) or had a breakout source (median, 0.35 mV) moving away from nonconducting tissue (30%). In reentrant circuits (14/20) the path length was measured (87-202 mm), with 9 of 14 also supporting a bystander circuit (path lengths, 147-234 mm). In breakout tachycardias, splitting of wavefronts resulted in 2 to 4 incomplete circuits. RM-guided ablation interrupted the tachycardia in 19 of 20 cases with the first ablation set. CONCLUSIONS: RM helps to define activation through low-voltage regions and aids ablation of atrial tachycardias.

A diagnostic algorithm to optimize data collection and interpretation of Ripple Maps in atrial tachycardias.

BACKGROUND: Ripple Mapping (RM) is designed to overcome the limitations of existing isochronal 3D mapping systems by representing the intracardiac electrogram as a dynamic bar on a surface bipolar voltage map that changes in height according to the electrogram voltage-time relationship, relative to a fiduciary point. OBJECTIVE: We tested the hypothesis that standard approaches to atrial tachycardia CARTO™ activation maps were inadequate for RM creation and interpretation. From the results, we aimed to develop an algorithm to optimize RMs for future prospective testing on a clinical RM platform. METHODS: CARTO-XP™ activation maps from atrial tachycardia ablations were reviewed by two blinded assessors on an off-line RM workstation. Ripple Maps were graded according to a diagnostic confidence scale (Grade I - high confidence with clear pattern of activation through to Grade IV - non-diagnostic). The RM-based diagnoses were corroborated against the clinical diagnoses. RESULTS: 43 RMs from 14 patients were classified as Grade I (5 [11.5%]); Grade II (17 [39.5%]); Grade III (9 [21%]) and Grade IV (12 [28%]). Causes of low gradings/errors included the following: insufficient chamber point density; window-of-interest<100% of cycle length (CL); <95% tachycardia CL mapped; variability of CL and/or unstable fiducial reference marker; and suboptimal bar height and scar settings. CONCLUSIONS: A data collection and map interpretation algorithm has been developed to optimize Ripple Maps in atrial tachycardias. This algorithm requires prospective testing on a real-time clinical platform.

Non-randomised comparison of acute and long-term outcomes of robotic versus manual ventricular tachycardia ablation in a single centre ischemic cohort.

INTRODUCTION: Robotically guided radiofrequency (RF) ablation offers greater catheter stability that may improve lesion depth. We performed a non-randomised comparison of patients undergoing ventricular tachycardia (VT) ablation either manually or robotically using the Hansen Sensei system for recurrent implantable defibrillator (ICD) therapy. METHODS: Patients with infarct-related scar underwent VT ablation using the Hansen system to assess feasibility compared with patients undergoing manual VT ablation during a similar time period. Power delivery during robotic ablation was restricted to 30 W at 60 s. VT inducibility was checked at the end of the procedure. Pre-ablation ICD therapy burdens over 6 months were compared with post-ablation therapy averaged to a 6-month period. RESULTS: Twelve consecutive patients who underwent robotic VT ablation were compared to 12 consecutive patients undergoing a manual ablation. Patient demographics and comorbidities were similar in the two groups. A higher proportion of robotic cases were urgent (9/12 (75%)) vs. manual (4/12 (33%)) (p = 0.1). Post-ablation VT stimulation did not induce clinical VT in 11/12 (92%) in each group. There were no peri-procedural complications related to ablation delivery. Patients were followed up for approximately 2 years. Averaged over 6 months, robotic ICD therapy burdens fell from 32 (5-400) events to 2.5 (0-11) (p = 0.015). Therapy burden fell from 14 (10-25) to 1 (0-5) (p = 0.023) in the manual group. There was no difference in long-term outcome (p = 0.60) and mortality (4/12 (33%), p = 1.0). CONCLUSION: Robotically guided VT ablation is both feasible and safe when compared to manual ablation with good acute and long-term outcomes.

Application of ripple mapping to visualize slow conduction channels within the infarct-related left ventricular scar.

BACKGROUND: Ripple mapping (RM) displays each electrogram at its 3-dimensional coordinate as a bar changing in length according to its voltage-time relationship with a fiduciary reference. We applied RM to left ventricular ischemic scar for evidence of slow-conducting channels that may act as ventricular tachycardia (VT) substrate. METHODS AND RESULTS: CARTO-3© (Biosense Webster Inc, Diamond Bar, CA) maps in patient undergoing VT ablation were analyzed on an offline MatLab RM system. Scar was assessed for sequential movement of ripple bars, during sinus rhythm or pacing, which were distinct from surrounding tissue and termed RM conduction channels (RMCC). Conduction velocity was measured within RMCCs and compared with the healthy myocardium (>1.5 mV). In 21 maps, 77 RMCCs were identified. Conduction velocity in RMCCs was slower when compared with normal left ventricular myocardium (median, 54 [interquartile range, 40-86] versus 150 [interquartile range, 120-160] cm/s; P<0.001). All 7 sites meeting conventional criteria for diastolic pathways coincided with an RMCC. Seven patients had ablation colocating to all identified RMCCs with no VT recurrence during follow-up (median, 480 [interquartile range, 438-841] days). Fourteen patients had ≥1 RMCC with no ablation lesions. Five had recurrence during follow-up (median, 466 [interquartile range, 395-694] days). One of the 2 patients with no RMCC locations ablated had VT recurrence at 605 days post procedure. RMCCs were sensitive (100%; negative predictive value, 100%) for VT recurrence but the specificity (43%; positive predictive value, 35.7%) may be limited by blind alleys channels. CONCLUSIONS: RM identifies slow conduction channels within ischemic scar and needs further prospective investigation to understand the role of RMCCs in determining the VT substrate.

Noninvasive electrocardiographic mapping to guide ablation of outflow tract ventricular arrhythmias.

BACKGROUND: Localizing the origin of outflow tract ventricular tachycardias (OTVT) is hindered by lack of accuracy of electrocardiographic (ECG) algorithms and infrequent spontaneous premature ventricular complexes (PVCs) during electrophysiological studies. OBJECTIVES: To prospectively assess the performance of noninvasive electrocardiographic mapping (ECM) in the pre-/periprocedural localization of OTVT origin to guide ablation and to compare the accuracy of ECM with that of published ECG algorithms. METHODS: Patients with symptomatic OTVT/PVCs undergoing clinically indicated ablation were recruited. The OTVT/PVC origin was mapped preprocedurally by using ECM, and 3 published ECG algorithms were applied to the 12-lead ECG by 3 blinded electrophysiologists. Ablation was guided by using ECM. The OTVT/PVC origin was defined as the site where ablation caused arrhythmia suppression. Acute success was defined as abolition of ectopy after ablation. Medium-term success was defined as the abolition of symptoms and reduction of PVC to less than 1000 per day documented on Holter monitoring within 6 months. RESULTS: In 24 patients (mean age 50 ± 18 years) recruited ECM successfully identified OTVT/PVC origin in 23/24 (96%) (right ventricular outflow tract, 18; left ventricular outflow tract, 6), sublocalizing correctly in 100% of this cohort. Acute ablation success was achieved in 100% of the cases with medium-term success in 22 of 24 patients. PVC burden reduced from 21,837 ± 23,241 to 1143 ± 4039 (P < .0001). ECG algorithms identified the correct chamber of origin in 50%-88% of the patients and sublocalized within the right ventricular outflow tract (septum vs free-wall) in 37%-58%. CONCLUSIONS: ECM can accurately identify OTVT/PVC origin in the left and the right ventricle pre- and periprocedurally to guide catheter ablation with an accuracy superior to that of published ECG algorithms.

Application of ripple mapping with an electroanatomic mapping system for diagnosis of atrial tachycardias.

BACKGROUND: Three-dimensional (3D) mapping is often used to guide ablation in atrial tachycardia (AT), but maps can be susceptible to annotation and interpolation errors. Ripple Mapping (RM) is a technique that displays electrogram time-voltage data simultaneously as dynamic bars on the surface shell to overcome these limitations. OBJECTIVES: We hypothesized that RM would be superior to established 3D activation mapping. METHODS: CARTO-XP™ maps of ATs were collected without any manual annotation and studied on a CARTO-based offline RM system. Paired unannotated CARTO-XP and Ripple Maps were presented to experienced CARTO users with limited RM training. These assessors were allowed to annotate the CARTO-XP maps, but were blinded to conventional EP data. RESULTS: CARTO-XP maps of AT (10 patients) were studied in RM format and the diagnosis was confirmed by entrainment in all cases and with termination of tachycardia in 9/10 cases. Blinded assessors (n = 11) reached the correct diagnosis using RM in 35/44 (80%) compared to 22/44 (50%) using CARTO-XP (P = 0.029). The time to the correct diagnosis was also shorter with RM (136 seconds vs. 212 seconds; P = 0.022). The causes of diagnostic errors using RM (insufficient point density, particularly in low-voltage areas, and the operator not assessing all available views) were overcome with an improved MatLab version showing both scar and dynamic bars on the same shell. CONCLUSION: RM does not need any manual annotation of local activation time and enables rapid diagnosis of AT with higher diagnostic accuracy than conventional 3D activation mapping.

Characterization of the left atrial neural network and its impact on autonomic modification procedures.

BACKGROUND: Left atrial (LA) ganglionated plexi (GP) are part of the intrinsic cardiac autonomic nervous system and implicated in the pathogenesis of atrial fibrillation. High frequency stimulation is used to identify GP sites in humans. The effect of ablation on neural pathways connecting GPs in humans is unknown. METHODS AND RESULTS: Thirty patients undergoing LA ablation with autonomic modification were recruited. In patients with persistent atrial fibrillation, endocardial continuous high frequency stimulation identified GP sites producing AV block. After right lower GP ablation (N=5), 2 of 15 sites remained positive, whereas after ablation of other GPs (N=5), leaving right lower GP intact, all 19 sites remained positive (right lower GP versus other GP, P<0.005), indicating that neural pathways between LAGPs and the AV node are via the right lower GP. In 20 patients with paroxysmal atrial fibrillation, synchronized high frequency stimulation identified sites initiating pulmonary vein (PV) ectopy. After PV isolation (N=8), no sites remained positive. After local GP ablation (N=9), 3 of 14 sites remained positive, suggesting neural connections to the PV were disrupted by both PV isolation and GP ablation. Heart rate variability indices reduced significantly after right upper GP ablation alone, suggesting that neural pathways from the LA to the SA node travel via the right upper GP. CONCLUSIONS: We have demonstrated neural pathways connecting LA GPs with the PVs, AV node, and SA node. The effects of high frequency stimulation at GP sites can be prevented by ablating the GP site or the neural pathway. This further delineates the mechanism via which PV isolation prevents atrial fibrillation and highlights important caveats for autonomic modification end points.