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Background Ablation of autonomic ectopy-triggering ganglionated plexuses (ET-GP) has been used to treat paroxysmal atrial fibrillation (AF). It is not known if ET-GP localisation is reproducible between different stimulators or whether ET-GP can be mapped and ablated in persistent AF. We tested the reproducibility of the left atrial ET-GP location using different high-frequency high-output stimulators in AF. In addition, we tested the feasibility of identifying ET-GP locations in persistent atrial fibrillation. Methods Nine patients undergoing clinically-indicated paroxysmal AF ablation received pacing-synchronised high-frequency stimulation (HFS), delivered in SR during the left atrial refractory period, to compare ET-GP localisation between a custom-built current-controlled stimulator (Tau20) and a voltage-controlled stimulator (Grass S88, SIU5). Two patients with persistent AF underwent cardioversion, left atrial ET-GP mapping with the Tau20 and ablation (Precision™, Tacticath™ [n = 1] or Carto™, SmartTouch™ [n = 1]). Pulmonary vein isolation (PVI) was not performed. Efficacy of ablation at ET-GP sites alone without PVI was assessed at 1 year. Results The mean output to identify ET-GP was 34 mA (n = 5). Reproducibility of response to synchronised HFS was 100% (Tau20 vs Grass S88; [n = 16] [kappa = 1, SE = 0.00, 95% CI 1 to 1)][Tau20 v Tau20; [n = 13] [kappa = 1, SE = 0, 95% CI 1 to 1]). Two patients with persistent AF had 10 and 7 ET-GP sites identified requiring 6 and 3 min of radiofrequency ablation respectively to abolish ET-GP response. Both patients were free from AF for > 365 days without anti-arrhythmics. Conclusions ET-GP sites are identified at the same location by different stimulators. ET-GP ablation alone was able to prevent AF recurrence in persistent AF, and further studies would be warranted.

Background Ganglionated plexuses (GPs) are implicated in atrial fibrillation (AF). Endocardial high‐frequency stimulation (HFS) delivered within the local atrial refractory period can trigger ectopy and AF from specific GP sites (ET‐GP). The aim of this study was to understand the role of ET‐GP ablation in the treatment of AF. Methods Patients with paroxysmal AF indicated for ablation were recruited. HFS mapping was performed globally around the left atrium to identify ET‐GP. ET‐GP was defined as atrial ectopy or atrial arrhythmia triggered by HFS. All ET‐GP were ablated, and PVs were left electrically connected. Outcomes were compared with a control group receiving pulmonary vein isolation (PVI). Patients were followed‐up for 12 months with multiple 48‐h Holter ECGs. Primary endpoint was ≥30 s AF/atrial tachycardia in ECGs. Results In total, 67 patients were recruited and randomized to ET‐GP ablation (n = 39) or PVI (n = 28). In the ET‐GP ablation group, 103 ± 28 HFS sites were tested per patient, identifying 21 ± 10 (20%) GPs. ET‐GP ablation used 23.3 ± 4.1 kWs total radiofrequency (RF) energy per patient, compared with 55.7 ± 22.7 kWs in PVI (p =

The ganglionated plexuses (GPs) of the intrinsic cardiac autonomic system may play a role in atrial fibrillation (AF).We hypothesized that ablating the ectopy-triggering GPs (ET-GPs) prevents AF.GANGLIA-AF (ClinicalTrials.gov identifier NCT02487654) was a prospective, randomized, controlled, 3-center trial. ET-GPs were mapped using high frequency stimulation, delivered within the atrial refractory period and ablated until nonfunctional. If triggered AF became incessant, atrioventricular dissociating GPs were ablated. We compared GP ablation (GPA) without pulmonary vein isolation (PVI) against PVI in patients with paroxysmal AF. Follow-up was for 12 months including 3-monthly 48-hour Holter monitors. The primary end point was documented ≥30 seconds of atrial arrhythmia after a 3-month blanking period.A total of 102 randomized patients were analyzed on a per-protocol basis after GPA (n = 52; 51%) or PVI (n = 50; 49%). Patients who underwent GPA had 89 ± 26 high frequency stimulation sites tested, identifying a median of 18.5% (interquartile range 16%-21%) of GPs. The radiofrequency ablation time was 22.9 ± 9.8 minutes in GPA and 38 ± 14.4 minutes in PVI (P.0001). The freedom from ≥30 seconds of atrial arrhythmia at 12-month follow-up was 50% (26 of 52) with GPA vs 64% (32 of 50) with PVI (log-rank, P = .09). ET-GPA without atrioventricular dissociating GPA achieved 58% (22 of 38) freedom from the primary end point. There was a significantly higher reduction in antiarrhythmic drug usage postablation after GPA than after PVI (55.5% vs 36%; P = .05). Patients were referred for redo ablation procedures in 31% (16 of 52) after GPA and 24% (12 of 50) after PVI (P = .53).GPA did not prevent atrial arrhythmias more than PVI. However, less radiofrequency ablation was delivered to achieve a higher reduction in antiarrhythmic drug usage with GPA than with PVI.

Background: The mechanisms underlying atrial fibrillation (AF) remain controversial. We developed Representation of Electrical Tracking or Origin-Mapping to characterize activation wavefronts by direction and uniformity, accumulating data as an orbital plot and analyzed as frequency histograms. We applied this technique to patients undergoing AF ablation to determine if AF activation is random. Methods: Patients undergoing persistent AF ablation were recruited, and an AFocusII was positioned at multiple left atrial locations and kept steady for 1 minute to collect electrograms. The AFocusII was returned to the original site and position after >10 minutes for a repeat 1-minute data collection. Data were exported to custom Representation of Electrical Tracking or Origin-Mapping software, and 30 seconds consecutive time windows at each location were studied using frequency histograms of wavefronts. R50 (the range in degrees containing 50% of the total activation) was used as a method to enable statistical comparisons of activation patterns. Electrogram characterization into categories of complex fractionated atrial electrograms by Ensite Precision was subjected to similar analysis. Results: Consecutive 30 seconds segments were studied at 161 locations in 18 pts. Mean overlap between frequency histograms was 79.5%±7.7 (95% CI, 78.3–80.7). Nine patients underwent delayed mapping at the same location, and mean overlap between the first 30 seconds and >10 minute interval was 73%±11.8 and 71.9%±13.6 for consecutive 30-second segments. Stability was confirmed using R50 (Bland-Altman mean difference: 0.87°; limits of agreement: −34.0 to 36.0; r =0.005; P =0.95). A greater variance in R50 was observed between different locations within a patient than the variance within the same locations (intraclass correlation=0.765; P P r =0.36, P Conclusions: There appears to be preferential activation patterns during persistent AF indicating spatiotemporal stability. This has important implication to our mechanistic understanding of persistent AF.

Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation Background Cardiac resynchronization therapy delivered via biventricular pacing is thought to improve haemodynamic function through resynchronization of ventricular activation. Biventricular pacing also improves ventricular filling by shortening atrioventricular delay. Quantifying the relative contributions of these two mechanisms requires atrioventricular delay to be altered while left bundle branch block is preserved. This occurs when the His bundle is paced at an output below the left bundle branch block correction threshold. Purpose We performed His bundle pacing with preservation of left bundle branch block to measure the relative contributions of atrioventricular delay shortening and ventricular resynchronisation to the overall haemodynamic benefit of biventricular pacing. Methods Patients with left bundle branch block referred for conventional cardiac resynchronization therapy with biventricular pacing were recruited. Using a high precision, beat-by-beat systolic blood pressure assessment protocol, we assessed the haemodynamic effects of biventricular pacing and temporary His bundle pacing with left bundle branch block preservation at a full range of atrioventricular delays. We used non-invasive epicardial mapping (ECGI) to assess left ventricular activation time. Left bundle branch block preservation was defined as Results In 19 patients, His bundle pacing with preservation of left bundle branch block produced a peak systolic blood pressure improvement of 5.1mmHg (95% confidence interval: 2.2 to 8.0, p = 0.0013) compared to AAI pacing. In 16 of these patients, biventricular pacing was performed and produced a peak systolic blood pressure improvement of 7.1mmHg (3.8 to 10.4, p Conclusion Biventricular pacing in left bundle branch block improves haemodynamic function through ventricular resynchronization and shortening of atrioventricular delay. The majority of benefit appears to be produced by atrioventricular delay shortening. When left bundle branch block is not corrected, His bundle pacing may still produce considerable haemodynamic improvement through this mechanism. Abstract Figure.

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.

Funding Acknowledgements Type of funding sources: Other. Main funding source(s): BRAVO trial: BHF SP/10/002/28189, FS/10/038, FS/11/92/29122, FS/13/44/30291) National Institute for Health Research Imperial Biomedical Research Centre. HOPE-HF trial: British Heart Foundation (CS/15/3/31405, FS/13/44/30291, FS/15/53/31615, FS/14/27/30752, FS/10/038). Introduction The optimal atrioventricular (AV) delay for implantable cardiac devices can be derived by echocardiography or beat-by-beat blood pressure measurements. However, both of these approaches are labour intensive and neither could be incorporated into an implantable cardiac device for frequent repeated optimisations. Laser Doppler perfusion monitoring (LDPM) measures blood flow through tissue. LDPM has been miniaturised ready to be incorporated into future implantable cardiac devices. Purpose We studied if LDPM is a clinically reliable alternative method to blood-pressure measurements to determine optimal AV delay. Methods Data from 58 patients undergoing 94 clinical AVD optimisations using LDPM and simultaneous non-invasive beat-by-beat blood pressure was obtained. The optimal AV delay for each method and for each optimisation was determined using a curve of haemodynamic response to switching from AAI (reference state) to DDD (test state) at a series of AV delays (40, 80, 120, 160, 200, 240 ms). We then compared the derived optimal AV delays between the two measurement approaches. We also assessed the impact of the paced heart-rate on agreement between laser Doppler and Blood-Pressure derived optimal AV delays. Results The AV delay derived using LDPM was not clinically significant different from that derived by blood pressure changes. The median difference was -9ms (IQR -26 to 7, p = 0.05). Variability between the two methods was low (median absolute deviation 17ms). Optimisations performed at higher heart-rates resulted in a non-significant smaller difference between the LDPM and blood-pressure derived AV delays (median absolute deviation 12 vs 22 ms, p = 0.11). Conclusions Optimal AVDs derived from non-invasive blood-pressure or laser Doppler perfusion methods are clinically equivalent. The addition of laser Doppler to future implantable cardiac devices may enable devices to dynamically and reliably optimise AV delays. Abstract Figure 1

Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation Background: His bundle pacing can be achieved in two ways selective His bundle pacing, where the His bundle is captured alone, and non-selective His bundle pacing, where local myocardium is also captured resulting a pre-excited ECG appearance. We assessed the impact of this ventricular pre-excitation on left and right ventricular dys-synchrony. Methods We recruited patients who displayed both selective and non-selective His bundle pacing. We performed non-invasive epicardial electrical mapping to determine left and right ventricular activation times and patterns. Results In the primary analysis (n = 20, all patients), non-selective His bundle pacing did not prolong LVAT compared to select His bundle pacing by a pre-specified non-inferiority margin of 10ms (LVAT prolongation: -5.5ms, 95% confidence interval (CI): -0.6 to -10.4, non-inferiority p In patients with narrow intrinsic QRS (n = 6), non-selective His bundle pacing preserved left ventricular activation time (-2.9ms, 95%CI: -9.7 to 4.0, p = 0.331) but prolonged QRS duration (31.4ms, 95%CI: 22.0 to 40.7, p = 0.0003) and mean right ventricular activation time (16.8ms, 95%CI: -5.3 to 38.9, p = 0.108) compared to selective His bundle pacing. Activation pattern of the left ventricular surface was unchanged between selective and non-selective His bundle pacing. Non-selective His bundle pacing produced early basal right ventricular activation, which was not observed with selective His bundle pacing. Conclusions Compared to selective His bundle pacing, local myocardial capture during non-selective His bundle pacing produces right ventricular pre-excitation resulting in prolongation of QRS duration. However, non-selective His bundle pacing preserves the left ventricular activation time and pattern of selective His bundle pacing. When choosing between selective and non-selective His bundle pacing, left ventricular dyssynchrony is not an important factor. Abstract Figure: Selective vs Non-Selective HBP

Background His bundle pacing (HBP) is an alternative to biventricular pacing (BVP) for delivering cardiac resynchronisation therapy (CRT) in patients with heart failure and left bundle branch block (LBBB). It is not known whether ventricular activation times and patterns achieved by HBP are equivalent to intact conduction systems and not all patients with LBBB are resynchronised by HBP. Objective To compare activation times and patterns of His-CRT with BVP-CRT, LBBB and intact conduction systems. Methods In patients with LBBB, non-invasive epicardial mapping (ECGI) was performed during BVP and temporary HBP. Intrinsic activation was mapped in all subjects. Left ventricular activation times (LVAT) were measured and epicardial propagation mapping (EPM) was performed, to visualise epicardial wavefronts. Normal activation pattern and a normal LVAT range were determined from normal subjects. Results 45 patients were included, 24 with LBBB and LV impairment and 21 with normal 12-lead ECG and LV function. In 87.5% of patients with LBBB, His-CRT successfully shortened LVAT by ≥10ms. In 33.3%, His-CRT resulted in complete ventricular resynchronisation, with activation times and patterns indistinguishable from normal subjects. EPM identified propagation discontinuity artifacts in 83% of patients with LBBB. This was the best predictor of whether successful resynchronisation was achieved by HBP (logarithmic odds ratio (logOR) 2.19, 95% CI 0.07 to 4.31, p=0.04). Conclusion Non-invasive electrocardiographic mapping appears to identify patients whose LBBB can be resynchronized by HBP. In contrast to BVP, His-CRT may deliver the maximum potential ventricular resynchronization, returning activation times and patterns to those seen in normal hearts. This article is protected by copyright. All rights reserved.

Funding Acknowledgements Research grant from Abbott Introduction We have recently described a novel evaluation of AF voltage which correlates better with MRI-DE defined scar than sinus rhythm voltage. We evaluated the clinical efficacy of additional voltage-based substrate modification in the Persistent AF patient cohort in a single centre case series. Methods 22 PsAF patients undergoing catheter ablation were recruited. Left atrial electroanatomical maps were created in AF before any ablation was performed in all patients. Mean peak to peak AF voltage mapping was undertaken using 8s segments of AF ( Results Of the 22 patients currently under follow up, 16 patients are more than 12 months after their initial procedure. 11/16 patients have had no recurrence and no patient is currently on anti-arrhythmic medication. Conclusion From our series, 69% of PsAF patients remain arrhythmia free at one year follow up post blanking period with a single procedure. Ablation of low voltage areas appears to infer incremental benefit in the Persistent AF population. Table 1 Mean Age, yrs 64 ± 9 Male 19 (86.3) Diabetes mellitus 1 (4.5) Hypertension 7 (31.8) TIA/CVA 2 (9) Left ventricular EF ≥55% 22 (100.0) LA size (diameter, according to British Society of Echocardiography Guidelines) Normal -Mild 12 (54.5) Moderate - Severe 10 (45.5) Mean AF duration, months 24.2 ± 20.8 Current antiarrhythmic strategy Amiodarone 3 (13.6) Sotalol 1 (4.5) Current anticoagulation Warfarin 3 (13.6) Direct oral anticoagulants 19 (86.3) Values are mean ± SD or N (%) or duration in months ± SD AF = atrial fibrillation; CVA= cerebrovascular accident; EF = ejection fraction; LA = left atrium; TIA = transient ischaemic attack. Baseline characteristics of patients (n = 22) Abstract Figure. Ablation sets and AF Voltage

Funding Acknowledgements Our research group receives an educational grant from Abbott Inc. Introduction. Outcomes from catheter ablation of persistent AF (psAF) are not favourable. The two prevailing major directions to improve success are left atrial (LA) substrate ablation, and non pulmonary vein driver ablation. In LA substrate ablation guided by intracardiac voltage, there is debate on the most fitting mapping rhythm and the appropriate cut offs for low voltage zones (LVZ). Non pulmonary vein driver ablation requires extensive experience and relies on complex pattern recognition by the operator, introducing subjectivity, that may lead to reduced reproducibility. AF drivers have been shown to localise to LVZs. We propose an objective, patient-tailored method of identifying rapid activity within LVZs to locate drivers of psAF. Methods. Eleven patients (61 ± 10.8 years of age, 9 male) undergoing first time catheter ablation for psAF were included. 3D maps were collected with a double spiral 20 pole catheter, in non-cardiac triggered mode, recording 8s segments at each bipole. Mean AF voltage (AFV) a AF cycle length (AFCL) was calculated for each 8s segment using automated algorithms. Grades of rapid activity and low voltage were defined as the 10th 20th and 30th percentile of all collected points within a patient. Percentile-matched composite LVZ-ARA maps were created on a research platform. Results. Mean LVZ percentage of the total mapped area was 4.67 ± 2.4%, 13.95 ± 3.8%, 23.81 ± 5.7% for the 10th, 20th and 30th percentiles respectively (Table 1). Mean, percentile matched LVZ-ARA overlap area percentage of the total mapped area was 0.3 ± 0.25% (10th-10th), 0.86 ± 0.58 (20th-20th), 3.1 ± 1.9% (30th-30th). ARAs represented a small proportion of all LVZs. Location of overlap areas differed significantly between patients and were marked with colours. Multi-colour areas including purple represent LVZ, multi-colour areas excluding purple, show LVZ-ARA overlap (examples in Fig 1). Conclusion. Analysis of LVZ-ARA overlap by mean AFV and AFCL provides an objective method of identifying potential drivers that localise to LVZs. The identified overlap areas constituted small, occasionally disparate areas within the LVZ of the LA. By adjusting the AFCL and AFV percentiles, the overlap areas can be tailored at the operator’s discretion, maintaining reproducible, objective decision making, without the need for complex pattern recognition. If ablation is planned, established techniques can be used to target the overlap areas, such as homogenisation or transection and connection to anatomical or ablative non-conductive tissues. AFCL 10th AFCL 20th AFCL 30th AFV 10th AFV 20th AFV 30th All patients 128 ± 13 ms 144 ± 10 ms 150 ± 9 ms 0.15 ± 0.02 mV 0.19 ± 0.03 mV 0.24 ± 0.04 mV Mean values of percentile cut offs. AFCL: AF cycle length; AFV: AF voltage Abstract Figure. Fig 1

Funding Acknowledgements Our research group receives an educational grant from Abbott Inc. Introduction. There is evidence to suggest that structural remodelling in psAF potentially gives rise to areas of rapid cycle length activity that may act as driving mechanisms. We describe a new method to compare rapid activity (RA) in psAF prior to and after pulmonary vein isolation, in extended AF segments (EAFS). We focus on patterns of RA, based on the hypothesis that AF drivers are transient but recur in the same locations. Methods. Five patients (61 ± 8 years of age, 3 male) for catheter ablation of psAF were included. 3D maps were collected with a double spiral 20 pole catheter. In stable locations, pre and post PVI, 37s EAFS were recorded using 8s segments, automatically every 1s, creating a 7s overlap between segments. Dominant cycle length (DCL) was determined for every 8s segment by a fully automated algorithm. RA was defined as the rapidest 20th percentile for each patient. RA episodes consisted of continuous segments with rapid DCL (black lines in Fig 1) and terminated with a non-rapid segment (red lines on Fig 1). Episodes were truncated where overlap occurred (Box 1 and Box 2 in Fig 1). The pattern of RA was assessed by the number, cumulative duration and mean duration of RA episodes within an EAFS pre and post PVI. Results. Mean DCL of EAFS increased significantly in 4/5 patients after PVI, the number of EAFS with rapid activity showed a reduction in all patients. The percentage of new sites with RA post PVI was 27%. The number of sites that retained RA post PVI was 14 ± 11.3 (58.3%; Table 1). Of these, number and cumulative duration of RA did not change in 4/5 patients, and mean duration of RA remained stable in 5/5. Conclusion. An automated DCL algorithm shows that, in most cases, global AFCL prolongs significantly with PVI overall, but selected foci retain RA and RA patterns. These may represent active drivers, as their activity appears to be independent of their surroundings. Table 1 Patient ID Number of segments Mean AFCL ± SD of all segments Number of EAFS with rapid activity Pre-PVI Post-PVI P Pre-PVI Post-PVI New sites 1 145 135 ± 8.9 141 ± 9.8 Abstract Figure.

INTRODUCTION: We hypothesized that very high density mapping of typical atrial flutter (AFL) would facilitate a more complete understanding of its circuit. Such very high density mapping was performed with the Rhythmia mapping system using its 64 electrode basket catheter. METHODS AND RESULTS: Data were acquired from 13 patients in AFL. Functional anatomy of the right atrium (RA) was readily identified during mapping including the Crista Terminalis and Eustachian ridge. The leading edge of the activation wavefront was identified without interruption and its conduction velocity (CV) calculated. CV was not different at the cavotricuspid isthmus (CTI) compared to the remainder of the RA (1.02 vs. 1.03 m/s, p = 0.93). The sawtooth pattern of the surface EKG flutter waves were compared to the position of the dominant wavefront. The downslope of the surface EKG flutter waves represented on average, 73% ± 9% of the total flutter cycle length. During the downslope the activation wavefront travelled significantly further than during the upslope (182 ± 21 ms vs. 68 ± 29 ms, p

Aims Rate adaptation of the action potential ensures spatial heterogeneities in conduction across the myocardium are minimized at different heart rates providing a protective mechanism against ventricular fibrillation (VF) and sudden cardiac death (SCD), which can be quantified by the ventricular conduction stability (V-CoS) test previously described. We tested the hypothesis that patients with a history of aborted SCD due to an underlying channelopathy or cardiomyopathy have a reduced capacity to maintain uniform activation following exercise. Methods and results Sixty individuals, with (n = 28) and without (n = 32) previous aborted-SCD event underwent electro-cardiographic imaging recordings following exercise treadmill test. These included 25 Brugada syndrome, 13 hypertrophic cardiomyopathy, 12 idiopathic VF, and 10 healthy controls. Data were inputted into the V-CoS programme to calculate a V-CoS score that indicate the percentage of ventricle that showed no significant change in ventricular activation, with a lower score indicating the development of greater conduction heterogeneity. The SCD group, compared to those without, had a lower median (interquartile range) V-CoS score at peak exertion [92.8% (89.8–96.3%) vs. 97.3% (94.9–99.1%); P Conclusion Data from this pilot study demonstrate the potential use of this technique in risk stratification for the inherited cardiac conditions.

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.

BACKGROUND Conventional mapping techniques during atrial fibrillation (AF) are difficult to apply because of cycle length irregularity. Mapping studies are usually restricted to short durations of AF in limited regions because of the laborious manual annotation of local activation time (LAT). The purpose of this study was to test an automated algorithm to map activation during AF, with comparable accuracy to manual annotation. METHODS Left atrial (LA) mapping was performed using a 20-pole double loop catheter (AFocusII) in 30-second data segments from 16 patients. The new algorithm (RETRO-Mapping) was designed to detect wavefront propagation between electrodes, and display activating wavefronts on a two-dimensional representation of the catheter. Activation patterns were validated against their bipolar electrograms and with isochronal maps. The mapping protocol was approved by the research ethics committee (13/LO1169 and 14/LO1367). RESULTS During AF, uniform wavefront activation direction (mean ± SD, degrees) from manually constructed isochronal maps was comparable to RETRO-Propagation Map (RETRO-PM) and RETRO-Automated Direction (RETRO-AD): 1 ± 6.9 for RETRO-PM; and 2 ± 6.6 for RETRO-AD. There was no significant difference in activation direction assigned to 1373 uniform wavefronts during AF when comparing RETRO-PM with RETRO-AD (Bland-Altman mean difference: -0.1 degrees; limits of agreement: -8.0 to 8.3; 95% CI -0.4 to 0.2; (r = 0.01) R2 =

Aims Abnormal rate adaptation of the action potential is proarrhythmic but is difficult to measure with current electro-anatomical mapping techniques. We developed a method to rapidly quantify spatial discordance in whole heart activation in response to rate cycle length changes. We test the hypothesis that patients with underlying channelopathies or history of aborted sudden cardiac death (SCD) have a reduced capacity to maintain uniform activation following exercise. Methods and results Electrocardiographical imaging (ECGI) reconstructs >1200 electrograms (EGMs) over the ventricles from a single beat, providing epicardial whole heart activation maps. Thirty-one individuals [11 SCD survivors; 10 Brugada syndrome (BrS) without SCD; and 10 controls] with structurally normal hearts underwent ECGI vest recordings following exercise treadmill. For each patient, we calculated the relative change in EGM local activation times (LATs) between a baseline and post-exertion phase using custom written software. A ventricular conduction stability (V-CoS) score calculated to indicate the percentage of ventricle that showed no significant change in relative LAT ( Conclusion We present a method to rapidly quantify changes in global activation which provides a measure of conduction heterogeneity and proof of concept by demonstrating SCD survivors have a reduced capacity to maintain uniform activation following exercise.

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. 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. 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). Robotically guided VT ablation is both feasible and safe when compared to manual ablation with good acute and long-term outcomes.

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.

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.

Ripple Mapping: A Novel 3D EGM Display. 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 TM 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. (J Cardiovasc

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 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.

Background— The activation pattern of localized reentry (LR) in atrial tachycardia remains incompletely understood. We used the ultra–high density Rhythmia mapping system to study activation patterns in LR. Methods and Results— LR was suggested by small rotatory activations (carousels) containing the full spectrum of the color-coded map. Twenty-three left-sided atrial tachycardias were mapped in 15 patients (age: 64±11 years). 16 253±9192 points were displayed per map, collected over 26±14 minutes. A total of 50 carousels were identified (median 2; quartiles 1–3 per map), although this represented LR in only n=7 out of 50 (14%): here, rotation occurred around a small area of scar ( Conclusions— The activation pattern of LR is of small stable rotational activations (carousels), and this drove 30% (7/23) of our postablation atrial tachycardias. However, this appearance is most often pseudo-reentrant and must be differentiated by interpretation of electrograms in the candidate circuit and activation in the wider surrounding region.

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 ( Conclusions— Ripple mapping can be used to identify conduction channels within scar to guide functional substrate ablation.

Aims Recurrent arrhythmias after ablation procedures are often caused by recovery of ablated tissue. Robotic catheter manipulation systems increase catheter tip stability which improves energy delivery and could produce more transmural lesions. We tested this assertion using bipolar voltage attenuation as a marker of lesion quality comparing robotic and manual circumferential pulmonary vein ablation for atrial fibrillation (AF). Methods and results Twenty patients were randomly assigned to robotic or manual AF ablation at standard radiofrequency (RF) settings for our institution (30 W 60 s manual, 25 W 30 s robotic, R30). A separate group of 10 consecutive patients underwent robotic ablation at increased RF duration, 25 W for 60 s (R60). Lesions were marked on an electroanatomic map before and after ablation to measure distance moved and change in bipolar electrogram amplitude during RF. A total of 1108 lesions were studied (761 robotic, 347 manual). A correlation was identified between voltage attenuation and catheter movement during RF (Spearman's rho −0.929, P < 0.001). The ablation catheter was more stable during robotic RF; 2.9 ± 2.3 mm (R30) and 2.6 ± 2.2 mm (R60), both significantly less than the manual group (4.3 ± 3.0 mm, P < 0.001). Despite improved stability, there was no difference in signal attenuation between the manual and R30 group. However, there was increased signal attenuation in the R60 group (52.4 ± 19.4%) compared with manual (47.7 ± 25.4%, P = 0.01). When procedures under general anaesthesia (GA) and conscious sedation were analysed separately, the improvement in signal attenuation in the R60 group was only significant in the procedures under GA. Conclusions Robotically assisted ablation has the capability to deliver greater bipolar voltage attenuation compared with manual ablation with appropriate selection of RF parameters. General anaesthesia confers additional benefits of catheter stability and greater signal attenuation. These findings may have a significant impact on outcomes from AF ablation procedures.

INTRODUCTION Robotic remote catheter ablation potentially provides improved catheter-tip stability, which should improve the efficiency of radiofrequency energy delivery. Percentage reduction in electrogram peak-to-peak voltage has been used as a measure of effectiveness of ablation. We tested the hypothesis that improved catheter-tip stability of robotic ablation can diminish signals to a greater degree than manual ablation. METHODS In vivo NavX maps of 7 pig atria were constructed. Separate lines of ablation were performed robotically and manually, recording pre- and postablation peak-to-peak voltages at 10, 20, 30, and 60 seconds and calculating signal amplitude reduction. Catheter ablation settings were constant (25W, 50 degrees , 17 mL/min, 20-30 g catheter tip pressure). The pigs were sacrificed and ablation lesions correlated with NavX maps. RESULTS Robotic ablation reduced signal amplitude to a greater degree than manual ablation (49 +/- 2.6% vs 29 +/- 4.5% signal reduction after 1 minute [P = 0.0002]). The mean energy delivered (223 +/- 184 J vs 231 +/- 190 J, P = 0.42), power (19 +/- 3.5 W vs 19 +/- 4 W, P = 0.84), and duration of ablation (15 +/- 9 seconds vs 15 +/- 9 seconds, P = 0.89) was the same for manual and robotic. The mean peak catheter-tip temperature was higher for robotic (45 +/- 5 degrees C vs 42 +/- 3 degrees C [P 50% signal reduction was greater for robotic (37%) than manual (21%) ablation (P = 0.0001). CONCLUSION Robotically assisted ablation appears to be more effective than manual ablation at signal amplitude reduction, therefore may be expected to produce improved clinical outcomes.

Background Mapping of regular cardiac arrhythmias is frequently performed using sequential point-by-point annotation of local activation relative to a fixed timing reference. Assigning a single activation for each electrogram is unreliable for fragmented, continuous, or double potentials. Furthermore, these informative electrogram characteristics are lost when only a single timing point is assigned to generate activation maps. Objective The purpose of this study was to develop a novel method of electrogram visualization conveying both timing and morphology as well as location of each point within the chamber being studied. Methods Data were used from six patients who had undergone electrophysiological study with the Carto electroanatomic mapping system. Software was written to construct a three-dimensional surface from the imported electrogram locations. Electrograms were time gated and displayed as dynamic bars that extend out from this surface, changing in length and color according to the local electrogram voltage-time relationship to create a ripple map of cardiac activation. Results Ripple maps were successfully constructed for sinus rhythm (n = 1), atrial tachycardia (n = 3), and ventricular tachycardia (n = 2), simultaneously demonstrating voltage and timing information for all six patients. They showed low-amplitude continuous activity in four of five tachycardias at the site of successful ablation, consistent with a reentrant mechanism. Conclusion Ripple mapping allows activation of the myocardium to be tracked visually without prior assignment of local activation times and without interpolation into unmapped regions. It assists the identification of tachycardia mechanism and optimal ablation site, without the need for an experienced computer-operating assistant.

Background A novel remotely controlled steerable guide catheter has been developed to enable precise manipulation and stable positioning of any eight French (Fr) or smaller electrophysiological catheter within the heart for the purposes of mapping and ablation. Objective To report our initial experience using this system for remotely performing catheter ablation in humans. Methods Consecutive patients attending for routine ablation were recruited. Various conventional diagnostic catheters were inserted through the left femoral vein in preparation for treating an accessory pathway (n = 1), atrial flutter (n = 2) and atrial fibrillation (n = 7). The steerable guide catheter was inserted into the right femoral vein through which various irrigated and non-irrigated tip ablation catheters were used. Conventional endpoints of loss of pathway conduction, bidirectional cavotricuspid isthmus block and four pulmonary vein isolation were used to determine acute procedural success. Results Ten patients underwent remote catheter ablation using conventional and/or 3D non-fluoroscopic mapping technologies. All procedural endpoints were achieved using the robotic control system without manual manipulation of the ablation catheter. There was no major complication. A radiation dosimeter positioned next to the operator 2.7 m away from the X-ray source showed negligible exposure despite a mean cumulative dose area product of 7,281.4 cGycm2 for all ten ablation procedures. Conclusions Safe and clinically effective remote navigation of ablation catheters can be achieved using a novel remotely controlled steerable guide catheter in a variety of arrhythmias. The system is compatible with current mapping and ablation technologies Remote navigation substantially reduces radiation exposure to the operator. Electronic supplementary material The online version of this article (doi:10.1007/s10840-007-9184-z) contains supplementary material, which is available to authorized users.

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.

Purpose This study aims to evaluate a method to detect heart rate variability (HRV) changes using short ECG segments during ablation for arrhythmias. Methods HRV was averaged from sequentially shorter time windows from 5-min ECG recordings in 15 healthy volunteers. The 40-s window was identified as the shortest duration that yielded reproducible values in high frequency (HF) and low frequency (LF) HRV. This method was validated in patients undergoing tilt table testing to see if the expected modulation in HRV that occurs prior to syncope could be detected from multiple 40-s recordings. Lastly, this method was used to assess HRV changes in 75 patients undergoing ablation for atrial fibrillation (AF) and other arrhythmias, to see if autonomic modulation as a result of ablation could be detected. A further 14 patients had stepwise HRV measurements at different stages of the AF ablation procedure to determine whether intra-procedural HRV changes could be detected. Results HRV, averaged from multiple 40-s recordings, demonstrated the expected increase immediately preceding syncope compared with baseline (LF: 341 ± 311–1,536 ± 1,368 ms2, p

Robotically assisted catheter ablation has been proven feasible in patients with a variety of atrial arrhythmias. The potential to provide improved catheter tip maneuvering and stability potentially makes it ideal for complex ablation procedures. We present the case of a patient with complex congenital heart disease with previous Rastelli repair and recurrent ventricular tachycardia (VT) who underwent robotically assisted mapping and ablation for right ventricular VT, utilizing substrate mapping techniques.

Introduction: Histological data after VT ablation in humans is rare. We present a case of a patient who had ablation for VT storm and who died remotely from non-arrhythmic causes. Methods and Results: A 69-year-old male with ischemic cardiomyopathy and a dual-chamber implantable cardioverter defibrillator (ICD) presented with VT storm and multiple ICD therapies. A voltage map of the left-ventricular (LV) scar was created using CARTO™. VT was induced. An isochronal map identified the VT exit site at the scar border. No diastolic potentials were seen in this territory, so VT exit site ablation was performed, as well as at a putative entry site. VT cycle length and morphology changed during ablation, but termination only occurred with burst pacing. Post-ablation, the patient had no further shocks. He died seven months later from acute pancreatitis. The two ablation sites were identified on the post-mortem heart and used to correlate with the electroanatomical map. Scar area correlated well, measuring approximately 58.4 cm2 macroscopically and 63.3 cm2 on the electroanatomical map. Histology at VT exit site demonstrated areas of viable epicardial myocardium, suggesting that the circuit was at the epicardial scar border, which would explain the lack of diastolic potentials. Ablation scar did not reach the epicardium and therefore, ablation may have modified the exit site without complete interruption of the VT circuit. Conclusions: In this case, ablation was unable to terminate the VT due to failure to reach the epicardium, but was sufficient to modify the tachycardia, thereby reducing ICD therapy.