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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.

Background: Patients receiving implantable cardioverter-defibrillators (ICDs) often have severely impaired left ventricular function and a poor prognosis. Having an ICD in situ effectively denies them the possibility of a quick, arrhythmic death. It is still unclear if and when the end of life and device deactivation should be discussed with patients and how much patients want to know prior to ICD implantation. Methods: Patients with an active ICD for chronic heart failure were interviewed regarding their attitude toward the ICD, their recollection of the consent procedure, and how they felt the end of life should be discussed with ICD patients (n = 54). Patients who had received ICD therapies (n = 25) were reviewed as a subgroup with extended questions regarding attitudes toward device deactivation. Results: Fifty-four patients were recruited. Most patients were not aware that the ICD could be deactivated. The vast majority of patients (84%) wanted to be involved in the deactivation decision; 40% felt this discussion should be prior to ICD implantation but others felt the discussion should only occur if the patient was terminally ill (16%) or in the last few days of life (5%). Conclusion: Patients with ICDs are routinely counseled about the benefits of ICDs, but options for device deactivation are not well understood by patients. Most patients would like to be involved in deactivation decisions and we feel this should be discussed well in advance. (PACE 2011; 34:1628–1633)

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.

This study aimed at assessing the feasibility and long-term efficacy of left atrial appendage occlusion (LAAO) in a "real world" setting.Although LAAO has recently emerged as an alternative to oral anticoagulants in patients with atrial fibrillation for the prevention of thromboembolic stroke, "real world" data about the procedure with different devices are lacking.Eight centers in the United Kingdom contributed to a retrospective registry for LAAO procedures undertaken between July 2009 and November 2014.A total of 371 patients (72.9 ± 8.3 years old, 88.9% males) were enrolled. The overall procedure success was 92.5%, with major events in 3.5% of cases. The device choice was Watchman in 63% of cases, Amplatzer Cardiac Plug in 34.7%, Lariat in 1.7%, and Coherex WaveCrest in 0.6%. A significant improvement in procedure success (from 89.2% to 95.7%; P = 0.018) and reduction of acute major complications (from 6.5% to 0.5%; P = 0.001) were observed between procedures in the first and the second half of the recruitment time. An annual 90.1% relative risk reduction (RRR) for ischemic stroke, an 87.2% thromboembolic events RRR, and a 92.9% major bleeding RRR were observed, if compared with the predicted annual risks based on CHADS2, CHA2DS2-Vasc, and HAS-BLED scores, respectively, over a follow-up period of 24.7 ± 16.07 months.LAAO can be performed safely in a real world setting with good implant success rates and procedural outcomes. The long-term benefits of the procedure are reassuring in terms of both ischemic events and avoidance of severe bleeding associated with anticoagulation in this patient group. © 2016 Wiley Periodicals, Inc.

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.

We report the case of a man found unconscious three weeks following atrial fibrillation (AF) ablation. Cranial and thoracic imaging demonstrated multiple areas of pneumo-embolic infarction secondary to an atrio-oesophageal fistula (AEF). AEF is a recognised, but rare, complication of AF ablation.1–8 Early recognition is critical as the mortality is 100% without surgical intervention. We consider the postulated mechanisms of AEF formation, the spectrum of clinical presentation, investigations and treatment.

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.We hypothesized that RM would be superior to established 3D activation mapping.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.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.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.

Introduction Implantable cardio-defibrillators (ICDs) have proven benefit in treating lethal ventricular arrhythmias and preventing sudden death (SD) in hypertrophic cardiomyopathy (HCM), making risk stratification essential. We retrospectively evaluate the effectiveness of the 2014 European Society of Cardiology (ESC) risk scoring system in our cohort of HCM patients. Methods We evaluated the ESC risk scoring system which employs mathematical and statistical modelling of 7 disease variables to predict SD risk over 5 years, with a recommendation for ICD implant if SD risk ≥6%. From our cohort of HCM patients previously evaluated at our centre, we retrospectively calculated the ESC 5 year SD risk score at point of implant and measured it against ICD outcome. Decision of ICD implant, prior to the introduction of the ESC scoring system, was based on clinical history and number of conventional risk markers as defined by the American College of Cardiology and Heart Association. Results 52 out of 199 HCM patients (mean age 51 ± 13 yrs) underwent ICD implantation for primary prevention, with 8 (15%) having appropriate therapy for sustained ventricular tachycardia/fibrillation (VT/VF) over an average follow up period of 6.2 ± 4.9 yrs. There was no difference in the ESC risk scores between patients with or without device therapy (4.79% ± 1.5 vs 5.37% ± 3.3, p = 0.68) (Table 1). 5 of 8 (62%) patients with appropriate therapies for VT/VF had scores ranging from 3.08–5.05% and would not have reached the threshold for an ICD recommendation. In two an ICD would not be recommended and may be considered in the other three. Conclusion The current ESC scoring system potentially leaves many high-risk patients unprotected or with ambiguous ICD implant guidance. Lowering the current threshold may improve accuracy.

Introduction Ventricular Tachycardia (VT) is a common cause of mortality post myocardial infarction. Any mortality benefit of an implantable cardiac defibrillator (ICD) may be offset by the significant morbidity caused by VT shocks from the device. The VT circuit is dependent upon channels of surviving myocardium within the infarct substrate. As VT is often poorly tolerated, ablation of characteristic electrograms (fractionated and late potentials) associated with these channels in sinus rhythm is preferred to reduce ICD therapies, though recurrence rates remain high. Ripple Mapping (RM) displays all electrogram components from each anatomical point as a dynamic bar that protrudes from its 3D location. We have described how RM might visualize “conducting channels” (RM-CCs) of these characteristic electrograms within the infarcted substrate in a retrospective series. In this study, we used RM prospectively (CARTO3v4™) to characterize the VT substrate to guide ablation. Methods Consecutive pts referred for VT ablation following episodes of sustained VT or ICD therapies post distant MI were included. High point density bipolar LV endocardial electrograms were collected in sinus rhythm or ventricular pacing within the infarct “scar” ( Results 15 consecutive pts (median age 68yrs, LVEF 30%) were studied (6 month pre-procedural ICD therapies: median 19 ATP events (IQR=4–93) and 1 shock (IQR=0–3)). Scar ( Conclusions RM identifies conducting channels within the post-infarct scar that might support re-entrant VT and can be used to guide substrate based ablation to reduce future ICD therapies.

We describe the case report of an 86-year-old Afro-Caribbean parkinsonian gentleman with intermittent Mobitz II heart block and syncope who received a DDD pacemaker. Due to Parkinson’s syndrome, the patient rotated the atrial lead around the pacemaker, causing the famous "Twiddler’s syndrome", a rare clinical issue which can easily be diagnosed with a simple chest X-ray.

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.

Background: Aortic valve replacement (AVR) can be performed safely in selected elderly patients with aortic stenosis (AS). However, the survival benefits of AVR over conservative treatment have not been convincingly demonstrated in AS patients aged above 80. Aim: To investigate the outcomes of patients aged 80 and over with symptomatic, severe AS and by analyzing the effects of patient's choice in either agreeing or refusing to undergo AVR, determine the survival benefits afforded by AVR. Design: Cohort study. Methods: Subjects aged 80 and over with severe symptomatic AS, diagnosed between 2001 and 2006 were segregated into three groups: subjects who underwent AVR (Group A); patients who were fit for AVR but declined surgery due to personal choice (Group B) and those who were not fit for surgery and were managed conservatively (Group C). Follow-up was conducted by out-patient attendances, review of medical records and telephone interviews. The primary endpoint was all-cause mortality. Results: A total of 103 patients (86.0 ± 4.2 years, 41% male) were identified and no patient was lost during follow-up. In Group A ( n = 17), all 15 patients who underwent AVR were alive after 3.6 ± 1.4 years follow-up and 2 died whilst awaiting AVR. Seventy-four percent of Group B ( n = 24) and 76% of Group C ( n = 62) died during follow-up. Group A had significantly better survival than B and C. ( P < 0.01) Amongst patients fit for AVR with similar operative risks (Groups A and B), refusal to undergo surgery (hazard ratio 12.61, P = 0.001) was the only predictor of mortality in a multivariate model. Conclusions: For elderly AS patients fit for surgery, the patient's decision to refuse AVR is associated with a >12-fold increase in mortality risk. These findings have significant implications for informed decision-making when managing the fit, elderly patient with AS.

Background: It would be useful to identify patients at high risk of implantable cardioverter defibrillator (ICD) therapy via additional antiarrhythmic measures to minimize the morbidity of ICD therapies. Objective: We assessed baseline characteristics for predictors of device therapy in a general ICD population. We also compared the likelihood of therapy delivery by replacement ICDs implanted for battery depletion with the original implants. Methods: Clinical and ICD interrogation data from patients followed up at a UK center were analyzed looking for predictors of appropriate ICD therapy. Univariate and multivariate analysis was performed using Cox regression. We compared time to first appropriate therapy between first and second ICDs in patients who had undergone ICD replacement for battery depletion by log-rank testing. Results: One hundred and sixty-one patients were studied (129 men, age 65.7 ± 12.9 years, follow-up 908 ± 676 days). Appropriate therapy was delivered in 68 patients (42%). Univariate risk factors for appropriate ICD therapy were presentation with stable ventricular tachycardia (VT) (P = 0.0002), ischemic etiology (P = 0.03), tiered therapy programmed ICDs (P = 0.01), and beta-blocker use (P = 0.001). Stable VT and beta blocker use were independent predictors of ICD therapy on multivariate analysis. Thirty-three patients (20%) had at least one ICD replacement. Time to first appropriate therapy was no different between first and second ICD implants (P = 0.8). Conclusion: Patients who present with cardiovascularly stable VT have a higher probability of receiving appropriate ICD therapy than those who do not. Following battery depletion of an original ICD, the replacement device is no less likely to administer therapy than the first.

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.

Introduction: Robotically-guided ablation offers theoretical advantages with greater catheter stability that can improve lesion depth. We performed a non-randomised comparison of patients undergoing ventricular tachycardia (VT) ablation either manually or using the Hansen robotic system. Methods: Consecutive patients with infarct-related scar underwent VT ablation using the Hansen system to assess feasibility, and were compared with patients undergoing manual VT ablation during the study period. All cases underwent a transeptal endocardial approach, using CARTO™ and irrigated catheter ablation guided by activation and entrainment manoeuvres if VT was sustained and tolerated, or substrate modification. The 6 month pre-ablation Implantable Cardioverter Defibrillator (ICD) therapy (Anti-tachycardia pacing (ATP) + shocks) was compared with the post ablation burden represented as a 6 monthly rate of each patient's total therapy burden during follow up ((6/follow-up duration (mths)) x total therapies post ablation)). Results: 25pts had VT ablations for infarct related scar during the study period. 13 pts had robotically guided ablation and 12 pts had manual ablation. Patients in both the robotic and manual groups had significantly impaired left ventricular function (EF 27±14% vs. 32 + /-11% respectively; p=0.32). The previous coronary revascularisationapproach, use of cardiac resynchronisation and amiodarone were similar in both groups. However 31% (4/13) of patients undergoing robotic ablation had been referred due to a failed manual approach and persisting high therapy burden as compared to 8% (1/12) redo procedures in the manual group (p=0.37). This was reflected by a trend towards higher pre-ablation therapy burden in the robotic as compared to the manual group (mean 312±566 vs. 11±9, p=0.08; median 11 vs. 9.5, p=0.50). In each group, 1 patient presented with slow incessant VT below the device therapy zone, and 1 patient had their device implanted post ablation. Post-procedure, the clinical VT was non-inducible in 85% (11/13) of the robotic group and in 92% (11/12) of the manual group. There were no peri-procedural complications. Mean follow-up was 23.5 months. Long-term mortality rates were similar (31%, 4/13 vs. 25%, 3/12; p=1.0). Post ablation, the 6 monthly therapy burden fell in both the robotic (mean reduction=290±560, median 3, p=0.047 Wilcoxon signed rank test) and manual (mean reduction=5.3±19, median 6.5, p=0.03) group. The overall reduction in therapy across all patients was 93% in the robotic and by 48% in the manual group. Conclusions: In this feasibility study, robotic VT ablation had a similar safety profile to manual ablation and a trend towards greater therapy reduction in a sicker cohort of patients. Table comparing acute procedural outcomes, 6 month pre/post ablation ICD therapies, and mortality rates between the robotic and manual groups. †Students t-test. §Fisher's exact test. ‖ Wilcoxon signed rank test. ![Graphic][1] [1]: /embed/inline-graphic-1.gif

Introduction The cardiac neural network comprises ganglionated plexi (GP) adjacent to each pulmonary vein (PV) which can trigger AV block and PV ectopy. We hypothesised that AV block in response to GP stimulation is mediated through the right lower GP (RLGP) and could be abolished by ablation of the RLGP, whereas a local PV ectopy response could be abolished by selective local GP ablation. Methods and Results 10 patients undergoing left atrial (LA) ablation with autonomic modification were recruited. Continuous HFS was delivered endocardially at presumed GP sites using a Grass Stimulator (20 Hz, 10 ms pulse duration, 10 V). GP sites with connections to the AV node (producing AV block) were marked on LA geometry. RLGP group (N=5) had RF ablation of RLGP and 2 of 15 sites remained positive (p Conclusions Our study shows that neural inputs from LA GPs act on the AV node via the RLGP “gateway” and if AV block is used to identify GP sites for autonomic modulation, intact connections via the RLGP are required. We propose using synchronised HFS to identify and ablate GP sites initiating ectopic firing from the PV, as it only requires intact local connections to the PV. PVI acutely prevents this ectopic activity, possibly by transecting neural inputs to the veins. However, reconnection of PVs is common and RF ablation of the GP site alone may prevent ectopic firing within PVs.