BACKGROUND:Mapping wavefronts within the triangle of Koch is challenging owing to multiple small and large amplitude signals within a short time interval. Ripple mapping was designed to overcome these limitations. OBJECTIVE:We tested the feasibility of delineating wavefronts within the triangle of Koch during slow-fast atrioventricular nodal reentrant tachycardia (AVNRT). METHODS:Patients undergoing electrophysiological studies were recruited. Right atrial CARTO maps were collected during atrial pacing, ventricular pacing, and typical AVNRT. Using ripple mapping, we marked His activation during atrial pacing, the earliest retrograde atrial activation during ventricular pacing, the earliest signal during AVNRT (E-AVNRT), and the earliest retrograde right atrial activation during AVNRT. RESULTS:72 patients were recruited, with typical AVNRT in 40 patients and a full mapping protocol in 30 patients (6327 ± 948 points collected). The E-AVNRT was 14.7 ± 5.3 mm inferior to the earliest His identified during atrial pacing. A wavefront consistent with slow pathway activation started at E-AVNRT taking 22.2 ± 4.8 ms to reach the His cloud with a line of block demarcating the atrial side. This same line formed the ventricular border of atrial activation during atrial pacing, consistent with slow pathway activation over the right inferior nodal extension. These wavefront signals became sharper approaching His but consistently activated a region inferior to the His cloud, consistent with the right inferior nodal extension activating the lower nodal bundle. Earliest retrograde fast pathway-mediated right atrial activation during AVNRT was 57.3 ± 27.1 ms later and 11.7 ± 6.0 mm from E-AVNRT and distinct from the earliest atrial activation during ventricular pacing (7.0 ± 3.2 mm). Successful ablation sites were closer to E-AVNRT than unsuccessful sites (6.4 ± 3.0 vs 14.8 ± 5.6 mm; 95% confidence interval 5.2-7.6 vs 12.2-17.4 mm; P < .01). CONCLUSION:Ripple mapping can delineate slow and fast pathway activation during AVNRT. Lower nodal bundle signals "lead" during AVNRT, inferior to the conventional His cloud. Ripple mapping-guided AVNRT ablation may be feasible.

This case report presents the successful implantation of a left bundle area pacing lead in a 64-year-old male with a history of bundle branch ventricular tachycardia and consequent therapeutic ablation of the right bundle branch. Despite extensive conduction disease, effective physiological pacing was achieved as part of a cardiac synchronisation pacing

Aims Implantable cardioverter defibrillator (ICD) therapies have been associated with increased mortality and should be minimized when safe to do so. We hypothesized that machine learning-derived ventricular tachycardia (VT) cycle length (CL) variability metrics could be used to discriminate between sustained and spontaneously terminating VT. Methods and results In this single-centre retrospective study, we analysed data from 69 VT episodes stored on ICDs from 27 patients (36 spontaneously terminating VT, 33 sustained VT). Several VT CL parameters including heart rate variability metrics were calculated. Additionally, a first order auto-regression model was fitted using the first 10 CLs. Using features derived from the first 10 CLs, a random forest classifier was used to predict VT termination. Sustained VT episodes had more stable CLs. Using data from the first 10 CLs only, there was greater CL variability in the spontaneously terminating episodes (mean of standard deviation of first 10 CLs: 20.1 +/- 8.9 vs. 11.5 +/- 7.8 ms, P < 0.0001). The auto-regression coefficient was significantly greater in spontaneously terminating episodes (mean auto-regression coefficient 0.39 +/- 0.32 vs. 0.14 +/- 0.39, P < 0.005). A random forest classifier with six features yielded an accuracy of 0.77 (95% confidence interval 0.67 to 0.87) for prediction of VT termination. Conclusion Ventricular tachycardia CL variability and instability are associated with spontaneously terminating VT and can be used to predict spontaneous VT termination. Given the harmful effects of unnecessary ICD shocks, this machine learning model could be incorporated into ICD algorithms to defer therapies for episodes of VT that are likely to self-terminate.

Ventricular tachycardia (VT) reduces cardiac output through high heart rates, loss of atrioventricular synchrony, and loss of ventricular synchrony. We studied the contribution of each mechanism and explored the potential therapeutic utility of His bundle pacing to improve cardiac output during VT. Study 1 aimed to improve the understanding of mechanisms of harm during VT (using pacing simulated VT). In 23 patients with left ventricular impairment, we recorded continuous ECG and beat-by-beat blood pressure measurements. We assessed the hemodynamic impact of heart rate and restoration of atrial and biventricular synchrony. Study 2 investigated novel pacing interventions during clinical VT by evaluating the hemodynamic effects of His bundle pacing at 5 bpm above the VT rate in 10 patients. In Study 1, at progressively higher rates of simulated VT, systolic blood pressure declined: at rates of 125, 160, and 190 bpm, -22.2

[This corrects the article DOI: 10.1016/j.cvdhj.2020.07.001.].

Background: Epicardial ganglionated plexuses (GP) have an important role in the pathogenesis of atrial fibrillation (AF). The relationship between anatomical, histological and functional effects of GP is not well known. We previously described atrioventricular (AV) dissociating GP (AVD-GP) locations. In this study, we hypothesised that ectopy triggering GP (ET-GP) are upstream triggers of atrial ectopy/AF and have different anatomical distribution to AVD-GP. Objectives: We mapped and characterised ET-GP to understand their neural mechanism in AF and anatomical distribution in the left atrium (LA). Methods: 26 patients with paroxysmal AF were recruited. All were paced in the LA with an ablation catheter. High frequency stimulation (HFS) was synchronised to each paced stimulus for delivery within the local atrial refractory period. HFS responses were tagged onto CARTOTM 3D LA geometry. All geometries were transformed onto one reference LA shell. A probability distribution atlas of ET-GP was created. This identified high/low ET-GP probability regions. Results: 2302 sites were tested with HFS, identifying 579 (25%) ET-GP. 464 ET-GP were characterised, where 74 (16%) triggered >= 30s AF/AT. Median 97 (IQR 55) sites were tested, identifying 19 (20%) ET-GP per patient. > 30% of ET-GP were in the roof, mid-anterior wall, around all PV ostia except in the right inferior PV (RIPV) in the posterior wall. Conclusion: ET-GP can be identified by endocardial stimulation and their anatomical distribution, in contrast to AVD-GP, would be more likely to be affected by wide antral circumferential ablation. This may contribute to AF ablation outcomes.

BACKGROUND Bipolar electrogram voltage during sinus rhythm (V-SR) has been used as a surrogate for atrial fibrosis in guiding catheter ablation of persistent atrial fibrillation (AF), but the fixed rate and wavefront characteristics present during sinus rhythm may not accurately reflect underlying functional vulnerabilities responsible for AF maintenance. OBJECTIVE The purpose of this study was determine whether, given adequate temporal sampling, the spatial distribution of mean AF voltage (V-mAF) better correlates with delayed-enhancement magnetic resonance imaging (MRI-DE)-detected atrial fibrosis than V-SR. METHODS AF was mapped (8 seconds) during index ablation for persistent AF (20 patients) using a 20-pole catheter (660 +/- 28 points/map). After cardioversion, V-SR was mapped (557 +/- 326 points/map). Electroanatomic and MRI-DE maps were co-registered in 14 patients. RESULTS The time course of V-mAF was assessed from 1-40 AF cycles (similar to 8 seconds) at 1113 locations. V-mAF stabilized with sampling >4 seconds (mean voltage error 0.05 mV). Paired point analysis of V-mAF from segments acquired 30 seconds apart (3667 sites; 15 patients) showed strong correlation (r = 0.95; P <.001). Delayed enhancement (DE) was assessed across the posterior left atrial (LA) wall, occupying 33% +/- 13%. V-mAF distributions were (median [IQR]) 0.21 [0.14-0.35] mV in DE vs 0.52 [0.34-0.77] mV in non-DE regions. V-SR distributions were 1.34 [0.65-2.48] mV in DE vs 2.37 [1.27-3.97] mV in non-DE. V-mAF threshold of 0.35 mV yielded sensitivity of 75% and specificity of 79% in detecting MRI-DE compared with 63% and 67%, respectively, for V-SR (1.8-mV threshold). CONCLUSION The correlation between low-voltage and posterior LA MRI-DE is significantly improved when acquired during AF vs sinus rhythm. With adequate sampling, mean AF voltage is a reproducible marker reflecting the functional response to the underlying persistent AF substrate.

The British Heart Rhythm Society's Clinical Practice Guidelines on the Management of Patients Developing QT Prolongation on Antipsychotic Medication are written for heart rhythm consultants, primary care physicians, specialist registrars, nurses and physiologists who may be requested to review ECGs or advise on cases where antipsychotic-induced QT prolongation is suspected or proven. The guidance is adapted from the latest Maudsley Prescribing Guidelines in Psychiatry, published in 2018.

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 (TM) (Boston Scientific) 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 activationwavefront was identifiedwithout interruption and its conduction velocity (CV) was 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 electrocardiogram(EKG) flutter waves was 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 traveled significantly further than during the upslope (182 +/- 21 milliseconds vs. 68 +/- 29 milliseconds, P< 0.0001) with no change in CV between the two phases (0.88 vs. 0.91 m/s, P = 0.79). Conclusion: CV at the CTI is not slower than other RA regions during typical AFL. The gradual downslope of the sawtooth EKG is not due to slow conduction at the CTI suggesting that success of ablation at this site relates to anatomical properties rather than the presence of a "slow isthmus."

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 (<0.03 mV; 12±6 mm diameter). In LR, electrograms along the carousel encompassed the full tachycardia cycle length, and surrounding activation moved away from the carousel in all directions. Ablating fractionated electrograms (117±18 ms; 44±13% of tachycardia cycle length) within the carousel interrupted the tachycardia in every LR case. All remaining carousels were pseudo-reentrant (n=43/50 [86%]) occurring in areas of wavefront collision (n=21; median 0.5; quartiles 0-2 per map) or as artifact because of annotation of noise or interpolation in areas of incomplete mapping (n=22; median 1, quartiles 0-2 per map). Pseudo-reentrant carousels were incorrectly ablated in 5 cases having been misinterpreted as LR. 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.

Purpose: 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%. We calculated the ESC SD risk score and measured it against ICD outcome in patients previously evaluated at our centre. In addition, we also collected data on conventional risk markers as defined by the American College of Cardiology and Heart Association. Results: 52 out of 219 HCM patients (mean age 51 ± 13 yrs) underwent ICD implantation for primary prevention, with 8 (15%) having appropriate therapy for VT/VF over an average follow up period of 6.2 ± 4.9yrs. 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 had scores ranging from 3.08-5.05% and would not have met the threshold for an ICD recommendation. 7 patients received an ICD for secondary prevention, with VT/VF being the presenting rhythm. Interestingly, 1 of 7 (14%) patient within this group would not have met the threshold for ICD recommendation if not for the presenting event.

Purpose: The incidence of inappropriate shocks would be expected to be reduced if ICD's had a reliable method for assessing hemodynamic status. Laser Doppler Perfusion Monitoring (LDPM) measures microvascular tissue perfusion. In this study we aim to assess whether LDPM reliably detects hemodynamic changes associated with VF. Methods: 18 consecutive patients referred for ICD implantation were recruited. During VF induction continuous non-invasive: beat-by-beat blood pressure, Doppler blood flow to the brain and non- invasive laser Doppler signals (with probes positioned on the chest and finger) were recorded. Summary of Results: During VF the laser Doppler signals were markedly reduced, the timing of the changes in signal matched those observed in blood pressure and transcranial Doppler flow. In order to minimize the effect of noise we calculated the oscillatory power of the LDPM signal. In all patients during VF the signal always fell to a value less than 2% of the absolute value. We did not observe values below 2% in any of the baseline recordings made during sinus rhythm.

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.

oral session 1: Atrial fibrillation ablation Sunday, April 19, 2015 10:30 am – 12:00 pm Room: Derain

OBJECTIVES:The purpose of this study was to investigate whether heart failure patients with narrow QRS duration (or right bundle branch block) but with long PR interval gain acute hemodynamic benefit from atrioventricular (AV) optimization. We tested this with biventricular pacing and (to deliver pure AV shortening) direct His bundle pacing. BACKGROUND:Benefits of pacing for heart failure have previously been indicated by acute hemodynamic studies and verified in outcome studies. A new target for pacing in heart failure may be PR interval prolongation, which is associated with 58% higher mortality regardless of QRS duration. METHODS:We enrolled 16 consecutive patients with systolic heart failure, PR interval prolongation (mean, 254 ± 62 ms) and narrow QRS duration (n = 13; mean QRS duration: 119 ± 17 ms) or right bundle branch block (n = 3; mean, QRS duration: 156 ± 18 ms). We successfully delivered temporary direct His bundle pacing in 14 patients and temporary biventricular pacing in 14 participants. We performed AV optimization using invasive systolic blood pressure obtaining parabolic responses (mean R2: 0.90 for His, and 0.85 for biventricular pacing). RESULTS:The mean increment in systolic BP compared with intrinsic ventricular conduction was 4.1 mm Hg (95% confidence interval [CI]: +1.9 to +6.2 mm Hg for His and 4.3 mm Hg [95% CI: +2.0 to +6.5 mm Hg] for biventricular pacing. QRS duration lengthened with biventricular pacing (change = +22 ms [95% CI: +18 to +25 ms]) but not with His pacing (change = +0.5 ms [95% CI: -2.6 to +3.6 ms). CONCLUSIONS:AV-optimized pacing improves acute hemodynamic function in patients with heart failure and long PR interval without left bundle branch block. That it can be achieved by single-site His pacing shows that its mechanism is AV shortening. The improvement is ∼60% of the effect size previously reported for biventricular pacing in left bundle branch block. Randomized, blinded trials are warranted to test for long-term beneficial effects.

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 non-invasive 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 electro-physiologists. 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 Hotter 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.

Malfunction of Subpectorally Implanted Cardiac Resynchronization Therapy. Background: Implantable cardioverter defibrillator (ICD) implantation has increased significantly over the last 10 years. Concerns about the safety and reliability of ICD systems have been raised, with premature lead failure and battery malfunctions accounting for the majority of reported adverse events. We describe the unique mode of presentation, diagnosis, and management of cardiac resynchronization therapy defibrillators (CRT‐D) malfunctions that were caused by weakened bonding between the generator and header. Methods and Results: Between June 2008 and December 2009, 22 Teligen™ ICDs and 24 Cognis™ CRT‐Ds were implanted subpectorally at our institution, until a product advisory was issued. Of 24 Cognis™ CRT‐D implants, 3 patients presented with CRT‐D malfunctions. All our cases presented with initially intermittent and then persisting increases in shock lead impedance, associated with nonphysiological noise in the shock electrogram channels. These issues were rectified by generator change. Postexplant laboratory analysis confirmed inadequate bonding between device header and titanium casing in all cases, resulting in loosening and rocking of the header followed by fatigue‐induced fracture of the shock circuitry. Conclusion: Weakened bonding between the header and generator casing of subpectorally implanted CRT‐Ds can result in fractures and malfunction of the HV circuit. Physicians monitoring patients with devices affected by the product advisory should remain vigilant in order to diagnose and manage similar device malfunction expediently. (J Cardiovasc Electrophysiol, Vol. 24, pp. 351‐355, March 2013)

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.