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Mapping and ablation of atrial tachycardia (AT) is commonly performed in lateral tunnel Fontan (LTF) patients, yet there is little information on the need of baffle puncture to access the pulmonary venous atrium (PVA). This study aimed to evaluate the most common chamber location of critical sites for majority of AT in LTF patients. Consecutive LTF patients underwent catheter-based high-density mapping and ablation of AT from Nov. 2015 to Mar. 2019. Critical sites were identified by a combination of activation and entrainment mapping. Acute procedural success was defined as AT termination with ablation and non-inducibility of any AT. Predictors for ablation failure were evaluated in retrospect. Fifteen catheter ablation procedures were performed in 9 patients. A total of 15 clinical ATs (mean TCL 369 ± 91 ms) were mapped. The mechanism was macro re-entry in 11 (73%) and micro re-entry in 2. In 11 ATs (73%), 94 ± 5% of tachycardia cycle length (TCL) were mapped inside the tunnel. The commonest site of successful ablation in the tunnel was on the lateral wall (60%). Trans-baffle access was obtained during 5 of 15 procedures (33%). Overall, procedural success was achieved in 9 of 15 procedures (60%). There were no complications. Recurrence of AT was 42% over a follow-up period of 4.3 ± 3.2 years. Faster TCL of 200–300 ms showed a trend towards ablation failure, (OR 17, 95% CI 0.7 to 423, p = 0.08). Catheter ablation can be performed effectively for ATs in LTF patients usually from inside the tunnel. ATs with critical sites in the PVA are uncommon. This information will help plan ablation in LTF patients without resorting to initial trans-baffle access.

Funding Acknowledgements Type of funding sources: None. Introduction Arrhythmias are frequently encountered in adult congenital heart disease (ACHD) and respond poorly to pharmacological therapies. Catheter ablation is challenging due to anatomical variation and complexity of the arrhythmia substrate. High density multi electrode mapping (MEM) with automatic annotation of activation time may aid mapping of arrhythmia, decrease procedure time and improve the accuracy of targeting of ablation therapy. Purpose To compare the acute and long term outcomes and procedural characteristics of catheter ablation in ACHD patients with and without automatic annotation of activation with MEM. Methods Retrospective analysis of the acute and long term outcomes of ACHD patients in a single centre undergoing ablation procedures from 1 Jan 2014 to 18 August 2017 was undertaken. 2 groups were identified. Group 1 included patients who had arrhythmia mapping performed with the CARTO 3D electroanatomic mapping system without the use of automatic signal annotation. Most patients in this group had sequential mapping performed with the ablation catheter (78%), the rest had multi-electrode mapping with the PentaRay 20 pole catheter. Group 2 included patients who had arrhythmia mapping performed with the CARTO 3D electroanatomic mapping system using the automated CONFIDENSE mapping algorithm. Results Group 1: n = 27, mean age 44.6 +/-3 years. Male 46.6%. Group 2: n = 38, mean age 44.0 +/- 1.9 years. Male 56.7%. All patients had CHD of at least moderate complexity. 25% of patients in group 1 and 45% in group 2 were repeat ablations. 45 arrhythmias were induced in group 1 of which 29 were targeted and 74 arrhythmias were induced in group 2 of which 46 were targeted. Acute success rates (after attempts at reinduction) were 96.3% in group 1 and 94.7% in group 2. Recurrences of arrhythmia occurred significantly less in patients in group 2 compared to group 1 (44.7% and 70.4% respectively, p Conclusions The use of multi-electrode mapping with an automatic annotation algorithm was associated with a significantly lower risk of recurrence during the follow up period of this study.

Deep learning recommendation models (DLRMs) are used across many business-critical services at Facebook and are the single largest AI application in terms of infrastructure demand in its data-centers. In this paper we discuss the SW/HW co-designed solution for high-performance distributed training of large-scale DLRMs. We introduce a high-performance scalable software stack based on PyTorch and pair it with the new evolution of Zion platform, namely ZionEX. We demonstrate the capability to train very large DLRMs with up to 12 Trillion parameters and show that we can attain 40X speedup in terms of time to solution over previous systems. We achieve this by (i) designing the ZionEX platform with dedicated scale-out network, provisioned with high bandwidth, optimal topology and efficient transport (ii) implementing an optimized PyTorch-based training stack supporting both model and data parallelism (iii) developing sharding algorithms capable of hierarchical partitioning of the embedding tables along row, column dimensions and load balancing them across multiple workers; (iv) adding high-performance core operators while retaining flexibility to support optimizers with fully deterministic updates (v) leveraging reduced precision communications, multi-level memory hierarchy (HBM+DDR+SSD) and pipelining. Furthermore, we develop and briefly comment on distributed data ingestion and other supporting services that are required for the robust and efficient end-to-end training in production environments.

Recommendation model DNNs have gained significant attention due to their vital role in recommending the best content to the user. However, in order to further increase accuracy, DNNs are becoming more complex with more data to be trained, making them infeasible for training on a single node. Distributed training is a solution to tackle this problem by employing multiple nodes for training. The importance of recommendation models necessitates to design customized HW/SW platforms for training such networks in order to minimize the communication overheads among different nodes. However, exploring this design space is difficult due to the presence of many HW/SW parameters and the limitations to change the HW parameters in real systems.In this paper, we port the previously proposed ASTRA-SIM simulation platform on top of the versatile NS3 network simulator by introducing a portable network interface for ASTRA-SIM. Using NS3 enables modeling a wide variety of networks with much better accuracy. Furthermore, we enhance NS3 with detailed modeling of TCP/IP.Finally, we study various HW/SW platforms for the DLRM recommendation model with TCP/IP as the network protocol and analyze the communication overheads in the presence of various interconnect configurations.

Background Atrial tachyarrhythmias (AAs) are the main source of morbidity and mortality in adult congenital heart disease (ACHD). Direct-current cardioversion (DCCV) is an effective method to acutely terminate AAs, but many patients require repeated DCCV. Little is known about the impact of radiofrequency catheter ablation (RFCA) of AAs on the incidence of repeated DCCV in patients with ACHD. The purpose of this study was to evaluate the impact of RFCA on the incidence of DCCV in patients with ACHD. Methods A total of 157 patients with ACHD undergoing DCCV in our hospital from 2011 to 2018 (female n = 76 [48.4%], mean age 37.8 ± 12.5 y), were reviewed. The median follow-up period was 31.8 months (interquartile range 16.3-55.1 mo). Results Out of the total of 157 patients, 102 (65.0%) underwent RFCA for AAs, and 55 (35.0%) were treated without RFCA. Successful RFCA with termination of AAs during ablation was 62.7%. More than one-half of the patients had complex forms of CHD (62.4%). During follow-up, 57 patients (55.9%) who had RFCA developed recurrence of AAs, and 36 patients (35.2%) underwent repeated DCCV. Thirty-three (60.0%) out of 55 patients without RFCA required repeated cardioversion. Compared with patients without RFCA, RFCA significantly reduced the need for repeated DCCV by 40% (hazard ratio [HR] 0.60, 95% confidence interval [CI] 0.23-0.80; P = 0.009). In multivariate analysis, successful RFCA was associated with reduced risk of DCCV (HR 0.41, 95% CI 0.19-0.92; P = 0.031). Conclusions AAs remain common despite RFCA in patients with ACHD. Nevertheless, RFCA is associated with a marked reduction in the need for repeated DCCV.

Management of ventricular arrhythmia in structural heart disease is complicated by the toxicity of the limited antiarrhythmic options available. In others, proarrhythmia and deleterious hemodynamic and noncardiac effects prevent practical use. This necessitates new thinking in therapeutic agents for ventricular arrhythmia in structural heart disease. Ivabradine, a funny current (If) inhibitor, has proven safety in heart failure, angina, and inappropriate sinus tachycardia. Although it is commonly known that funny channels are primarily expressed in the sinoatrial node, atrioventricular node, and conducting system of the ventricle, ivabradine is known to exert effects on metabolism, ion homeostasis, and membrane electrophysiology of remodeled ventricular myocardium. This review considers novel concepts and evidence from clinical and experimental studies regarding this paradigm, with a potential role of ivabradine in ventricular arrhythmia.

Background Implantable cardioverter-defibrillators (ICDs) have been proven to prevent sudden cardiac death in adult congenital heart disease (ACHD) patients. Although the left side is chosen by default, implantation from the right side is often required. However, little is known about the efficacy and safety of right-sided ICDs in ACHD patients. Methods In this study we reviewed a total of 191 ACHD patients undergoing ICD/cardioverter resynchronisation therapy-defibrillator (CRT-D) implantation at our hospital between 2001 and 2019 (134 men and 57 women; age [mean ± standard deviation], 41.5 ± 14.8 years). Results Twenty-seven patients (14.1%) had right-sided devices. The most common causes of right-sided implantation were persistent left superior vena cava and vein occlusion (37.0%). Although procedure time (202.8 ± 60.5 minutes vs 143.8 ± 69.1 minutes, P = 0.008) was longer and the procedural success was lower (92.6% vs 99.4%, P = 0.008) for right-sided devices, no difference in R-wave and pacing threshold were noted. Among the 47 patients (24.6%) who underwent defibrillation threshold testing (DFT), no difference in DFT was observed (25.2 ± 5.3 J vs 23.8 ± 4.1 J, P = 0.460). During the median follow-up of 42.4 months, appropriate ICD therapy was observed in 5 (18.5%) and 30 (18.3%) patients for right- and left-sided ICDs/CRTDs, respectively (P = 0.978). No significant difference was seen in complications between them. Conclusions Implantation of an ICD on the right side is technically challenging, but it is feasible as an alternative approach for ACHD patients with contraindications to left-sided device implantation.

Objective Although heart failure (HF) is the leading cause of premature death in adult congenital heart disease (ACHD), little population-specific data exist. This study reports early experience from a dedicated, sub-specialty adult congenital heart disease-heart failure (ACHD-HF) clinic, aiming to identify risk factors for adverse outcome. Methods Between 2012 and 2015, 126 patients (57% male) attended the ACHD-HF clinic. Baseline and follow-up data were analysed and compared across 4 anatomical/physiological subgroups: cyanotic ACHD, Fontan circulation (1V), biventricular circulation with a subaortic right ventricle (2V-RV) and biventricular circulation with a subaortic left ventricle (2V-LV). Predictors of the composite primary outcome: death, transplant or ventricular assist device (VAD) were identified using multivariable Cox proportional hazard models. Results Mean age at first visit was 38±13years. Patients were grouped as follows: cyanotic ACHD 10%, 1V 24%, 2V-RV 29% and 2V-LV 37%. During a median follow-up of 1.7 (IQR 0.8–2.9) years, 38 patients (30%) reached the primary outcome. Event-free survival was 89%, 78% and 63% at 1, 2 and 3years. Forty (31.7%) patients experienced 69 HF hospitalisations. Between-group differences were noted for systolic function, valvular regurgitation, pacing prevalence and invasive hemodynamics. Multivariable analysis revealed 2V-RV subgroup ( p =0.001), NYHA class ( p =0.002) B-type natriuretic peptide >164pg/ml ( p =0.003) and sodium p =0.036) as independently associated with death, transplant or VAD. Conclusions Our young ACHD-HF patients experienced high adverse event rates during a short period of follow-up. The prognostic markers identified will aid clinicians to stratify short-term risk and thereby guide advanced HF management decisions in ACHD.

We present the case of a patient who presented in a dire situation with ventricular tachycardia (VT) storm, which did not respond to intubation, antiarrhythmics, or catheter ablation. This presentation is in the background of palliatively treated metastatic malignancy. We needed a strategy to treat VT to enable the step-down from intensive care and to restart systemic palliation. To that end we employed a strategy of electroanatomical mapping–guided stereotactic body radiotherapy (SBRT) with good effect.

Ventricular fibrillation (VF) is a lethal cardiac arrhythmia traditionally believed to be chaotic in nature. However, recent research studies have shown that certain events of interest during VF may exhibit local (or regional) organization. These time-varying and spatially migrating organized activities manifest themselves into different signal morphologies within electrograms acquired during VF. Performing targeted (or constrained) signal decomposition of electrograms to extract such signal morphologies associated with events of clinical interest will be of significant value. We present one such targeted adaptive signal decomposition of intra-cardiac electrograms during VF, to automatically extract morphologies previously observed in relation to the vicinity of rotor phenomenon (i.e. an event of interest during VF). Using a Gabor dictionary and Matching Pursuits (MP), the proposed method successfully performed targeted signal decomposition in highlighting signal structures that could be used to determine the ventricular electrogram's vicinity to a rotor in the epicardium. A comparative analysis using the MP with a proposed choice function ( P P

Restructured power system helps to meet the active power requirements of the consumers in an effective way. In an Independent System Operator (ISO) model of restructured power system, Available Transfer Capability (ATC) is calculated so as to determine how much extra power can be injected into one site apart from base consumption. ATC computation plays a significant role during power transactions because it helps the participants to schedule their transaction more effectively and quickly. This paper mainly focuses on ATC calculation using linear sensitivity factors for normal mode and line outage mode.

The risk of ventricular arrhythmias in the adult congenital heart disease population increases with age. The mechanism, type, and frequency vary depending on the complexity of the defect, whether it has been repaired, and the type and timing of repair. Risk stratification for sudden death in patients with congenital heart disease is often challenging. Current recommendations provide a useful guide for management of these patients and risk stratification continues to evolve. Internal cardiac defibrillator implantation is often challenging due to limited transvenous access, often resulting in the need for epicardial or subcutaneous devices.

The study carried out here was focused on developing conventional monolithic controlled release matrix tablet of Atorvastatin calcium using carbomer as release controlling polymer. This system ensures the drug release at the alkaline pH region where the drug has got maximum solubility. Further the study was concentrated on comparing the impact of gelling agent polyvinyl pyrrolidone on drug release. Quality by design tools were considered during formulation development and the polymer concentrations were optimized adopting the statistical tool, design of experiments (DoE). The optimized formulation of present study exhibited desired controlled drug release characteristics in the alkaline pH conditions and at acidic environment the drug dissolution was minimal as intended.

Ventricular arrhythmias (VA) are life-threatening pathophysiological conditions that seriously impact the normal functioning of the heart. Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the two well known types of VA. VF is the lethal of the VAs and could be characterized by its organizational progression over time. The success of cardiac resuscitation strongly depends on the type of VA, its evolution over time and response to therapy. Due to the time critical nature of VF, computationally efficient quantification of VAs and swift feedback are essential. This work attempted to arrive at computationally efficient and data-driven techniques based on Empirical Mode Decomposition for classifying and tracking VAs over time. The approaches are divided into two aims: (1) ‘in-hospital’ scenarios for characterizing the dynamics of VA episodes to assist clinicians in planning long-term therapy options, and (2) ‘out-of-hospital’ scenarios for providing near real-time feedback to detect/track the progression of VAs over time to assist medical personnel select/modify therapy options. Using an ECG database of 61 60-s VA segments obtained for classifying VT vs. VF and sub-classifying VF into organized VF (OVF) and disorganized VF (DVF), maximum classification accuracies of 96.7% (AUC = 0.993) and 87.2% (AUC = 0.968) were obtained for classifying VT vs. VF and OVF vs. DVF during ‘in-hospital’ analysis. Additionally, two near real-time approaches were presented for ‘out-of-hospital’ analysis where average accuracies of 71% and 73% were achieved for VT/VF and OVF/DVF classification, as well as demonstrating strong potential for monitoring VA progressions over time.

Arrhythmias are a leading cause of morbidity in adults with congenital heart disease. Numerous challenges to managing arrhythmias include vascular access issues, intracardiac shunts, unconventional locations of the conduction system, and anatomical complexities. Technological advances are improving our ability to diagnose and treat arrhythmias. Implantable loop recorders and various technologies developed for consumers to record electrocardiographic tracings using smartphone applications, watches, and dedicated portable devices are expanding our armamentarium of diagnostic tools. Remote magnetic-guided catheter ablation is enhancing access to otherwise difficult to reach arrhythmia substrates. Cryoablation allows perinodal arrhythmias to be safely treated in patients with displaced or difficult to predict locations of the atrioventricular conduction system. Interventions that minimize radiation exposure to near 0 levels are gaining interest and pulmonary vein isolation procedures to treat atrial fibrillation are increasingly performed. Cardiac implantable electronic devices compatible with magnetic resonance imaging have become the norm. Subcutaneous defibrillators and leadless pacemakers are providing effective solutions to patients in whom transvenous leads are contraindicated or not desired. His-bundle pacing is emerging as a viable option to provide more physiological pacing. Progressive advances in multicomponent communicating leadless devices carry the promise of providing leadless dual chamber pacing and cardiac resynchronization therapy in the near future. The safety of transvenous lead extraction procedures is likely to improve with advances such as the low-pressure balloon to manage superior vena cava lacerations. Awareness of these developments and referral to sites with dedicated expertise could contribute to further improving outcomes in adults with congenital heart disease.

Ventricular arrhythmias (VA) can lead to lethal conditions depending on their characteristics and temporal progression. Hence, it is essential to detect the type of VA and track its transitions over time to provide feedback in choosing appropriate therapy options. In this work, Empirical Mode Decomposition was used to extract intrinsic mode functions (IMFs) and construct the Hilbert energy spectrum (HS) from the 60-s long ECG segments during VAs. From the HS, instantaneous mean frequency and squared instantaneous bandwidth were extracted to track the progression of VAs. In addition, the energy ratio variance was computed from the IMFs. Using the extracted features, quantification of the performance was evaluated by a two-stage binary classification with a linear discriminant analysis based classifier and leave-one-out cross validation. A classification accuracy of 84% was achieved in classifying VT from VF, and 75% was achieved in classifying the correctly classified VF from the first stage into organized and disorganized VF.

Background Successful activation mapping of ventricular tachycardia (VT) is dependent on the identification of a region of diastolic conduction by use of point-by-point sequential mapping. It is important to identify the site of transition from diastolic conduction to systolic activation of healthy myocardium (exit site) and differentiate this from nonvulnerable regions of the circuit. Objective We sought to determine the temporal and component characteristics of exit-site electrograms using simultaneous multielectrode endocardial mapping and to differentiate them from bystander sites during activation mapping. Methods Sixteen VTs induced in 12 patients with ischemic cardiomyopathy who underwent multielectrode mapping during VT performed with a custom-made 112-bipolar-electrode endocardial array were analyzed retrospectively. The activation sequence in systole and diastole was annotated, and the timing at exit and bystander sites of the near-field component was characterized in relation to surface electrocardiogram activation and to the far-field component. Spectral content of bipolar electrograms recorded at these sites was additionally analyzed to identify the near-field to far-field interval. Results The mean activation time at exit sites was 60.0 ± 31.5 ms (range 21–113 ms) ahead of surface QRS but was not significantly different from bystander sites (72.0 ± 55.0 ms, P = .63). However, the time delay from local to far-field activity was significantly lower at exit sites than at bystander sites (24.9 ± 15.6 vs 86.6 ± 92.0 ms, P = .003), which was confirmed by spectral analysis (10.0 ± 13.1 vs 89.0 ± 64.5 ms, P = .003). Conclusion Our analysis suggests that temporal-component analysis of diastolic electrograms during activation mapping of VT provides a practical method to differentiate nonvulnerable sites from the exit site without the need for pacing maneuvers.

Background— High-frequency periodic sources during cardiac fibrillation can be detected by phase mapping techniques. To enable practical therapeutic options for modulating periodic sources (existing techniques require high density multielectrode arrays and real time simultaneous mapping capability), a method to identify electrogram morphologies colocalizing to rotors that can be implemented on few electrograms needs to be devised. Method and Results— Multichannel ventricular fibrillation electrogram data from 7 isolated human hearts using Langendorff setup and intraoperative clinical data from 2 human hearts were included in the analysis. The spatial locations of rotors were identified using phase maps constructed from 112 electrograms. Electrograms were analyzed for repeating patterns and discriminating signal morphologies around the locations of rotors and nonrotors were identified and quantified. Features were extracted from the unipolar electrogram patterns, which corroborated well with the spatial location of rotors. The results suggest that using the proposed modulation index feature, and as low as 1 sample point in the vicinity of the rotors, an accuracy as high as 86% ( P Conclusions— Unipolar electrogram extracted modulation index–based detection of rotors is feasible with few electrodes and has greater detection rate than bipolar approach. This strategy may be suitable for nonarray-based single mapping catheter enabled detection of rotors.

The risk of ventricular arrhythmias in the adult congenital heart disease population increases with age. The mechanism, type, and frequency vary depending on the complexity of the defect, whether it has been repaired, and the type and timing of repair. Risk stratification for sudden death in patients with congenital heart disease is often challenging. Current recommendations provide a useful guide for management of these patients and risk stratification continues to evolve. Internal cardiac defibrillator implantation is often challenging due to limited transvenous access, often resulting in the need for epicardial or subcutaneous devices.

Aims Current conventional ablation strategies for ventricular tachycardia (VT) aim to interrupt reentrant circuits by creating ablation lesions. However, the critical components of reentrant VT circuits may be located at deep intramural sites. We hypothesized that bipolar ablations would create deeper lesions than unipolar ablation in human hearts. Methods and results Ablation was performed on nine explanted human hearts at the time of transplantation. Following explant, the hearts were perfused by using a Langendorff perfusion setup. For bipolar ablation, the endocardial catheter was connected to the generator as the active electrode and the epicardial catheter as the return electrode. Unipolar ablation was performed at 50 W with irrigation of 25 mL/min, with temperature limit of 50°C. Bipolar ablation was performed with the same settings. Subsequently, in a patient with an incessant septal VT, catheters were positioned on the septum from both the ventricles and radiofrequency was delivered with 40 W. In the explanted hearts, there were a total of nine unipolar ablations and four bipolar ablations. The lesion depth was greater with bipolar ablation, 14.8 vs. 6.1 mm ( P < 0.01), but the width was not different (9.8 vs. 7.8 mm). All bipolar lesions achieved transmurality in contrast to the unipolar ablations. In the patient with a septal focus, bipolar ablation resulted in termination of VT with no inducible VTs. Conclusion By using a bipolar ablation technique, we have demonstrated the creation of significantly deeper lesions without increasing the lesion width, compared with standard ablation. Further clinical trials are warranted to detail the risks of this technique.

A 21-year-old woman presented to the emergency room with palpitations and lightheadedness. Her ECG at presentation showed broad complex tachycardia at 235 beats per minute with right bundle branch morphology, inferior rightward axis, and positive concordance in the precordial leads (Figure 1A). The tachycardia was terminated with electric cardioversion after adenosine had no effect. The subsequent ECG demonstrated sinus rhythm, PR interval 100 ms, a positive delta wave in leads V1, II, III, and aVF, isoelectric in lead I and negative in aVR (Figure 1B). Subsequent echocardiography demonstrated a structurally normal heart. She proceeded to an electrophysiological study. Figure 1. Surface ECGs of ( A ) presenting tachycardia and of ( B ) sinus rhythm after cardioversion. Editor’s Perspective see p 502 The baseline AH interval was 57 ms and HV was 13 ms. Atrial activation during ventricular pacing featured simultaneous activation of the lateral coronary sinus (CS) and septal (His) electrodes (not pictured). Programmed atrial extrastimuli reproducibly induced broad QRS complex tachycardia (Figure 1A). Attempts to entrain the tachycardia from the atrium induced atrial fibrillation that spontaneously terminated. Attempts to entrain tachycardia from the ventricle terminated tachycardia. Therefore, scanning sensed atrial extrastimuli during tachycardia were delivered …

Dual chamber pacemakers have inbuilt advanced safety systems such as ventricular safety standby (crosstalk detection) to prevent ventricular oversensing resulting in inappropriate pacing inhibition. We describe a case where this safety mechanism does not reliably work and the management required to rectify the situation in an educational format.

A 29-year-old male presented with palpitations without a documented tachycardia. ECG showed minimal preexcitation (Figure 1A), and echo confirmed a normal heart. At electrophysiological study in the drug-free state, the HV interval was 13 ms in sinus rhythm, and ventricular (V) activation in the right para-Hisian region preceded the surface delta wave (Figure 2A). Programmed stimulation from the septal right atrium (A) increased preexcitation at shorter S1–S2 intervals (below 600–360 ms), as evidenced by a subtle loss of physiological left-to-right ventricular (RV) septal activation (loss of r wave in V1 and q waves in I, aVL) and an increasingly negative HV interval. The S2–δ interval also prolonged with progressive preexcitation. Figures 1B and 2B show increased preexcitation elicited at an S1–S2 interval of 220 ms. Atrioventricular (AV) effective refractory period was shorter than 600–220 ms, and dual AV nodal physiology was absent. These features along with the existence of escape junctional preexcited beat (Figure 1C and 2C) supported the presence of a right-sided manifest nodoventricular (NV) pathway bypassing a portion of the AV node, and ruled against typical anterograde AV bypass tracts, Mahaim fibers from AV ring, and fasciculoventricular pathways. Figure 1. 12-lead ECGs during sinus rhythm ( A ), programmed extrastimulation from septal right atrium at S1–S1=600 ms and S1–S2=220 ms ( B ), and a junctional beat ( C ). Figure 2. Intracardiac electrograms during sinus rhythm ( A ), programmed extrastimulation from septal right atrium at S1–S1=600 ms and S1–S2=220 ms ( B ), and a junctional beat ( C ). C , His-potential (H) preceded the onset of ventricular and atrial activation, which was consistent with a junctional beat. Surface preexcitation and HV interval (13 ms) during the junctional beat were identical to that in sinus rhythm, suggesting the origin of the accessory pathway from a portion distal in the atrioventricular junction. Channels shown from top to bottom are surface ECG …

AIMS: Left ventricular (LV) epicardial pacing (LVEpiP) in human myopathic hearts does not decrease global epicardial activation delay compared with right ventricular (RV) endocardial pacing (RVEndoP); however, the effect on transmural activation delay has not been evaluated. To characterize the transmural electrical activation delay in human myopathic hearts during RVEndoP and LVEpiP compared with global epicardial activation delay. METHODS AND RESULTS: Explanted hearts from seven patients (5 male, 46 ± 10 years) undergoing cardiac transplantation were Langendorff-perfused and mapped using an epicardial sock electrode array (112 electrodes) and 25 transmural plunge needles (four electrodes, 2 mm spacing), for a total of 100 unipolar transmural electrodes. Electrograms were recorded during LVEpiP and RVEndoP, and epicardial (sock) and transmural (needle) activation times, along with patterns of activation, were compared. There was no difference between the global epicardial activation times (LVEpiP 147 ± 8 ms vs. RVEndoP 156 ± 17 ms, P = 0.46). The mean LV transmural activation time during LVEpiP was significantly shorter than that during RVEndoP (125 ± 44 vs. 172 ± 43 ms, P

We present the case of a 68-year-old man with dilated cardiomyopathy who had an implantable cardioverter defibrillator implanted for primary prevention (Unify Assura with a Durata 7122Q ventricular lead, St. Jude Medical). The device was programmed DDDR 60–110 beats per minute and Table shows more specific programming parameters. View this table: Table. Programming Parameters for Bradycardia and Tachycardia Therapies From the Patient’s Defibrillator See Editor’s Perspective by Asirvatham and Stevenson Six months after implantation, routine device interrogation revealed many asymptomatic episodes logged as nonsustained lead noise (NSLN). The electrograms from one of these episodes are shown in Figure 1A. What is the differential diagnosis? Figure 1. A , A stored electrogram from the patients implantable cardioverter defibrillator that was classified as nonsustained right ventricular lead noise. Respective electrograms and marker channels are labeled and are consistent for each panel. Numbered arrows indicate key points in the tracing for discussion. Intervals annotated with a (−) on the ventricular marker channel indicate that the current interval is within the tachycardia zone, however, the interval average (average of the current interval and the previous 3 intervals) is not. These beats do not count toward tachycardia detection. B , Electrograms in sinus rhythm for comparison. C and D , Tachycardias recorded on different occasions. AP indicates atrial pace; F, beat in the ventricular fibrillation zone; NSLN, nonsustained lead noise; SIR, sensor-indicated rate; VP, ventricular pace; VS, ventricular sense; and VSP, ventricular safety pace. A rhythm strip showing sinus rhythm is shown for comparison in Figure 1B and similar episodes of tachycardia are shown in Figure 1C and 1D from subsequent interrogation. These subsequent figures assist in clarifying the rhythm diagnosis; however, further questions arise as to the behavior of …

Patients with congenital heart disease and particularly those with previous surgical repair are potentially at risk of brady- and tachy-arrhythmias over the course of their lifetime. Arrhythmias can be associated with significant morbidity and potential mortality in the patient with congenital heart disease and account for a substantial proportion of all hospital admissions in this cohort. The selection of appropriate anti-arrhythmic therapy for these patients presents unique challenges and aspects of care such as ventricular dysfunction, risk of bradyarrhythmia etc. must be taken into consideration. Commonly used and newer agents pertinent to the patient with congenital heart disease will be highlighted here. It should be noted that there is a remarkable paucity of data with respect to the efficacy and safety of anti-arrhythmic agents in this patient cohort and much of what has been reported is derived from small patient series. In addition, published guidelines on arrhythmia management generally do not address the specific needs of this population and, in the absence of randomized controlled trials, management decisions tend to be based on data extrapolated from other patient populations. Nonetheless, with careful appraisal of the potential confounders facing the individual patient when selecting an anti-arrhythmic management strategy, the goals of effective and safe therapy can be attained.

Identification and classification of ventricular arrhythmias such as rhythmic ventricular tachycardia (VT) and disorganized ventricular fibrillation (VF) are vital tasks in guiding implantable devices to deliver appropriate therapy in preventing sudden cardiac deaths. Recent studies have shown VF can exhibit strong regional organizations, which makes the overlap zone between the fast paced rhythmic VT and VF even more ambiguous. Considering that implantable cardioverter-defibrillator (ICD) are primarily rate dependent detectors of arrhythmias and that there may be patients who suffer from arrhythmias that fall in the overlap zone, it is essential to identify the degree of affinity of the arrhythmia toward VT or organized/disorganized VF. The method proposed in this work better categorizes the overlap zone using Wavelet analysis of surface ECGs. Sixty-three surface ECG signal segments from the MIT-BIH database were used to classify between VT, organized VF (OVF), and disorganized VF (DVF). A two-level binary classifier was used to first extract VT with an overall accuracy of 93.7% and then the separation between OVF and DVF with an accuracy of 80.0%. The proposed approach could assist clinicians to provide optimal therapeutic solutions for patients in the overlap zone of VT and VF.

Background: Epidemiological studies have assessed T-wave alternans (TWA) as a possible mechanism of cardiac arrhythmias related to air pollution in high-risk subjects and have reported associations with increased TWA magnitude. Objective: In this controlled human exposure study, we assessed the impact of exposure to concentrated ambient particulate matter (CAP) and ozone (O3) on T-wave alternans in resting volunteers without preexisting cardiovascular disease. Methods: Seventeen participants without preexisting cardiovascular disease were randomized to filtered air (FA), CAP (150 μg/m3), O3 (120 ppb), or combined CAP + O3 exposures for 2 hr. Continuous electrocardiograms (ECGs) were recorded at rest and T-wave alternans (TWA) was computed by modified moving average analysis with QRS alignment for the artifact-free intervals of 20 beats along the V2 and V5 leads. Exposure-induced changes in the highest TWA magnitude (TWAMax) were estimated for the first and last 5 min of each exposure (TWAMax_Early and TWAMax_Late respectively). ΔTWAMax (Late–Early) were compared among exposure groups using analysis of variance. Results: Mean ± SD values for ΔTWAMax were –2.1 ± 0.4, –2.7 ± 1.1, –1.9 ± 1.5, and –1.2 ± 1.5 in FA, CAP, O3, and CAP + O3 exposure groups, respectively. No significant differences were observed between pollutant exposures and FA. Conclusion: In our study of 17 volunteers who had no preexisting cardiovascular disease, we did not observe significant changes in T-wave alternans after 2-hr exposures to CAP, O3, or combined CAP + O3. This finding, however, does not preclude the possibility of pollution-related effects on TWA at elevated heart rates, such as during exercise, or the possibility of delayed responses.

It is unknown whether ventricular fibrillation (VF) studied in experimental models represents in vivo human VF. First, we examined closed chest in vivo VF induced at defibrillation threshold testing (DFT) in four patients with ischemic cardiomyopathy pretransplantation. We examined VF in these same four hearts in an ex vivo human Langendorff posttransplantation. VF from DFT was compared with VF from the electrodes from a similar region in the right ventricular endocardium in the Langendorff using two parameters: the scale distribution width (extracted from continuous wavelet transform) and VF mean cycle length (CL). In a second substudy group where multielectrode phase mapping could be performed, we examined early VF intraoperatively (in vivo open chest condition) in three patients with left ventricular cardiomyopathy. We investigated early VF in the hearts of three patients in an ex vivo Langendorff and compared findings with intraoperative VF using two metrics: dominant frequency (DF) assessed by the Welch periodogram and the number of phase singularities (lasting >480 ms). Wavelet analysis ( P = 0.9) and VF CL were similar between the Langendorff and the DFT groups (225 ± 13, 218 ± 24 ms; P = 0.9), indicating that wave characteristics and activation rate of VF was comparable between the two models. Intraoperative DF was slower but comparable with the Langendorff DF over the endocardium (4.6 ± 0.1, 5.0 ± 0.4 Hz; P = 0.9) and the epicardium (4.5 ± 0.2, 5.2 ± 0.4 Hz; P = 0.9). Endocardial phase singularity number (9.6 ± 5, 12.1 ± 1; P = 0.6) was lesser in number but comparable between in vivo and ex vivo VF. VF dynamics in the limited experimental human studies approximates human in vivo VF.

Dual chamber pacemakers have inbuilt advanced safety systems such as ventricular safety standby (crosstalk detection) to prevent ventricular oversensing resulting in inappropriate pacing inhibition. We describe a case where this safety mechanism does not reliably work and the management required to rectify the situation in an educational format. This article is protected by copyright. All rights reserved

The risk of sudden cardiac death (SCD) is increased aftermyocardial infarction (MI), especially inpatients with left ventricular ejection fraction (LVEF) less than or equal to 35%. Themortality benefit of implantable cardioverter defibrillators (ICDs) in SCD has been shown in randomized primary and secondary prevention trials. Reduced LVEF is also an important risk parameter that predicts both all-cause mortality and sudden arrhythmic death. ICD therapy led to a 31%reduction of all-causemortality in patients with LVEF less than or equal to 30% and remote MI in the landmark Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II). The Sudden Cardiac Death in Heart Failure Trial (SCDHeFT) gave additional support to these findings in patients with heart failure with ischemic or nonischemic cardiomyopathy and with LVEF less than or equal to 35%.

Rationale: Ventricular fibrillation (VF) leads to global ischemia. The modulation of ischemia-dependent pathways may alter the electrophysiological evolution of VF. Objective: We addressed the hypotheses that there is regional disease-related expression of K ATP channels in human cardiomyopathic hearts and that K ATP channel blockade promotes spontaneous VF termination by attenuating spatiotemporal dispersion of refractoriness. Methods and Results: In a human Langendorff model, electric mapping of 6 control and 9 treatment (10 μmol/L glibenclamide) isolated cardiomyopathic hearts was performed. Spontaneous defibrillation was studied and mean VF cycle length was compared regionally at VF onset and after 180 seconds between control and treatment groups. K ATP subunit gene expression was compared between LV endocardium versus epicardium in myopathic hearts. Spontaneous VF termination occurred in 1 of 6 control hearts and 7 of 8 glibenclamide-treated hearts ( P =0.026). After 180 seconds of ischemia, a transmural dispersion in VF cycle length was observed between epicardium and endocardium ( P =0.001), which was attenuated by glibenclamide. There was greater gene expression of all K ATP subunit on the endocardium compared with the epicardium ( P Transmural =ERP Epicardium −ERP Endocardium ) was verified with pacing protocols. ΔERP Transmural in control was 5±2 ms and increased to 36±5 ms with ischemia. This effect was greatly attenuated by glibenclamide (ΔERP Transmural for glibenclamide+ischemia=4.9±4 ms, P =0.019 versus control ischemia). Conclusions: K ATP channel subunit gene expression is heterogeneously altered in the cardiomyopathic human heart. Blockade of K ATP channels promotes spontaneous defibrillation in cardiomyopathic human hearts by attenuating the ischemia-dependent spatiotemporal heterogeneity of refractoriness during early VF.

Effective chest compressions during prolonged ventricular fibrillation (VF) have been shown to increase the chances of successful defibrillation to a rhythm associated with a sustainable cardiac output. There is currently no effective method of recording the degree of antegrade coronary artery flow during chest compression in VF.This study sought to quantify the relationship between the antegrade coronary flow and the characteristics of human VF using near real-time wavelet-based electrocardiographic markers.VF experiments were conducted in 8 isolated human hearts. The Langendorff perfusion enabled different flow rates (perfusion) during VF, which allowed for the simulation of chest compression with different efficacies. After the initiation of VF, the hearts were maintained in ischemia (no flow) for 3 minutes, followed by a 2-minute reperfusion and defibrillation. The experiments were repeated at flows of 0%, 30%, and 100% of baseline perfusion, and volume-conducted surface electrograms were recorded and analyzed using continuous wavelet transform in 5-second frames.Near real-time wavelet features were derived that demonstrated significant differences in the multicomponent nature of VF signals and predicted perfusion rate characteristics for different flow rates (i.e., 0%, 30%, and 100%; P.0006). A pattern classifier was trained using the feature values from 5 hearts, and the flow rates for 3 additional hearts were predicted with an accuracy of 90%.VF electrogram characteristics as measured by wavelet analysis relate to antegrade coronary flow rate during VF. These findings suggest that chest compression efficacy of physiological importance could be monitored using near real-time wavelet analysis.

A narrow QRS tachycardia with eccentric atrial activation is presented with features favoring an orthodromic atrioventricular re-entrant tachycardia including an extranodal paraHisian response, and a short corrected post-pacing interval to tachycardia cycle length difference following right ventricular entrainment. However, during entrainment, the H-H interval was entrained by the pacing train several beats prior to the A-A interval which would suggest an atrioventricular nodal re-entry tachycardia. We discuss the diagnosis and its mechanism.