[Practical guidance for the implantation of non-transvenous ICD systems]. / Praktische Anleitung zur Implantation nicht-transvenöser ICD-Systeme.

As an alternative to transvenous ICD systems, two non-transvenous ICD systems have been established in recent years: The subcutaneous ICD (S-ICD), which has been established for several years, has a presternal electrode that is implanted subcutaneously and offers a shock function and, to a limited extent, post-shock pacing. In addition, the extravascular ICD (EV-ICD) has been available in Europe since 2023 which does not require transvenous electrodes and offers the option of providing patients with antibradycardic and antitachycardic stimulation in combination with a conventional ICD function. The lead of this device is implanted substernally. Initial implantation results are promising in terms of safety and effectiveness. Both systems avoid possible complications of transvenous electrodes. This article provides practical guidance for the implantation technique and possible complications.

Intracardiac Echocardiography: An Invaluable Tool in Electrophysiological Interventions for Atrial Fibrillation and Supraventricular Tachycardia.

Researchers have investigated ways to develop optimal imaging techniques to increase the safety and effectiveness of electrophysiological (EP) procedures. Intracardiac echocardiography (ICE) is an advanced imaging tool that can directly visualize cardiac anatomical structures in high resolution, assess tissue heterogeneity and arrhythmogenic substrates, locate intracardiac catheters, monitor catheter-tissue contact and ablation injury in real-time, excluding intracardiac thrombi, and quickly detect procedural complications. Additionally, real-time imaging via ICE can be integrated with a three-dimensional (3D) electroanatomical mapping (EAM) system to reconstruct cardiac anatomy. This technique also promotes the development of zero-radiation EP procedures. Many EP studies and procedures have implemented ICE because it has several advantages over fluoroscopy and transesophageal echocardiography (TEE). ICE-guided EP procedures can be performed under conscious sedation; esophageal intubation and additional anesthesiologists are not required. Atrial fibrillation (AF) and supraventricular tachycardias (SVT) are the most common tachyarrhythmias in clinical settings. A comprehensive understanding of critical anatomical structures, such as the atrial septum, fossa ovalis (FO), and great heart vessels, is needed for the successful catheter ablation of these arrhythmias.

The characterization of functional conduction block in patients with multiple types of atrial tachycardia- A discussion on the mechanism of multiple atrial tachycardia.

BACKGROUND: High-resolution mapping offers superior accuracy in delineating conduction features; however, certain characteristics are still linked to elevated recurrence rates of atrial tachycardia (AT), suggesting the influence of additional mechanisms. This study systematically assessed the substrate of functional conduction block (FCB) regions in relation to the mechanisms of multiple ATs. METHODS: In this study, the Carto system facilitated the mapping of ATs in 13 patients undergoing ablation, each presenting with more than two AT variants. FCB regions were marked and further analyzed. RESULTS: A total of 33 sustained ATs were mapped across the patient cohort. FCB regions showed convertibility in 7 of 13 patients (54%). Three kinds of presentations can be summarized by the FCB region: Firstly, the FCB region could act as the main obstacle sustaining the localized reentrant pathway, for which rounding obviously has a direct correlation with the mechanism of the AT (27%). Secondly, the FCB regions could act as obstacle lines to reorganize the propagation of the reentry in localized AT and macroreentrant AT (55%). Lastly, the FCB region could act as a bystander and may not be related to the mechanism of the ATs (18%). The potentials in FCB regions mostly performed low voltages or fragmented potentials (FPs) in the ATs which they did not perform the conduction block (90%). CONCLUSION: In multiple ATs, FCB regions may not be uncommon. The participation of FCB regions in the mechanism of ATs showed three different kinds of performance. The dynamic nature of this substrate may provide insight into the reasons for the high recurrence of related ATs.

Use of the advisor™ HD Grid mapping catheter in transcatheter ablation of atrial arrhythmias in palliated CHD and children without CHD.

OBJECTIVE: In this study, we describe our experience utilising Advisor™ High Density (HD) Grid mapping catheter in transcatheter ablation of intraatrial re-entrant and focal atrial tachycardias with or without CHD. METHODS: Forty-five consecutive patients with intraatrial re-entrant and focal atrial tachycardia who underwent a transcatheter ablation procedure by using Advisor™ HD Grid mapping catheter and high-density mapping system in our hospital from January 2017 to January 2023 were included into the study. RESULTS: The mean age of the patients was 14.2 ± 7.3 years (6-32 years), and the mean weight was 48.3 ± 16.2 kg (22-83 kg). Of the total 45 patients, 21 were intraatrial re-entrant tachycardia and 25 were focal atrial tachycardia. Of the 21 re-entrant circuits, 15 were classified as cavotricuspid isthmus-dependent and 5 were non-cavotricuspid isthmus-dependent. In one patient, two re-entrant circuits were identified. A transbaffle ablation was successfully performed from the left atrium in one patient. Of the 25 focal atrial tachycardia, 19 were from right atrium and 6 were from left atrium. A cryoablation was performed in only one patient and radiofrequency ablation in others. The mean procedure time was 180 ± 64 minutes. The mean follow-up period was 69.3 ± 35.3 months. Acute success was 95.5%. Recurrence was noted in two patients (4.4%). CONCLUSION: Advisor™ HD Grid mapping catheter was found to be safe and achieved an acceptable success in transcatheter ablation of patients with intraatrial re-entrant tachycardia and focal atrial tachycardias.

An annotation-independent algorithm based on electrogram characteristics to guide the identification of ventricular tachycardia isthmuses in patients with structural heart disease.

BACKGROUND: Criteria such as electrograms voltage or late potentials have been largely utilized in the past to help identify areas of substrate maps that are within the ventricular tachycardia (VT) isthmus; yet their specificity and positive predictive value are quite low. The Lumipoint fractionation tool of the Rhythmia system illuminates regions with fractionated electrograms irrespective of their timing and annotation. We aimed to ascertain whether the use of this tool can rapidly identify areas within VT isthmuses from substrate maps. METHODS: Thirty patients with structural cardiomyopathy in whom a complete right ventricular-paced substrate map and a full reconstruction of the diastolic isthmus during VT could be obtained were enrolled. The VT isthmus border was projected on each substrate map to verify whether the areas illuminated by Lumipoint fell within those borders. The behavior of the electrograms detected at the illuminated areas of the substrate maps was studied during a right ventricular drive train and extra stimulus protocol: if the near field potentials showed a delayed conduction after a single extra stimulus, defined as a minimum of 10 ms increase of the time interval between the far field and the near field activation measured during the drive train, the electrogram was said to have a "decremental" behavior. RESULTS: The logistic analysis showed that areas with fractionated electrograms illuminated by the Lumipoint software and showing the greatest decremental behavior fell within the VT isthmus borders (OR = 1.66, CI: 1.41-1.75, p<0.001; OR=1.57 CI: 1.32-1.72, p<0.001, respectively) with a sensitivity, specificity, and positive predictive value of 87%, 96%, and 97%, respectively. CONCLUSIONS: Fractionated electrograms illuminated by the automated Lumipoint software on right ventricular-paced substrate maps showing the greatest decremental behavior fall within the VT isthmus borders with a probability of 0.97, irrespective of their timing, annotation, or voltage, without any need for subjective assessment of their involvement in slow conduction areas.

Potential feasibility of a novel over-the-wire microelectrode catheter for recording coronary sinus electrograms in patients with cardiac resynchronization therapy devices.

The placement of an electrode catheter into the coronary sinus (CS) is important for differentiating multiple atrial tachycardias (ATs). Based on its high selective performance in placement into small veins, inserting a novel over-the-wire 2.7Fr microcatheter (EPstar Fix AIV; Japan Lifeline) into the CS may be feasible even in patients implanted with a cardiac resynchronization therapy device.

Arrhythmias induced by dextrose-insulin challenge test in nondiagnostic Brugada ECG patterns.

INTRODUCTION: Dynamic ECG changes in Brugada syndrome (BrS) are influenced by several factors, may not be apparent, and can be unmasked by a drug test. METHODS AND RESULTS: Four of six patients with nondiagnostic Brugada ECG index patterns underwent a dextrose-insulin challenge test that resulted in J-ST segment elevation and triggered arrhythmias. CONCLUSION: Insulin action may be due in part to an outward shift in the K+ current at the end of action potential phase 1 and the dispersion of repolarization, leading to local re-entry with arrhythmogenicity. This effect is likely a phenomenon-specific to BrS.

The emergence and destiny of automated methods to differentiate wide QRS complex tachycardias.

Accurate differentiation of wide complex tachycardias (WCTs) into ventricular tachycardia (VT) or supraventricular wide complex tachycardia (SWCT) using non-invasive methods such as 12­lead electrocardiogram (ECG) interpretation is crucial in clinical practice. Recent studies have demonstrated the potential for automated approaches utilizing computerized ECG interpretation software to achieve accurate WCT differentiation. In this review, we provide a comprehensive analysis of contemporary automated methods for VT and SWCT differentiation. Our objectives include: (i) presenting a general overview of the emergence of automated WCT differentiation methods, (ii) examining the role of machine learning techniques in automated WCT differentiation, (iii) reviewing the electrophysiology concepts leveraged existing automated algorithms, (iv) discussing recently developed automated WCT differentiation solutions, and (v) considering future directions that will enable the successful integration of automated methods into computerized ECG interpretation platforms.

Congenital Ventricular Diverticulum.

Herein, we describe a 54-year-old patient with a congenital ventricular diverticulum (CVD), referred to our emergency department for presyncope episodes and multiple re-entrant ventricular tachycardias (VT). Significantly, echocardiographic findings were not clear, and the diagnosis was made by cardiac magnetic resonance imaging (CMRI), which showed the presence of an apical accessory cavity connected to the ventricle and contracting synchronously. CMRI allowed the differential diagnosis with other outpouching cardiac defects. The patient underwent a subcutaneous implantable cardioverter defibrillator (S-ICD) implant and was referred for heart transplantation (HT). The diagnosis, treatment, and main findings of the CVD are discussed in this case report.

Comparison of two artificial intelligence-augmented ECG approaches: Machine learning and deep learning.

BACKGROUND: Artificial intelligence-augmented ECG (AI-ECG) refers to the application of novel AI solutions for complex ECG interpretation tasks. A broad variety of AI-ECG approaches exist, each having differing advantages and limitations relating to their creation and application. PURPOSE: To provide illustrative comparison of two general AI-ECG modeling approaches: machine learning (ML) and deep learning (DL). METHOD COMPARISON: Two AI-ECG algorithms were developed to carry out two separate tasks using ML and DL, respectively. ML modeling techniques were used to create algorithms designed for automatic wide QRS complex tachycardia differentiation into ventricular tachycardia and supraventricular tachycardia. A DL algorithm was formulated for the task of comprehensive 12­lead ECG interpretation. First, we describe the ML models for WCT differentiation, which rely upon expert domain knowledge to identify and formulate ECG features (e.g., percent monophasic time-voltage area [PMonoTVA]) that enable strong diagnostic performance. Second, we describe the DL method for comprehensive 12­lead ECG interpretation, which relies upon the independent recognition and analysis of a virtually incalculable number of ECG features from a vast collection of standard 12­lead ECGs. CONCLUSION: We have showcased two different AI-ECG methods, namely ML and DL respectively. In doing so, we highlighted the strengths and weaknesses of each approach. It is essential for investigators to understand these differences when attempting to create and apply novel AI-ECG solutions.

Ventricular tachycardia ablation in children.

INTRODUCTION: The ablation of ventricular tachycardia, including premature ventricular contractions, is an approved, albeit infrequent procedure in pediatric patients. Data are scarce regarding the outcomes of this procedure. The purpose of this study was to share a high-volume center experience and patient outcomes for catheter ablation of ventricular ectopy and ventricular tachycardia in pediatric population. METHODS: Data were retrieved from the institutional data bank. Outcomes over time were evaluated, and procedural details were compared. RESULTS: A total of 116 procedures were performed on 102 pediatric patients between July 2009 and May 2021 at the Rajaie Cardiovascular Medical and Research Center in Tehran, Iran. Ablation was not performed in 4 procedures (3.4%) due to high-risk substrates. Of the remaining 112 ablations performed, 99 (88.4%) were successful. However, one patient died due to a coronary complication. There were no significant differences observed in early ablation results based on patients' age, sex, cardiac anatomy, or ablation substrates (P > 0.05). Follow-up records were available for 80 procedures, and 13 (16.3%) of those experienced recurrence. During long-term follow-up, none of the variables mentioned above were statistically different between patients with or without arrhythmia recurrence. CONCLUSION: The overall success rate of pediatric ventricular arrhythmia ablation is favorable. We found no significant predictor for the procedural success rate concerning acute and late outcomes. Larger multicenter studies are needed to elucidate the predictors and outcomes of the procedure.

Utility and limitations of coherent mapping algorithm utilizing vectors and global propagation patterns in atrial tachycardia.

Background: A novel mapping algorithm utilizing vectors and global patterns of propagation (Coherent™, Biosense Webster) has been developed to help identify the mechanism of atrial tachycardia (AT). We aimed to determine the diagnostic accuracy of coherent mapping compared with that of ripple mapping. Methods and results: This study included 41 consecutive patients with 84 ATs (47 reentrant and 37 focal ATs). Two independent electrophysiologists confirmed the diagnoses using coherent mapping before the ripple map-guided ablation. AT termination was achieved in 75 of 84 ATs (89%) at first ablation lesion set. Four of the remaining nine ATs, which were terminated before an index radiofrequency (RF) application, were non-inducible after RF delivery at the first lesion set, whereas the other five ATs were terminated at the second lesion set. Diagnostic agreement between coherent and ripple maps was achieved in 51 of 84 ATs (61%): 28 of the 47 macroreentrant ATs (60%) and 23 of the 37 focal ATs (62%; P = 0.826). In typical macroreentrant ATs, including left atrial roof, perimitral, and cavotricuspid isthmus-dependent ATs, coherent maps achieved diagnostic agreement in 23 of 29 ATs (79%), which was higher than that in other ATs (51%, P = 0.018): 13 of 26 macroreentrant ATs (50%) and 15 of 29 focal ATs (52%, P = 1.000). Conclusion: Ripple map-guided AT ablation achieved a high termination rate in the first lesion set. Coherent mapping yielded a favorable diagnostic accuracy for typical macroreentrant ATs, though its value for diagnosing other ATs was limited.

[How to: clinical use of antiarrhythmic drugs]. / How to: Antiarrhythmika in der klinischen Anwendung.

Antiarrhythmic drugs are important for the noninvasive rhythm control therapy of heart rhythm disorders. Antiarrhythmic drugs, which can be categorized into subgroups based on their different effects on ion channels, are clinically used for various types of arrhythmias. Knowledge about these specific electrophysiological effects contributes to a better understanding in order to select the correct drug for each specific arrhythmia. This review summarizes mechanisms, indications, contraindications, and side effects of the different antiarrhythmic drugs and, thus, supports their adequate use in daily clinical routine.

In-hospital mortality and major complications related to radiofrequency catheter ablations of over 10 000 supraventricular arrhythmias from 2005 to 2020: individualized case analysis of multicentric administrative data.

AIMS: The incidence of in-hospital post-interventional complications and mortality after ablation of supraventricular tachycardia (SVT) vary among the type of procedure and most likely the experience of the centre. As ablation therapy of SVT is progressively being established as first-line therapy, further assessment of post-procedural complication rates is crucial for health care quality. METHODS AND RESULTS: We aimed at determining the incidence of in-hospital mortality and bleeding complications from SVT ablations in German high-volume electrophysiological centres between 2005 and 2020. All cases were registered by the German Diagnosis Related Groups-and the German Operation and Procedure Classification (OPS) system. A uniform search for SVT ablations from 2005 to 2020 with the same OPS codes defining the type of ablation/arrhythmia as well as the presence of a vascular complication, cardiac tamponade, and/or in-hospital death was performed. An overall of 47 610 ablations with 10 037 SVT ablations were registered from 2005 to 2020 among three high-volume centres. An overall complication rate of 0.5% (n = 38) was found [median age, 64; ±15 years; female n = 26 (68%)]. All-cause mortality was 0.02% (n = 2) and both patients had major prior co-morbidities precipitating a lethal outcome irrespective of the ablation procedure. Vascular complications occurred in 10 patients (0.1%), and cardiac tamponade was detected in 26 cases (0.3%). CONCLUSION: The present case-based analysis shows an overall low incidence of in-hospital complications after SVT ablation highlighting the overall very good safety profile of SVT ablations in high-volume centres. Further prospective analysis is still warranted to guarantee continuous quality control and optimal patient care.

The short-long-short-short sequence and polymorphic ventricular tachycardias storm.

We described a case of a patient who developed repetitive episodes of polymorphic ventricular tachycardias with a stereotypical pattern of initiation. A short-long-short-short (S-L-S-S) cardiac cycle sequence preceded all episodes and was considered to be the underlying initiative mechanism for these fatal arrhythmic events. In the patient, the paroxysmal atrial fibrillation was responsible for S-L-S-S sequence. It had been suggested that the electrophysiological mechanism by which the S-L-S-S cardiac sequence induces ventricular tachyarrhythmias was reentrant excitation, not early afterdepolarization and triggered activity. Early attempts to restore and maintain sinus rhythm by administration of antiarrhythmic drug with amiodarone, the patient experienced no atrial fibrillation and ventricular tachycardia recurrence.

Recurrent nocturnal ST-T deviation and nonsustained ventricular tachycardias recorded with a smartwatch: A case report.

A 44-year-old male patient presented to our clinic with nocturnal palpitations. The smartwatch electrocardiogram (ECG) demonstrated ST-segment deviation and non-sustained ventricular tachycardias. The patient suffered from coronary one-vessel disease. The coronary angiography revealed de novo proximal left anterior descending stenosis and in-stent restenosis, which necessitated coronary stenting. However, the recurrent palpitations reappeared 2 weeks later. The smartwatch ECGs again demonstrated ST-segment deviation and wide QRS tachycardia, reassessments with coronary angiography and magnetic resonance imaging revealed no relevant ischemia. The patient was diagnosed with vasospastic angina. His symptoms disappeared after percutaneous administration of nitrates.This case highlights the utility of smartwatch ECGs to support clinical diagnosis, decisions, and follow-up in the case of ischemic attacks. Learning objective: This case report highlights the importance of an adequate anamnesis and the meaningful use of wearable devices. The smartwatch enables the patient to record electrocardiograms (ECGs) easily and immediately during symptoms. That is one of the major advantages of this new technology, because we can even detect events that are too subtle to be detected in the normal 24-h Holter ECG. This case highlights the utility of smartwatch ECGs to support clinical diagnosis and decisions by establishing a valid symptom-ECG correlation.

Wide complex tachycardia discrimination tool improves physicians' diagnostic accuracy.

BACKGROUND: Timely and accurate discrimination of wide complex tachycardias (WCTs) into ventricular tachycardia (VT) or supraventricular WCT (SWCT) is critically important. Previously we developed and validated an automated VT Prediction Model that provides a VT probability estimate using the paired WCT and baseline 12-lead ECGs. Whether this model improves physicians' diagnostic accuracy has not been evaluated. OBJECTIVE: We sought to determine whether the VT Prediction Model improves physicians' WCT differentiation accuracy. METHODS: Over four consecutive days, nine physicians independently interpreted fifty WCT ECGs (25 VTs and 25 SWCTs confirmed by electrophysiological study) as either VT or SWCT. Day 1 used the WCT ECG only, Day 2 used the WCT and baseline ECG, Day 3 used the WCT ECG and the VT Prediction Model's estimation of VT probability, and Day 4 used the WCT ECG, baseline ECG, and the VT Prediction Model's estimation of VT probability. RESULTS: Inclusion of the VT Prediction Model data increased diagnostic accuracy versus the WCT ECG alone (Day 3: 84.2% vs. Day 1: 68.7%, p 0.009) and WCT and baseline ECGs together (Day 3: 84.2% vs. Day 2: 76.4%, p 0.003). There was no further improvement of accuracy with addition of the baseline ECG comparison to the VT Prediction Model (Day 3: 84.2% vs. Day 4: 84.0%, p 0.928). Overall sensitivity (Day 3: 78.2% vs. Day 1: 67.6%, p 0.005) and specificity (Day 3: 90.2% vs. Day 1: 69.8%, p 0.016) for VT were superior after the addition of the VT Prediction Model. CONCLUSION: The VT Prediction Model improves physician ECG diagnostic accuracy for discriminating WCTs.

Randomized comparison of atrioventricular node re-entry tachycardia and atrial flutter catheter ablation with and without fluoroscopic guidance: ZeroFluoro study.

AIMS: Interventional cardiology procedures may expose patients and staff to considerable radiation doses. We aimed to assess whether exposure to ionizing radiation during catheter ablation of supraventricular tachycardia (SVT) can be completely avoided. METHODS AND RESULTS: In this prospective randomized study, patients with SVT (atrioventricular re-entrant tachycardia n = 94, typical atrial flutter n = 29) were randomly assigned in a 1:1 ratio to catheter ablation with conventional fluoroscopic guidance (CF group) or with the EnSite Precision mapping system [zerofluoro (ZF) group]. Acute procedural parameters, increased stochastic risk of cancer incidence and 6-month follow-up data were assessed. Between May 2019 and August 2020, 123 patients were enrolled. Clinical parameters were comparable. Median procedural time was 60.0 and 58.0 min, median fluoroscopy time and estimated median effective dose were 240 s vs. 0 and 0.38 mSv vs. 0 and arrhythmia recurrence was 5% and 7.9% in the CF and ZF groups, respectively. The acute success rate was 98.4% in both groups. No procedure-related complications were reported. At an average age of 55.5 years and median radiation exposure of 0.38 mSv, the estimate of increased incidence was approximately 1 in 14 084. The estimated mortality rate was 1 per 17 857 exposed persons. CONCLUSIONS: The procedural safety and efficacy of the zero-fluoroscopic approach are similar to those of conventional fluoroscopy-based ablation for atrioventricular nodal re-entrant tachycardia and atrial flutter. Under the assumption of low radiation dose, the excessive lifetime risk of malignancy in the CF group due to electrophysiology procedure is reasonably small, whilst totally reduced in zero fluoroscopy procedures.

Optogenetic manipulation of cardiac electrical dynamics using sub-threshold illumination: dissecting the role of cardiac alternans in terminating rapid rhythms.

Cardiac action potential (AP) shape and propagation are regulated by several key dynamic factors such as ion channel recovery and intracellular Ca2+ cycling. Experimental methods for manipulating AP electrical dynamics commonly use ion channel inhibitors that lack spatial and temporal specificity. In this work, we propose an approach based on optogenetics to manipulate cardiac electrical activity employing a light-modulated depolarizing current with intensities that are too low to elicit APs (sub-threshold illumination), but are sufficient to fine-tune AP electrical dynamics. We investigated the effects of sub-threshold illumination in isolated cardiomyocytes and whole hearts by using transgenic mice constitutively expressing a light-gated ion channel (channelrhodopsin-2, ChR2). We find that ChR2-mediated depolarizing current prolongs APs and reduces conduction velocity (CV) in a space-selective and reversible manner. Sub-threshold manipulation also affects the dynamics of cardiac electrical activity, increasing the magnitude of cardiac alternans. We used an optical system that uses real-time feedback control to generate re-entrant circuits with user-defined cycle lengths to explore the role of cardiac alternans in spontaneous termination of ventricular tachycardias (VTs). We demonstrate that VT stability significantly decreases during sub-threshold illumination primarily due to an increase in the amplitude of electrical oscillations, which implies that cardiac alternans may be beneficial in the context of self-termination of VT.