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Zusammenfassung Hintergrund Telemonitoring dient der Überwachung von implantierbaren Kardioverter-Defibrillatoren (ICD). Trotz der wissenschaftlich nachgewiesenen Effektivität und Sicherheit der telemetrischen Versorgung zeigen Studien, dass das Angebot nicht bei allen Patienten mit der Nutzung und Akzeptanz des Telemonitorings einhergeht. Fragestellung Ziel dieses Forschungsvorhabens ist die Untersuchung der Einstellungen von ICD-Patienten zum Telemonitoring. Dabei ist von Interesse, welche Aspekte Einfluss auf die Haltung und Entscheidungsfindung nehmen. Methode Die Datenerhebung erfolgte anhand teilstrukturierter leitfadengestützter Einzelinterviews. Es wurden insgesamt 14 Patienten mit subkutanem ICD und sowohl primär als auch sekundärprophylaktischer Indikation rekrutiert. Die Datenauswertung erfolgte nach inhaltlich strukturierender qualitativer Vorgehensweise. Ergebnis Die Studie hat gezeigt, dass die Patienten mit Telemonitoring einen hohen Nutzen sehen, bei geringem Bedenken hinsichtlich der digitalen Technik. Bei Patienten ohne Telemonitoring verhält es sich umgekehrt. Die medizinischen Vorerfahrungen der Patienten haben einen wesentlichen Einfluss auf die Akzeptanz des Telemonitorings. Die technische Umsetzung und die praktische Handhabung des Telemonitorings wurden von Patienten aller Altersgruppen als einfach und unkompliziert angesehen. Diskussion Die Ergebnisse lassen darauf schließen, dass die primär- und sekundärprophylaktische Indikation für eine ICD-Implantation einen Einfluss auf die Einstellung zum Telemonitoring und somit auf dessen Akzeptanz haben. Die Ergebnisse geben Anlass zu weiterer qualitativer Forschung im Hinblick auf die Nutzerakzeptanz zum Telemonitoring anderer ICD-Systeme.

Background: Coexistence of atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF) is common, affecting morbidity and prognosis. This study evaluates outcome after cryoballoon ablation for AF in HFpEF compared with patients without heart failure. Methods: A total of 102 AF patients with left ventricular ejection fraction ≥50% undergoing cryoballoon ablation were prospectively enrolled. Baseline evaluation included echocardiography, stress echocardiography, 6-minute walk test, biomarkers, and quality of life assessment (Short-Form-36). Procedural parameters and clinical, functional and echocardiographic end points at follow-up ≥12 months after AF ablation were compared between patients with and without HFpEF. Results: Patients with HFpEF (n=24) were older (median, 74 years versus 65 years; P =0.001) more often female (83% versus 28%; P P P =0.008), reduced left atrial-appendage velocity (median, 36 cm/s versus 59 cm/s; P P P =0.003), repeat AF ablation (39% versus 14%; P =0.01) and AF-related rehospitalization (26% versus 7%; P =0.016). Heart failure symptoms and elevated cardiac biomarkers persisted, even in patients with HFpEF with successful rhythm control at follow-up. Echocardiographic follow-up showed progression of adverse left atrial remodeling and no relevant improvement in diastolic function in HFpEF. Quality of life improved in patients without HFpEF, whereas patients with HFpEF still exhibited a lower physical component summary score (median, 41.5 versus 53.4; P Conclusions: Patients with HFpEF constitute a distinct subgroup with elevated risk for AF recurrence after cryoballon ablation. Functional hallmarks of HFpEF persist, irrespective of rhythm status at follow-up. Future research is needed to optimize treatment strategies in patients with HFpEF. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04317911.

The enterovirus Coxsackievirus B3 (CVB3) is known to be a major source for the development of cardiac dysfunctions like viral myocarditis (VMC) and dilatative cardiomyopathy (DCM), but also results in bradycardia and fatal cardiac arrest. Besides clinical reports on bradycardia and sudden cardiac death, very little is known about the influence of CVB3 on the activity of human cardiac pacemaker cells. Here, we address this issue using the first human induced pluripotent stem cell (hiPSC)-derived pacemaker-like cells, in which the expression of a transgenic non-infectious variant of CVB3 can be controlled dose- and time-dependently. We found that CVB3 drastically changed hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) distribution and function in hiPSC-derived pacemaker-like tissue. In addition, using HCN4 cell expression systems, we found that HCN4 currents were decreased with altered voltage dependency of activation when CVB3 was expressed. Increased autophagosome formation and autophagosomal HCN4 insertion was observed in hiPSC-derived pacemaker-like cells under CVB3 expression as well. Individual effects of single, non-structural CVB3 proteins were analyzed and demonstrated that CVB3 proteins 2C and 3A had the most robust effect on HCN4 activity. Treatment of cells with the Rab7 inhibitor CID 106770 or the CVB3-3A inhibitor GW5074 led to the recovery of the cytoplasmatic HCN4 accumulation into a healthy appearing phenotype, indicating that malfunctioning Rab7-directed autophagosome transport is involved in the disturbed, cytoplasmatic HCN4 accumulation in CVB3-expressing human pacemaker-like cells. Summarizing, the enterovirus CVB3 inhibits human cardiac pacemaker function by reducing the pacemaker channel plasma membrane density, an effect that can be corrected by pharmacological intervention of endocytic vesicle trafficking.

Cardiac arrhythmias are a major cause of death and disability. A large number of experimental cell and animal models have been developed to study arrhythmogenic diseases. These models have provided important insights into the underlying arrhythmia mechanisms and translational options for their therapeutic management. This position paper from the ESC Working Group on Cardiac Cellular Electrophysiology provides an overview of (i) currently available in vitro, ex vivo, and in vivo electrophysiological research methodologies, (ii) the most commonly used experimental (cellular and animal) models for cardiac arrhythmias including relevant species differences, (iii) the use of human cardiac tissue, induced pluripotent stem cell (hiPSC)-derived and in silico models to study cardiac arrhythmias, and (iv) the availability, relevance, limitations, and opportunities of these cellular and animal models to recapitulate specific acquired and inherited arrhythmogenic diseases, including atrial fibrillation, heart failure, cardiomyopathy, myocarditis, sinus node, and conduction disorders and channelopathies. By promoting a better understanding of these models and their limitations, this position paper aims to improve the quality of basic research in cardiac electrophysiology, with the ultimate goal to facilitate the clinical translation and application of basic electrophysiological research findings on arrhythmia mechanisms and therapies.

Aims Right bundle branch block (RBBB) after heart transplantation (HTX) is a common finding, but its impact on post‐transplant survival remains uncertain. This study investigated the post‐transplant outcomes of patients with complete RBBB (cRBBB) ≤ 30 days after HTX. Methods This registry study analysed 639 patients receiving HTX at Heidelberg Heart Center between 1989 and 2019. Patients were stratified by diagnosis of cRBBB ≤ 30 days after HTX. Analysis included recipient and donor data, medication, echocardiographic features, graft rejections, atrial fibrillation, heart rates, permanent pacemaker implantation and mortality after HTX including causes of death. Results One hundred thirty‐nine patients showed cRBBB ≤ 30 days after HTX (21.8%), 20 patients with pre‐existing cRBBB in the donor heart (3.2%) and 119 patients with newly acquired cRBBB (18.6%). Patients with newly acquired cRBBB had a worse 1‐year post‐transplant survival (36.1%, P

Background Non-paroxysmal (NPAF) forms of atrial fibrillation (AF) have been reported to be associated with an increased risk for systemic embolism or death. Methods Comparison of procedural details and long-term outcomes in patients (pts) with paroxysmal AF (PAF) against controls with NPAF in the prospective, multicentre observational registry of patients undergoing LAAC (LAARGE). Results A total of 638 pts (PAF 274 pts, NPAF 364 pts) were enrolled. In both groups, a history of PVI was rare (4.0% vs 1.6%, p = 0.066). The total CHA2DS2-VASc score was lower in the PAF group (4.4 ± 1.5 vs 4.6 ± 1.5, p = 0.033), while HAS-BLED score (3.8 ± 1.1 vs 3.9 ± 1.1, p = 0.40) was comparable. The rate of successful implantation was equally high (97.4% vs 97.8%, p = 0.77). In the three-month echo follow-up, LA thrombi (2.1% vs 7.3%, p = 0.12) and peridevice leak > 5 mm (0.0% vs 7.1%, p = 0.53) were numerically higher in the NPAF group. Overall, in-hospital complications occurred in 15.0% of the PAF cohort and 10.7% of the NPAF cohort (p = 0.12). In the one-year follow-up, unadjusted mortality (8.4% vs 14.0%, p = 0.039) and combined outcome of death, stroke and systemic embolism (8.8% vs 15.1%, p = 0.022) were significantly higher in the NPAF cohort. After adjusting for CHA2DS2-VASc and previous bleeding, NPAF was associated with increased death/stroke/systemic embolism (HR 1.67, 95% CI 1.02–2.72, p = 0.041). Conclusion Atrial fibrillation type did not impair periprocedural safety or in-hospital MACE patients undergoing LAAC. However, after one year, NPAF was associated with higher mortality. Graphic abstract

Ann-Kathrin Rahm,1– 3 Dominik Gramlich,1– 3 Teresa Wieder,1,2 Mara Elena Müller,1– 3 Axel Schoeffel,1,2 Fadwa A El Tahry,1 Patrick Most,1,2 Tanja Heimberger,1,3 Steffi Sandke,1,3 Tanja Weis,1,3 Nina D Ullrich,4 Thomas Korff,4,5 Patrick Lugenbiel,1– 3 Hugo A Katus,1– 3 Dierk Thomas1– 3 1Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, 69120, Germany; 2HCR (Heidelberg Center for Heart Rhythm Disorders), University Hospital Heidelberg, Heidelberg, 69120, Germany; 3DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, 69120, Germany; 4Institute of Physiology and Pathophysiology, Department of Cardiovascular Physiology, Heidelberg University, Heidelberg, 69120, Germany; 5European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Mannheim, 68167, GermanyCorrespondence: Dierk ThomasDepartment of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, Heidelberg, 69120, GermanyTel +49 6221 568855Fax +49 6221 565514Email dierk.thomas@med.uni-heidelberg.deAim: Effective antiarrhythmic treatment of atrial fibrillation (AF) constitutes a major challenge, in particular, when concomitant heart failure (HF) is present. HF-associated atrial arrhythmogenesis is distinctly characterized by prolonged atrial refractoriness. Small-conductance, calcium-activated K+ (KCa, SK, KCNN) channels contribute to cardiac action potential repolarization and are implicated in AF susceptibility and therapy. The mechanistic impact of AF/HF-related triggers on atrial KCa channels is not known. We hypothesized that tachycardia, stretch, β-adrenergic stimulation, and hypoxia differentially determine KCa 2.1– 2.3 channel remodeling in atrial cells.Methods: KCNN1-3 transcript levels were assessed in AF/HF patients and in a pig model of atrial tachypacing-induced AF with reduced left ventricular function. HL-1 atrial myocytes were subjected to proarrhythmic triggers to investigate the effects on Kcnn mRNA and KCa channel protein.Results: Atrial KCNN1-3 expression was reduced in AF/HF patients. KCNN2 and KCNN3 suppression was recapitulated in the corresponding pig model. In contrast to human AF, KCNN1 remained unchanged in pigs. Channel- and stressor-specific remodeling was revealed in vitro. Lower expression levels of KCNN1/KCa 2.1 were linked to stretch and β-adrenergic stimulation. Furthermore, KCNN3/KCa 2.3 expression was suppressed upon tachypacing and hypoxia. Finally, KCNN2/KCa 2.2 abundance was specifically enhanced by hypoxia.Conclusion: Reduction of KCa 2.1– 2.3 channel expression might contribute to the action potential prolongation in AF complicated by HF. Subtype-specific KCa 2 channel remodeling induced by tachypacing, stretch, β-adrenergic stimulation, or hypoxia is expected to differentially determine atrial remodeling, depending on patient-specific activation of each triggering factor. Stressor-dependent KCa 2 regulation in atrial myocytes provides a starting point for mechanism-based antiarrhythmic therapy.Keywords: atrial fibrillation, calcium, KCa channel, KCNN, remodeling, SK channel

Aims The risk of developing atrial fibrillation (AF) and its complications continues to increase, despite good progress in preventing AF-related strokes. Methods and results This article summarizes the outcomes of the 7th Consensus Conference of the Atrial Fibrillation NETwork (AFNET) and the European Heart Rhythm Association (EHRA) held in Lisbon in March 2019. Sixty-five international AF specialists met to present new data and find consensus on pressing issues in AF prevention, management and future research to improve care for patients with AF and prevent AF-related complications. This article is the main outcome of an interactive, iterative discussion between breakout specialist groups and the meeting plenary. AF patients have dynamic risk profiles requiring repeated assessment and risk-based therapy stratification to optimize quality of care. Interrogation of deeply phenotyped datasets with outcomes will lead to a better understanding of the cardiac and systemic effects of AF, interacting with comorbidities and predisposing factors, enabling stratified therapy. New proposals include an algorithm for the acute management of patients with AF and heart failure, a call for a refined, data-driven assessment of stroke risk, suggestions for anticoagulation use in special populations, and a call for rhythm control therapy selection based on risk of AF recurrence. Conclusion The remaining morbidity and mortality in patients with AF needs better characterization. Likely drivers of the remaining AF-related problems are AF burden, potentially treatable by rhythm control therapy, and concomitant conditions, potentially treatable by treating these conditions. Identifying the drivers of AF-related complications holds promise for stratified therapy.

Background The early recognition of paroxysmal atrial fibrillation (pAF) is a major clinical challenge for preventing thromboembolic events. In this prospective and multicentric study we evaluated prediction scores for the presence of pAF, calculated from non-invasive medical history and echocardiographic parameters, in patients with unknown AF status. Methods The 12-parameter score with parameters age, LA diameter, aortic root diameter, LV,ESD, TDI Aʹ, heart frequency, sleep apnea, hyperlipidemia, type II diabetes, smoker, ß-blocker, catheter ablation, and the 4-parameter score with parameters age, LA diameter, aortic root diameter and TDI A’ were tested. Presence of pAF was verified by continuous electrocardiogram (ECG) monitoring for up to 21 days in 305 patients. Results The 12-parameter score correctly predicted pAF in all 34 patients, in which pAF was newly detected by ECG monitoring. The 12- and 4-parameter scores showed sensitivities of 100% and 82% (95%-CI 65%, 93%), specificities of 75% (95%-CI 70%, 80%) and 67% (95%-CI 61%, 73%), and areas under the receiver operating characteristic (ROC) curves of 0.84 (95%-CI 0.80, 0.88) and 0.81 (95%-CI 0.74, 0.87). Furthermore, properties of AF episodes and durations of ECG monitoring necessary to detect pAF were analysed. Conclusions The prediction scores adequately detected pAF using variables readily available during routine cardiac assessment and echocardiography. The model scores, denoted as ECHO-AF scores, represent simple, highly sensitive and non-invasive tools for detecting pAF that can be easily implemented in the clinical practice and might serve as screening test to initiate further diagnostic investigations for validating the presence of pAF. Graphic abstract Prospective validation of a novel prediction model for paroxysmal atrial fibrillation based on echocardiography and medical history parameters by long-term Holter ECG

Background Pulmonary vein isolation is an established strategy for catheter ablation of atrial fibrillation (AF). However, in a significant number of patients, a repeat procedure is mandatory due to arrhythmia recurrence. In this study, we report safety data and procedural details of patients undergoing index ablation versus repeat ablation in a registry-based real-life setting. Methods Patients from the German Ablation Registry, a prospective, multicentre registry of patients undergoing ablation between January 2007 and January 2010 were included. Results A total of 4155 patients were enrolled in the study. Group I (index ablation) consisted of 3377/4155 (82.1%) and group II (repeat ablation) of 738/4155 (17.9%). Patients in group I had a significantly higher ratio of paroxysmal AF (69.3% vs 61.9%, p p p p 2 vs 3325 cGy × cm2, p = 0.001), and shorter study duration (181.2 min. vs 163.6 min., p p = 0.39), MACE (0.4% vs 0.3%, p = 0.58), MACCE (0.8% vs 0.6%, p = 0.47), composite safety endpoint (1.5% vs 1.4%, p = 0.76), and arrhythmia recurrence (43.8% vs 41.9%, p = 0.37) during 1-year follow-up. Both groups reported to have improved or no symptoms (80.4% vs 77.8%, p = 0.13). Conclusion Repeat catheter ablation is safe and provides a symptomatic relief comparable to index ablation. Repeat procedures are significantly shorter and use less fluoroscopy.

BACKGROUND Mesenchymal stem cells (MSC) modified by gene transfer to express cardiac pacemaker channels such as HCN2 or HCN4 were shown to elicit pacemaker function after intracardiac transplantation in experimental animal models. Human MSC derived from adipose tissue (haMSC) differentiate into cells with pacemaker properties in vitro, but little is known about their behavior after intracardiac transplantation. AIM To investigate whether haMSC elicit biological pacemaker function in vivo after transplantation into pig hearts. METHODS haMSC under native conditions (nhaMSC) or after preconditioning by medium differentiation (dhaMSC) (n = 6 pigs each, 5 × 106 cells per animal) were injected into the porcine left ventricular free wall. Animals receiving PBS injection served as controls (n = 6). Four weeks later, total atrioventricular (AV)-block was induced by radiofrequency catheter ablation, and electronic pacemaker devices were implanted for backup stimulation and heart rate monitoring. Ventricular rate and rhythm of pigs were evaluated during a follow-up of 15 d post ablation by 12-lead-ECG with heart rate assessment, 24-h continuous rate monitoring recorded by electronic pacemaker, assessment of escape recovery time, and pharmacological challenge to address catecholaminergic rate response. Finally, hearts were analyzed by histological and immunohistochemical investigations. RESULTS In vivo transplantation of dhaMSC into the left ventricular free wall of pigs elicited spontaneous and regular rhythms that were pace-mapped to ventricular injection sites (mean heart rate 72.2 ± 3.6 bpm; n = 6) after experimental total AV block. Ventricular rhythms were stably detected over a 15-d period and were sensitive to catecholaminergic stimulation (mean maximum heart rate 131.0 ± 6.2 bpm; n = 6; P < 0.001). Pigs, which received nhaMSC or PBS presented significantly lower ventricular rates (mean heart rates 47.2 ± 2.5 bpm and 37.4 ± 3.2 bpm, respectively; n = 6 each; P < 0.001) and exhibited little sensitivity towards catecholaminergic stimulation (mean maximum heart rates 76.4 ± 3.1 bpm and 60.5 ± 3.1 bpm, respectively; n = 6 each; P < 0.05). Histological and immunohistochemical evaluation of hearts treated with dhaMSC revealed local clusters of transplanted cells at the injection sites that lacked macrophage or lymphocyte infiltrations or tumor formation. Intense fluorescence signals at these sites indicated membrane expression of HCN4 and other pacemaker-specific proteins involved in cardiac automaticity and impulse propagation. CONCLUSION dhaMSC transplanted into pig left ventricles sustainably induced rate-responsive ventricular pacemaker activity after in vivo engraftment for four weeks. The data suggest that preconditioned MSC may further differentiate along a pacemaker-related lineage after myocardial integration and may establish superior pacemaker properties in vivo.

Aims Non-vitamin K antagonist oral anticoagulants (NOACs) are widely used in the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation (AF). The efficacy of NOACs has been attributed in part to pleiotropic effects that are mediated through effects on thrombin, factor Xa, and their respective receptors. Direct pharmacological effects of NOACs and cardiac ion channels have not been addressed to date. We hypothesized that the favourable clinical outcome of NOAC use may be associated with previously unrecognized effects on atrial repolarizing potassium channels. Methods and results This study was designed to elucidate acute pharmacological effects of NOACs on cloned ion channels Kv11.1, Kv1.5, Kv4.3, Kir2.1, Kir2.2, and K2P2.1 contributing to IKr, IKur, Ito, IK1, and IK2P K+ currents. Human genes, KCNH2, KCNA5, KCND3, KCNJ2, KCNJ12, and KCNK2, were heterologously expressed in Xenopus laevis oocytes, and currents were recorded using voltage-clamp electrophysiology. Apixaban, dabigatran, edoxaban, and rivaroxaban applied at 1 µM did not significantly affect peak current amplitudes of Kv11.1, Kv1.5, Kv4.3, Kir2.1, Kir2.2, or K2P2.1 K+ channels. Furthermore, biophysical characterization did not reveal significant effects of NOACs on current–voltage relationships of study channels. Conclusion Apixaban, dabigatran, edoxaban, and rivaroxaban did not exhibit direct functional interactions with human atrial K+ channels underlying IKr, IKur, Ito, IK1, and IK2P currents that could account for beneficial clinical outcome associated with the drugs. Indirect or chronic effects and potential underlying signalling mechanisms remain to be investigated.

Background Modulation of the cardiac autonomic nervous system by pulmonary vein isolation (PVI) influences the sinoatrial nodal rate. Little is known about the causes, maintenance and prognostic value of this phenomenon. We set out to explore the effects of cryoballoon PVI (cryo-PVI) on sinus rate and its significance for clinical outcome. Methods and results We evaluated 110 patients with paroxysmal atrial fibrillation (AF), who underwent PVI using a second-generation 28 mm cryoballoon by pre-, peri- and postprocedural heart rate acquisition and analysis of clinical outcome. Ninety-one patients could be included in postinterventional follow-up, indicating that cryo-PVI resulted in a significant rise of sinus rate by 16.5% (+ 9.8 ± 0.9 beats/min, p Conclusions Cryo-PVI causes a significant rise of sinus rate that is more pronounced in subjects with previous sinus bradycardia. Patient follow-up indicates persistence of this effect and suggests an increased risk of AF recurrence in patients with postprocedural bradycardia. Graphic abstract

Graphic abstract

Europace : the European journal of pacing, arrhythmias and cardiac electrophysiology euac062 (2022). doi:10.1093/europace/euac062, Published by Oxford Univ. Press, Oxford

Background: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with impaired health-related quality of life (HRQoL), high symptom severity, and poor cardiovascular outcomes. Both clinical and psychological factors may contribute to symptom severity and HRQoL in AF. Methods: Using data from the observational Atrial Fibrillation Rhine-Neckar Region (ARENA) trial, we identified medical and psychosocial factors associated with AF-related symptom severity using European Heart Rhythm Association symptom classification and HRQoL using 5-level EuroQoL- 5D. Results: In 1218 AF patients (mean age 71.1 ± 10.5 years, 34.5% female), female sex (OR 3.7, p < 0.001), preexisting coronary artery disease (CAD) (OR 1.7, p = 0.020), a history of cardioversion (OR 1.4, p = 0.041), cardiac anxiety (OR 1.2; p < 0.001), stress from noise (OR 1.4, p = 0.005), work-related stress (OR 1.3, p = 0.026), and sleep disturbance (OR 1.2, p = 0.016) were associated with higher AF-related symptom severity. CAD (β = −0.23, p = 0.001), diabetes mellitus (β = −0.25, p < 0.001), generalized anxiety (β = −0.30, p < 0.001), cardiac anxiety (β = −0.16, p < 0.001), financial stress (β = −0.11, p < 0.001), and sleep disturbance (β = 0.11, p < 0.001) were associated with impaired HRQoL. Conclusions: Psychological characteristics, preexisting CAD, and diabetes may play an important role in the identification of individuals at highest risk for impaired HRQoL and high symptom severity in patients with AF.

In atrioventricular nodal reentrant tachycardia (AVNRT), catheter ablation is considered as first-line therapy. Despite high success rates, some patients present with arrhythmia recurrence or develop other types of arrhythmias over time. To assess the incidence of symptomatic arrhythmias after initially successful AVNRT ablation and to analyze their clinical implications in a real-world cohort. We included 2,795 patients from the German Ablation Registry undergoing first ablation of AVNRT between 01/2007 and 01/2010. In patients alive at long-term follow-up, patient-specific characteristics and long-term follow-up data were compared between patients with (group A) and without (group B) any symptomatic arrhythmia during follow-up. Symptomatic arrhythmias occurred in 17.2% of patients during a mean follow-up of 678 days after AVNRT ablation. The patients with symptomatic arrhythmias were more often female and suffered from structural heart disease. Arrhythmia occurrence was clinically relevant regarding symptoms and patient satisfaction. Serious adverse events including stroke, transient ischemic attack, pacemaker implantation, as well as continued use of antiarrhythmic medication occurred more often in group A. A second ablation procedure was performed in 26% of symptomatic patients to optimize the symptomatic outcome, whereas cardiovascular events or patient satisfaction were not further improved. During long-term follow-up, one out of six patients experienced symptomatic arrhythmias after AVNRT ablation, associated with an increase of serious adverse events. A subset of patients required medical or interventional antiarrhythmic therapy, possibly attributable to the co-existence of other arrhythmias. Screening for arrhythmic and cardiac co-morbidity before and after ablation may support comprehensive therapy planning and outcome.

Atrial fibrillation (AF) is the most frequent sustained arrhythmia and can lead to structural cardiac changes, known as tachycardia-induced cardiomyopathy (TIC). HCN4 is implicated in spontaneous excitation of the sinoatrial node, while channel dysfunction has been associated with sinus bradycardia, AF and structural heart disease. We here asked whether HCN4 mutations may contribute to the development of TIC, as well. Mutation scanning of HCN4 in 60 independent patients with AF and suspected TIC followed by panel sequencing in carriers of HCN4 variants identified the HCN4 variant P883R [minor allele frequency (MAF): 0,88%], together with the KCNE1 variant S38G (MAF: 65%) in three unrelated patients. Family histories revealed additional cases of AF, sudden cardiac death and cardiomyopathy. Patch-clamp recordings of HCN4-P883R channels expressed in HEK293 cells showed remarkable alterations of channel properties shifting the half-maximal activation voltage to more depolarized potentials, while channel deactivation was faster compared to wild-type (WT). Co-transfection of WT and mutant subunits, resembling the heterozygous cellular situation of our patients, revealed significantly higher current densities compared to WT. In conclusion HCN4-P883R may increase ectopic trigger and maintenance of AF by shifting the activation voltage of If to more positive potentials and producing higher current density. Together with the common KCNE1 variant S38G, previously proposed as a genetic modifier of AF, HCN4-P883R may provide a substrate for the development of AF and TIC.

Cardiac two-pore-domain potassium (K2P) channels have been proposed as novel antiarrhythmic targets. K2P13.1 (THIK-1) channels are expressed in the human heart, and atrial K2P13.1 levels are reduced in patients with atrial fibrillation (AF) or heart failure. The first objective of this study was to investigate acute effects of antiarrhythmic drugs on human K2P13.1 currents. Second, we assessed atrial K2P13.1 remodeling in AF pigs to validate the porcine model for future translational evaluation of K2P13.1-based antiarrhythmic concepts. K2P13.1 protein expression was studied in domestic pigs during AF induced by atrial burst pacing. AF was associated with 66% reduction of K2P13.1 levels in the right atrium at 21-day follow-up. Voltage clamp electrophysiology was employed to elucidate human K2P13.1 channel pharmacology in Xenopus oocytes. Propafenone (−26%; 100 μM), mexiletine (−75%; 1.5 mM), propranolol (−38%; 200 μM), and lidocaine (−59%; 100 μM) significantly inhibited K2P13.1 currents. By contrast, K2P13.1 channels were not markedly affected by quinidine, carvedilol, metoprolol, amiodarone and verapamil. Concentration-dependent K2P13.1 blockade by mexiletine occurred rapidly with membrane depolarization and was frequency-independent. Mexiletine reduced K2P13.1 open rectification properties and shifted current-voltage relationships towards more negative potentials. In conclusion, atrial expression and AF-associated downregulation of K2P13.1 channels in a porcine model resemble human findings and support a general role for K2P13.1 in AF pathophysiology. K2P13.1 current sensitivity to antiarrhythmic drugs provides a starting point for further development of an emerging antiarrhythmic paradigm.

HCN channels underlie the depolarizing funny current (If) that contributes importantly to cardiac pacemaking. If is upregulated in failing and infarcted hearts, but its implication in disease mechanisms remained unresolved. We generated transgenic mice (HCN4tg/wt) to assess functional consequences of HCN4 overexpression-mediated If increase in cardiomyocytes to levels observed in human heart failure. HCN4tg/wt animals exhibit a dilated cardiomyopathy phenotype with increased cellular arrhythmogenicity but unchanged heart rate and conduction parameters. If augmentation induces a diastolic Na+ influx shifting the Na+/Ca2+ exchanger equilibrium towards ‘reverse mode’ leading to increased [Ca2+]i. Changed Ca2+ homeostasis results in significantly higher systolic [Ca2+]i transients and stimulates apoptosis. Pharmacological inhibition of If prevents the rise of [Ca2+]i and protects from ventricular remodeling. Here we report that augmented myocardial If alters intracellular Ca2+ homeostasis leading to structural cardiac changes and increased arrhythmogenicity. Inhibition of myocardial If per se may constitute a therapeutic mechanism to prevent cardiomyopathy., The depolarizing funny current contributing to cardiac pacemaking is upregulated in the myocardium of failing and infarcted hearts, but whether the current is implied in disease mechanisms is unclear. Here the authors generate HCN4 transgenic mice and show that upregulation of funny current to the levels observed in human heart failure alters calcium homeostasis leading to cardiac remodelling and arrhythmia.

Pathogenic long QT mutations often comprise high phenotypic variability and particularly variants in ANK2 (long QT syndrome 4) frequently lack QT prolongation. We sought to elucidate the genetic and functional background underlying the clinical diversity in a 3-generation family with different cardiac arrhythmias. Next-generation sequencing-based screening of patients with QT prolongation identified the index patient of the family carrying an ANK2-E1813K variant and a previously uncharacterized KCNH2-H562R mutation in a double heterozygous conformation. The patient presented with a severe clinical phenotype including a markedly prolonged QTc interval (544 ms), recurrent syncope due to Torsade de Pointes tachycardias, survived cardiopulmonary resuscitation, progressive cardiac conduction defect, and atrial fibrillation. Evaluation of other family members identified a sister and a niece solely carrying the ANK2-E1813K variant, who showed age-related conduction disease. An asymptomatic second sister solely carried the KCNH2-H562R mutation. Voltage-clamp recordings in Xenopus oocytes revealed that KCNH2-H562R subunits were non-functional but did not exert dominant-negative effects on wild-type subunits. Expression of KCNH2-H562R in HEK293 cells showed a trafficking deficiency. Co-expression of the C-terminal regulatory domain of ANK2 in Xenopus oocytes revealed that ANK2-E1813K diminished currents mediated by the combination of wild-type and H562R KCNH2 subunits. Our data suggest that ANK2 functionally interacts with KCNH2 leading to a stronger current suppression and marked aggravation of long QT syndrome in the patient carrying variants in both proteins.

Ventrikulare Extrasystolen (VES) sind ein haufiger, oft zufalliger und meist harmloser Befund. Bei sehr haufigem Auftreten mit Beschwerden oder Verschlechterung der linksventrikularen Funktion besteht eine Behandlungsindikation. Idiopathische ventrikulare Tachykardien (VT) finden sich uberwiegend bei Patienten mit strukturell gesundem Herz. Diese VES/VT haben meist einen fokalen Ursprung. Der wahrscheinlichste Mechanismus sind verzogerte Nachdepolarisationen. Die Lokalisation des Ursprungortes basiert auf der Erstellung eines Aktivierungsmaps mit oder ohne Kombination eines Pacemappings. Die charakteristischen anatomischen Ursprungsstellen idiopathischer VES/VT sind die Ausflussbahnen des rechten und linken Ventrikels einschlieslich der Aortenwurzel. Weitere typische Lokalisationen sind der Trikuspidal- oder Mitralklappenring, Papillarmuskeln und Purkinje-Fasern. Die Katheterablation ist bei symptomatischen, monomorphen VES/VT eine Alternative zu antiarrhythmischer Medikation. Die Erfolgsrate ist hoch, wobei das Mapping und die Ablation oftmals eine Herausforderung darstellen konnen. Dieser Artikel ist der funfte Teil einer Serie zur gezielten Fort- und Weiterbildung im Bereich „Spezielle Rhythmologie – Invasive Elektrophysiologie“. Er beschreibt pathophysiologische Grundlagen, Formen sowie typische Befunde, die bei einer elektrophysiologischen Untersuchung erhoben werden konnen.

The wearable cardioverter defibrillator (WCD) can protect patients against sudden cardiac death during temporarily increased or unknown risk of ventricular arrhythmias or in the situation of implantable cardioverter-defibrillator (ICD) explantation due to infection. In unusual cases, misinterpretation of the ECG by the tachycardia detection and discrimination algorithm of the WCD can occur which can lead to inappropriate acoustic alerts or inappropriate WCD therapy. We explain the mechanisms of inappropriate WCD therapy in two cases from daily clinical practice together with potential strategies to avoid such events in this special group of patients.Die tragbare Defibrillatorweste („wearable cardioverter defibrillator“, WCD) kann bei passager erhöhtem oder unklarem Risiko für ventrikuläre Arrhythmien oder bei Notwendigkeit einer infektionsbedingten ICD-Explantation einen temporären Schutz vor plötzlichem Herztod bieten. In besonderen Fällen kann es zu einer EKG-Fehlinterpretation durch den WCD-Detektionsalgorithmus kommen, welche zu inadäquaten akustischen Alarmtonabgaben oder inadäquaten WCD-Therapien führen kann. Dargestellt werden der Hintergrund von inadäquaten WCD-Schockabgaben anhand zweier Fälle aus dem klinischen Alltag sowie mögliche Strategien zur Vermeidung derartiger Ereignisse in diesem besonderen Kollektiv.

Atrial fibrillation (AF) with concomitant heart failure (HF) poses a significant therapeutic challenge. Mechanism‐based approaches may optimize AF therapy. Small‐conductance, calcium‐activated K+ (KCa, KCNN) channels contribute to cardiac action potential repolarization. KCNN1 exhibits predominant atrial expression and is downregulated in chronic AF patients with preserved cardiac function. Epigenetic regulation is suggested by AF suppression following histone deacetylase (HDAC) inhibition. We hypothesized that HDAC‐dependent KCNN1 remodeling contributes to arrhythmogenesis in AF complicated by HF. The aim of this study was to assess KCNN1 and HDAC1–7 and 9 transcript levels in AF/HF patients and in a pig model of atrial tachypacing‐induced AF with reduced left ventricular function. In HL‐1 atrial myocytes, tachypacing and anti‐Hdac siRNAs were employed to investigate effects on Kcnn1 mRNA levels. KCNN1 expression displayed side‐specific remodeling in AF/HF patients with upregulation in left and suppression in right atrium. In pigs, KCNN1 remodeling showed intermediate phenotypes. HDAC levels were differentially altered in humans and pigs, reflecting highly variable epigenetic regulation. Tachypacing recapitulated downregulation of Hdacs 1, 3, 4, 6, and 7 with a tendency towards reduced Kcnn1 levels in vitro, indicating that atrial high rates induce remodeling. Finally, Kcnn1 expression was decreased by knockdown of Hdacs 2, 3, 6, and 7 and enhanced by genetic Hdac9 inactivation, while anti‐Hdac 1, 4, and 5 siRNAs did not affect Kcnn1 transcript levels. In conclusion, KCNN1 and HDAC expression is differentially remodeled in AF complicated by HF. Direct regulation of KCNN1 by HDACs in atrial myocytes provides a basis for mechanism‐based antiarrhythmic therapy.

Aims Heart failure (HF) is linked to electrical remodeling that promotes ventricular arrhythmias. Underlying molecular signaling is insufficiently understood, in particular concerning patients with early disease stages. Previous observations suggest a key role for epigenetic mechanisms in cardiac remodeling processes. We hypothesized that histone deacetylases (HDACs) 1 and 2 contribute to cellular electrophysiological dysregulation in ventricular cardiomyocytes during HF development. Materials and methods HDAC and ion channel expression was quantified in a porcine model of early HF induced by short-term atrial tachypacing, resulting in atrial fibrillation with rapid ventricular rate response. Anti-Hdac1 and anti-Hdac2 siRNA treatment was employed in neonatal murine cardiomyocytes (NMCM) to study effects of HDACs on ion channel mRNA expression and action potential duration (APD). Key findings Early HF was characterized by mild reduction of left ventricular ejection fraction, prolonged QTc intervals, and increased ventricular effective refractory periods. Delayed repolarization was linked to significant downregulation of HDAC2 in left ventricular (LV) tissue. In addition, there was a tendency towards reduced transcript expression of KCNJ2/Kir2.1 K+ channels. In NMCM, knock-down of Hdac2 recapitulated AP prolongation. Finally, siRNA-mediated suppression of Hdac2 reduced Kcnh2/Kv11.1 K+ channel expression. Significance Suppression of HDAC2 is linked to ventricular electrical remodeling of APD and ion channel expression in early stages of heart failure. This previously unrecognized mechanism may serve as basis for future approaches to prevention and treatment of ventricular arrhythmias.