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Background: Acutely effective repeated radiofrequency catheter ablation (RFCA) after previous atrial fibrillation ablation depends on several parameters, including local impedance (LI), contact force (CF), and power., Objective: We aimed to investigate the relationship of LI, CF, and power to the LI drop in a repeated atrial RFCA environment., Methods: Consecutive patients undergoing repeated atrial RFCA were studied. High-quality local electrograms were analyzed for morphology changes indicating effective RFCA and associated LI dynamics. The influence of baseline LI, mean CF, and power on the LI drop was analyzed. Investigated power levels included ≤25 W, 30 W, and ≥40 W., Results: There were 1390 RFCA points from 48 patients (48% female; median age, 70 years) analyzed; 40.5% of 309 analyzed electrograms showed effective RFCA morphology changes with a higher median LI drop (effective, 19.7 Ω; partially effective, 14.1 Ω; P < .001). CF showed the highest correlation to the LI drop within high baseline LI and when applying ≥40 W (low baseline LI, R = 0.39; intermediate, R = 0.66; high, R = 0.72). Within low baseline LI regions, CF levels showed a lower correlation to the LI drop (≤25 W, R = 0.30; 30 W, R = 0.35; ≥40 W, R = 0.39). A mean CF ≥10 g resulted in elevated LI drops with higher power compared with lower power within all baseline LI tertiles (P < .001 each)., Conclusion: Within high baseline LI regions, CF plays a greater role for the maximum LI drop when higher power is chosen. A mean CF ≥10 g ensures increased LI drops with increasing power levels., Competing Interests: Disclosures F.A.A.: previous invited Fellow of the German Heart Rhythm Fellowship by Boston Scientific; travel grants from Bayer Pharmaceuticals; speaker: Bristol Myers Squibb; A.-K.K.: invited Fellow of the German Heart Rhythm Fellowship by Boston Scientific; travel support from Abbott; C.M.: speaker and consulting: Abbott, Boston Scientific; speaker: Biosense Webster, Bristol Myers Squibb. K.S., E.Z., and B.W. have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Objective and Background:  Data on incidence of in-hospital pulmonary embolisms (PE) after catheter ablation (CA) are scarce. To gain further insights, we sought to provide new findings through case-based analyses of administrative data., Methods:  Incidences of PE after CA of supraventricular tachycardias (SVT), atrial fibrillation (AF), atrial flutter (AFlu), and ventricular tachycardias (VT) in three German tertiary centers between 2005 and 2020 were determined and coded by the G-DRG (German Diagnosis Related Groups System) and OPS (German Operation and Procedure Classification) systems. An administrative search was performed with a consecutive case-based analysis., Results:  Overall, 47,344 ablations were analyzed (10,037 SVT; 28,048 AF; 6,252 AFlu; 3,007 VT). PE occurred in 14 (0.03%) predominantly female ( n  = 9; 64.3%) patients with a mean age of 55.3 ± 16.9 years, body mass index 26.2 ± 5.1 kg/m 2 , and left ventricular ejection fraction of 56 ± 13.6%. PE incidences were 0.05% ( n  = 5) for SVT, 0.02% ( n  = 5) for AF, and 0.13% ( n  = 4) for VT ablations. No patient suffered PE after AFlu ablation. Five patients (35.7%) with PE after CA had no prior indication for oral anticoagulation (OAC). Preprocedural international normalized ratio in PE patients was 1.2 ± 0.5. Most patients with PE following CA presented with symptoms the day after the procedure ( n  = 9) after intraprocedural heparin application of 12,943.2 ± 5,415.5 IU. PE treatment included anticoagulation with either phenprocoumon ( n  = 5) or non-vitamin K-dependent OAC ( n  = 9). Two patients with PE died after VT/AF ablation, respectively. The remaining patients were discharged without sequels., Conclusion:  Over a 15-year period, incidence of PE after ablation is low, particularly low in patients with ablation for AF/AFlu. This is most likely due to stricter anticoagulation management in these patients compared with those receiving SVT/VT ablation procedures and could argue for continuation of OAC prior to ablation. Optimizing periprocedural anticoagulation management should be subject of further prospective trials., Competing Interests: None declared., (Thieme. All rights reserved.)

Aims: In-hospital complications of catheter ablation for atrial fibrillation (AF), atrial flutter (AFL), and ventricular tachycardia (VT) may be overestimated by analyses of administrative data., Methods and Results: We determined the incidences of in-hospital mortality, major bleeding, and stroke around AF, AFL, and VT ablations in four German tertiary centres between 2005 and 2020. All cases were coded by the G-DRG- and OPS-systems. Uniform code search terms were applied defining both the types of ablations for AF, AFL, and VT and the occurrence of major adverse events including femoral vascular complications, iatrogenic tamponade, stroke, and in-hospital death. Importantly, all complications were individually reviewed based on patient-level source records. Overall, 43 031 ablations were analysed (30 361 AF; 9364 AFL; 3306 VT). The number of ablations/year more than doubled from 2005 (n = 1569) to 2020 (n = 3317) with 3 times and 2.5 times more AF and VT ablations in 2020 (n = 2404 and n = 301, respectively) as compared to 2005 (n = 817 and n = 120, respectively), but a rather stable number of AFL ablations (n = 554 vs. n = 612). Major peri-procedural complications occurred in 594 (1.4%) patients. Complication rates were 1.1% (n = 325) for AF, 1.0% (n = 95) for AFL, and 5.3% (n = 175) for VT. With an increase in complex AF/VT procedures, the overall complication rate significantly increased (0.76% in 2005 vs. 1.81% in 2020; P = 0.004); but remained low over time. Following patient-adjudication, all in-hospital cardiac tamponades (0.7%) and strokes (0.2%) were related to ablation. Major femoral vascular complications requiring surgical intervention occurred in 0.4% of all patients. The in-hospital mortality rate adjudicated to be ablation-related was lower than the coded mortality rate: AF: 0.03% vs. 0.04%; AFL: 0.04% vs. 0.14%; VT: 0.42% vs. 1.48%., Conclusion: Major adverse events are low and comparable after catheter ablation for AFL and AF (∼1.0%), whereas they are five times higher for VT ablations. In the presence of an increase in complex ablation procedures, a moderate but significant increase in overall complications from 2005-20 was observed. Individual case analysis demonstrated a lower than coded ablation-related in-hospital mortality. This highlights the importance of individual case adjudication when analysing administrative data., Competing Interests: Conflict of interest: L.E. discloses consultant fees, speaking honoraria, and travel expenses from Abbott, Bayer Healthcare, Biosense Webster, Biotronik, Boehringer, Boston Scientific, Bristol-Myers Squibb, Daiichi Sankyo, Medtronic, Pfizer, and Sanofi Aventis. Research has been supported by German Research Foundation (DFG) and German Heart Foundation outside the submitted work. The other authors declared no conflicts of interest regarding this study., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia in patients with accessory pathways (AP) are common supraventricular tachycardias. High long-term efficacy of about 97% (AVNRT) and 92% (AP) has been observed in children and adults. The risk of occurring atrioventricular block is low (0.4-0.8% during AVNRT, 0.1-0.2% for AP). Catheter ablation shows a lower efficacy of 87-93% and elevated atrioventricular block risk up to 10% in patient groups with complex congenital heart disease. Nonsynchronized ventricular activation during preexcitation or permanent reentrant tachycardias can induce heart failure, and remission of left ventricular function can be expected in > 90% after successful catheter ablation. Therefore, catheter ablation is the long-term therapy of choice for AVNRT and AP with high efficacy and safety for most patient populations., (© 2023. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Background: Atrial tachycardias (AT) occurring in patients after previous atrial fibrillation (AF) ablation are increasingly observed in clinical practice. Catheter ablation is the treatment of choice but an optimal workflow to improve patient outcome has not been defined. The purpose of this study was to assess procedural and clinical outcome depending on baseline rhythm at the beginning of AT ablation., Methods: A total of 380 patients (69 (61-75) years, 56.6% male) who underwent catheter ablation for consecutive AT after previous AF ablation were studied., Results: At the beginning of the procedure, 140 patients (36.8%) presented in sinus rhythm (SR), 208 (54.7%) with AT and 32 (8.4%) with AF. Patients in SR or with AT underwent shorter procedures (173 (132-213) minutes vs. 161 (120-203) minutes vs. 226 (154-249) minutes; p = 0.002) with more frequent termination to SR (87.9% vs. 81.3% vs. 56.3%; p < 0.001) than patients with AF. Acute procedural success did not differ between patients in SR or with AT but was higher compared to those with AF (96.4% vs. 97.1% vs. 87.5%; p = 0.033). During a follow-up of 290 (181-680) days, patients in baseline SR experienced arrhythmia recurrences less often (36.4% vs. 49.5% vs. 68.8%; p = 0.002) than patients with AT or AF., Conclusion: Baseline rhythm during AT ablation predicts procedural and clinical outcome. Whereas acute procedural success does not differ between patients in SR or with AT, patients presenting in SR have a more favorable mid-term success rate., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)

Aging is a major risk factor for impaired cardiovascular health. Because the aging myocardium is characterized by microcirculatory dysfunction, and because nerves align with vessels, we assessed the impact of aging on the cardiac neurovascular interface. We report that aging reduces nerve density in the ventricle and dysregulates vascular-derived neuroregulatory genes. Aging down-regulates microRNA 145 (miR-145) and derepresses the neurorepulsive factor semaphorin-3A. miR-145 deletion, which increased Sema3a expression or endothelial Sema3a overexpression, reduced axon density, mimicking the aged-heart phenotype. Removal of senescent cells, which accumulated with chronological age in parallel to the decline in nerve density, rescued age-induced denervation, reversed Sema3a expression, preserved heart rate patterns, and reduced electrical instability. These data suggest that senescence-mediated regulation of nerve density contributes to age-associated cardiac dysfunction.

Background: The sympathetic nervous system plays an integral role in cardiac physiology. Nerve fibers innervating the left ventricle are amenable to transvenous catheter stimulation along the coronary sinus (CS)., Objectives: The aim of the present study was to modulate left ventricular control by selective intracardiac sympathetic denervation., Methods: First, the impact of epicardial CS ablation on cardiac electrophysiology was studied in a Langendorff model of decentralized murine hearts (n = 10 each, ablation and control groups). Second, the impact of transvenous, anatomically driven axotomy by catheter-based radiofrequency ablation via the CS was evaluated in healthy sheep (n = 8) before and during stellate ganglion stimulation., Results: CS ablation prolonged epicardial ventricular refractory period without (41.8 ± 8.4 ms vs 53.0 ± 13.5 ms; P = 0.049) and with β 1-2 -adrenergic receptor blockade (47.8 ± 7.8 ms vs 73.1 ± 13.2 ms; P < 0.001) in mice. Supported by neuromorphological studies illustrating a circumferential CS neural network, intracardiac axotomy by catheter ablation via the CS in healthy sheep diminished the blood pressure increase during stellate ganglion stimulation (Δ systolic blood pressure 21.9 ± 10.9 mm Hg vs 10.5 ± 12.0 mm Hg; P = 0.023; Δ diastolic blood pressure 9.0 ± 5.5 mm Hg vs 3.0 ± 3.5 mm Hg; P = 0.039)., Conclusions: Transvenous, anatomically driven axotomy targeting nerve fibers along the CS enables acute modulation of left ventricular control by selective intracardiac sympathetic denervation., Competing Interests: Funding Support and Author Disclosures This work was supported by the German Centre for Cardiovascular Research, Berlin, Germany (FKZ 81Z0710112 to Dr Meyer). The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Aims: Cardiac arrhythmia originating from the papillary muscle (PM) can trigger ventricular fibrillation (VF) and cause sudden cardiac death even in the absence of structural heart disease. Most premature ventricular contractions, however, are benign and hitherto difficult to distinguish from a potentially fatal arrhythmia. Altered repolarization characteristics are associated with electrical instability, but electrophysiological changes which precede degeneration into VF are still not fully understood., Methods and Results: Ventricular arrhythmia (VA) was induced by aconitine injection into PMs of healthy sheep. To investigate mechanisms of degeneration of stable VA into VF in structurally healthy hearts, endocardial high-density and epicardial mapping was performed during sinus rhythm (SR) and VA. The electrical restitution curve, modelling the relation of diastolic interval and activation recovery interval (a surrogate parameter for action potential duration), is steeper in VA than in non-arrhythmia (ventricular pacing and SR). Steeper restitution curves reflect electrical instability and propensity to degenerate into VF. Importantly, we find the parameter repolarization time in relation to cycle length (RT/CL) to differentiate self-limiting from degenerating arrhythmia with high specificity and sensitivity., Conclusion: RT/CL may serve as a simple index to aid differentiation between self-limiting and electrically instable arrhythmia with the propensity to degenerate to VF. RT/CL is independent of cycle length and could easily be measured to identify electrical instability in patients., Competing Interests: Conflict of interest: P.M. received travel grant and fellowship programme by Biotronik. C.M. received compensation for participation as consultant for Biotronik, Biosense Webster, Boston Scientific, and on speaker’s bureau for Abbott, Biotronik, Boston Scientific, and Medtronic. All remaining authors have declared no conflicts of interest., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology.)

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., Competing Interests: Conflict of interest: None declared., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Optimal lesion formation during catheter-based radiofrequency current (RFC) ablation depends on electro-mechanical tip-tissue coupling measurable via contact force (CF) and local impedance (LI) monitoring. We aimed to investigate CF and LI dynamics in patients with previous atrial fibrillation (AF) ablation who frequently present with heterogenous arrhythmia substrate. Methods: Data from consecutive patients presenting for repeat AF or atrial tachycardia ablation using a novel open-irrigated single-tip ablation catheter were studied. RFC applications were investigated regarding CF, LI and the maximum LI drop (∆LI) for evaluation of ablation efficacy. ∆LI > 20 Ω was defined as a successful RFC application. Results: A total of 730 RFC applications in 20 patients were analyzed. Baseline CF was not associated with baseline LI (R = 0.06, p = 0.17). A mean CF < 8 g during ablation resulted in lower ∆LI (<8 g: 13 Ω vs. ≥ 8 g: 16 Ω, p < 0.001). Baseline LI showed a better correlation with ∆LI (R = 0.35, p < 0.001) compared to mean CF (R = 0.17, p < 0.001). Mean CF correlated better with ∆LI in regions of low (R = 0.31, p < 0.001) compared to high (R = 0.21, p = 0.02) and intermediate voltage (R = 0.17, p = 0.004). Combined CF and baseline LI predicted ∆LI > 20 Ω (area under the receiver operating characteristic curve (AUC) 0.75) better compared to baseline LI (AUC 0.72), mean CF (AUC 0.60), force-time integral (AUC 0.59) and local bipolar voltage (0.55). Conclusion: Combination of CF and LI may aid monitoring real-time catheter-tissue electro-mechanical coupling and lesion formation within heterogenous atrial arrhythmia substrate in patients with repeat AF or atrial tachycardia ablation., (Copyright © 2022 Alken, Scherschel, Kahle, Masjedi and Meyer.)

Background: The importance of peripheral chemoreceptors for cardiorespiratory neural control is known for decades. Pure oxygen inhalation deactivates chemoreceptors and increases parasympathetic outflow. However, the relationship between autonomic nervous system (ANS) activation and resulting respiratory as well as heart rate (HR) dynamics is still not fully understood., Methods: In young adults the impact of (1) 100 % pure oxygen inhalation (hyperoxic cardiac chemoreflex sensitivity (CHRS) testing), (2) the cold face test (CFT) and (3) the cold pressor test (CPT) on heart rate variability (HRV), hemodynamics and respiratory rate was investigated in randomized order. Baseline ANS outflow was determined assessing respiratory sinus arrhythmia via deep breathing, baroreflex sensitivity and HRV., Results: Baseline ANS outflow was normal in all participants (23 ± 1 years, 7 females, 3 males). Hyperoxic CHRS testing decreased HR (after 60 ± 3 vs before 63 ± 3 min -1 , p = 0.004), while increasing total peripheral resistance (1053 ± 87 vs 988 ± 76 dyne*s + m 2 /cm 5 , p = 0.02) and mean arterial blood pressure (93 ± 4 vs 91 ± 4 mm Hg, p = 0.02). HRV indicated increased parasympathetic outflow after hyperoxic CHRS testing accompanied by a decrease in respiratory rate (15 ± 1vs 19 ± 1 min -1 , p = 0.001). In contrast, neither CFT nor CPT altered the respiratory rate (18 ± 1 vs 18 ± 2 min -1 , p = 0.38 and 18 ± 1 vs 18 ± 1 min -1 , p = 0.84, respectively)., Conclusion: Changes in HR characteristics during deactivation of peripheral chemoreceptors but not during the CFT and CPT are related with a decrease in respiratory rate. This highlights the need of respiratory rate assessment when evaluating adaptations of cardiorespiratory chemoreceptor control., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Aims: Bipolar radiofrequency ablation (B-RFA) has been reported as a bail-out strategy for the treatment of therapy refractory ventricular arrhythmias (VA). Currently, existing setups have not been standardized for B-RFA, while the impact of conventional B-RFA approaches on lesion formation remains unclear., Methods and Results: (i) In a multicentre observational study, patients undergoing B-RFA for previously therapy-refractory VA using a dedicated B-RFA setup were retrospectively analysed. (ii) Additionally, in an ex vivo model lesion formation during B-RFA was evaluated using porcine hearts. In a total of 26 procedures (24 patients), acute success was achieved in all 14 ventricular tachycardia (VT) procedures and 7/12 procedures with premature ventricular contractions (PVC), with major complications occurring in 1 procedure (atrioventricular block). During a median follow-up of 211 days in 21 patients, 6/11 patients (VT) and 5/10 patients (PVC) remained arrhythmia-free. Lesion formation in the ex vivo model during energy titration from 30 to 50 W led to similar lesion volumes compared with initial high-power 50 W B-RFA. Lesion size significantly increased when combining sequential unipolar and B-RFA (1429 mm3 vs. titration 501 mm3 vs. B-RFA 50 W 423 mm3, P < 0.001), an approach used in overall 58% of procedures and more frequently applied in procedures without VA recurrence (92% vs. 36%, P = 0.009). Adipose tissue severely limited lesion formation during B-RFA., Conclusion: Using a dedicated device for B-RFA for therapy-refractory VA appears feasible and safe. While some patients need repeat ablation, success rates were encouraging. Sequential unipolar and B-RFA may be favourable for lesion formation., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2021. For permissions, please email: journals.permissions@oup.com.)

Worldwide, ∼4 million people die from sudden cardiac death every year caused in more than half of the cases by ischaemic cardiomyopathy (ICM). Prevention of sudden cardiac death after myocardial infarction by implantation of a cardioverter-defibrillator (ICD) is the most common, even though not curative, therapy to date. Optimized ICD programming should be strived for in order to decrease the incidence of ICD interventions. Catheter ablation reduces the recurrence of ventricular tachycardias (VTs) and is an important adjunct to sole ICD-based treatment or pharmacological antiarrhythmic therapy in patients with ICM, as conclusively demonstrated by seven randomized controlled trials (RCTs) in the last two decades. However, none of the conducted trials was powered to reveal a survival benefit for ablated patients as compared to controls. Whereas thorough consideration of an early approach is necessary following two recent RCTs (PAUSE-SCD, BERLIN VT), catheter ablation is particularly recommended in patients with recurrent VT after ICD therapy. In this context, novel, pathophysiologically driven ablation strategies referring to deep morphological and functional substrate phenotyping based on high-resolution mapping and three-dimensional visualization of scars appear promising. Emerging concepts like sympathetic cardiac denervation as well as radioablation might expand the therapeutical armamentarium especially in patients with therapy-refractory VT. Randomized controlled trials are warranted and on the way to investigate how these translate into improved patient outcome. This review summarizes therapeutic strategies currently available for the prevention of VT recurrences, the optimal timing of applicability, and highlights future perspectives after a PAUSE in BERLIN., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2021. For permissions, please email: journals.permissions@oup.com.)

Aims: Cardiac involvement in COVID-19 is associated with adverse outcome. However, it is unclear whether cell-specific consequences are associated with cardiac SARS-CoV-2 infection. Therefore, we investigated heart tissue utilizing in situ hybridization, immunohistochemistry, and RNA-sequencing in consecutive autopsy cases to quantify virus load and characterize cardiac involvement in COVID-19., Methods and Results: In this study, 95 SARS-CoV-2-positive autopsy cases were included. A relevant SARS-CoV-2 virus load in the cardiac tissue was detected in 41/95 deceased (43%). Massive analysis of cDNA ends (MACE)-RNA-sequencing was performed to identify molecular pathomechanisms caused by the infection of the heart. A signature matrix was generated based on the single-cell dataset 'Heart Cell Atlas' and used for digital cytometry on the MACE-RNA-sequencing data. Thus, immune cell fractions were estimated and revealed no difference in immune cell numbers in cases with and without cardiac infection. This result was confirmed by quantitative immunohistological diagnosis. MACE-RNA-sequencing revealed 19 differentially expressed genes (DEGs) with a q-value <0.05 (e.g. up: IFI44L, IFT3, TRIM25; down: NPPB, MB, MYPN). The upregulated DEGs were linked to interferon pathways and originate predominantly from endothelial cells. In contrast, the downregulated DEGs originate predominately from cardiomyocytes. Immunofluorescent staining showed viral protein in cells positive for the endothelial marker ICAM1 but rarely in cardiomyocytes. The Gene Ontology (GO) term analysis revealed that downregulated GO terms were linked to cardiomyocyte structure, whereas upregulated GO terms were linked to anti-virus immune response., Conclusion: This study reveals that cardiac infection induced transcriptomic alterations mainly linked to immune response and destruction of cardiomyocytes. While endothelial cells are primarily targeted by the virus, we suggest cardiomyocyte destruction by paracrine effects. Increased pro-inflammatory gene expression was detected in SARS-CoV-2-infected cardiac tissue but no increased SARS-CoV-2 associated immune cell infiltration was observed., (© The Author(s) 2021. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Fibroblasts contribute to approximately 20% of the non-cardiomyocytic cells in the heart. They play important roles in the myocardial adaption to stretch, inflammation, and other pathophysiological conditions. Fibroblasts are a major source of extracellular matrix (ECM) proteins whose production is regulated by cytokines, such as TNF-α or TGF-β. The resulting myocardial fibrosis is a hallmark of pathological remodeling in dilated cardiomyopathy (DCM). Therefore, in the present study, the secretome and corresponding transcriptome of human cardiac fibroblasts from patients with DCM was investigated under normal conditions and after TNF-α or TGF-β stimulation. Secreted proteins were quantified via mass spectrometry and expression of genes coding for secreted proteins was analyzed via Affymetrix Transcriptome Profiling. Thus, we provide comprehensive proteome and transcriptome data on the human cardiac fibroblast's secretome. In the secretome of quiescent fibroblasts, 58% of the protein amount belonged to the ECM fraction. Interestingly, cytokines were responsible for 5% of the total protein amount in the secretome and up to 10% in the corresponding transcriptome. Furthermore, cytokine gene expression and secretion were upregulated upon TNF-α stimulation, while collagen secretion levels were elevated after TGF-β treatment. These results suggest that myocardial fibroblasts contribute to pro-fibrotic and to inflammatory processes in response to extracellular stimuli.

Background: Myocardial slow conduction is a cornerstone of ventricular tachycardia (VT). Prolonged electrogram (EGM) duration is a useful surrogate parameter and manual annotation of EGM characteristics are widely used during catheter-based ablation of the arrhythmogenic substrate. However, this remains time-consuming and prone to inter-operator variability. We aimed to develop an algorithm for 3-D visualization of EGM duration relative to the 17-segment American Heart Association model., Methods: To calculate and visualize EGM duration, in sinus rhythm acquired high-density maps of patients with ischemic cardiomyopathy undergoing substrate-based VT ablation using a 64-mini polar basket-catheter with low noise of 0.01 mV were analyzed. Using a custom developed algorithm based on standard deviation and threshold, the relationship between EGM duration, endocardial voltage and ablation areas was studied by creating 17-segment 3-D models and 2-D polar plots., Results: 140,508 EGMs from 272 segments (n = 16 patients, 94% male, age: 66±2.4, ejection fraction: 31±2%) were studied and 3-D visualization of EGM duration was performed. Analysis of signal processing parameters revealed that a 40 ms sliding SD-window, 15% SD-threshold and >70 ms EGM duration cutoff was chosen based on diagnostic odds ratio of 12.77 to visualize rapidly prolonged EGM durations. EGMs > 70 ms matched to 99% of areas within dense scar (<0.2 mV), in 95% of zones within scar border zone (0.2-1.0 mV) and detected ablated areas having resulted in non-inducibility at the end of the procedure. Ablation targets were identified with a sensitivity of 65.6% and a specificity of 94.6% avoiding false positive labeling of prolonged EGMs in segments with healthy myocardium., Conclusion: The novel algorithm allows rapid visualization of prolonged EGM durations. This may facilitate more objective characterization of arrhythmogenic substrate in patients with ischemic cardiomyopathy., Competing Interests: Dr. Meyer reports compensation for participation on a speaker´s bureau relevant to this topic and serving as a consultant for Biosense Webster, Boston Scientific, and Abbott. All other authors declare no competing interests. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

The tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b/PEX5R) is an interaction partner and auxiliary subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are key for rhythm generation in the brain and in the heart. Since TRIP8b is expressed in central neurons but not in cardiomyocytes, the TRIP8b-HCN interaction has been studied intensely in the brain, but is deemed irrelevant in the cardiac conduction system. Still, to date, TRIP8b has not been studied in the intrinsic cardiac nervous system (ICNS), a neuronal network located within epicardial fat pads. In vitro electrophysiological studies revealed that TRIP8b-deficient mouse hearts exhibit increased atrial refractory and atrioventricular nodal refractory periods, compared to hearts of wild-type littermates. Meanwhile, heart rate, sino-nodal recovery time, and ventricular refractory period did not differ between genotypes. Trip8b mRNA was detected in the ICNS by quantitative polymerase chain reaction. RNAscope in situ hybridization confirmed Trip8b localization in neuronal somata and nerve fibers. Additionally, we found a very low amount of mRNAs in the sinus node and atrioventricular node, most likely attributable to the delicate fibers innervating the conduction system. In contrast, TRIP8b protein was not detectable. Our data suggest that TRIP8b in the ICNS may play a role in the modulation of atrial electrophysiology beyond HCN-mediated sino-nodal control of the heart.

The autonomic nervous system is a substantial driver of cardiac electrophysiology. Especially the role of its sympathetic branch is an ongoing matter of investigation in the pathophysiology of ventricular arrhythmias (VA). Neurons in the stellate ganglia (SG) - bilateral star-shaped structures of the sympathetic chain - are an important component of the sympathetic infrastructure. The SG are a recognized target for treatment via cardiac sympathetic denervation in patients with therapy-refractory VA. While neuronal remodeling and glial activation in the SG have been described in patients with VA, the underlying cellular and molecular processes that potentially precede the onset of arrhythmia are only insufficiently understood and should be elucidated to improve autonomic modulation. Mouse models allow us to study sympathetic neuronal remodeling, but identification of the murine SG is challenging for the inexperienced investigator. Thus, in-depth cellular and molecular biological studies of the murine SG are lacking for many common cardiac diseases. Here, we describe a basic repertoire for dissecting and studying the SG in adult mice for analyses at RNA level (RNA isolation for gene expression analyses, in situ hybridization), protein level (immunofluorescent whole mount staining), and cellular level (basic morphology, cell size measurement). We present potential solutions to overcome challenges in the preparation technique, and how to improve staining via quenching of autofluorescence. This allows for the visualization of neurons as well as glial cells via established markers in order to determine cell composition and remodeling processes. The methods presented here allow characterizing the SG to gain further information on autonomic dysfunction in mice prone to VA and can be complemented by additional techniques investigating neuronal and glial components of the autonomic nervous system in the heart.

Importance: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be documented in various tissues, but the frequency of cardiac involvement as well as possible consequences are unknown., Objective: To evaluate the presence of SARS-CoV-2 in the myocardial tissue from autopsy cases and to document a possible cardiac response to that infection., Design, Setting, and Participants: This cohort study used data from consecutive autopsy cases from Germany between April 8 and April 18, 2020. All patients had tested positive for SARS-CoV-2 in pharyngeal swab tests., Exposures: Patients who died of coronavirus disease 2019., Main Outcomes and Measures: Incidence of SARS-CoV-2 positivity in cardiac tissue as well as CD3+, CD45+, and CD68+ cells in the myocardium and gene expression of tumor necrosis growth factor α, interferon γ, chemokine ligand 5, as well as interleukin-6, -8, and -18., Results: Cardiac tissue from 39 consecutive autopsy cases were included. The median (interquartile range) age of patients was 85 (78-89) years, and 23 (59.0%) were women. SARS-CoV-2 could be documented in 24 of 39 patients (61.5%). Viral load above 1000 copies per μg RNA could be documented in 16 of 39 patients (41.0%). A cytokine response panel consisting of 6 proinflammatory genes was increased in those 16 patients compared with 15 patients without any SARS-CoV-2 in the heart. Comparison of 15 patients without cardiac infection with 16 patients with more than 1000 copies revealed no inflammatory cell infiltrates or differences in leukocyte numbers per high power field., Conclusions and Relevance: In this analysis of autopsy cases, viral presence within the myocardium could be documented. While a response to this infection could be reported in cases with higher virus load vs no virus infection, this was not associated with an influx of inflammatory cells. Future investigations should focus on evaluating the long-term consequences of this cardiac involvement.

Aims: S100B, a well-known damage-associated molecular pattern protein is released acutely by central and peripheral nerves and upon concomitant denervation in pulmonary vein isolation (PVI). We aimed to investigate whether the ablation technique used for PVI impacts S100B release in patients with paroxysmal atrial fibrillation (AF)., Methods and Results: The study population consisted of 73 consecutive patients (age: 62.7 ± 10.9 years, 54.8% males) undergoing first-time PVI with either radiofrequency (RF; n = 30) or cryoballoon (CB; n = 43) for paroxysmal AF. S100B determined from venous plasma samples taken immediately before and after PVI increased from 33.5 ± 1.8 to 91.1 ± 5.3 pg/mL (P < 0.0001). S100B release in patients undergoing CB-PVI was 3.9 times higher compared to patients with RF-PVI (ΔS100B: 21.1 ± 2.7 vs. 83.1 ± 5.2  pg/mL, P < 0.0001). During a mean follow-up of 314 ± 186 days, AF recurrences were observed in 18/71 (25.4%) patients (RF-PVI: n = 9/28, CB-PVI: n = 9/43). Univariate Cox regression analysis indicated that an increase in S100B was associated with higher freedom from AF in follow-up (hazard ratio per 10  pg/mL release of S100B: 0.83; 95% confidence interval: 0.72-0.95; P = 0.007)., Conclusion: The ablation technique used for PVI has an impact on the release of S100B, a well-established biomarker for neural damage., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Introduction: Tailored catheter ablation of atrial tachycardias (ATs) is increasingly recommended as a potentially easy treatment strategy in the era of high-density mapping (HDM). As follow-up data are sparse, we here report outcomes after HDM-guided ablation of ATs in patients with prior catheter ablation or cardiac surgery., Methods and Results: In 250 consecutive patients (age 66.5 ± 0.7 years, 58% male) with ATs (98% prior catheter ablation, 13% prior cardiac surgery) an HDM-guided catheter ablation was performed with the support of a 64-electrode mini-basket catheter. A total of 354 ATs (1.4 ± 0.1 ATs per patient; mean cycle length 304 ± 4.3 ms; 64% macroreentry, 27% localized reentry, and 9% focal) with acute termination of 95% were targeted in the index procedure. A similar AT as in the index procedure recurred in five patients (2%) after a median follow-up time of 535 days (interquartile range (IQR) 25th-75th percentile: 217-841). Tailored ablation of reentry ATs with freedom from any arrhythmia was obtained in 53% after a single procedure and in 73% after 1.4 ± 0.4 ablation procedures (range: 1-4). A total of 228 patients (91%) were free from any arrhythmia recurrence after 210 days (IQR: 152-494) when including optimal usual care., Conclusions: Tailored catheter ablation of ATs guided by HDM has a high acute success rate. The recurrence rate of the index AT is low. In patients with extensive atrial scaring further ablation procedures need to be considered to achieve freedom from any arrhythmia., (© 2020 The Authors. Journal of Cardiovascular Electrophysiology Published by Wiley Periodicals LLC.)

Background: Phrenic nerve injury (PNI) remains one of the most frequent complications during cryoballoon-based pulmonary vein isolation (CB-PVI). Since its introduction in 2013, the use of compound motor action potential (CMAP) for the prevention of PNI during CB-PVI is increasing; however, systematic outcome data are sparse., Methods: The CMAP technique was applied in conjunction with abdominal palpation during pacing manoeuvres (10 mV, 2 ms) from the superior vena cava for 388 consecutive patients undergoing CB-PVI between January 2015 and May 2017 at our tertiary arrhythmia centre. Cryoablation was immediately terminated when CMAP amplitude was reduced by 30%., Results: Reductions in CMAP amplitude were observed in 16 (4%) of 388 patients during isolation of the right veins. Of these, 11 (69%) patients did not manifest a reduction in diaphragmatic excursions. The drop in CMAP amplitude was observed in 10 (63%) patients during ablation of the right superior pulmonary veins (PVs) and in 7 (44%) patients during ablation of the right inferior PVs. Postprocedural persistent PNI was observed in three of four patients for a duration of 6 months, with one of these patients remaining symptomatic at the 24-month follow-up. One of the four patients was lost to long-term follow-up., Conclusions: All PNIs occurred during right-sided CB-PVI and were preceded by a reduction in CMAP amplitude. Thus, the standardized use of CMAP surveillance during CB-PVI is easily applicable, reliable and compared with other studies, results in a lower number of PNIs., Competing Interests: The authors have declared that no competing interests exist.

The Hamburg City Health Study (HCHS) is a large, prospective, long-term, population-based cohort study and a unique research platform and network to obtain substantial knowledge about several important risk and prognostic factors in major chronic diseases. A random sample of 45,000 participants between 45 and 74 years of age from the general population of Hamburg, Germany, are taking part in an extensive baseline assessment at one dedicated study center. Participants undergo 13 validated and 5 novel examinations primarily targeting major organ system function and structures including extensive imaging examinations. The protocol includes validate self-reports via questionnaires regarding lifestyle and environmental conditions, dietary habits, physical condition and activity, sexual dysfunction, professional life, psychosocial context and burden, quality of life, digital media use, occupational, medical and family history as well as healthcare utilization. The assessment is completed by genomic and proteomic characterization. Beyond the identification of classical risk factors for major chronic diseases and survivorship, the core intention is to gather valid prevalence and incidence, and to develop complex models predicting health outcomes based on a multitude of examination data, imaging, biomarker, psychosocial and behavioral assessments. Participants at risk for coronary artery disease, atrial fibrillation, heart failure, stroke and dementia are invited for a visit to conduct an additional MRI examination of either heart or brain. Endpoint assessment of the overall sample will be completed through repeated follow-up examinations and surveys as well as related individual routine data from involved health and pension insurances. The study is targeting the complex relationship between biologic and psychosocial risk and resilience factors, chronic disease, health care use, survivorship and health as well as favorable and bad prognosis within a unique, large-scale long-term assessment with the perspective of further examinations after 6 years in a representative European metropolitan population.

Patients with type 2 diabetes mellitus (T2DM) have a greater risk of developing life-threatening cardiac arrhythmias. Because the underlying mechanisms and potential influence of diabetic autonomic neuropathy are not well understood, we aimed to assess the relevance of a dysregulation in cardiac autonomic tone. Ventricular arrhythmia susceptibility was increased in Langendorff-perfused hearts isolated from mice with T2DM ( db/db ). Membrane properties and synaptic transmission were similar at cardiac postganglionic parasympathetic neurons from diabetic and control mice; however, a greater asynchronous neurotransmitter release was present at sympathetic postganglionic neurons from the stellate ganglia of db/db mice. Western blot analysis showed a reduction of tyrosine hydroxylase (TH) from the ventricles of db/db mice, which was confirmed with confocal imaging as a heterogeneous loss of TH-immunoreactivity from the left ventricular wall but not the apex. In vivo stimulation of cardiac parasympathetic (vagus) or cardiac sympathetic (stellate ganglion) nerves induced similar changes in heart rate in control and db/db mice, and the kinetics of pacing-induced Ca 2+ transients (recorded from isolated cardiomyocytes) were similar in control and db/db cells. Antagonism of cardiac muscarinic receptors did not affect the frequency or severity of arrhythmias in db/db mice, but sympathetic blockade with propranolol completely inhibited arrhythmogenicity. Collectively, these findings suggest that the increased ventricular arrhythmia susceptibility of type 2 diabetic mouse hearts is due to dysregulation of the sympathetic ventricular control. NEW & NOTEWORTHY Patients with type 2 diabetes mellitus have greater risk of suffering from sudden cardiac death. We found that the increased ventricular arrhythmia susceptibility in type 2 diabetic mouse hearts is due to cardiac sympathetic dysfunction. Sympathetic dysregulation is indicated by an increased asynchronous release at stellate ganglia, a heterogeneous loss of tyrosine hydroxylase from the ventricular wall but not apex, and inhibition of ventricular arrhythmias in db/db mice after β-sympathetic blockade.

Background: Ultra-high density mapping (HDM) is a promising tool in the treatment of patients with complex arrhythmias. In adults with congenital heart disease (CHD), rhythm disorders are among the most common complications but catheter ablation can be challenging due to heterogenous anatomy and complex arrhythmogenic substrates. Here, we describe our initial experience using HDM in conjunction with novel automated annotation algorithms in patients with moderate to great CHD complexity., Methods: We studied a series of consecutive adult patients with moderate to great CHD complexity and an indication for catheter ablation due to symptomatic arrhythmia. HDM was conducted using the Rhythmia™ mapping system and a 64-electrode mini-basket catheter for identification of anatomy, voltage, activation pattern and critical areas of arrhythmia for ablation guidance. To investigate novel advanced mapping strategies, postprocedural signal processing using the Lumipoint™ software was applied., Results: In 19 patients (53±3 years; 53% male), 21 consecutive ablation procedures were conducted. Procedures included ablation of atrial fibrillation (n=7; 33%), atrial tachycardia (n=11; 52%), atrioventricular accessory pathway (n=1; 5%), the atrioventricular node (n=1; 5%) and ventricular arrhythmias (n=4; 19%). A total of 23 supraventricular and 8 ventricular arrhythmias were studied with the generation of 56 complete high density maps (atrial n=43; ventricular n=11, coronary sinus n=2) and an average of 12,043±1,679 mapping points. Multiple arrhythmias were observed in n=7 procedures (33% of procedures; range of arrhythmias detected 2-4). A total range of 1-4 critical areas were defined per procedure and treated within a radiofrequency application time of 16 (interquartile range 12-45) minutes. Postprocedural signal processing using Lumipoint™ allowed rapid annotation of fractionated signals within specific windows of interest. This supported identification of a practical critical isthmus in 20 out of 27 completed atrial and ventricular tachycardia activation maps., Conclusions: Our findings suggest that HDM in conjunction with novel automated annotation algorithms provides detailed insights into arrhythmia mechanisms and might facilitate tailored catheter ablation in patients with moderate to great CHD complexity., Competing Interests: Conflicts of Interest: C Meyer: speaker for Boston Scientific and Abbott; consultant for Biosense Webster. The other authors have no conflicts of interest to declare., (2019 Cardiovascular Diagnosis and Therapy. All rights reserved.)

Biological pacemakers could be a promising alternative to electronic pacemakers and human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CM) may represent a suitable source for implantable cells. To further unravel this potential a thorough understanding of pacemaker function with regard to coupling processes both in the physiological and in the graft-host context is required. Here we developed a 2-component cardiac organoid model with a hiPSC-CM embryoid body (EB) as trigger casted into a rat engineered heart tissue (EHT) as arrhythmic beating substrate. Contractility recordings revealed that the EB controlled the beating activity of the EHT, leading to a regular hiPSC-CM-like beating pattern instead of the irregular beating typically seen in rat EHT. Connectivity was observed with action potential (AP) measurements and calcium transients transmitting from the EB directly into the rat EHT. Immunohistochemistry and genetically labeled hiPSC-CMs demonstrated that EB-derived and rat cells intermingled and formed a transitional zone. Connexin 43 expression followed the same pattern as histological and computer models have indicated for the human sinoatrial node. In conclusion, hiPSC-CM EBs function as a biological pacemaker in a 2-component cardiac organoid model, which provides the possibility to study electrophysiological and structural coupling mechanisms underlying propagation of pacemaker activity., (Copyright © 2019. Published by Elsevier Ltd.)

Atrial fibrillation (AF), the most common sustained heart rhythm disorder worldwide, is linked to dysfunction of the intrinsic cardiac autonomic nervous system (ICNS). The role of ICNS damage occurring during catheter-based treatment of AF, which is the therapy of choice for many patients, remains controversial. We show here that the neuronal injury marker S100B is expressed in cardiac glia throughout the ICNS and is released specifically upon catheter ablation of AF. Patients with higher S100B release were more likely to be AF free during follow-up. Subsequent in vitro studies revealed that murine intracardiac neurons react to S100B with diminished action potential firing and increased neurite growth. This suggests that release of S100B from cardiac glia upon catheter-based treatment of AF is a hallmark of acute neural damage that contributes to nerve sprouting and can be used to assess ICNS damage., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Introduction: Respiratory sinus arrhythmia (RSA) describes heart rate (HR) changes in synchrony with respiration. It is relevant for exercise capacity and mechanistically linked with the cardiac autonomic nervous system. After pulmonary vein isolation (PVI), the current therapy of choice for patients with paroxysmal atrial fibrillation (AF), the cardiac vagal tone is often diminished. We hypothesized that RSA is modulated by PVI in patients with paroxysmal AF., Material and Methods: Respiratory sinus arrhythmia, measured by using a deep breathing test and heart rate variability parameters, was studied in 10 patients (64 ±3 years) with paroxysmal AF presenting in stable sinus rhythm for their first catheter-based PVI. Additionally, heart rate dynamics before and after PVI were studied during sympathetic/parasympathetic coactivation by using a cold-face test. All tests were performed within 24 h before and 48 h after PVI., Results: After PVI RSA (E/I difference: 7.9 ±1.0 vs. 3.5 ±0.6 bpm, p = 0.006; E/I ratio: 1.14 ±0.02 vs. 1.05 ±0.01, p = 0.003), heart rate variability (SDNN: 31 ±3 vs. 14 ±3 ms, p = 0.006; RMSSD: 17 ±2 vs. 8 ±2 ms, p = 0.002) and the HR response to sympathetic/parasympathetic coactivation (10.2 ±0.7% vs. 5.7 ±1.1%, p = 0.014) were diminished. The PVI-related changes in RSA correlated with the heart rate change during sympathetic/parasympathetic coactivation before vs. after PVI (E/I difference: r = 0.849, p = 0.002; E/I ratio: r = 0.786, p = 0.007). One patient with vagal driven arrhythmia experienced AF recurrence during follow-up (mean: 6.5 ±0.6 months)., Conclusions: Respiratory sinus arrhythmia is reduced after PVI in patients with paroxysmal AF. Our findings suggest that this is related to a decrease in cardiac vagal tone. Whether and how this affects the clinical outcome including exercise capacity need to be determined., Competing Interests: The authors declare no conflict of interest., (Copyright: © 2019 Termedia & Banach.)

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine known to play a major role in inflammatory diseases such as myocardial infarction (MI), where its expression increases. Cardio protective functions of MIF during ischemia have been reported. Recently, the structurally related MIF-2 was identified and similar effects are assumed. We wanted to further investigate the role of MIF and MIF-2 on inflammatory processes during MI. Therefore, we subjected mice to experimentally induced MI by coronary occlusion for one and five days. During the acute phase of MI, the gene expression of Mif was upregulated in the infarct zone, whereas Mif-2 was downregulated, suggesting a minor role of MIF-2. Simulating ischemic conditions or mechanical stress in vitro, we demonstrated that Mif expression was induced in resident cardiac cells. To investigate possible auto /paracrine effects, cardiomyocytes and cardiac fibroblasts were individually treated with recombinant murine MIF, which in turn induced Mif expression and the expression of pro-inflammatory genes in cardiac fibroblasts. Cardiomyocytes did not respond to recombinant MIF with pro-inflammatory gene expression. While MIF stimulation alone did not change the expression of pro-fibrotic genes in cardiac fibroblasts, ischemia reduced their expression. Mimicking the increased MIF levels during MI, we exposed cardiac fibroblasts to simulated ischemia in the presence of MIF, which led to further reduced expression of pro-fibrotic genes. The presented data show that MIF was expressed by resident cardiac cells during MI. In vitro, Mif expression was induced by different external stimuli in cardiomyocytes and cardiac fibroblasts. Addition of recombinant MIF protein increased the expression of pro-inflammatory genes in cardiac fibroblasts including Mif expression itself. Thereby, cardiac fibroblasts may amplify Mif expression during ischemia promoting cardiomyocyte survival., Competing Interests: The authors declare no conflict of interest.

Increased adrenomedullin (ADM) levels are associated with various cardiac diseases such as myocardial infarction (MI). ADM is cleaved off from the full-length precursor protein proadrenomedullin (ProADM) during its posttranslational processing. To date, no biological effect of ProADM is reported, while ADM infusion leads to antiapoptotic effects and improved cardiac function. Using an MI mouse model, we found an induction of ProADM gene as well as protein expression during the early phase of MI. This was accompanied by apoptosis and increasing inflammation, which substantially influence the post-MI remodeling processes. Simulating ischemia in vitro, we demonstrate that ProADM expression was increased in cardiomyocytes and cardiac fibroblasts. Subsequently, we treated ischemic cardiomyocytes with either ProADM or ADM and found that both proteins increased survival. This effect was diminishable by blocking the ADM 1 receptor. To investigate whether ProADM and ADM play a role in the regulation of cardiac inflammation, we analyzed chemokine expression after treatment of cells with both proteins. While ProADM induced an expression of proinflammatory cytokines, thus promoting inflammation, ADM reduced chemokine expression. On leukocytes, both proteins repressed chemokine expression, revealing antiinflammatory effects. However, ProADM but not ADM dampened concurrent activation of leukocytes. Our data show that the full-length precursor ProADM is biologically active by reducing apoptosis to a similar extent as ADM. We further assume that ProADM induces local inflammation in affected cardiac tissue but attenuates exaggerated inflammation, whereas ADM has low impact. Our data suggest that both proteins are beneficial during MI by influencing apoptosis and inflammation., Competing Interests: The authors declare no conflict of interest.

Engineered heart tissue (EHT) from rat cells is a useful tool to study ventricular biology and cardiac drug safety. Since atrial and ventricular cells differ significantly, EHT and other 3D cell culture formats generated from ventricular cells have been of limited value to study atrial biology. To date, reliable in vitro models that reflect atrial physiology are lacking. Therefore, we established a novel EHT model using rat atrial cells (atrial EHT, aEHT) to assess atrial physiology, contractility and drug response. The tissue constructs were characterized with regard to gene expression, histology, electrophysiology, and the response to atrial-specific drugs. We observed typical functional properties of atrial tissue in our model such as more regular spontaneous beating with lower force, shorter action potential duration, and faster contraction and relaxation compared to ventricular EHT (vEHT). The expression of atrial-specific genes and proteins was high, whereas ventricle-specific transcripts were virtually absent. The atrial-selective drug carbachol had a strong negative inotropic and chronotropic effect on aEHT only. Taken together, the results demonstrate the feasibility of aEHT as a novel atrial 3D model and as a benchmark for tissue engineering with human induced pluripotent stem cell-derived atrial-like cardiomyocytes. Atrial EHT faithfully recapitulates atrial physiology and shall be useful to study atrial molecular physiology in health and disease as well as drug response.