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Introduction Hypertrophic cardiomyopathy (HCM) is a relatively frequent (1/500) heart disease that could result in arrhythmia and sudden death. It is mainly caused by sarcomere gene mutations. Disease mechanisms are still poorly known due to limited access to humanized experimental models. Cardiomyocytes derived from iPSc of mutated patients could serve as a platform for modeling the disease and help identifying novel therapeutic strategies. Objective To derive and differentiate into cardiomyocytes an iPSc line from a patient with an HCM hot-spot mutation and its isogenic control. Method From patient's fibroblasts we derived an iPSC line harboring the heterozygous MYH7 R403L (c.1208G > T) mutation (Okita et al). The mutation was corrected using CRISPR/Cas9 editing to produce an isogenic pair. Genomic editing, pluripotency and cardiogenicity of the clones were evaluated. Results The 2 derived iPSc clones proved to be pluripotent after phosphatase alkaline labelling, RT-qPCR on specific mRNA and proteins immunolabelling (Oct4, Nanog, Sox2, SSEA4). High TaqMan hPSC Scorecard confirmed tri-lineage differentiation potential. Normal karyotype indicated genomic integrity and STR analysis of donor fibroblasts and iPSc lines proved filiation of the clones. The mutated clone was electroporated with spCas9 and a gRNA targeting a PAM 3-bp away from the mutated allele and a correcting ssODN DNA donor. Homologous recombination events were selected by allele-specific ddPCR and reversion of the mutation was confirmed by Sanger sequencing. The 2 lines were able to differentiate into beating cellular sheets and cells stained positive for aACTN2 indicating cardiomycocyte differentiation. FACS on cTNT positive cells counts 75% of cardiomyocytes in independent differentiation experiment after 3 weeks. Conclusion We established an isogenic pair of iPSc lines from a HCM patient with MYH7 mutation defining a model for cellular and molecular study of HCM.

Background Dilated cardiomyopathy (DCM) is a major cause of systolic heart failure and therefore a major public health issue. Purpose Our objective was to better understand the genetic bases of dilated cardiomyopathy. Methods We conducted a 1000G based genome-wide association study for 9,152,885 SNPs on 2,719 sporadic DCM cases and 4,440 controls of European origin followed by a replication step. We then sought for the most likely culprit genes at the new replicated loci through a dedicated strategy including in silico data mining (including tissue specific gene expressions, expression and methylation quantitative trait loci) as well as functional 4C-sequencing analysis on iPSC-derived cardiomyocytes ( Fig. 1 ). Results We identified two new DCM loci, on chromosome 3p25.1 (lead SNP rs62232870, p = 8.7 × 10−11 and 7.7 × 10−4 in the discovery and replication steps, respectively) and chromosome 22q11.23 (lead SNP rs7284877, P = 3.3 × 10−8 and 1.4 × 10−3, respectively), while confirming two previously identified ones, BAG3 and HSPB7. A Genetic Risk Score was built from the number of risk allele at these four loci and revealed a 27% increased risk of DCM for individuals with 8 risk alleles compared to individuals with 5 risk alleles (median of the referral population). At chr3p25, our selection strategy pinpointed SLC6A6 as the most likely culprit gene. SLC6A6 encodes a taurine transporter whose involvement in myocardial dysfunction and DCM is supported by numerous observations in humans and animals. At the 22q11.23 locus, the same strategy strongly suggested SMARCB1 as the best candidate gene. Conclusion This study provides new insights in the genetic architecture of DCM and sheds light on novel biological pathways underlying heart failure, with the potential for a therapeutic perspective especially through taurine modulation.

Background Cardiomyopathies comprise a heterogeneous group of diseases, often of genetic origin. Genetic counselling and testing are recommended but the practices in real-life have not been evaluated. Purpose We assessed the current practice of genetic counselling and testing in the prospective ESC EORP cardiomyopathy registry. Methods and results 3208 adult patients from sixty-nine centres in 18 countries were enrolled. Genetic counselling was performed in 60.8% of all patients (75.4% in hypertrophic (HCM), 39.2% in dilated (DCM), 70.8% in arrhythmogenic right ventricular (ARVC) and 49.2% in restrictive cardiomyopathy (RCM), P Conclusions This is the first detailed report on the real-life practice of genetic counselling and testing in cardiomyopathies in Europe. Genetic counselling and testing were performed in a substantial proportion of patients but less often than recommended by European guidelines, and much less in DCM than in HCM and ARVC, despite evidence for genetic background.

Background Hypertrophic cardiomyopathy (HCM) is a genetic disease with delayed cardiac expression. Family screening strategy includes cardiac screening that may be guided by predictive genetic testing (PGT). However, little is known about the impact of PGT and the risk factors present at the very early stage of the disease. Purpose Our study aims to evaluate the impact of predictive genetic testing on the rate of initiation of cardiac screening, to estimate the penetrance of HCM and to determine the frequency of risk factors (RF) for sudden cardiac death in individuals at preclinical stage without HCM. Results We studied 60 consecutive relatives in a single center (31 women and 29 men, mean age: 34 ± 16.3 years) without history of HCM before genetic testing and who were mutation carriers after PGT. Cardiac screening was initiated before PGT in only 37%, and was started after PGT in 63%. Echocardiographic criteria for HCM were observed in 17% (28% of men but 6% of women, 17% of MYH7 mutation carriers but 0% in MYBPC3 carriers). Among mutation carriers without hypertrophy (n = 50), 1 had non-sustained ventricular tachycardia, 2 had non-explained syncope and 5 presented with family history of sudden death. In addition, 14% had dilated left atrium, 2% a high risk mutation and 8% practiced intense physical activity. Moreover, 10% (2/21) of carriers who performed MRI had cardiac fibrosis and 3% (1/32) of carriers who performed Holter monitoring had significant premature ventricular beat (PVB > 240/day). Conclusion The assessment of HCM causal mutations in relatives seems to be an important step to initiate cardiac screening. The penetrance of HCM seems to be higher in the male population and in MYH7 rather than in other genes mutation carriers. Mutations carriers at a preclinical stage without hypertrophy may have individual risk factors of sudden cardiac death. Further study of a larger population may be useful to confirm these results.

Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): CHU Rennes, Inserm, LTSI – UMR 1099, F-35000 Rennes, France Assistance Publique-Hôpitaux de Paris-Centre Université de Paris, University of Paris onbehalf REMY register Paroxysmal or chronic atrial fibrillation (AF) is frequent in hypertrophic cardiomyopathy (HCM),(20%-25% of patients), and is often considered as an important disease turning point. The aim of this study is to determine HCM-phenogroups with different risk of AF-occurrence at 5-year. We applied the Bayesian method to differentiate phenogroups of patients with different risks of AF across a French hospital registry of adult HCM(REMY). Data were prospectively recorded on 5 years follow-up. 1431 HCM patients were recruited, including 1275 analyzed. The population included 412 women. AF-occurred in 167 (11.6%) patients. 3 phenogroups were defined according to their common characteristics. Patients at the highest risk were more often female, with more frequent comorbidities, greatest anteroposterior LA diameter, diastolic dysfunction, outflow-tract obstruction or mitral valve abnormality, and presented higher sPAP or right ventricular dysfunction. These also had a higher risk of all-cause hospitalizations and death. Based on a clustering analysis, 3 phenogroups of HCM according to the risk of AF occurrence can be identified. It can indicate which patients should be more monitored. 3 different AF-risk groups Intermediate risk group n = 524 High-risk group n= 207 Low-risk group n = 544 P Gender = Males (%) 338 (64.5) 103 (49.8) 422 (77.6)

Background Saw-tooth Cardiomyopathy is a very rare disease, that should not be confused with left ventricular non compaction, and only few cases have been described. Methods and results We describe the case of a 33-year-old man who presented with atypical chest pain. The ECG showed left posterior fascicular block. Left ventricular non-compaction (LVNC) was initially suspected by echocardiography. Cardiac MRI found no criteria for LVNC but typical protrusions of muscular bridges in the left ventricle with dense compacted myocardium leading to the diagnosis of Saw-Tooth Cardiomyopathy. No arrhythmic event nor heart failure were noticed. In the family there was no cardiac history nor sudden death. We performed genetic analysis by sequencing a large panel of 71 genes associated with cardiomyopathies [Roche Nimblegen capture probes, sequencing on Miseq (Illumina)]. No pathogenic variant was found according to ACMG criteria ( Fig. 1 ). Conclusion Less than ten cases of Saw-Tooth Cardiomyopathy (ST-CMP) were previously reported in literature and ST-CMP was initially reported as a variant of LVNC. In fact, myocardial features of ST-CMP are very different from LVNC and ST-CMP should be considered as a separate entity. Some cases were discovered during infancy suggesting prenatal development. Our case first illustrates this distinct entity since none of LVNC criteria were met but typical Saw-tooth muscular bridges that were better exhibited on MRI. Second, our case is the first to report on genetic testing and familial investigations. We did not observed other cardiomyopathy in the family and we did not identify any pathogenic mutation in known cardiomyopathy genes. Although we cannot exclude a non-genetic cause, this result may suggest a genetic cause outside the genes usually related to cardiomyopathies and suggest the search for a new gene through exome or genome sequencing.

Background The EORP Cardiomyopathy Registry is a prospective, observational, multinational registry of consecutive patients with cardiomyopathies. The objective of this report is to describe the outcomes at one year of follow-up of adult patients (> 18 years old) enrolled in the registry. Methods A total of 3208 patients [median age: 55.0 (43.0;64.0) years, males: 65.1%] were recruited at baseline. Follow-up data at 1 year were obtained in 2,713 patients (84.6%), including 1420 with hypertrophic (HCM), 1,105 dilated (DCM), 128 arrhythmogenic right ventricular (ARVC) and 60 restrictive cardiomyopathy (RCM) ( Fig. 1 ). Results Improvement of symptoms (NYHA, chest pain, syncope) was globally observed over time (P Conclusions Despite symptomatic improvement in most cases, there is still a significant burden of arrhythmic and heart failure events in patients with cardiomyopathies. Outcomes were different not only according to cardiomyopathy subtypes but also in relatives versus index patients.

Introduction Hereditary heart diseases are most often characterized by autosomal dominant inheritance and delayed cardiac expression. Predictive genetic testing (PGT) is offered to asymptomatic relatives to allow targeted medical care with early therapeutics in order to reduce the risk of complications. Purpose The aim of this study was to evaluate the psychological and socio-professional impact of predictive genetic testing in hereditary heart diseases through a prospective and retrospective study. Methods & results This multicentric French study involved 20 expert centers in hereditary heart diseases. We included 517 adult relatives (42.3 ± 16.7 years, 60.6% females) who performed PGT (prospective study: n = 264, retrospective study: n = 253). The opinion and experience were collected via auto-questionnaires, at various moments in the prospective study, with different items and validated scales (STAI and IES). In the prospective study, family history was characterized by cardiomyopathy (88.4%) and channelopathies (11.6%). The main motivations for performing the test were: “to remove doubt” (65.3%), “for children” (64.0%), “to benefit from medical supervision” (34.9%). A mutation was present in 39.4% of relatives. No regret was expressed after testing (only 2.3% regrets). The result did not lead to a socio-professional change or family relationship change in 60.7%. Among those who had a change, it was perceived as unfavorable for only 3%. The level of anxiety (STAI) increases before the test result and decreased to return to baseline. Subjects with depression history were more likely to develop anxiety at long-term after multivariate analyses (P = 0.004). Conclusions Our results show that contrary to a widespread opinion, the medical benefit was not the main motivation for predictive genetic testing. In most cases, no or marginal adverse psychological and socio-professional impact of genetic testing was observed when performed by a team expert in predictive testing.

Background/Introduction Pathogenic variantsin FLNC encoding filamin C have been firstly reported to cause myopathies, and were recently linked to isolated cardiac phenotypes. Purpose Our aim was to estimate the prevalence of FLNC pathogenic variants in cardiomyopathies and to study the relations between phenotype and genotype. Methods DNAs from a cohort of 1150 unrelated index-patients with an isolated cardiomyopathy (700 hypertrophic, 300 dilated, 50 restrictive cardiomyopathies, and 100 left ventricle non-compactions) have been sequenced on a custom panel of 52 cardiomyopathy disease-causing genes. Results A FLNC pathogenic variant was identified in 28 patients corresponding to a prevalence ranging from 1 to 8% depending on the cardiomyopathy subtypes. Truncating variants were always identified in patients with dilated cardiomyopathy, while missense or in-frame variants were found in other phenotypes. This work reported for the first time a left ventricular non-compaction associated with FLNC pathogenic variant. In the cohort, nine patients (32%) were implanted with an automatic defibrillator. In 7 families (25%), history of sudden cardiac death (SCD) before 50 years was reported. A personal or family history of sudden cardiac death (SCD) was significantly higher in patients with truncating variants than in patients carrying missense variants (P = 0.01). Four patients died of cardiac cause including 3 from SCD and 1 from heart failure. Conclusion This work highlights the role of FLNC in cardiomyopathies. A correlation between the type of the variant and the cardiomyopathy subtype was observed as well as with SCD risk. These new data should be taken into consideration for patient's management and primary prevention of sudden cardiac death.

Introduction Hereditary heart diseases (cardiomyopathy & channelopathies) are most often characterized by autosomal dominant inheritance and delayed cardiac expression. The risk of complications of these diseases are sudden cardiac death and heart failure. Medical management allow to reduce significantly, but does not cancel, the risk of complications. If the causal mutation is known, couples with a pregnancy project may discuss the use of prenatal genetic diagnosis (PND) or preimplantation genetic diagnosis (PGD). The use of PND or PGD in these diseases is controversial and the medical, ethical and psychological issues are particularly complex. Purpose The aim of this study was (i) to collect at national level the procedures of PNDs and PGDs in the context of “isolated” hereditary heart disease; (ii) obtain the opinion of patients about this issue. Methods and Results The data collected with help of the French Biomedicine Agency show that 18 PND were carried out in France between 2009 and 2017 and 13 PGD between 2013 and 2017. So, number of PND and PGD for hereditary heart disease is rare in comparison of the relatively high prevalence of these diseases. The opinion of 20 patients (95% with cardiomyopathy), followed at Pitie-Salpetriere referral center for hereditary heart diseases, was prospectively collected via auto-questionnaires. Their answers show that few know the options (PND, PGD, gamete donation, adoption): only 25% are aware of all the alternatives. Despite this, 45% of patients mentioned that they did not want more information about these procreation options. Moreover, 45% consider the use of a PND to be fully acceptable or acceptable and 75% for the use of PGD, although they would not ask for themselves. Conclusions We report the first data about procreation procedures in France, and wishes of patients, in non-syndromic hereditary heart diseases. This may help to better manage these complex issues in clinical practice.

Introduction Hypertrophic cardiomyopathy (HCM) has a sarcomeric origin in more than half of cases. Correlations between a mutation presence and the clinical, electrical and echocardiographic phenotype are not clearly characterised. Aims To determine the link for HCM patients between the genotype/phenotype, and the impact of a found mutation. Method We studied a group of 104 patients with a HCM diagnosis (average age: 56 ± 15 years). Clinical, echocardiographic, electrocardiographic as well as genetic data were evaluated and compared. Results Genotype-positive patients were more likely to be younger (50,9 ± 17.5 years versus 39,9 ± 17.6, P Conclusion Genotype-phenotype link for HCM patients is low and both the ECG and the echocardiography are not relevant. The presence of a mutation is associated with an increased risk of sudden death. Genetic testing for HCM patients remains essential considering the impact of non-genetic factors.

Transient receptor potential vanilloid 4 (TRPV4) is expressed at the membrane of mouse ventricular myocytes and colocalizes with non-T-tubular L-type calcium channels. Deletion of trpv4 gene in mice results in shortened QT interval on electrocardiogram and reduced action potential duration of ventricular myocytes. Pharmacological activation of TRPV4 channel leads to increased action potential duration and increased calcium transient amplitude in trpv4−/− but not in trpv4−/− ventricular myocytes. To the contrary, TRPV4 channel pharmacological inhibition reduces action potential duration in trpv4+/+ but not in trpv4−/− myocytes. Integration of TRPV4 channel in a computational model of mouse action potential shows that the channel carries an inward current contributing to slowing down action potential repolarization and to increase calcium transient amplitude, similarly to what is observed experimentally. This study highlights for the first time the involvement of TRPV4 channel in ventricular electrical activity.

Introduction As opposed to ventricular arrhythmias (VA), clinical implications of atrial tachyarrhythmias (AT) in arrhythmogenic right ventricular cardiomyopathy (ARVC) remain scarcely explored. This study sought to evaluate the prevalence and prognostic significance of AT in ARVC. Methods In total, 171 patients diagnosed with ARVC between 1985 and 2018 in a single tertiary center were retrospectively included. Were defined as follows: AT: sustained atrial fibrillation, atrial flutter and focal atrial tachycardia; major adverse cardiovascular events (MAE) as a composite criterion including heart failure, cardiac assistance, transplantation, and death. Results After a median follow-up of 6 years (IQR 3 to 11), prevalence of AT, MAE and VA were respectively of 16%, 8% and 60%. AT occurred later in the disease course: mean age 54 ± 14.4, while 50% of patients had VA at diagnosis. Age at diagnosis (hazard-ratio [HR]: 1.05, 95% CI [1.02–1.08]; P Conclusion AT are common in ARVC and AT is associated with intensive sport activity and MAE. Our results mandate careful monitoring of ARVC patients with new-onset AT.

Background Screening for Fabry disease (FD) remains suboptimal in non-specialized centers. Aims We aimed to evaluate the diagnostic value of electrocardiographic (ECG) scores of left ventricular hypertrophy (LVH) and the diagnostic value of a combined ECG and echocardiographic model for FD. Methods We retrospectively reviewed the ECG and echocardiogram of 61 patients (age: 55.6 ± 11.5 years, 57% men) with FD and LVH, and compared them to 59 patients (age: 44.8 ± 18.3 years, 66% men) with sarcomeric hypertrophic cardiomyopathy (HCM). Six ECG criteria for LVH were specifically analyzed: – Sokolow-Lyon index, – Cornell voltage index 3) Gubner index, – Romhilt-Estes score, – Sokolow-Lyon voltage × QRS duration product, – Cornell voltage × QRS duration product. Results Right Bundle Branch Block (RBBB) was more frequent in FD (54% vs. 22%, P = 0.001). QRS duration, Gubner score, and Sokolov-Lyon product were significantly higher in FD. Maximal thickness wall (MTW) was higher in sarcomeric HCM group (21.9 ± 5.1 mm vs. 15.5 ± 2.9 mm in Fabry, P Conclusion Our model combining easy-to-assess ECG and echocardiographic parameters may be helpful to improve screening and reduce diagnosis delay of FD.

Background Dilated cardiomyopathy (DCM) is a disease with an increasingly recognized role of genetic background. However, the role of genetic variants on the prognosis of patients with DCM is still poorly understood. Objectives This retrospective study investigated the prognostic role of genetic variants in a cohort of independent DCM patients, excluding patients with a pathogenic variant on the LMNA gene. Methods 162 DCM index case patients were analyzed by next-generation sequencing using a panel of (at least) 51 genes involved in the disease. The following composite outcome measures were assessed severe ventricular arrhythmia (sustained tachycardia or fibrillation) or sudden death, and advanced heart failure defined by a heart failure death, heart transplantation or destination therapy left ventricular assist device implantation. Results We identified pathogenic variants in 50% patients in 22 genes; the most frequently involved genes were Titin (21% of variants), DSP (10%) and RMB20 (10%). Patients mutation carrier, as compared to non-carrier, had more frequently advanced heart failure (28% versus 9%, P Conclusions DCM patients who are mutation carrier are associated with more hemodynamic events than non-carrier. Genetic background may therefore be useful for prognostic stratification and management of DCM patients.

Background The etiological spectrum of hypertrophic cardiomypathies (HCM) is wide and some rare causes are largely underdiagnosed. Purpose Our aim is to assess the impact of the next generation sequencing (NGS) for the diagnosis of two rare genetic diseases: Fabry disease and hereditary transthyretin amyloidosis (GLA & TTR genes) in a population with HCM. Method We analysed 300 independent patients with HCM through a next generation sequencing (NGS) strategy using a panel of 107 genes involved in hereditary cardiomyopathies. The sequencing was performed by liquid-based capture of targeted areas (Nimblegen®) using HiSeq2500 device (Illumina®). The data were specifically reanalysed for this study, adjusting rules for pathogenicity interpretation based on ACMG guidelines and considering some high variant frequencies in these two genes. Results We studied 300 patients, 217 males & 83 females, mean age of 46 years. The NGS resulted in the identification of 266 variants (all classes included) in the 2 genes of interest (GLA: 189 variants, TTR: 77 variants). Further analysis led us to identify 4 causal mutations (pathogenic or probably pathogenic): 3 in GLA (p.Arg118Cys, p.Val269Ala, p.Ala143Thr) and one in TTR (p.Val142Ile). Fabry disease or amyloidosis were not diagnosed before NGS analysis. In the cohort, the prevalence was 1.3% for Fabry disease and 0.3% for ATTR. Conclusion NGS using a large panel is able to identify rare causes of HCM which were not previously suspected. The observed prevalences are comparable to those reported in the literature for the Fabry disease but are lower than those reported for the ATTR which could be due to the relatively young age of the patients in our analysed cohort. Our results support a systematic NGS screening with a large panel including GLA and TTR genes in patients referred for HCM. This screening is especially important as patients carrying Fabry or ATTR diseases may benefit from new specific therapies.

Background Appropriate advice for the practice of sport in patients with a cardiomyopathy is a challenging issue. Recent evolution towards more comprehensive and tailored recommendations may facilitate the clinical practice. However, neither their application in real life has been evaluated nor the concordance within clinicians. Methods We submitted six cases from real life to an expert panel of eighteen clinicians (7 cardiomyopathy experts, 7 arrhythmia experts, 4 sport physicians). The six athletes had Hypertrophic (HCM, n = 3), Dilated (DCM, n = 2), Right ventricular arythmogenic (ARVC, n = 1) cardiomyopathy. Advice for the practice of sport (competitive or recreational, globally or regarding the main usual activity of the athlete or according to detailed sports classification) was collected through a structured questionnaire. Results Experts authorize the practice of the usual sport in 28% of total cases. Global concordance within experts is significant but low (Kendall W = 0.34, P Conclusions Divergent advices were observed between experts regarding sports activity that can be authorized in athletes with a cardiomyopathy. Advices were also frequently discordant with recent European recommendations. These results underline difficulties for athletes’ personalized recommendation and the need for large prospective studies to progress towards optimal management.

Introduction Advances in human induced pluripotent stem cell (hiPSC) technology and the ability to create patient-derived hiPSC lines has raised the possibility for studying pathology-associated specific mutations consequences. However, studies focusing on cardiac pathologies suffer from the lack of maturity of hiPSC-derived cardiomyocytes (CM) cultured in 2D conditions, the difficulty for measuring physiologic parameters such as contractility because of their impaired cellular structure, and the lack of organized interfaces between CM. EHT, which were shown to favor hiPSC maturation both at the intra- and intercellular levels, represent a promising tool to overcome these hurdles. Objective We describe the establishment of the EHT technology together with readouts to assess CM maturation degree. Methods hiPSC were differentiated into CM through a small molecule-based protocol. 3D strip-format fibrin-based EHT were then generated from freshly isolated CM and kept in culture for > 3 weeks under auxotonic stretch conditions to allow progressive CM maturation. Results Over the culture period, the force developed by the EHT, contraction-relaxation parameters and beating frequency–reflecting together CM maturation–were assessed by video-optical recording. MUSCLEMOTION® was used for data extraction. At the end of the culture period, EHT were fixed for intracellular structures evaluation via immunofluorescence. Conclusion We report the successful establishment of a standardized protocol combining hiPSC differentiation into CM and their subsequent use for EHT production. We show that CM casted in 3D EHT submitted to auxotonic stretch conditions exhibit signs of advanced maturation. These results raise the possibility of the EHT technology transposition to patient-derived iPSC lines allowing for comparative studies between mutation carrying and isogenic control cell lines to define the impact of precise genetic mutations on CM contractile function and structure.

Introduction The right ventricular outflow tract (RVOT) is the main origin of idiopathic ventricular tachycardia (IVTs). Sympathetic stimulation is involved in IVTs but mechanisms underlying this preferential origin remain unknown. Objective To determine the role of s1- and s2-adrenergic receptors (s1-AR, s2-AR) in the regional modulation of right ventricular (RV) electrophysiological properties and arrhythmias. Methods Porcine RVs were isolated and perfused via both right and left coronary arteries. Epicardial (EPI) electrical activity was optically mapped (di-4-ANEPPS 20 μM) and APD measured at 80% repolarization (APD80) in the RVOT and posterior RV free wall region (RVFW). Regional mRNA and protein expression for s1-AR and s2-AR was determined respectively by RT-PCR and Western-Blot. Results Combined s1- and s2-AR stimulation (50 nM isoprenaline, ISO) shortened APD80 EPI with a larger effect in the RVFW than the RVOT. Interestingly, isolated s2-AR stimulation (10–25 μM salbutamol, SALBU with 4 μM metoprolol, METO) only decreased APD80 significantly in the RVOT EPI (P Conlcusion These results suggest a s2-AR specific regulation of RVOT electrophysiology but its role in the triggering of arrhythmias in this region requires further studies.