AbstractBackgroundArrhythmogenic Cardiomyopathy Research Articles

Transcriptome and methylome analyses of stromal cells from ACM patients reveal the additional role of alterations in mitochondrial homeostasis and chromatin organization in disease pathogenesis

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a rare genetic disorder of the heart, characterized by ventricular arrhythmias and contractile dysfunctions, which can cause sudden cardiac death and heart failure. Typically, the hallmarks of ACM ventricular myocardium are cardiomyocyte death, inflammation and fibro-adipose replacement, resulting in electrical and mechanical abnormalities of the tissue. Cardiac mesenchymal stromal cells (CMSC) participate to disease pathogenesis by differentiating towards adipocytes and myofibroblasts. Some altered pathways in ACM are known, but many pathogenetic molecular mechanisms are yet to be discovered. Purpose Our work aims to contribute to a comprehensive understanding of the pathogenic mechanism occurring in ACM, focusing on the molecular pathways underlying stromal cell involvement, through the functional validation of gene expression and epigenetic profile of ACM-CMSC. Methods We conducted total RNA transcriptome and DNA methylome analyses in ACM- and healthy control (HC)- CMSC to identify pathways differentially regulated in the two groups. We performed category enrichment and gene network analyses and we built transcript functional networks. To validate our findings, we measured the protein levels coded by selected genes differentially expressed by Western Blot analysis and we evaluated the relative pathways, such as mitochondria homeostasis, proliferation rate and epithelial-to-mesenchymal transition (EMT) through cytofluorimetric analyses. Results By transcriptomic analysis we found 529 genes differentially expressed; in particular, 327 genes were more expressed and 202 less expressed in ACM- vs HC-CMSC. Among those with the highest logFC and the lowest p value, we identified COX7C (implicated in mitochondrial respiration), S100A11 (involved in EMT) and CCND2 (one of the promoters of the cell cycle), whose protein expression was validated. Through the enrichment and gene network analysis we identified some pathways differentially regulated in ACM vs. HC. Some of these are known to be altered in ACM hearts, as matrix homeostasis and cell junction arrangement. Other pathways have never been associated to ACM, such as mitochondrial functioning and chromatin organization. By the DNA-methylation investigation, we identified 74 differentially methylated nucleotides and most of them were located on the mitochondrial genome. We also found that ACM-CMSC exhibited a greater number of mitochondria and a greater amount of mitochondrial reactive oxygen species than HC. Furthermore, ACM-CMSC showed a higher proliferation rate and a more pronounced EMT, compared to controls. Conclusions ACM-CMSC -omics revealed some new altered molecular pathways, not yet explored, which are relevant in the pathogenesis of the disease and may constitute novel targets for specific therapeutic approaches.

Cardiomyocyte - stromal cells interplay as a novel platform for mechanistic insights in arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic Cardiomyopathy (ACM) is an inherited heart disorder characterized by a high incidence of sudden death at young age. Mutations linked to ACM occur primarily in desmosomal genes (e.g. PKP2) [1]. Different cell types individually contribute to set the ACM phenotype with either functional abnormalities (cardiomyocytes; CM) [2]; or fibro-fatty substitution (cardiac mesenchymal stromal cells; CMSC) [3]; these two cell types interact and show a reciprocal influence [4]. The relative contribution of the different cell type derangements to determine disease evolution and electrical instability is still unclear. Purpose Based on this evidence, we hypothesize that the use of a multicellular cardiac system, modelling the functional interaction between CM and CMSC, will allow the understanding of the relative contribution of the different cell types to the ACM phenotypes. Methods Primary stromal cells (carrier of the PKP2 mutation c.2013delC) have been collected from a right ventricle biopsy sample; control stromal cells obtained from a biobank. iPSC reprogrammed from the same ACM patient and the isogenic line in which the PKP2 mutation c.2013delC was corrected [5] were used. Cardiac cocultures (cc) were assembled by combining 85% iPSC-CM and 15% primary CMSC, either mutated or control, in different combination (as in Table 1). Movies of contracting clusters have been collected and analysed by the MUSCLEMOTION tool [6]. Fibro-fatty accumulation have been evaluated by immunofluorescence analysis by confocal microscopy. Results Immunofluorescence analysis highlighted that ACM cc (cc 4) accumulate more lipids and collagen than healthy control (HC) ones (cc 3). Since intermediate fibro-fatty levels were observed in ‘mixed cc’ (cc 1 and 4), we conclude that ACM iPSC-CM are able to influence fibro-adipo-commitment of CMSC. Contraction studies showed a high propensity for cc monolayers which include ACM iPSC-CM (cc1 and cc2) to display arrhythmic events. An increase in the percentage of arrhythmic events was triggered when the ACM CMSC were replacing HC CMSC, indicating that ACM CMSC can affect iPSC-CM rhythm. Conclusion Overall, our data confirm the importance of the cardiomyocytes and stromal cells interplay during ACM pathogenesis. Furthermore, our novel advanced ACM cell model can recapitulate different phenotypes of ACM and offers a unique opportunity for validating pharmacological therapies to modulate ACM-related characteristics (e.g. fibro-adipose replacement, contractile defects and proarrhythmic events).

Stromal cell models of arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disease mainly associated with mutations in genes encoding cardiac desmosomes, most frequently Plakophilin-2 (PKP2). Primary cardiac mesenchymal stromal cells (CMSCs) were shown to contribute to the aberrant ACM cardiac remodeling based on their ability to differentiate into adipocytes and myofibroblasts, thus representing a useful in vitro model for the disease. The limitations associated with access to biopsies and finite passages in culture have been overcome by the advancement of stem cell technology, especially human induced pluripotent stem cells (hiPSCs) and their ability to differentiate towards cardiac stromal population. Specifically, CMSCs from hiPSCs provide a virtually unlimited cell sources that are genetically identical to patient cells of origin. Purpose The study compares hiPSC-derived stromal cells (hiPSC-D) and primary stromal cells (PRs), to explore the feasibility to use iPSC-D as an alternative in vitro model to study ACM. Methods PRs were isolated from ACM patients and healthy donors (HC). hiPSCs from a PKP2 mutated ACM patient (c.2013delC) and a sex/aged matched HC were used to produce iPSC-D. Flow cytometry analysis and specific differentiation induction (osteogenic, chondrogenic, adipogenic and pro-fibrotic) were performed to confirm mesenchymal lineage and multipotency. qRT-PCR and western blot analysis were performed to evaluate the expression of desmosomes, both gene and protein levels. Illumina transcriptomic profiling of both PRs and iPSC-D were compared and enriched pathways were identified by GSEA. Results Both PR and iPSC-D cells expressed mesenchymal surface markers and were able to differentiate towards osteogenic, chondrogenic, adipogenic and myofibroblast lineages. Desmosomal genes and proteins were expressed by both populations, showing a general trend toward lower expression of desmosomal markers in ACM compared to HC cells. Overall, higher expression of desmosomes was observed in iPSC-D stromal cells compared to their primary counterparts, independently on the genotype. As occurs for PRs, ACM iPSC-D exhibited an increased propensity to accumulate lipid droplets and collagen compared to HC cells. Moreover, both cell populations shared a highly similar transcriptomic profile, showing a significant linear correlation (R=0.85). Interestingly, PRs were enriched for genes associated with the immune response and differentiation processes, hinting to the hypothesis that an inflammatory stimulus received from the cardiac tissue might activate the innate immunity and drive the cell differentiation fates in the PRs. Conclusion(s) Both PR and iPSC-D cardiac stromal cells obtained from ACM patients can be used to model the disease, where the choice for the most suitable cell populations can be determined by the experimental strategy and/or the availability of human primary material.

Arrhythmogenic cardiomyopathy phenotype associated with the pathogenic founder variant c.1211dup in PKP2

Abstract Background Arrhythmogenic cardiomyopathy results in life-threatening ventricular arrhythmia and heart failure. Phenotypic features vary according to genetic aetiology. Genotype-phenotype research is therefore crucial for patient counselling and treatment decisions such as implantable cardioverter defibrillator therapy. By collecting data from patient records we characterized the clinical phenotype associated with variant c.1211dup (p.Val406Serfs*4) in the plakophilin-2 gene (PKP2), common in the Dutch population. Purpose We aimed to investigate the incidence of ventricular arrhythmia and heart failure in families carrying the PKP2 c.1211dup variant. Furthermore, we aimed to determine the founder status of this variant, and compare phenotype severity with other truncating PKP2 variants. Methods Clinical data were collected retrospectively from medical records of 106 PKP2 c.1211dup heterozygous carriers (>85% of known carriers in The Netherlands) in a Castor EDC database. Using occurrence of ventricular arrhythmia and heart failure, event-free survival was compared between males and females, and probands and family members, using log-rank tests. Using data from a central curated arrhythmogenic cardiomyopathy database, c.1211dup was compared to three other truncating PKP2 variants (c.235C>T (p.Arg79*), c.397C>T (p.Gln133*) and c.2489+1G>A (p.?)) on ventricular arrhythmia-free survival by a Cox proportional hazards model, corrected for sex and proband status. Results Forty-seven carriers (44%) were diagnosed with arrhythmogenic cardiomyopathy at 41 years on average. As shown in figure 1, 29 participants (27%) experienced episodes of ventricular arrhythmia and 12 (11%) developed heart failure, with male carriers showing significantly higher risks than females on both endpoints (p<0.05). Based on available magnetic resonance imagery and echocardiographic data, 46% of carriers showed either right ventricular dilatation and/or dysfunction, and a substantial minority of 37% showed some form of left ventricular involvement. Both geographical distribution of carriers (figure 2) and haplotype analysis suggested PKP2 c.1211dup to be a founder variant originating from the South-Western coast of the Netherlands. Finally, a Cox proportional hazards model suggested significant differences in ventricular arrhythmia-free survival between four PKP2 truncating founder variants, including c.1211dup. Conclusions The PKP2 c.1211dup variant is a Dutch founder variant associated with a typical right ventricular-dominant arrhythmogenic cardiomyopathy phenotype, but also notable left ventricular involvement. Males were most susceptible to the frequent ventricular arrhythmia, and less frequent heart failure was observed in general. Finally, c.1211dup possibly leads to a more severe phenotype than other Dutch PKP2 founder variants.Phenotype onset stratified by sexGeographic distribution carriers

C79 NEGATIVE T WAVES ON ECG: NOT JUST HYPERTROPHIC CARDIOMYOPATHY

Abstract Background Arrhythmogenic cardiomyopathy is still considered a rare and difficult–to–diagnose condition, yet a well–founded clinical–instrumental suspicion and proper diagnostic procedure can unveil this condition early from common instrumental findings. Clinical Case In September, a 34–year–old man presented to our center for the presence on the electrocardiogram of ventricular repolarization changes (negative T waves in D1, inferior site and in all precordial leads with mild ST elevation in V1– V2). He denied family history of cardiological events. In 2018, following a suspected preoperative EKG, he performed an echocardiogram and cardiac magnetic resonance imaging (CMR); these examinations showed mild left ventricular hypertrophy with preserved systolic function. Clinically, the patient reported rare episodes of palpitation presented on ambulatory EKG with the same repolarization changes as mentioned above. In consideration of the clinic–instrumental findings, a diagnostic workup with echocardiogram and CMR was started for suspicion of hypertrophic cardiomyopathy in the first hypothesis. On echocardiogram, an non dilated left ventricle was found with left ventricular ejection fraction, parietal thicknesses, and segmental kinetics within normal limits, in the absence of significant valvulopathy; however, frequent ventricular extrasystoles were reported during the examination. Given the EKG–graphic alterations, although there weren‘t any echocardiographic changes, a CMR was performed, showing extensive irregularity of the epicardial profile of the lateral and infero–lateral mid–apical wall, site of adipose infiltration, in which evidence of intramyocardial late gadolinium enhancement (LGE) was also present; the right ventricle showed extensive microbulging of the mid–basal free wall in the absence of adipose replacement or LGE. In view of the clinical–instrumental pattern, the diagnosis of "left dominant" arrhythmogenic cardiomyopathy with initial involvement of the right ventricle was made. Conclusions EKG–graphic interpretation may in some cases be the only instrumental data underlying clinical suspicion of arrhythmogenic cardiomyopathy, allowing early diagnosis of a condition at high risk of sudden cardiac death.

142 ADVANCED HEART FAILURE IN PATIENTS WITH ARRHYTHMOGENIC CARDIOMYOPATHY

Abstract Background Arrhythmogenic Cardiomyopathy (ACM) is a primary disease of the heart muscle, characterized by fibro-fatty myocardial replacement. Improvements in the clinical diagnosis and antiarrhythmic therapy, including the use of the defibrillator (ICD) and endo-epicardial catheter ablation, have increased the survival of these patients, who experience late complications such as advanced heart failure, which sometimes requires cardiac transplantation. Aim of the study To evaluate clinical, instrumental and genetic features of patients affected with ACM who developed heart failure (HF) and to sought for possible predictive factors of HF. Methods From the entire cohort of probands and family members followed at the Cardiomyopathy unit of our University (555 patients), 34 patients (29%), both probands (n= 26, 77%) and family members who experienced HF (6%) were selected (24 males, 71%). Their anamnestic, clinical, and instrumental data were compared with those without episodes of HF (n-HF). Results The mean age at diagnosis in HF cohort was 45.2 (±18) years. In 14 patients (41%) HF was the first symptom that led to diagnosis. According to 2010 TFC 30 patients (88%) had a definite diagnosis of ACM. The most frequently observed phenotype was the biventricular ACM (n=27, 79%). A disease-related genetic variant was found in 18 (53%) and DSP was the more common disease-gene, accounting for 24% of cases. The mean duration of follow-up was 12.6 (±11.0) years (min-max, 1-20 years). During this period a total of 14 subjects (41.2%) experienced life-threatening arrhythmias (LTA), while 13 patients (38.2%) died, of whom 11 (84.6%) because of refractory HF. Eighteen patients (53%) underwent cardiac transplantation (mean age 43±17 years), approximately 4 (±3.5) years after the onset of symptoms. Comparison with the n-HF cohort of ACM patients showed a significant difference on presence of T-wave inversion (TWI) in V1-V3 (p=0.001), TWI in V4-V6 (p=0.010), low QRS voltages both in precordial and limb leads (both p<0.001) and presence of left bundle-branch block and right bundle-branch block (both p<0.001). Regarding CMR, HF cohort was characterized by a significantly more dilated right and left ventricle EDV (both p<0.001), EF reduction (both p<0.001), presence of wall motion alterations (respectively, p=0.007 and p<0.001) and LGE (respectively, p=0.002 and p=0.005) compared to n-HF group. Regarding outcomes evaluation, the HF group showed more frequently LTA (HF=41.2% vs n-HF 21.5%, p=0.008). Finally, the presence of right bundle-branch block at ECG (OR=20.562, CI 1.884-224.413, p=0.013) and of impaired RV ejection fraction (OR=0.821, CI 0.719-0.937, p=0.004) were found to be independent predictors of HF. Conclusions Heart failure is a rare complication in patients affected with ACM, with a prevalence of 6% in our study. The mean age of onset of HF was 45.2 (±18) years. Furthermore, 18 patients (53%) had an unfavorable progression to heart transplantation. The presence of right bundle branch block at ECG and an impaired CMR RV-EF were found to be predictors of HF. Our results suggest the importance of scheduling a close follow-up in ACM patients who show initial signs and/or symptoms of HF, taking into consideration the fast rate of progression to refractory HF, once established.

979 ARRHYTHMOGENIC CARDIOMYOPATHY: LONG-TERM FOLLOW-UP OF A PROSPECTIVE MULTICENTRE COHORT

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is an inherited heart muscle disease characterized by fibro-fatty replacement of predominantly right, left or biventricular myocardium. The clinical course of ACM is characterized by high risk of abrupt arrhythmic ventricular events, potentially leading to sudden cardiac death (SCD), and by progressive impairment of biventricular systolic function, which may lead to heart failure (HF)-related death, with an estimated overall yearly mortality ranging from 0.08% to 3.6% among studies. Aim This study sought to assess the long-term follow-up of a cohort of ACM patients from the Piedmont region of Italy, specifically evaluating the cumulative incidence of SCD, HF-related death and heart transplantat. Methods Patients who received a definite ACM diagnosis according to the latest available International Task Force Criteria (ITFC) at three different institutions in Piedmont (“Cardinal Massaia” Hospital of Asti, “Azienda Ospedaliera Ordine Mauriziano” of Turin and “Città della Salute e della Scienza” Hospital of Turin) between 1982 and March 2022 were prospectively enrolled. Clinical, electrocardiographic and imaging data were collected at baseline and during follow-up. The occurrence of two coprimary composite endpoints was evaluated, namely the arrhythmic composite endpoint of SCD or aborted SCD and the HF-related composite endpoint, including heart transplant for end-stage HF or cardiac death due to pump failure. Independent predictors of the coprimary composite endpoints were also assessed by means of multivariable analysis. Results The overall population included 97 patients; mean age at diagnosis was 38.2 ± 14.3 years; 66 (68%) patients were male. Median follow-up was 12.9 years (interquartile range 0-38 years). The composite arrhythmic outcome occurred in 10 (10.3%) patients and the composite HF outcome occurred in 13 (13.5%) patients. Overall, 19 (19.6%) patients died: seven (37%) patients died from SCD, four (21%) patients died of end-stage HF and eight (42%) patients died from non-cardiac causes. The cumulative incidence of cardiac death was 1.65% per year. Aborted SCD occurred in 3 (3%) patients, sustained ventricular tachycardias in 51 (52%), HF in 17 (18%) and atrial fibrillation in 21 (22%); forty-seven (48%) underwent an implantable cardioverter defibrillator implantation (ICD) and 8 (8%) patients underwent heart transplant. Mean interval between ACM diagnosis and heart transplant was 130.4 ± 75.3 months. At univariable analysis, the presence at baseline of terminal activation duration (TAD) ≥ 55 ms on surface electrocardiogram (p value 0.037), right atrium dilatation at transthoracic echocardiography (p value 0.021) and cardiac magnetic resonance imaging (p value 0.031) and palpitations as main clinical presentation (p value 0.017) were associated with the occurrence of the arrhythmic endpoint. At multivariable analysis, baseline TAD ≥ 55 msec was the only predictor of the composite arrhythmic endpoint (odds ratio 12.5, 95% confidence interval 1.29 to 121.26, p value 0.029). At univariable analysis, the presence of epsilon waves (p value 0.017), TAD ≥ 55 ms (p value 0.020) and T wave inversion in leads V1-V3 (p value 0.022) on surface electrocardiogram, HF (p value 0.018) or atrial arrhythmias (p value < 0.001) at presentation and New York Heart Association (NYHA) class III to IV at diagnosis (p value 0.002) were significantly associated with the composite HF-related endpoint. At multivariable analysis, the presence of atrial arrhythmias at presentation was the only predictor of the HF-related composite endpoint (odds ratio 10.8, 95% confidence interval 1.29 to 90.32, p value 0.028). Conclusions In this multicenter cohort of 97 ACM patients, the cumulative incidence of cardiac death was 1.65% per year at long-term follow-up. Arrhythmic death accounted for the majority of cardiac fatal events (64%), confirming the peculiar predisposition to SCD of ACM patients. Evolution towards end-stage HF and cardiac death due to pump failure were common.

240 A PEDIATRIC CASE OF BIVENTRICULAR END-STAGE ARRHYTHMOGENIC CARDIOMYOPATHY

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a rare heart muscle disease characterized by cardiomyocyte necrosis and fibro-adipose substitution which contribute both to the genesis of malignant ventricular arrhythmias and the morpho-functional alterations of the ventricles. ACM has always been considered a right ventricular disease with secondary involvement of the left ventricle, but recently a left dominant phenotype has been also described. Case report A 14-year-old patient was admitted to our hospital after out-of-hospital cardiac arrest due to ventricular fibrillation, which occurred when she was at rest. A family history of sudden death and dilated cardiomyopathy was retrieved (her brother died at the age of 18 with a dilated heart), but other family members had never been screened to date. Cardiac magnetic resonance imaging (cMRI) appearance was consistent with biventricular dilatation along with severe systolic dysfunction (left ventricular ejection fraction 20%; right ventricular ejection fraction 25%). It showed also thinning and bulging of the basal free wall of the right ventricle proximal to the outflow tract (up to 4 mm) and multiple foci of subepicardial, mid-wall and transmural late gadolinium enhancement (LGE) in both ventricles. Signs of acute decompensated heart failure and a high arrhythmic burden were present. After cardiopulmonary stabilization, she underwent the implantation of a cardioverter-defibrillator (ICD). Conclusion We herein report an uncommon case of biventricular AC (‘definite diagnosis’ according to both Task force criteria 2010 and Padua criteria) with advanced morpho-functional dysfunction occurring already in pediatric age, without any alerting symptom until the cardiac arrest (the typical onset of the ACM in children). It shows how severe biventricular involvement may affect young patients with a rapid progression of the disease. It also stresses the need for a strict follow-up of the family members of a proband since his first diagnosis, highlighting the pivotal role of cMRI in the diagnosis of pediatric disease. This has not been thoroughly studied and lacks sensitive and specific diagnostic criteria.

1102 ARRYTHMOGENIC CARDIOMYOPATHY: LESSONS FROM A LARGE FAMILY

Abstract Background Arrhythmogenic cardiomyopathy is a genetically-inherited cardiomyopathy. PKP2 mutations are the most common cause of the disease, associated with conventional ARVC phenotype. Case presentation We presented a 14 years old sportswoman admitted to our emergency department for cardiac arrest-related to ventricular fibrillation. The patient was asymptomatic leading up to cardiac arrest. At admission, she met the diagnosis of AC with bi-ventricular involvement (T negative waves in V1-V6 and inferior leads; severe biventricular dysfunction with fibrofatty replacement involving both ventricles). Family history revealed that her cousin, a 15 years competitive athlete, received a recent diagnosis of ARVC, wherein pathogenetic variant p.Tyr857_Lys859 in heterozygosity in the PKP2 gene was found. As expected, the index case presented the same mutations in PKP2 gene, and no other mutations were found. Implanted cardioverter defibrillator (ICD) and strength follow-up, including heart failure management, was performed. Cascade screening of family members allowed us to identify 19 mutations carriers. Of these, 5 patients were identified to have disease expression. The first to be studied was her 9 years old sister, who involved in high level of sport activities. She presented abnormal ECG with negative T waves in V2-V4, significance burden of premature ventricular complex (PVC >500/24 h) with mild right ventricle dilatation. Of others family members, four patients presented early signs of myocardial disease and significant arrhythmias burden. Except for one patient, all these members were involved in amateur sport activities. Two members had signs of left ventricle (LV) involvement (inverted T waves in leads V4–V6 and inferior leads, LV wall motion abnormalities and late enhancement), whereas one patient (P3) showed a fulfilled ARVD. Three patients presented significant PVC on 24-hour ambulatory ECG monitoring (PVC >500/24 h) (P2, P3 and P5). The arrhythmic burden was more pronounced in two young patients having a sports activity (P2 and P3). This trend was also confirmed at exercise testing. Except for one patient, these findings appear to be related to sport activity, even if this is no high-intensity activity. Among other carriers of pathogenic mutation, three patients showed ECG abnormalities in infero-lateral leads and significance PVC at 24-hour ECG monitoring in absence of other findings related-cardiomyopathy. All family members carried PKP2 mutation were restricted in sports activities, and, in patients presented early disease and arrhythmogenic burden, treatment with beta-blockers was started. Conclusion In this family presenting PKP2 mutation, heterogenicity of disease expression and a close relationship with sport activity was found. This large family case encourages future ACM studies to better understand disease expression and their relationship with sports activity across the entire ACM phenotypic spectrum and ages. Also, this case underscores the importance of early familiar screening, including children involved high-level of sports activity.

Highly malignant disease in early-onset arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic cardiomyopathy (AC) is an inheritable and progressive cardiomyopathy characterized by high risk of ventricular tachyarrhythmias and sudden cardiac death. Pediatric patients are underrepresented in AC publications, and the AC penetrance and incidence of cardiac events in children have yet to be determined. Current guidelines recommend initiating family screening in first-degree relatives after age 10–12 years, but the clinical value of this approach has not been systematically evaluated. Purpose We aimed to explore the incidence of severe cardiac events in pediatric patients with AC and to describe the phenotype in early-onset AC. Furthermore, we wanted to estimate the penetrance of AC disease in genotype positive pediatric family members. Methods In a single-center follow-up study, we included consecutive AC pediatric patients and genotype positive family members ≤18 years of age. The patients were followed regularly with electrocardiographic, structural and arrhythmic characteristics according to the AC 2010 Task Force Criteria (TFC). Penetrance of AC disease was defined as fulfilling definite AC diagnosis by the 2010 TFC. We defined severe cardiac events as cardiac death, heart transplantation (HTx) or severe ventricular arrhythmias (VAs) (sustained ventricular tachycardia or aborted cardiac arrest). Results We included 62 individuals (11 probands, 51 family members). Fourteen events (5 HTx, 9 VAs) occurred during 6±4 years of follow-up, giving a cumulative incidence of 23% and a yearly incidence rate of 4%. Seven (50%) events occurred in patients ≤12 years of age (Figure 1). All children who underwent heart transplantation were ≤12 years. At inclusion, 13 patients (21%) fulfilled definite AC diagnosis (10 probands, 3 family members). At end of follow-up, AC diagnosis were fulfilled in 20 (32%) patients (11 probands, 9 family members), indicating progression of disease in 7 patients. Mean age at definite AC diagnosis was 13±4 years and 8 patients (40%) were ≤12 years old (Figure 1). All patients diagnosed with AC <12 years of age had biventricular disease with mean LVEF 30±9% and right ventricular fractional area change 21±5% at end of follow-up. Among the family members, 5 (10%) had signs of AC disease at the time of genetic diagnosis. At end of follow-up, AC penetrance was 18% and 3 (6%) experienced severe cardiac events at a mean age of 13±6 years. Conclusion In a pediatric AC cohort of probands and genotype positive family members, we found a high incidence of VA and HTx. Half of the events occurred in children ≤12 years of age, supporting a markedly severe phenotype in early-onset AC. AC penetrance among pediatric family members identified by screening was high, with a significant incident of events. Our findings emphasize the high risk features of early-onset AC disease and indicate a need to start AC family screening in children at an younger age than recommended by current guidelines. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Norwegian Research Council

Spectrum of rare and common genetic variants in arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a rare inherited cardiac disorder, whose genetic cause is elusive in about 50% of cases. ACM pathogenic mutations mainly involve desmosomal genes (PKP2, JUP, DSP, DSG2, DSC2). ACM presents a variable disease course, spanning from mild electrocardiographic alterations and/or contractile dysfunctions, to malignant ventricular arrhythmias and heart failure. Purpose In an attempt to broaden etiological diagnosis for ACM patients, this work was aimed at finding potential rare high-impact variants in genes not previously associated with ACM. Secondarily, we meant to assess the impact of genetic polymorphisms on the disease clinical severity. Methods We clinically characterized 82 consecutive ACM probands and performed next-generation sequencing, exploring a panel of 174 genes associated with inherited cardiovascular diseases. We evaluated the pathogenicity of rare variants, according to the American College of Medical Genetics / Association for Molecular Pathology guidelines, to select candidates with potential ACM causative role. Further, a genotype-phenotype correlation analysis between common polymorphisms and clinical variables was performed to find genetic factors associated with specific ACM phenotypes. Finally, we carried out event-free survival analyses, linking specific variants to arrhythmias in 8,6±0,7 years follow-up, to estimate their possible impact on arrhythmic risk. Results We identified 141 rare genetic variants, of which 23 were classified of high impact, including variants in genes never associated with ACM (e.g. ABCC9, APOB, MIB1). These genes deserve future studies as they could participate in ACM pathogenesis. In addition, we found 69 genotype-phenotype significant associations (p≤0.005) between common variants and clinical parameters. Variants associated to arrhythmic phenotypes were found with genes linked to arrhythmias (e.g. KCNQ1, HCN4) and other cardiomyopathies (e.g. MYBPC3, MYL2). Associations involving substrate impairments were found with genes linked to muscle dysfunctions (e.g. LAMA2, SGCD). Arrhythmia-associated polymorphisms, included in survival analyses, were found to be associated with an increased occurrence of arrhythmic events during patients' follow-up. Conclusion The identification of rare high impact variants in novel genes potentially associated with ACM and the observation of genotype-phenotype correlations constitute the starting point to address the current lack of knowledge of the genetic landscape of ACM. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministero Italiano della Salute - Ricerca corrente

C63 PHENOTYPE – GENOTYPE RELATIONSHIP IN ARRHYTHMOGENIC CARDIOMYOPATHY

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a primary disease of the myocardium with arrhythmic manifestations and fibro–fatty replacement either of the right (RV) or the left ventricle (LV) at the cardiac magnetic resonance (CMR). Over the last decade, different mutations in cardiac genes associated with heterogeneous phenotypes have been identified. Aim To investigate the genotype–phenotype relationships in ACM patients. Firstly, the phenotypic expression was defined in definite mutation carriers. Secondly, the prognostic significance of mutations was assessed across different phenotypes. Methods The study population included 281 patients with suspected ACM, based on family history, clinical and electrocardiographic evaluation, echocardiographic and CMR findings (Fig.1), studied at our Institution since 2012. All patients underwent genetic evaluation using Sanger sequencing and NGS of mutations in desmosomal (desmoplakin [DSP], plakophilin–2[PKP2], plakoglobin[JUP], desmoglein–2 [DSG2], desmocollin–2 [DSC2]) or non desmosomal genes. The composite endpoint included cardiac death, sustained and non–sustained ventricular tachycardia (VT), ventricular fibrillation (VF), appropriate defibrillator shock/antitachycardia pacing (ATP). Results The genetic test was positive in 113 patients (40%), 82 (73%) for desmosomal genes (41 DSP, 15 DSG2, 15 PKP2, 5 JUP, 6 DSC2), and 31 (27%) for non–desmosomal genes (4 titin, 2 TMEM 43, 2 lamin A/C, 23 others). Gene–positive compared to gene–negative (n = 168, 60%) patients showed a higher prevalence of LV ejection fraction (EF)<50% (14%vs.6%, p<0.011), LV and RV LGE (62%vs.46%, p < 0.001, 20%vs.12%, p<0.02), RV dilatation (27%vs.17%, p<0.041) (Table 1). DSG2 mutations were associated mainly to biventricular (7/15,46%) or RV involvement (4/15,26%), while DSP mutations to LV involvement (24/41,58%). During a median 36–month follow–up (IQ.range 12–56), 55 patients (19%) experienced the composite endpoint (35 non–sustained VT; 11 sustained VT – 3 ATP, 1 defibrillator–shock–; 9 VF, all treated by defibrillator–shock). At Kaplan–Meier analysis, DSP mutations were associated with the worst prognosis (Fig. 3). Conclusion Diverse genotypes were differently associated with LV dysfunction/LGE, RV dilatation/LGE. DSP mutations were associated with higher arrhythmic risk. Genetic screening may result in a better risk stratification, useful for clinical decision–making.

Generation and phenotyping of a novel knock-in mouse model of desmoplakin dependent arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic Cardiomyopathy (AC) is a genetic cardiac disorder, mainly caused by mutations in genes encoding desmosomal proteins, and accounts for most stress-related arrhythmic sudden cardiac deaths (SCD) in the young and athletes. The AC myocardium is hallmarked by cardiomyocyte (CM) death and fibro-fatty replacement, which generate a pro-arrhythmogenic substrate. Several pathogenetic factors in AC remain obscure and better understanding of the disease mechanisms is required to develop novel efficacious therapies to prevent SCD, which are sorely missing. The lexical analogy between desmosomes and desmosomal proteins has originally biased AC research towards CMs, the paradigmatic desmosome-bearing cells in heart. However, the myocardium is composed by different cell types, many of which express desmosomal proteins, albeit in the absence of desmosomes, including CMs, sympathetic neurons, vascular cells and fibroblasts. Notably, AC mutations are transmitted at germline, and thus may manifest in all cell types expressing desmosomal proteins. This might explain why the majority of preclinical AC models, using CM specific over-expression or deletion of the disease-causing mutation, failed to fully recapitulate the human disease phenotype. Hypothesis On these bases, we aimed to generate a knock-in (KI) AC mouse model for comprehensively studying AC pathogenesis. Methods As Desmoplakin (DSP) mutations occur in a large part of the Italian AC population, we used CRISP/Cas9 to generate a KI mouse strain harboring the Serine-to-Alanine substitution of S311, the murine homolog of human S299 [Bauce et al, 2005]. We successfully obtained DSPS311A/WT KI founders, which were viable and fertile and after backcrossing for >10 generations, used to expand the new mouse strain. Mouse cardiac phenotype was characterized, at different stages (1,2,4,6,9 mo.) by functional (i.e. ECHO, telemetry-ECG, chronic exercise) and structural (i.e. EM, standard histology, confocal IF, TUNEL assay) analyses. Molecular/biochemical analyses probed the state of the main pathways involved in AC. Results Our analyses showed that, starting from 4 mo., DSP homozygous KI mice display contractile dysfunction, worsening during aging, and fibrotic myocardial remodelling with focal fatty lesions, accompanied by frequent arrhythmic beats, which become sustained ventricular arrhythmias upon Noradrenaline administration. Hearts showed desmosome alterations, particularly at advanced disease stages, and lateralization of cx43, which corresponded to the phenotype of human AC hearts. Heterozygous mice showed similar alterations, which only took longer to appear. Exercise accelerated disease progression and increased the incidence of SCD (DSPS311A: SCD=63%, n=11; ctrls: SCD=8%, n=12). Conclusion Our KI mice replicate the clinical and pathological phenotype of DSP-linked biventricular AC and are thus suited for the mechanistic study of the multicellular origin of the disease. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): PRIN Miur 2015

Next-generation sequencing identified novel Desmoplakin frame-shift variant in patients with Arrhythmogenic cardiomyopathy

BackgroundArrhythmogenic cardiomyopathy (AC) is one of the leading causes for sudden cardiac death (SCD). Recent studies have identified mutations in cardiac desmosomes as key players in the pathogenesis of AC. However, the specific etiology in individual families remains largely unknown.MethodsA 4-generation family presenting with syncope, lethal ventricular arrhythmia and SCD was recruited. Targeted next generation sequencing (NGS) was performed and validated by Sanger sequencing. Plasmids containing the mutation and wild type (WT) were constructed. Real-time PCR, western-blot and immunofluorescence were performed to detect the functional change due to the mutation.ResultsThe proband, a 56-year-old female, presented with recurrent palpitations and syncope. An ICD was implanted due to her family history of SCD/ aborted SCD. NGS revealed a novel heterozygous frame-shift variant (c.832delG) in Desmoplakin (DSP) among 5 family members. The variant led to frame-shift and premature termination, producing a truncated protein. Cardiac magnetic resonance (CMR) of the family members carrying the same variant shown myocardium thinning and fatty infiltration in the right ventricular, positive bi-ventricular late gadolinium enhancement and severe RV dysfunction, fulfilling the diagnostic criteria of AC. HEK293T cells transfected with mutant plasmids expressed truncated DSP mRNA and protein, upregulation of nuclear junction plakoglobin (JUP) and downregulation of β-catenin, when compared with WT.ConclusionWe infer that the novel c.832delG variant in DSP was associated with AC in this family, likely through Wnt/β-catenin signaling pathway.

2288Oxidized LDL/CD36/PPARg circuitry is a trigger of adipogenesis in arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic Cardiomyopathy (ACM) is a genetic condition hallmarked by ventricular fibro-fatty replacement and arrhythmias. Cardiac mesenchymal stromal cells (C-MSC) differentiate into adipocytes in ACM hearts, through the activation of PPARγ, caused by ACM mutations (e.g. PKP2). The clinical phenotype of ACM is variable for poorly understood reasons. The only recognized cofactor is physical exercise, which is known to increases oxidative stress. An accepted marker of exercise-induced oxidative stress is 13HODE, a component of oxLDL and direct activator of PPARγ. In macrophages, during foam cell formation, 13HODE creates a feed-forward loop increasing both PPARγ and the oxLDL receptor CD36, resulting in fat accumulation. Purpose To investigate oxLDL effects on ACM adipogenesis and to dissect the involved pathways. Methods We analyzed plasmas (n=42) and ventricular tissues (n=4) of ACM patients and matched healthy controls (HC). For in vitro experiments, ACM and HC C-MSC (n=10) have been used, while in vivo experiments have been conducted in heterozygous Pkp2 knock-out mice (Pkp2+/−; n=10). Results We observed higher plasma oxLDL in ACM patients compared to HC (ACM 246.70±55.89 vs HC 102.5±17.95ng/ml; p=0.019). oxLDL levels also discriminate between ACM patients with overt phenotype and their unaffected relatives carriers of the same causative mutations (p=0.03). We observed higher oxidative stress (MDA intensity 40.87±11.76 fold; p=0.015) and CD36 levels (14.72±2.10 fold; p=0.0007) in ACM ventricular tissue, compared to HC. In basal conditions, ACM C-MSC showed greater oxidative stress (MDA intensity 8.83±2.78 fold p=0.017) and higher expression of PPARγ (1.47±0.14 fold; p=0.009) compared to HC C-MSC. The adipogenic stimulation led to a parallel increase of CD36 and lipid accumulation, mainly in ACM C-MSC (slopes statistically different p=0.016). OxLDL and 13HODE administration increased lipid accumulation in ACM C-MSC (ORO staining ACM vs ACM+oxLDL p=0.01; ACM vs ACM+13HODE p=0.014). On the contrary, the antioxidant N-Acetylcysteine (NAC) prevented lipid accumulation in ACM C-MSC (ORO staining ACM+13HODE vs ACM+13HODE+NAC p=0.0009). Through CD36 silencing of ACM C-MSC, we obtained a significantly lower lipid accumulation than non-silenced cells (ORO staining 0.35±0.10 fold; p=0.003). Pkp2+/− mice do not spontaneously accumulate adipocytes in the heart, however Pkp2+/− C-MSC are more prone to lipid accumulation in vitro than WT cells (p=0.007). Accordingly, mice have low plasma oxLDL and cardiac oxidative stress. By increasing plasma cholesterol and oxidative stress through high fat diet, we observed fibro-fatty substitution in Pkp2+/− hearts (p=0.046). Figure 1 Conclusions These findings reveal a modulatory role of oxidized lipids in ACM adipogenesis at a cellular, tissue and clinical level, enlightening novel targets for pharmacological strategies to prevent adipogenic substitution and consequent ACM clinical phenotypes. Acknowledgement/Funding Telethon Foundation; Italian Ministry of Health

P3688Familial recurrent autoimmune myocarditis associated with a truncating nonsense mutation of the desmoplakin gene

Abstract Background Arrhythmogenic cardiomyopathy (AC) is an important cause of ventricular arrhythmias in children and young adults. AC is associated with mutation of desmosomal proteins, however, cardiac disease penetrance is incomplete and the clinical course varies widely without recognizable exogenous or epi/genetic co-factors. Importantly, DSP mutation carriers may also display entirely non-cardiac e.g. dermatological phenotypes. Methods and results In two brothers with recurrent fulminant myocarditis, mutation screening of 218 cardiomyopathy-related genes identified a truncating mutation Arg1458* of desmoplakin (DSP). DSP immunhistology unexpectedly revealed complete loss (“knockout”) of DSP protein in endomyocardial biopsies (EMBs), but none of the histological anomalies of AC. Criteria for histological diagnosis of myocarditis were not either fulfilled, and cardiac MRI revealed no features associated with AC. Screening for infections was negative, there was no substance abuse, medication or vaccination. Possible disease triggers were competitive sport events. Myosin and troponin I autoantibodies were detected at titers up to 1:320. We used allele-specific RT-PCR to distinguish if the patients' allele classified as “normal” was actually defective due to promotor mutation or epigenetic silencing. RT-PCRs were done on EMBs and peripheral blood mononuclear cells (PBMCs). In a cohort of dilated cardiomyopathy (DCM) patients we were able to detect DSP transcripts in both, PBMC and left-ventricular heart tissue. RNA sequencing of human PBMC subpopulations suggested that DSP transcription may be restricted to certain immune cell subtypes. RT-PCRs revealed that both Arg1458* carriers have a functional second DSP allele, indicating that their “DSP knockout” occurs at the protein level and may be due to protein instability and degradation within desmosomes. We screened additional existing cohorts for such variants and identified stopgain variant Gln307Ter in a 37-yrs-old woman with ARVC. This patient's sister died from heart failure at the age of 39. In a 59-yrs-old female LVNC patient, stopgain variant Y1391X was identified. Here, family history was unclear, her brother probably died from coronary artery disease. In a 71-yrs-old female DCM patient with no family history, stopgain variant Tyr1512Ter was identified. Conclusions The described patients with DSP truncations strongly suggest the existence of additional genetic or exogenous modifiers driving pathogenesis either way. DSP defects may cause recurrent myocarditis, and mutation screening is advisable to enable early detection of high-risk patients with similar phenotypes. Our finding of complete myocardial DSP protein loss emphasizes that DNA sequencing may miss critical molecular disturbances. It is indispensable to also analyze transcriptome and protein level in the tissue actually affected in a patient in order to recognize his/her individual pathogenesis.

P5556Impact of viral genome detection in endo-myocardial biopsy of arrhythmogenic cardiomyopathy substrate

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a genetically inherited cardiomyopathy characterized by myocardial fibro-fatty replacement. A pathogenetic role of viral myocardial infections in ACM natural history has been proposed over the years, although no definitive conclusion has been reached yet. Purpose To describe viral genome presence into a cohort of ACM biopsy proven patients (pts) and its impact on clinical features and outcome. Methods A cohort of all ACM pts undergoing an invasive third level evaluation at our institution was enrolled. All pts underwent a cardiac magnetic resonance (MR), an invasive electrophysiological study (EPS) with endo-cavitary electro-anatomical mapping (EAM), and a EAM guided endo-myocardial biopsy (EMB). Viral genome research through molecular biology techniques was performed on all biopsied samples. According to arrhythmic risk evaluation, a trans-catheter ablation (TCA) and/or an internal cardioverter device (ICD) implant was performed. Clinical arrhythmic presentation, MR data, arrhythmia inducibility at EPS, EAM and EMB characteristic, and arrhythmic events at a 12-month follow up visit were retrieved in all pts and compared between the viral genome positive (v+ACM) and negative group (v-ACM). Results Forty-five pts were enrolled in our study (48±13 years; 66% male); the EMB samples of 7 (15%) pts presented a lymphocytic infiltrate and tested positive for viral genome (n=3 B19 Parvovirus; n=2 for Citomegalovirus; n=2 for Ebstein-Bar Virus) [Figure1]. At arrhythmic presentation, complex ventricular arrhythmias (NSVT, SVT and FV) were more frequent in the v+ACM group (86% vs 50%; p=0.039). Both left and right ventricular ejection fraction at MR resulted more depressed in the v+ACM group (44±7 vs 52±2 and 47±2 vs 52±2; p=0.047 and p=0.041). Complex ventricular arrhythmia inducibility at EPS was more frequent in v+ACM (72% vs 34%; p=0.032), while no differences in pathological potentials rate and extension at unipolar and bipolar EAM were found. TCA was performed in 55% and 57% and an ICD was implanted in 29% and 42% in the v+ACM and v-ACM group respectively. No differences in 12-months arrhythmic event rates (39% vs 42%) between the two groups were described. EBM at different magnifications/stains Conclusion In our cohort a viral infection super-imposed to the fibrofatty infiltration was found in 15% of the patients. ACM pts testing positive for viral genome at the EMB had a more severe arrhythmic disease presentation, a more impaired heart function, and a higher rate of complex ventricular arrhythmias at disease presentation, but seemed to respond as well as viral genome negative ACM to ablative and pharmacological treatment

P3828Zebrafish models for arrhythmogenic cardiomyopathy type 8: a starting platform for exercise stress test and drug treatment

Abstract Background Arrhythmogenic Cardiomyopathy (AC) is an inherited heart disease characterized by progressive substitution of the myocardium with fibro-fatty tissue, leading to electrical instability and high risk of sudden death, particularly in young subjects and athletes. In recent years, our laboratory has produced zebrafish (zf) mutant lines modelling AC type 8, an AC form linked to mutations in the junctional protein Desmoplakin (Dsp). Mutations in the DSP gene have been identified in both dominant and recessive AC cases, characterized by left-dominant and biventricular forms of the disease. Sports medicine has highlighted that they are the most dangerous forms, being less easily identifiable by ECG. Purpose Taking advantage of our zf Dsp mutant lines, we aim to fully characterize the pathological phenotype, analyze the perturbation of cell communication pathways, evaluate the role of the physical exercise, and test the efficacy of candidate drugs. Methods Among our zf lines we have identified double mutant animals, bearing both zf dspa and dspb mutations in heterozygous condition, as the best model able to recapitulate the human AC phenotype. This model underwent physical stress tests in the presence/absence of candidate drug treatment. Phenotyping included heart rhythm measurement, gene expression analysis using Real Time PCR and signaling pathway transgenes, immune-histochemistry, whole-mount in situ hybridization, standard histology and ultrastructural TEM analysis. Results Preliminary results from mutant phenotyping indicate alterations in heart rate, sudden cardiac death, structural alterations of the myocardium associated with junctional disorganization and, in parallel, dysregulation of Wnt, Hippo and TGFbeta pathways. Specifically, Dsp mutant animals can range from an 8% decrease to a 14% increase of heart rhythm compared to the physiological range (120–140 beats per minute in zf larvae). At the adult stage, about 1% of the fish mutant population dies suddenly. The histological examination shows a 50% reduction of the myocardial cell mass, in parallel with a 50% decrease of Dsp signal, detected by TEM, associated with the so-called “pale desmosome” phenotype. Signaling dysregulation includes an 80% loss of Wnt/Beta-catenin, a 300% increase of TGFbeta and a 500% increase of Hippo/YAP-TAZ signaling in the cardiac tissue. Physical stress tests and pathway-directed drug treatment have clarified that these factors can modulate the pathological phenotype, as preliminarily evidenced by the rescue of Wnt signal decrease to normal levels through SB216763 treatment of Dsp-deficient individuals at rest. Conclusion Preliminary evidences corroborate the zf organism as a suitable model for AC cellular and molecular phenotyping, exploitable for the dissection of the genetic events leading to the onset and progression of the disease, and applicable to the analysis of chemical and mechanical modulators of AC-associated features. Acknowledgement/Funding Cariparo 2017 SHoCD; TRANSAC; CPDA133979/13; RP-2014-ehz745.06700394

1175Structural progression increases the risk of ventricular arrhythmias in patients with arrhythmogenic cardiomyopathy

Abstract Background Arrhythmogenic cardiomyopathy (AC) is an inheritable cardiomyopathy with incomplete penetrance, variable phenotype severity and poorly described disease progression. It is characterized by high risk of life-threatening ventricular arrhythmias and sudden cardiac death in young individuals. Risk stratification and selection of patients presenting without history of life-threatening arrhythmic events for cardioverter-defibrillator implantation in primary prevention remains challenging. Purpose We aimed to assess the impact of disease progression on arrhythmic outcomes in AC patients. Methods We included consecutive AC probands and mutation-positive family members with at least one complete follow-up evaluation. Echocardiographic and electrical parameters were defined according to the 2010 Revised Task Force criteria at inclusion and at last follow-up. Structural progression was defined as development of new echocardiographic diagnostic criteria. Electrical progression was defined as the development of new diagnostic depolarization, repolarization and/or premature ventricular complex count criteria during follow-up. Non-sustained ventricular tachycardia or ventricular tachycardia occurring during follow-up defined incident ventricular arrhythmic events. Results We included a total of 144 patients (48% female, 47% probands, 40±16 years old). At inclusion, 54 patients (37%) had a history of arrhythmic events, 30 patients (21%) had overt structural disease and 114 (79%) had no or minor structural disease. During 7.0 (IQR: 4.5 to 9.4) years of follow-up, 49 patients (43%) with no or minor structural disease at inclusion developed new structural criteria being defined as progressors. Among 80 participants with no or minor structural disease and no arrhythmic history at inclusion, a first arrhythmic event occurred in 14 (17%). The incidence of arrhythmic events was higher in progressors (11/27, 41%) than in non-progressors (3/53, 6%) (p<0.001) (Figure). Structural progression was associated with higher risk of first arrhythmic events during follow-up when adjusted for sex, age at inclusion and follow-up duration, independent of electrical progression (7.6, 95% CI [1.5, 37.2], P=0.01). Incident arrhythmic events distribution Conclusion Almost half of patients without overt structural cardiac disease at genetic diagnosis develop new structural criteria during 7 years follow-up and 17% experienced their first ventricular arrhythmic event. Structural progression was independently associated with ventricular arrhythmic events during follow-up. These findings highlight the increased risk of arrhythmias when structural abnormalities are detected. Their finding may initiate the evaluation for primary prevention cardioverter-defibrillator implantation.

P3687Abnormal voltage recordings in patients with ventricular arrhythmias: comparison between right and left cardiomyopathy

Abstract Background Arrhythmogenic Cardio-Myopathy (ACM) is characterized by epi-endocardial fibro-fatty replacement. Depending on the most affected ventricle, right dominant (RDACM) or left dominant (LDACM) phenotypes can be defined. RDACM voltage mapping characteristics have already been described, with late potentials strongly correlating with arrhythmia recurrence risk; LDACM voltage features have not been described yet. Purpose To analyze voltage map characteristics in LDACM patients (pts) and compare them with RDACM; to assess if there is any correlation between late potentials and recurrence rate in LDACM as well. Methods We retrospectively enrolled all consecutive ACM patients treated c/o our center and diagnosed according to the 2010 Task Force Criteria. Procedural and follow up data were collected. Patient were sorted by ventricular involvement lateralization. Recurrence rates were evaluated and linearly regressed for the presence of late potentials. Results 89 ACM patients were enrolled (67 RDACM, 22 LDACM; 76% males, 69±4 y.o.) in our study. All patients underwent endocardial voltage mapping; procedurally, 43 (48%) pts underwent catheter ablation, while 46 (52%) were managed conservatively with anti-arrhythmic drugs. Bipolar pathological potentials were found in 43 (64%) and 13 (59%), unipolar pathological potentials in 45 (67%) and 14 (63%), while late potentials in 19 (31%) and 8 (36%) in the RDACM and LDACM group respectively [p = 0.66, p=0.63, and p=0.33]. The average follow-up was 18 months [14–48]; 15 (22%) in the RDACM and 9 (40%) in LDACM arrhythmic recurrences were respectively encountered; recurrences in both groups were regressed for the presence of late potentials. Results were as follows: the presence of late potentials correlated with recurrences with an 4,3 [1.15–16.1; p=0.03] OR and with an 11 [0.4–85; p=0.022] OR in the RDACM and LDACM group respectively. Conclusion Pathologically low unipolar, bipolar and late potentials can be found in comparable % both in RDACM and LDACM; like in RDACM, late potentials represent an important risk factor for arrhythmic recurrence in LDACM as well.