Early-onset Atrial Fibrillation Research Articles

Abstract 4127792: Age-stratified Monogenic and Polygenic Contributions for Atrial Fibrillation in the All of Us Research Program

Background: Rare and common genetic variation both contribute to atrial fibrillation (AF), but the effects may not be uniform across ages. The All of Us Research Program contains whole-genome sequencing of 100,574 adult participants with electronic health records. Hypothesis: Rare genetic variants are associated with early-onset AF; common genetic variants are associated with late-onset AF. Aims: To quantify the diagnostic yield provided by rare and common genetic variation in AF across age. Methods: The clinical, monogenic, and polygenic contributions to AF were assessed in a cross-sectional group of participants in the NIH-funded All of Us Research Program, stratified by three age groups: <45 years (n=22,290), 45-60 years (n= 26,805), >60 years (n=51,659). Variant discovery was performed for pathogenic or likely pathogenic (P/LP) variants among 145 candidate cardiac genes with dominant inheritance for cardiomyopathy and arrhythmia. A previously established polygenic risk score (PRS) was calculated. After adjusting for known clinical factors, multivariable analysis quantified the associations between monogenic and polygenic factors versus AF status in each age group. Results: There were 100,574 participants: 7,811 with AF and 92,763 without AF. The presence of ≥1 P/LP variant(s) were associated with AF across all age groups, with stronger associations in the age <45 group (OR 2.3 [95% CI 1.4-4.1]) compared older groups (OR 1.5 [95% CI 1.1-2.1] in age 45-60, and OR 1.4 [95% CI 1.2-1.7] in age >60). In contrast, PRS was not associated with AF in participants <45 years (OR 1.02 [95% CI 0.88-1.17]) but was associated with AF in the older groups: OR 1.54 [95% CI 1.31-1.80] in age 45-60 and OR 1.49 [95% CI 1.40-1.59] for age >60. Overall, clinical risk factors are highly associated with AF (AUC 0.84 [0.83-0.85]); adding polygenic and monogenic factors contribute only marginal improvement (AUC 0.86 [0.85-0.87]). Conclusion: In this cross-sectional dataset, monogenic and polygenic factors have opposite associations with AF. Monogenic variants are associated with early-onset AF, whereas PRS has no association with AF at younger ages. Clinical risk factors continue to explain the majority of the variation in AF status.

Abstract 4138278: A Titin Missense Variant Causes Atrial Fibrillation

Background: Rare loss-of-function variants in TTN , the gene encoding the sarcomeric protein titin, have been causally associated with atrial fibrillation (AF). Missense TTN variants ( TTN mv) are generally regarded as benign in relation to dilated cardiomyopathy, but their role in AF is unknown. Hypothesis: TTN mv are associated with clinical outcomes and AF pathogenesis. Aims: We aimed to determine if TTN mv are associated with AF/heart failure (HF) hospitalizations and investigate if a rare missense variant ( TTN -T32756I) caused AF using human induced pluripotent stem cell-derived atrial cardiomyocytes (iPSC-aCMs). Methods: Whole exome sequencing was performed in 131 adults at an urban academic healthcare system who identified as non-Hispanic Black (NHB) or Hispanic/Latinx (HL). Multivariable Cox proportional hazard models were used to assess cumulative risk of AF/HF hospitalization. Isogenic TTN -T32756I iPSC-aCM mutants were generated using the CRISPR-Cas9 technique. We used confocal microscopy to assess sarcomeric integrity, MuscleMotion to assess contractility, and optical voltage mapping and patch-clamping to assess the electrophysiological (EP) properties. Results: We identified 137 TTN mvs in 76/131 (58.0%) of subjects, which were most commonly in the TTN A-band. 64 AF-related and 110 HF-related hospitalizations occurred after a median follow-up time of 4.16 years. Hospitalization risk was higher in TTN mv carriers (HR 1.81, Fig. 1A ). We also identified three patients with early-onset AF who shared a rare missense variant T32756I. TTN-T32756I -iPSC-aCMs displayed aberrant contractility ( Fig. 1B-D ), shortened action potential duration ( Fig. 1G-H ), increased activity of cardiac K + channel ( Fig. 1I ), and dysregulated Ca 2+ homeostasis ( Fig. 1J ) without compromising sarcomeric integrity ( Fig. 1E-F ). The titin-binding protein, Four-and-a-Half Lim domains 2 (FHL2), also has increased binding with KCNQ1 and its modulatory subunit KNCE1 in TTN-T32756I -iPSC-aCMs, which may enhance the slow delayed rectifier K + current ( I ks ). Suppression of FHL2 normalized I ks , supporting FHL2 as a mediator of the increased I ks ( Fig. 1K) . Conclusion: In a single-center multi-ethnic AF cohort, TTN mv were associated with increased AF/HF hospitalization, and the T32756I- TTN mv causes ion channel remodeling and an AF-like EP phenotype. These findings establish a mechanistic link between TTN mv, K + ion channels, and sarcomeric regulatory proteins that may represent a novel therapeutic target.

Prevalence and implications of cardiomyopathy-associated genetic variants in early-onset atrial fibrillation

Abstract Background Atrial fibrillation (AF) is a common and morbid arrhythmia. Despite a substantial heritable component, genetics does not currently play a role in personalized medicine for AF. Rare genetic variants in genes associated with inherited cardiomyopathies (CMP) are enriched in AF patients. However, prior studies on rare variants in AF mainly relied on hospital-based populations, and knowledge on clinical outcomes remains limited. Purpose We aimed to evaluate the potential diagnostic yield and prognostic implication of pathogenic or likely pathogenic (PLP) genetic variants for CMP in persons with AF, using large population-based cohorts. Methods This study utilized sequencing data and electronic health records (EHR) from the All of Us Researh Program (AllofUs) and UK Biobank (UKB). Using ClinVar, we curated a set of PLP variants in 36 CMP-associated genes and assessed the carrier prevalence overall, in participants with AF, and in participants with early-onset AF (below 65, 55 and 45 years). Next, we used Cox proportional hazards models to evaluate the association between variant carrier status and incident risk of heart failure or CMP, after AF diagnosis. In all time-to-event analyses, individuals with prevalent heart failure or CMP at AF diagnosis were excluded and models were adjusted for age, sex, and principal components of ancestry. Sensitivity analyses were performed requiring a minimum period from AF to HF or CMP, of 1, 3 and 6 months. Results After excluding related individuals, we identified 32,281 (8.19%) and 9,666 (6.06%) AF cases in UKB and AllofUs, respectively. Compared to the overall populations (UKB: 1.15%; AllofUs: 1.36%), PLP variants for CMP were about ~5 times more prevalent in AF with onset before 45 (UKB: 4.98%; AllofUs: 5.26%), ~3 times more prevalent in AF with onset before 55 (UKB: 3.41%; AllofUs: 4.34%) and ~2 times more prevalent in all AF patients (UKB: 2.03%; AllofUs: 2.67%). In turn, AF patients carrying PLP variants had increased risk of developing heart failure or CMP, after AF diagnosis (AllofUs HR 1.81, 1.44-2.29, p<1e10-6, UKB:HR=1.39 1.08-1.78, p<0.01), which remained present when requiring a minimum of 6 months after AF diagnosis (AllofUs:HR 1.70, 1.29-2.25, p<0.001; UKB:HR=1.59, 1.21-2.07, p<0.001). Effect sizes were greater when limiting analysis to AF patients with onset before 65 (cases=1021, HR 1.91, 1.35-2.68, p<0.0001) and before 55 years (cases=384, HR 2.53, 1.55-4.1, p <0.001) in AllofUs. UK Biobank did not reflect this increase (cases<65=513, HR<65=1.27, 0.63-2.39, p<65>0.05). Considering only HF events in AllofUs, the effect remained present (HR 1.70, 1.32-2.19, p<0.0001). Conclusion The yield of CMP-associated PLP variants is substantial among persons with early-onset AF, even when considering a 55 year cutoff. AF patients with PLP variants have an increased risk of future heart failure or CMP. Our results further support the clinical relevance of genetic testing in early-onset AF.Prevalence of CMP variants in AF by age

Association between genetic predisposition of AF and the risk of ischemic stroke and thromboembolism

Abstract Background Ischemic stroke and thromboembolism are the major complications of atrial fibrillation (AF), however, its association with genetic background of AF remains unclear. To investigate the association between genetic predisposition of AF underlying common variants and the risk of ischemic stroke and thromboembolism. Methods We included unrelated individuals with non-valvular AF from UK biobank. The polygenic risk scores of AF (PRSAF) was calculated for each individual using the effect weight from a previous study which has been validated in both European and mixed-ancestry population[1, 2]. The SNPs from the original score were lifted over to GRCh38 and 6514708 of 6730541 were available in the UK biobank genotype data. The clinical data was defined by ICD-10 code. The primary endpoint is ischemic stroke or thromboembolism resulting in hospitalization after first AF diagnosis. Results A total of 28810 unrelated patients were included in the study. Among them, 4064 had PRSAF over 90th percentile of the general population, and were considered having high genetic risk. The rest 18746 with per SD increase in PRSAF lower than 90th percentile of the general population were considered having lower genetic risk. Generally, age and sex adjusted model demonstrated that per standard deviation change in PRSAF is associated with 9% increase in the risk of stroke or thromboembolism (HR=1.09, 95%CI: 1.03-1.14), and patients with high genetic risk was associated with 15% increase in the risk of stroke or thromboembolism (HR=1.15, 95%CI: 1.02-1.31).The result remained stable when further adjusted for clinical risk factors (1.09, 95%CI: 1.04-1.15 per SD increase in PRSAF) and competing risk of death (1.10, 95%CI: 1.05-1.16 per SD increase in PRSAF). There was no interaction between CHA2DS2-VASc score risk stratification and the per SD increase in PRSAF (P interaction = 0.751, Figure 1A). However, the association between per SD increase in PRSAF and the event tended to be affected by age at AF onset (HR = 1.02 95%CI: 0.94, 1.11 for early onset AF; HR = 1.12 95%CI: 1.05, 1.19 for non-early onset AF, P for interaction = 0.062, Figure 1B). Multi-variate COX regression including PRSAF, components of CHA2DS2-VASc score, and other AF risk factors revealed that history of stroke/thromboembolism, age over 65 years, hypertension, diabetes and high AF genetic risk were significantly associated with the outcome (Figure 1C). To evaluate the importance of these risk factors, average population attributable fraction for 10-year risk of stroke/thromboembolism in the study population was calculated, indicating that genetic risk of AF is responsible for 3.26% (0.89%-5.63%) of the events (Figure 1D). Conclusion Genetic predisposition of AF underlying common variants is associated with ischemic stroke and thromboembolism independent of clinical risk factors. But its role in different AF populations, like early onset AF, remains further investigation.Figure 1

Early-onset atrial fibrillation is a risk marker for cardiomyopathy: genetic insights from the UK Biobank

Abstract Introduction Atrial fibrillation (AF) is a common cardiac arrhythmia associated with an increased risk of stroke, heart failure and premature death. Genetic associations between AF and rare variants have been identified in several cardiomyopathy-associated genes, and previous studies have shown a high prevalence of deleterious variants among individuals with early onset of AF. Consequently, genetic testing has been suggested in patients with AF onset before 45 years of age. Purpose This study aimed to explore the prevalence and distribution of deleterious genetic variants in cardiomyopathy genes according to age at AF diagnosis. Methods The UK Biobank is a large population-based biobank, comprised of clinical and genetic information on more than 500,000 individuals, enrolled between 2006 and 2010. We analyzed whole-exome sequencing data among unrelated individuals of European ancestry. The cohort was stratified by age at AF onset (AF onset <45 years, AF onset between 45-54 years, AF onset between 55-64 years, AF onset >=65 years, and individuals with no AF diagnosis). We evaluated the presence of rare (minor allele frequency <0.1%) genetic variants in core cardiomyopathy genes, according to guidelines by the American College of Medical Genomics and focused on variants predicted to lead to loss of function. Individuals with a diagnosis of cardiomyopathy prior to AF were excluded. Results Among 374,365 unrelated individuals of European ancestry, 29,119 were diagnosed with AF. Of these, 685 had onset of AF<45 years (2.35%), 2465 had onset between 45-54 years (8.46%), 7778 had onset between 55-64 years (26.71%), and 18191 had onset at or above 65 years of age (62.48%). A total of 884 were carriers of rare loss-of-function variants in cardiomyopathy genes. Among carriers, the majority of variants were in key genes for dilated cardiomyopathy (TTN), hypertrophic cardiomyopathy (MYBPC3), and arrhythmogenic right ventricular cardiomyopathy (PKP2). We observed an inverse dose-response-like relationship between prevalence of the rare genetic variants and age at AF diagnosis. The highest prevalence of carriers was observed among individuals with onset before 45 years (4.96%). In comparison, the proportion of carriers was 3.45% in individuals with AF onset between 45-54 years, 2.96% in individuals with AF onset between 55-64 years, 2.75% in individuals with onset at or after 65 years, and 2.05% among individuals without AF diagnosis. Conclusions Using whole exome sequencing, we identified a high proportion of carriers of deleterious variants in actionable genes of cardiomyopathies among individuals with early onset of AF. We observed an inverse dose-response-like relationship between age of AF diagnosis and prevalence of deleterious genetic variants. Our findings support that very early onset of AF, before 45 years of age, is a potential risk marker for cardiomyopathy and support that genetic screening may be relevant in this patient group.

Sex differences in early-onset atrial fibrillation in Norwegian primary care: a retrospective national database analysis

BackgroundIndividual variation in the need for healthcare constitutes knowledge gaps for young atrial fibrillation (AF) patients. We aimed to estimate the prevalence and primary care burden of early-onset AF in...

Clinical presentation and genetic characterization of early-onset atrial fibrillation in patients affected by long QT syndrome: A single-center experience.

Early-onset atrial fibrillation (AF) has already been observed in approximately 2% of patients with genetically proven long QT syndrome (LQTS). This frequency is higher than population-based estimates of early-onset AF. However, the concomitant expression of AF in LQTS is likely underestimated. The purpose of this study was to examine the clinical presentation, genetic background, and outcomes of a cohort of patients with LQTS and early-onset AF referred to a single tertiary center. Twenty-seven patients diagnosed with congenital LQTS were included in the study based on the documentation of early-onset (age ≤50 years) clinical or subclinical AF episodes in all available medical records, including standard electrocardiograms, wearable monitor or cardiac implantable electronic devices. Seventeen patients experienced clinical AF during the follow-up period. Subclinical AF was detected in 10 patients through insertable or wearable cardiac monitors. In our series, the mean heart rate during AF episodes was found to be relatively low despite the patients' young age and the low or minimal effective doses of beta-blockers used for QTc interval control. All patients exhibiting LQTS and early-onset AF were genotype positive, carrying mutations in the KCNQ1 (66%), KCNH2, KCNE1, and SCN5A genes. Notably, most of these patients carried the same p.(R231C) mutation in the KCNQ1 gene (59%) and were from the same families, suggesting concurrent expression of familial AF and LQTS. LQTS patients are prone to developing clinical and subclinical AF, even at a younger age. The occurrence of early-onset AF in the LQTS population could be more frequent than previously assumed. AF should be considered as a potential dysrhythmia related to LQTS. Our study emphasizes the importance of carefully researching clinical and/or subclinical episodes of AF through strict heart rhythm monitoring in the LQTS population.

Genetic testing in early-onset atrial fibrillation.

Atrial fibrillation (AF) is a globally prevalent cardiac arrhythmia with significant genetic underpinnings, as highlighted by recent large-scale genetic studies. A prominent clinical and genetic overlap exists between AF, heritable ventricular cardiomyopathies, and arrhythmia syndromes, underlining the potential of AF as an early indicator of severe ventricular disease in younger individuals. Indeed, several recent studies have demonstrated meaningful yields of rare pathogenic variants among early-onset AF patients (∼4%-11%), most notably for cardiomyopathy genes in which rare variants are considered clinically actionable. Genetic testing thus presents a promising opportunity to identify monogenetic defects linked to AF and inherited cardiac conditions, such as cardiomyopathy, and may contribute to prognosis and management in early-onset AF patients. A first step towards recognizing this monogenic contribution was taken with the Class IIb recommendation for genetic testing in AF patients aged 45 years or younger by the 2023 American College of Cardiology/American Heart Association guidelines for AF. By identifying pathogenic genetic variants known to underlie inherited cardiomyopathies and arrhythmia syndromes, a personalized care pathway can be developed, encompassing more tailored screening, cascade testing, and potentially genotype-informed prognosis and preventive measures. However, this can only be ensured by frameworks that are developed and supported by all stakeholders. Ambiguity in test results such as variants of uncertain significance remain a major challenge and as many as ∼60% of people with early-onset AF might carry such variants. Patient education (including pretest counselling), training of genetic teams, selection of high-confidence genes, and careful reporting are strategies to mitigate this. Further challenges to implementation include financial barriers, insurability issues, workforce limitations, and the need for standardized definitions in a fast-moving field. Moreover, the prevailing genetic evidence largely rests on European descent populations, underscoring the need for diverse research cohorts and international collaboration. Embracing these challenges and the potential of genetic testing may improve AF care. However, further research-mechanistic, translational, and clinical-is urgently needed.

A COMPLEX CASE OF EARLY ONSET ATRIAL FIBRILLATION IN AN ENDURANCE ATHLETE: THE IMPORTANCE OF FAMILY HISTORY

Abstract Introduction Early onset atrial fibrillation (AF) in an endurance athlete represents a challenge for the cardiologist, especially in apparent absence of an overt structural heart disease. Different genetic variants have been associated with early onset AF but indications to genetic testing are still under definition. Case A 54–year–old man (BMI 19 kg/sqm), previous competitive athlete (Nordic running and walking) presented to the Emergency Department with sudden onset palpitations and dyspnea due to high penetrance AF (145 bpm). Family history (FH) was positive for cerebrovascular accidents in both parents and for early onset (<60 years) AF in the father. The man had a recent history of borderline hypertension, of effort related syncope of and of infundibular, isolated, premature ventricular complexes during a maximal exercise stress test (otherwise negative for ischemia) which ultimately led to the denial of competitive sport eligibility. Sinus rhythm (SR) was acutely restored with flecainide and the patient was discharged with low dose nadolol. Cardiac US showed normal left ventricular (LV) dimensions and thicknesses (10 mm), with regular LVEF (60%) and global longitudinal strain (–18%), mildly dilated left atrium (LAVI 36 ml/sqm) and bi–leaflet mitral valve prolapse without significant mitral regurgitation, mitro–anular disjunction nor Pickelhaube sign; 24h Holter ECG showed SR with rare supraventricular (SV) ectopic beats and a 4 beats SV run. Due to the recurrence of short episodes of palpitations, rhythm control with flecainide and antithrombotic prophylaxis were started and AF ablation was planned. Genetic testing for early onset AF identified a nonsense variant (c.84665delG; p.Gly28222fs*2) in TTN gene, classified as likely pathogenic (C4), so far not reported in scientific literature. Also, despite a moderate–low cardiovascular risk as assessed by SCORE2, mostly due to the FH and the desire to engage in high intensity exercise, coronary CT was prescribed, which showed a critical coronary disease leading to stenting on left anterior descending artery and intermediate branch. Cardiac MRI was planned. Conclusions Early onset AF in endurance athletes should not be underrated and a thorough examination including a detailed family history should be performed. TTN is the single gene most frequently associated with early onset AF in absence of an overt structural heart disease, but the subsequent clinical evolution is still largely unknown.

Association Between Family History and Early-Onset Atrial Flutter Across Racial and Ethnic Groups.

Genetic and familial contributions to early-onset atrial fibrillation are described primarily in individuals of European ancestry. However, the role of racial and familial contributions in the pathogenesis of early-onset atrial flutter (EOAFL) is unclear. In this cross-sectional study, participants were enrolled prospectively from 2015 to 2021 in multiple academic centers with a diagnosis of atrial flutter (AFL) confirmed by ECG. EOAFL was defined as a diagnosis of AFL before age 66 years with no concomitant or previous diagnosis of atrial tachyarrhythmias. Family history was adjudicated through baseline questionnaires and direct family interviews about the diagnosis of atrial tachyarrhythmias, stroke, and cardiomyopathy. The primary exposure was a positive family history in first-degree relatives, and the primary outcome was the odds of EOAFL versus late-onset AFL. A total of 909 patients were enrolled. Participants with a positive family history of atrial tachyarrhythmias were younger, less likely to be of Black race, and more likely to have EOAFL. The adjusted odds ratio (OR) for EOAFL in those with a positive family history was 1.8 (95% CI, 1.1-3.0). There was an increased odds of EOAFL in those of Black race (OR, 2.1 [95% CI, 1.4-3.2]), alcohol use (OR, 1.6 [95% CI, 1.0-2.6]), and obstructive sleep apnea (OR, 1.9 [95% CI, 1.0-3.4]). Use of cardioselective β blockers or calcium channel blockers before the diagnosis of AFL were associated with a lower odds of EOAFL (OR, 0.5 [95% CI, 0.2-0.9]). These findings suggest a potentially hereditary predisposition to EOAFL across race and ethnicity, warranting further study of the genetic contributions to AFL.

Why is early-onset atrial fibrillation uncommon in patients with Duchenne muscular dystrophy? Insights from the mdx mouse.

A reduction in both dystrophin and neuronal nitric oxide synthase (NOS1) secondary to microRNA-31 (miR-31) up-regulation contributes to the atrial electrical remodelling that underpins human and experimental atrial fibrillation (AF). In contrast, patients with Duchenne muscular dystrophy (DMD), who lack dystrophin and NOS1 and, at least in the skeletal muscle, have raised miR-31 expression, do not have increase susceptibility to AF in the absence of left ventricular (LV) dysfunction. Here, we investigated whether dystrophin deficiency is also associated with atrial up-regulation of miR-31, loss of NOS1 protein, and increased AF susceptibility in young mdx mice. Echocardiography showed normal cardiac structure and function in 12-13 weeks mdx mice, with no indication by assay of hydroxyproline that atrial fibrosis had developed. The absence of dystrophin in mdx mice was accompanied by an overall reduction in syntrophin and a lower NOS1 protein content in the skeletal muscle and in the left atrial and ventricular myocardium, with the latter occurring alongside reduced Nos1 transcript levels (exons 1-2 by quantitative polymerase chain reaction) and an increase in NOS1 polyubiquitination [assessed using tandem polyubiquitination pulldowns; P < 0.05 vs. wild type (WT)]. Neither the up-regulation of miR-31 nor the substantial reduction in NOS activity observed in the skeletal muscle was present in the atrial tissue of mdx mice. At difference with the skeletal muscle, the mdx atrial myocardium showed a reduction in the constitutive NOS inhibitor, caveolin-1, coupled with an increase in NOS3 serine1177 phosphorylation, in the absence of differences in the protein content of other NOS isoforms or in the relative expression NOS1 splice variants. In line with these findings, transoesophageal atrial burst pacing revealed no difference in AF susceptibility between mdx mice and their WT littermates. Dystrophin depletion is not associated with atrial miR-31 up-regulation, reduced NOS activity, or increased AF susceptibility in the mdx mouse. Compared with the skeletal muscle, the milder atrial biochemical phenotype may explain why patients with DMD do not exhibit a higher prevalence of atrial arrhythmias despite a reduction in NOS1 content.

Impact of diagnosis-to-ablation time on clinical outcomes in patients with early-onset atrial fibrillation.

Evidence was lacking for the early choice of radiofrequency ablation (RFA) among patients with early-onset atrial fibrillation (AF). This study aimed to explore whether earlier RFA was associated with better clinical outcomes among early-onset AF patients. Patients, who were diagnosed with AF before 45 years and underwent their first RFA procedures at baseline of the China Atrial Fibrillationregistry, were enrolled and divided into four diagnosis-to-ablation time (DAT) groups: DAT ≤ 1 year, 1 year < DAT ≤ 3 years, 3 years < DAT ≤ 6 years, and DAT > 6 years. Another group of nonablation patients, who were newly diagnosed with AF and younger than 45 years, were also included. Adjusted associations of groups with composite cardiovascular events (cardiovascular death, embolism, major hemorrhages, or cardiac rehospitalization) or recurrent AF were analyzed using Cox proportional hazards models. Among 1694 patients who underwent their first RFA at enrollment, incidences of composite cardiovascular outcomes were increasing with extension of DAT (DAT ≤ 1 year: 6.1/100 person-years, 1 year < DAT ≤ 3 years: 7.9/100 person-years, 3 years < DAT ≤ 6 years: 7.6/100 person-years, DAT > 6 years: 10.5/100 person-years; p < .001). In comparison with DAT > 6 years group, theDAT ≤ 1 year group was associated with reduced risk of cardiovascular events (adjusted hazard ratio, HR[95%confidence interval,CI] = 0.64 [0.47-0.87], p = .005) and AF recurrence (adjusted HR[95% CI] = 0.70 [0.57-0.88], p = .002). Associations remained similar after stratified by AF types. Compared to nonablation group (n = 413), DAT ≤ 1year patients tended to show lower cardiovascular risk (adjusted HR[95% CI] = 0.78 [0.58-1.05], p = .099) and lower risk of recurrent AF (adjusted HR[95% CI] = 0.46 [0.38-0.55], p < .001). A shorter DAT was associated with a lower risk of cardiovascular events and recurrent AF for early-onset AF patients.

Abstract 18478: Association of Family History and Cardiomyopathy-Associated Gene Variants of Unknown Significance in Ethnic Minority Patients With Early Onset Atrial Fibrillation

Introduction: Underrepresentation of ethnic minorities in genetic studies can complicate interpretation of variants of unknown significance (VUS) in these groups. Likely pathogenic or pathogenic (LP/P) cardiomyopathy (CM) gene variants are associated with early onset-atrial fibrillation (EOAF) in a cohort of predominantly European ancestry, but prevalence in minorities, and the role of VUS, is unclear. Three-generation family history (FH) may provide insight into the potential pathogenicity of VUS in ethnic minorities. Hypothesis: In patients with EOAF and low comorbidity burden carrying CM VUS, does positive FH suggest variant pathogenicity? Aims: To determine whether CM gene VUS in ethnic minority probands with EOAF are associated with a FH of arrhythmia, stroke, or heart failure. Methods: Of 301 individuals from the University of Illinois Health Multi-Ethnic AF Registry who underwent whole exome sequencing, we identified 89 with either LP/P variant, positive FH from medical records, or AF diagnosis age ≤55 years and ≤2 comorbidities. We examined 22 genes strongly associated with CM and graded pathogenicity according to American College of Medical Genetics criteria. A three-generation FH was obtained by contacting probands or family members. Results: A FH was obtained in 36 patients (Figure 1a; median age 52 years, 56% female, 83% African-American, 17% Hispanic/Latinx). LP/P variants were present in 3 (8%) probands, VUS in 10 (28%), and likely benign/benign (LB/B) or no variant in 23 (64%). A FH of arrhythmia, heart failure, or stroke was present in 27 subjects (75%) with a FH of heart failure more likely in VUS carriers compared to those with LB/B or no variant (70% vs 26%, p=0.02), with no difference in FH of arrhythmia or stroke. Conclusion: Probands with EOAF who carry CM VUS have greater rates of FH of heart failure than those without disease-associated variants. This suggests pathogenicity of CM VUS in ethnic minorities with EOAF.

Abstract 15046: Atrial Sarcomeric Dysfunction in Ttntv Mice Indicates a Causal Relationship Between Rare Variation in TTN and Early Onset Atrial Fibrillation in Patients

Background: Atrial fibrillation (AF) is a common cardiac arrhythmia with a substantial genetic component. Rare variation in TTN and other sarcomeric genes have been associated with AF, in particular in early-onset disease. Aim: To describe the burden of rare, functional variants in a Norwegian early-onset AF population and to perform functional characterization in a Ttn truncating variant ( Ttntv ) mouse model. Methods: We performed whole-genome sequencing in 90 individuals with onset of AF before age 50 years and calculated the burden of rare, functional variation for all genes. Variant frequencies and gene burden from gnomAD 3.1.2 NFE were used as controls. The burden was defined as the sum of allele counts for rare (MAF&lt;1%) and damaging variants (high and moderate impact) for each gene, and differences in burden was assessed using Fisher’s exact test. Functional characterization, including echocardiography, electron microscopy and mRNA expression analyses, was performed in atria from haploinsufficient Ttntv mice. Results: We identified an increased burden of rare, functional variation in 57 genes, including the sarcomeric genes TTN , MYH6 and OBSL1 , but also in the cell adhesion gene DCHS2 , in individuals with early-onset AF. Ttntv mice had normal cardiac function assessed by echocardiography, but electron microscopy revealed structural remodeling of the atria, with a patchy pattern of unorganized sarcomeres with focal fibrosis and lipid droplet accumulation. Molecular profiling of atria using RNA sequencing showed differential expression of genes related to cellular stress, sarcomeric structure and fibrosis, including increased levels of Anp , Malat1 and Kcna1 . Dchs2 displayed decreased expression in Ttntv atria. Conclusion: We identified an increased burden of rare, functional variation in genes associated with sarcomeric function in early-onset AF. Atrial myopathy with sarcomeric lesions, focal fibrosis, lipid droplet accumulation and altered gene expression of Anp , Malat1 and Kcna1 was found in atria of mice with Ttntv , suggesting a causal, pathophysiological relationship between TTN variants and AF. Interestingly, DCHS2 displayed both increased burden of rare variation in early-onset AF and decreased expression in Ttntv mouse atria.

Abstract 13572: Electrocardiographic Aging Derived From Artificial Intelligence is Associated With the Risk of Early- and New-Onset Atrial Fibrillation: A Multi-National Cohort Study

Background: The application of artificial intelligence (AI) algorithms to ECG provides promising age prediction methods. We investigated whether the age discrepancy between AI-predicted age from ECG (AI-ECG age) and chronological age, known as the AI-ECG age gap or electrocardiographic aging (ECG-aging), could predict atrial fibrillation (AF) risk. Methods: We developed an AI-ECG age prediction model using a single-center dataset (1,533,042 ECGs from 689,639 participants) and validated it using five independent, multi-national datasets (637,177 ECGs from 230,838 participants). The AI-ECG age gap was calculated in two cohorts from South Korea and the UK. Based on this age gap, participants were classified into two study groups: Normal ECG-aging (Normal EA, age gap &lt;7 years) and Early ECG-aging (Early EA, age gap ≥7 years). We assessed the predictive capability of ECG-aging for early- and new-onset AF risk. Results: In two cohorts followed up for 5.9±3.7 and 3.0±1.6 years with 37,208 and 40,989 participants, respectively, the mean AI-ECG age with mean age gap was 47.4±12.4 (-0.1±6.0) and 68.4±7.8 (4.7±8.7) years, respectively. The early EA group was associated with increased risk of new-onset AF with HR of 1.86 (95% confidence interval, 1.46-2.38) and 1.88 (1.54-2.29), and early-onset AF with OR of 2.23 (1.79-2.77) and 1.52 (1.34-1.73), compared to the normal EA group in each cohort, respectively. Furthermore, there was an increased risk of both early- and new-onset AF with an increasing AI-ECG age gap. Conclusions: ECG-aging derived from the AI model was associated with the risk of early- and new-onset AF, indicating its potential as a risk predictor for AF in primary prevention.

Abstract 14865: A Paradigm Shift in the Incidence of Early-Onset Atrial Fibrillation and Flutter

Introduction: Atrial fibrillation (AF) and atrial flutter (AFL) are the most prevalent cardiac arrhythmias. Although the incidence and disease burden have been increasing, once adjusted for age, the standardized incidence has been decreasing, reaching 57.10 per 100,000 as of 2019. This study aims to explore this epidemiological trend pertaining to the younger population which are often underrepresented in AF/AFL studies. Methods: Utilizing the Global Burden of Disease (GBD) database, we calculated the incidence and disability-adjusted life years (DALYs) of AF/AFL patients aged 15-49 years along with the age standardized rates (ASR) and annual percentage changes (APC) for the incidence and DALYs from 2010 to 2019. We also calculated these values for populations according to socio-demographic index (SDI) group, region, and gender. Result: From 2010 to 2019, the standardized incidence and DALYs of early onset AF/AFL (EOAF/AFL) had increased globally. The APC of ASR of incidence had been +0.15% (95% confidence interval (CI) 0.21%-0.08%) and the APC of ASR of DALYs had been 0.28% (95% CI 0.36%-0.21%), respectively. Women demonstrated higher APC of both ASRs of incidence (+0.45% (95% CI 0.40%-0.50%) and DALYs (+0.50% (95% CI 0.45%-0.55%) while men experienced a stable trend of ASR of incidence and declining trend of ASR of DALYs. Geographic analysis showed that Eastern Mediterranean population had the highest APCs of both ASRs of incidence (+1.53% (95% CI 0.40%-0.50%)) and DALYs (+1.61%95% CI 0.40%-0.50%)), while both ASR and DALYs declined in the United States Conclusion: The incidence and DALYs of EOAF/AFL had been increasing globally, especially among women. However, rates differed by geographic region. For example, Eastern Mediterranean regions showed the largest increases across all age groups. In contrast, the incidence of EOAF/AFL had continued to decline in the United States. Future study is warranted to explore the geographical impact on the risk factors of AF/AFL.

Loss of Cardiac Splicing Regulator RBM20 Is Associated With Early-Onset Atrial Fibrillation

We showed an association between atrial fibrillation and rare loss-of-function (LOF) variants in the cardiac splicing regulator RBM20 in 2 independent cohorts. In a rat model with loss of RBM20, we demonstrated altered splicing of sarcomere genes (NEXN, TTN, TPM1, MYOM1, and LDB3), and differential expression in key cardiac genes. We identified altered sarcomere and mitochondrial structure on electron microscopy imaging and found compromised mitochondrial function. Finally, we demonstrated that 3 novel LOF variants in RBM20, identified in patients with atrial fibrillation, lead to significantly reduced splicing activity. Our results implicate alternative splicing as a novel proarrhythmic mechanism in the atria.

Case report: Mutation in NPPA gene as a cause of fibrotic atrial myopathy

Early-onset atrial fibrillation (AF) can be the manifestation of a genetic atrial myopathy. However, specific genetic identification of a mutation causing atrial fibrosis is rare. We report a case of a young patient with an asymptomatic AF, diagnosed during a routine examination. The cardiac MRI revealed extensive atrial fibrosis and the electrophysiology study showed extensive areas of low voltage. The genetic investigation identified a homozygous pathogenic variant in the NPPA gene in the index case and the presence of the variant in heterozygosity in both parents.

Genetic testing in monogenic early-onset atrial fibrillation.

A substantial proportion of atrial fibrillation (AF) cases cannot be explained by acquired AF risk factors. Limited guidelines exist that support routine genetic testing. We aim to determine the prevalence of likely pathogenic and pathogenic variants from AF genes with robust evidence in a well phenotyped early-onset AF population. We performed whole exome sequencing on 200 early-onset AF patients. Variants from exome sequencing in affected individuals were filtered in a multi-step process, prior to undergoing clinical classification using current ACMG/AMP guidelines. 200 AF individuals were recruited from St. Paul's Hospital and London Health Sciences Centre who were ≤ 60 years of age and without any acquired AF risk factors at the time of AF diagnosis. 94 of these AF individuals had very early-onset AF ( ≤ 45). Mean age of AF onset was 43.6 ± 9.4 years, 167 (83.5%) were male and 58 (29.0%) had a confirmed family history. There was a 3.0% diagnostic yield for identifying a likely pathogenic or pathogenic variant across AF genes with robust gene-to-disease association evidence. This study demonstrates the current diagnostic yield for identifying a monogenic cause for AF in a well-phenotyped early-onset AF cohort. Our findings suggest a potential clinical utility for offering different screening and treatment regimens in AF patients with an underlying monogenic defect. However, further work is needed to dissect the additional monogenic and polygenic determinants for patients without a genetic explanation for their AF despite the presence of specific genetic indicators such as young age of onset and/or positive family history.

PO-01-108 ELUCIDATING THE MECHANISM OF ATRIAL FIBRILLATION IN LAMIN A/C HEART DISEASE USING HUMAN IPSC-DERIVED ATRIAL CARDIOMYOCYTES

Mutations in the LMNA gene, encoding the nuclear envelope proteins lamin A/C, cause cardiac arrhythmias, conduction disease, and dilated cardiomyopathy. Malignant arrhythmias such as atrial fibrillation (AF) and ventricular tachycardia are common and pose an increased risk of stroke and sudden cardiac death. To investigate the etiological mechanisms by which a heterozygous pathogenic LMNA-S143P mutation causes early-onset AF using mature human iPSC-derived atrial cardiomyocytes (hiPSC-aCM) generated from a large kindred with a strong cardiac phenotype. Detailed phenotyping of a 4-generation family pedigree and generation of hiPSCs from the proband using a comprehensive approach for the differentiation of mature hiPSC-aCMs. Action potential duration was measured by optical voltage mapping. Calcium transients were measured by confocal microscopy. The proband (III-3) is a 42-year-old female of European and Asian descent who developed symptomatic early-onset AF at age 35. She underwent direct current cardioversion (DCCV), pulmonary vein isolation, and implantation of a biventricular pacemaker. Cardiac MRI showed an enlarged left atrium with preserved left ventricular systolic function (EF 56%). A detailed family history revealed early-onset AF and AV block, congestive heart failure (CHF), and sudden death (Fig. 1). Genetic testing of the proband revealed a pathogenic missense mutation in LMNA (c427T>Cp. Ser143Pro). Mature LMNA-S143P-hiPSC-aCMs displayed prolongation of the atrial action potential duration (APD90) with delayed afterdepolarizations, abnormal calcium transients, and AF as compared to wild-type hiPSC-aCMs. Detailed phenotyping of a large LMNA kindred revealed a phenotype of AF, cardiac conduction disease, dilated cardiomyopathy, and sudden death. Our hiPSC-aCM studies uncovered a triggered mechanism for the AF with ion channel remodeling and pave the way for targeting calcium handling proteins as a potential therapeutic strategy in LMNA associated arrhythmias.