Wells, Quinn S.

BACKGROUND: Greater left atrial size is associated with a higher incidence of cardiovascular disease and mortality, but the full spectrum of diagnoses associated with left atrial enlargement in sex-stratified clinical populations is not well known. Our study sought to identify genetic risk mechanisms affecting left atrial diameter (LAD) in a clinical cohort. METHODS: Using Vanderbilt deidentified electronic health record, we studied 6163 females and 5993 males of European ancestry who had at least 1 LAD measure and available genotyping. A sex-stratified polygenic score was constructed for LAD variation and tested for association against 1680 International Classification of Diseases code–based phenotypes. Two-sample univariable and multivariable Mendelian randomization approaches were used to assess etiologic relationships between candidate associations and LAD. RESULTS: A phenome-wide association study identified 25 International Classification of Diseases code–based diagnoses in females and 11 in males associated with a polygenic score of LAD (false discovery rate q<0.01), 5 of which were further evaluated by Mendelian randomization (waist circumference [WC], atrial fibrillation, heart failure, systolic blood pressure, and coronary artery disease). Sex-stratified differences in the genetic associations between risk factors and a polygenic score for LAD were observed (WC for females; heart failure, systolic blood pressure, atrial fibrillation, and WC for males). By multivariable Mendelian randomization, higher WC remained significantly associated with larger LAD in females, whereas coronary artery disease, WC, and atrial fibrillation remained significantly associated with larger LAD in males. CONCLUSIONS: In a clinical population, we identified, by genomic approaches, potential etiologic risk factors for larger LAD. Further studies are needed to confirm the extent to which these risk factors may be modified to prevent or reverse adverse left atrial remodeling and the extent to which sex modifies these risk factors.

Abstract Aims Mitral valve prolapse (MVP) is a common valvular heart disease with a prevalence of &gt;2% in the general adult population. Despite this high incidence, there is a limited understanding of the molecular mechanism of this disease, and no medical therapy is available for this disease. We aimed to elucidate the genetic basis of MVP in order to better understand this complex disorder. Methods and results We performed a meta-analysis of six genome-wide association studies that included 4884 cases and 434 649 controls. We identified 14 loci associated with MVP in our primary analysis and 2 additional loci associated with a subset of the samples that additionally underwent mitral valve surgery. Integration of epigenetic, transcriptional, and proteomic data identified candidate MVP genes including LMCD1, SPTBN1, LTBP2, TGFB2, NMB, and ALPK3. We created a polygenic risk score (PRS) for MVP and showed an improved MVP risk prediction beyond age, sex, and clinical risk factors. Conclusion We identified 14 genetic loci that are associated with MVP. Multiple analyses identified candidate genes including two transforming growth factor-β signalling molecules and spectrin β. We present the first PRS for MVP that could eventually aid risk stratification of patients for MVP screening in a clinical setting. These findings advance our understanding of this common valvular heart disease and may reveal novel therapeutic targets for intervention.

Background: Sequencing Mendelian arrhythmia genes in individuals without an indication for arrhythmia genetic testing can identify carriers of pathogenic or likely pathogenic (P/LP) variants. However, the extent to which these variants are associated with clinically meaningful phenotypes before or after return of variant results is unclear. In addition, the majority of discovered variants are currently classified as variants of uncertain significance, limiting clinical actionability. Methods: The eMERGE-III study (Electronic Medical Records and Genomics Phase III) is a multicenter prospective cohort that included 21 846 participants without previous indication for cardiac genetic testing. Participants were sequenced for 109 Mendelian disease genes, including 10 linked to arrhythmia syndromes. Variant carriers were assessed with electronic health record–derived phenotypes and follow-up clinical examination. Selected variants of uncertain significance (n=50) were characterized in vitro with automated electrophysiology experiments in HEK293 cells. Results: As previously reported, 3.0% of participants had P/LP variants in the 109 genes. Herein, we report 120 participants (0.6%) with P/LP arrhythmia variants. Compared with noncarriers, arrhythmia P/LP carriers had a significantly higher burden of arrhythmia phenotypes in their electronic health records. Fifty-four participants had variant results returned. Nineteen of these 54 participants had inherited arrhythmia syndrome diagnoses (primarily long-QT syndrome), and 12 of these 19 diagnoses were made only after variant results were returned (0.05%). After in vitro functional evaluation of 50 variants of uncertain significance, we reclassified 11 variants: 3 to likely benign and 8 to P/LP. Conclusions: Genome sequencing in a large population without indication for arrhythmia genetic testing identified phenotype-positive carriers of variants in congenital arrhythmia syndrome disease genes. As the genomes of large numbers of people are sequenced, the disease risk from rare variants in arrhythmia genes can be assessed by integrating genomic screening, electronic health record phenotypes, and in vitro functional studies. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier; NCT03394859.

Background: Return of incidental genetic findings is recommended for pathogenic/likely pathogenic (P/LP) variants in Mendelian arrhythmia genes. The extent to which these variants are associated with arrhythmia phenotypes in unselected populations is unknown. Objective: Assess the impact of return of results (RoR) of P/LP variants in 4 arrhythmia genes in research participants not selected for cardiovascular disease. Methods: The cohort included 24,410 participants from the Electronic Medical Records and Genomics Network. Rare variants (minor allele frequency <1%) in KCNE1 , KCNH2 , KCNQ1 , and SCN5A were identified and classified according to ACMG guidelines. Arrhythmia phenotypes extracted from electronic health records (EHRs) included atrial fibrillation/flutter (AF/AFL), conduction system disease, long QT syndrome (LQTS), ventricular tachycardia/fibrillation (VT/VF), and premature ventricular contractions (PVCs). P/LP carriers’ phenotypes were compared to non-carriers using logistic regression adjusted for demographic covariates and site. Participants with P/LP variants were informed of their results and the impact of this RoR was assessed after 1 year of follow-up clinical care. Results: The participants included 53.7% females and 72.5% white individuals, with a median age of 57 years. 71 participants had a heterozygous P/LP variant in one of the 4 genes. LQTS diagnoses were associated with P/LP carrier status for all 4 genes ( KCNE1 OR 22.8, p=1.0e-4; KCNH2 OR 35.1, p=1.8e-7; KCNQ1 OR 27.3, p=3.6e-18; SCN5A OR 5.6, p=0.02). Carriers of SCN5A P/LP variants were also more likely to have PVCs (OR 4.3, p=0.003). Sensitivity analyses showed the associations predated the RoR. EHRs included a diagnosis of LQTS or Brugada Syndrome in 11/71 (16%) pre-RoR, and 16 more were diagnosed after RoR (27/71, 38%). A total of 47/71 (66%) participants had a documented arrhythmia phenotype 1 year after RoR, although 20 of these participants were not diagnosed with an inherited arrhythmia syndrome. Conclusion: Inherited arrhythmia diagnoses could be established in nearly half of participants with P/LP variants. These data indicate that return of incidental P/LP variants in these genes may facilitate the early diagnosis of arrhythmias.