The Risk of Atrial Fibrillation Increases with Earlier Onset of Obesity: A Mendelian Randomization Study

GWAS advancements to investigate disease associations and biological mechanisms

Genome-wide association studies (GWAS) have been instrumental in elucidating the genetic architecture of various traits and diseases. Despite the success of GWAS, inherent limitations such as identifying rare and ultra-rare variants, the potential for spurious associations, and in pinpointing causative agents can undermine diagnostic capabilities. This review provides an overview of GWAS and highlights recent advances in genetics that employ a range of methodologies, including Whole Genome Sequencing (WGS), Mendelian Randomization (MR), the Pangenome's high-quality T2T-CHM13 panel, and the Human BioMolecular Atlas Program (HuBMAP), as potential enablers of current and future GWAS research. State of the literature demonstrate the capabilities of these techniques in enhancing the statistical power of GWAS. WGS, with its comprehensive approach, captures the entire genome, surpassing the capabilities of the traditional GWAS technique focused on predefined Single Nucleotide Polymorphism (SNP) sites. The Pangenome's T2T-CHM13 panel, with its holistic approach, aids in the analysis of regions with high sequence identity, such as segmental duplications (SDs). Mendelian Randomization has advanced causative inference, improving clinical diagnostics and facilitating definitive conclusions. Furthermore, spatial biology techniques like HuBMAP, enable 3D molecular mapping of tissues at single-cell resolution, offering insights into pathology of complex traits. This study aims to elucidate and advocate for the increased application of these technologies, highlighting their potential to shape the future of GWAS research.

A causal relationship between appendicular lean mass and atrial fibrillation: A two sample Mendelian randomization study

BACKGROUND AND AIM

The relationship between appendicular lean mass (ALM) and most cardiovascular events has been established, but the direct association between ALM and atrial fibrillation (AF) remains uncertain.

METHODS AND RESULTS

Herein, we identified 494 single-nucleotide polymorphisms (SNPs) strongly associated with ALM as instrumental variables (P < 5E-8) based on a genome-wide association study (GWAS) with 450,243 European participants. Then, we employed five Mendelian randomization (MR) analysis methods to investigate the causal relationship between ALM and AF. All results indicated a causal relationship between ALM and AF, among Inverse variance weighted (P = 8.44E-15, odds ratio [OR]: 1.16, 95 % confidence interval [CI]: 1.114-1.198). Furthermore, we performed a sensitivity analysis, which revealed no evidence of pleiotropy (egger_intercept = 0.000089, P = 0.965) or heterogeneity (MR Egger, Q Value = 0.980; Inverse variance weighted, Q Value = 0.927). The leave-one-out method demonstrates that individual SNPs have no driven impact on the whole causal relationship. Multivariable MR analysis indicates that, after excluding the influence of hypertension and coronary heart disease, a causal relationship between ALM and AF still exists (P = 7.74E-40, OR 95 %CI: 1.389 (1.323-1.458)). Importantly, the Radial MR framework analysis and Robust Adjusted Profile Score (RAPS) further exhibit the robustness of this causal relationship.

CONCLUSION

A strong association between ALM and AF was confirmed, and high ALM is a risk factor for AF.

Causal relationship between nutritional assessment phenotypes and heart failure: A Mendelian randomization study

Introduction

Malnutrition is strongly associated with heart failure (HF); however, the causal link remains unclear. We used Mendelian randomization (MR) to infer causal associations between different nutritional assessment phenotypes and HF and to analyze whether these associations were mediated by common HF risk factors.

Methods

Two-sample bidirectional MR was used to infer causal associations between nutritional assessment phenotypes and HF. Mutual influences between different nutritional assessment phenotypes and potential correlations were estimated using multivariate MR methods. Two-step MR was used to quantify the mediating effects of common HF risk factors on the causal associations.

Results

Three phenotypes were positively associated with the development of HF: waist circumference (WC) (odds ratio [OR] = 1.74; 95% confidence interval [CI], 1.60-1.90; P = 3.95 × 10-39), body mass index (BMI) (OR = 1.70; 95%CI, 1.60-1.80; P = 1.35 × 10-73), and whole body fat mass (WBFM) (OR = 1.54; 95%CI, 1.44-1.65; P = 4.82 × 10-37). Multivariate MR indicated that WBFM remained positively associated with HF after conditioning on BMI and WC (OR = 2.05; 95%CI, 1.27-3.31; P = 0.003). Three phenotypes were negatively correlated with the development of HF: usual walking pace (UWP) (OR = 0.40; 95%CI, 0.27-0.60; P = 8.41 × 10-6), educational attainment (EA) (OR = 0.73; 95%CI, 0.67-0.79; P = 2.27 × 10-13), and total cholesterol (TC) (OR = 0.90; 95%CI, 0.84-0.96; P = 4.22 × 10-3). There was a bidirectional causality between HF and UWP (Effect estimate = -0.03; 95%CI, -0.05 to -0.01; P = 1.95 × 10-3). Mediation analysis showed that common risk factors for HF (hypertension, coronary artery disease, cardiomyopathy, and valvular heart disease) mediated these causal associations (all P < 0.05).

Conclusions

BMI, WC, and WBFM are potential risk factors for HF, and the correlation between WBFM and HF was significantly stronger than that between BMI and WC, and HF. EA, UWP, and TC are potential protective factors against HF. Common risk factors for HF mediate these causal pathways. Early identification of potential risk or protective factors for HF patients from the dimension of nutritional status is expected to further improve patient outcomes.

Effects of childhood obesity on heart failure and its associated risk factors in the European population: A Mendelian randomization study

BACKGROUND AND AIMS

Observational studies have shown that obesity considerably affects the cardiovascular system. Thus we conducted this Mendelian randomization (MR) analysis to evaluate the causal effect of childhood obesity on heart failure (HF) and its risk factors.

METHODS AND RESULTS

We obtained genetic instruments from genome-wide association studies (GWAS) that investigated childhood obesity, HF, type 2 diabetes mellitus (T2DM), atrial fibrillation (AF), coronary artery disease (CAD), myocardial infarction (MI), chronic kidney disease (CKD), valvular heart disease, myocarditis, hypertrophic cardiomyopathy, and hyperthyroidism. Inverse variance weighting (IVW), weighted median analysis, MR-Egger, and MR-pleiotropy residual sum and outlier (MR-PRESSO) were employed for MR analyses. In addition, the leave-one-out sensitivity test, MR-PRESSO global test, and Cochran's Q test were used for sensitivity analyses. Genetic evaluations showed that childhood obesity increases the risk of HF (odds ratio [OR] = 1.11, 95%CI: 1.05-1.17, p = 1.26 × 10-4), T2DM (OR = 1.17, 95%CI: 1.12-1.23, p = 8.80 × 10-12), AF (OR = 1.08, 95%CI: 1.05-1.12, p = 2.66 × 10-7), MI (OR = 1.08, 95%CI: 1.04-1.13, p = 3.35 × 10-4), and CAD (OR = 1.08, 95%CI: 1.03-1.13, p = 1.48 × 10-3). We found no association between childhood obesity and CKD, valvular heart disease, myocarditis, hypertrophic cardiomyopathy, or hyperthyroidism. Sensitivity analysis and Bonferroni's correction showed consistent results.

CONCLUSIONS

Our study provides new evidence for the relationship between childhood obesity and HF and its risk factors. The results indicate that individuals with a history of childhood obesity require more clinical attention to prevent the development of HF.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Patients With Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

Methodological approaches, challenges, and opportunities in the application of Mendelian randomisation to lifecourse epidemiology: A systematic literature review

Diseases diagnosed in adulthood may have antecedents throughout (including prenatal) life. Gaining a better understanding of how exposures at different stages in the lifecourse influence health outcomes is key to elucidating the potential benefits of disease prevention strategies. Mendelian randomisation (MR) is increasingly used to estimate causal effects of exposures across the lifecourse on later life outcomes. This systematic literature review explores MR methods used to perform lifecourse investigations and reviews previous work that has utilised MR to elucidate the effects of factors acting at different stages of the lifecourse. We conducted searches in PubMed, Embase, Medline and MedRXiv databases. Thirteen methodological studies were identified. Four studies focused on the impact of time-varying exposures in the interpretation of "standard" MR techniques, five presented methods for repeat measures of the same exposure, and four described methodological approaches to handling multigenerational exposures. A further 127 studies presented the results of an applied research question. Over half of these estimated effects in a single generation and were largely confined to the exploration of questions regarding body composition. The remaining mostly estimated maternal effects. There is a growing body of research focused on the development and application of MR methods to address lifecourse research questions. The underlying assumptions require careful consideration and the interpretation of results rely on select conditions. Whilst we do not advocate for a particular strategy, we encourage practitioners to make informed decisions on how to approach a research question in this field with a solid understanding of the limitations present and how these may be affected by the research question, modelling approach, instrument selection, and data availability.

Obesity-Related Atrial Fibrillation: Cardiac Manifestation of a Systemic Disease

Atrial fibrillation (AF) is the most common arrhythmia worldwide and is associated with increased morbidity and mortality. The mechanisms underlying AF are complex and multifactorial. Although it is well known that obesity is a strong risk factor for AF, the mechanisms underlying obesity-related AF are not completely understood. Current evidence proposes that in addition to overall hemodynamic changes due to increased body weight, excess adiposity raises systemic inflammation and oxidative stress, which lead to adverse atrial remodeling. This remodeling includes atrial fibrosis, atrial dilation, decreased electrical conduction between atrial myocytes, and altered ionic currents, making atrial tissue more vulnerable to both the initiation and maintenance of AF. However, much remains to be learned about the mechanistic links between obesity and AF. This knowledge will power the development of novel diagnostic tools and treatment options that will help combat the rise of the global AF burden among the obesity epidemic.