Abstract 10816: Causal Effect of Atrial Fibrillation on Cardiovascular Diseases - A Mendelian Randomization Analysis in the Million Veteran Program

Introduction: Observational studies have implicated atrial fibrillation (AF) as a risk factor for a number of cardiovascular diseases (CVD). Whether AF is causally related to these CVD is unknown. Methods: We included participants with both electronic health record-derived phenotypes and imputed genotype data in this study. A genetic instrument for AF consisting of 406 common variants was derived using a pruning and thresholding method (r2<0.3; p-value <5x10-8) on the 2018 AF Genetics Consortium GWAS summary statistics. 1- and 2-sample MR analyses were performed. In 2-sample MR, the inverse-variance weighted method was used as the primary analysis. Additional sensitivity analyses were performed to account for potential violations of the instrumental variable assumptions. Results: We included 615,635 participants in the study (440,690 European, 118,531 African, 48,908 Hispanic, 7,506 Asian ancestry). Genetic risk of AF was associated with heart failure in both 1-sample (OR/log odds of genetically predicted AF =1.18, 95% CI 1.15 - 1.20) and 2-sample MR (OR/log odds of genetically predicted AF =1.13, 95% CI 1.11 - 1.15). Additionally, genetic risk of AF was associated with heart failure subtypes and non-ischemic cardiomyopathy. There was no association between genetic risk of AF and pulmonary embolism (PE) or deep venous thrombosis (DVT), however, genetic risk of AF was associated with PE after excluding individuals with concurrent or prior DVT (OR1-sample MR 1.08, 95% CI 1.01 - 1.15; OR2-sample MR 1.06, 95% CI 1.03 - 1.08). Lastly, we confirmed an association between genetic risk of AF and ischemic stroke but not all-cause dementia. Our results were robust to a number of sensitivity analyses. Conclusions: In a large multi-ancestry study, we delineate the potential causal contribution of AF to a number of CVD and highlight support for a causal association between AF and isolated PE. Our findings inform how prevention and treatment of AF may affect CVD incidence and outcomes.