While there are many sub-aims to this study, the overarching goal is to define molecular mechanisms underlying atrial dysfunction. Here the investigator provide a power calculation based on detecting the genetic control points of gene expression (eQTLs) in the human atrial fibroblast. The investigator and many others have shown that tissue-specific eQTLs can be robustly identified at genome-wide significance in segregating populations of ~200. In this study the investigator propose eQTL association analysis in humans, which have previously been successfully performed in cohorts of less than 1000 subjects. The general applicability of this approach has been validated in multiple studies across multiple tissues in cohorts of between 200-1000 subjects.Based on published imaging genetic studies that have been successfully applied in small cohorts (<500) and the success of echo-based, semi-quantitative studies of ventricular dimensions, the investigator are confident that our quantitative studies of 750 individuals are powered to detect genome wide significant loci for the traits under study.