Atrial fibrillation (AF) is the most common cardiac arrhythmia affecting more than 35 million people worldwide. It is an age-dependent progressive disease that doubles mortality, degrades life-quality, and becomes increasingly difficult to treat with time. Therefore, it is essential to find new biological markers that allow early identification of individuals prone to develop AF and to optimize the treatment of the arrhythmia. Recently more than 100 genetic markers which are referred to as single nucleotide polymorphisms (SNPs) have each been associated with a modest increase in the risk of developing AF. Since all of us have several of these risk SNPs the challenge, in which this project aims to engage, is to identify combinations of SNPs that confer a high risk of AF and discover how they affect the function of the heart cells. This will then allow health professionals to use SNP analysis to improve risk prediction and to personalize the treatment of people with AF according to the risk SNPs they carry.