Cardiac arrhythmias account for about 1 death in 10 in industrialized countries. Although cardiac arrhythmias has been studied for well over a century, their underlying mechanisms remain largely unknown. Over the years, several factors that favor arrhythmias initiation were established. Among them are ionic and dynamical heterogeneity, remodeling and fibrosis of cardiac tissue. In addition a lot of attention was given to the arrhythmias which occur due to channelopathies which result in the long QT syndrome. In my talk I will present our recent studies on role of these arrhythmogenic factors performed using anatomically accurate model of ventricles of the human heart developed in our group.