Atrial fibrillation is the most common form of arrhythmias, apart from the extrasystolics beats. The prevalence of this abnormality is estimated at 1-2% of the general population and it is highly increasing with the age, reaching a value of 5-15% among the people with the age over 80. Moreover, it is estimated that this kind of arrhythmia is present among circa 6 million inhabitants of European continent. In recent decades, its prevalence increases significantly. This tendency is connected with the great progress made in medicine, as well in cardiology and thereby the rapid aging of the European population. The substantial lengthening of the life expectancy will probably imply the double number of the atrial fibrillation incidents in the next 50 years.