In the paper, the mechanisms have been discussed which lead to suppression of microreentry waves during fibrillation of atria. In this respect, the largest effectiveness of electric heart cardioversion was underlined. Arguments have been collected for more frequent than till-now application of cardioversion. Side effects of conventional cardioversion performed by means of chest electrodes have been stressed. Basing on data from literature, it was indicated that the heart damage grows larger along with increase of cardioverting energy. Assumptions have been presented on heart sparing low-energy intracardiac and transesophageal cardioversion of atrial fibrillation. There have been discussed the precautions that are to be observed for the safety of patient's esophagus and heart during transesophageal electric cardioversion of his atria