Today cardiac resynchronization treatment (CRT) belongs to standard procedures of non-pharmacological treatment of chronic heart failure (CHSZ). In majority of patients this disorder is accompanied with dys-synchronization of the mechanical contraction which is rectifiable by help of CRT. The decisive factor for patients with chronic heart failure is left ventricular dysfunction. Biventricular stimulation and shortening of AV interval can optimalise left ventricular dysfunction. First of all it is stimulation from several places: right atrium, right ventricle, and through coronary sinus also left ventricle (CRT-P). In European and Slovak guidelines it is clearly stated that the use of ICD (CRT-D) for primary prevention is indicated in patients with heart failure, with severe dysfunction of left ventricle regardless the original disease in which we can reasonably assume survival of more than one year. The aim of the new indication for biventricular stimulation, focused on adjustment of ventricular contraction coordination, is the following improvement of heart functioning.