Activity of the heart is assured by the myocardium motion with a composite path, which can be described with various quantitative indices, in particular the strain ones. The invention and implementation into clinical practice the "Speckle Tracking" ultrasonic technology, based on the two-dimensional echocardiography, allows to study of normal myocardium function as well as its functioning in various hart lesions, in particular, dilated cardiomyopathy (DCMP). Peculiarities of the features of longitudinal strain parameters of left ventricular (LV) walls in patients with DCMP, according to the occurrence of the total left branch of atrioventricular bundle block were studied. In DCMP the indices of longitudinal myocardial strain of the LV were strongly decreasing with the augmenting of heart failure signs. The appearance of the total left branch of atrioventricular bundle block, manifested by the total decrease of amplitude of longitudinal strain of the lateral and posterior walls of the LV, led to the augmenting of mitral regurgitation (up to 2+) and increase of the pulmonary hypertension, augmenting of circulatory deficiency signs.