Modern devices for heart ultra sound have tools, which help doctors to calculate some indicators, which are necessary for the diagnosis of different diseases. Theseindicatorsarecalculatedvia theleft ventricle area of the heart, whichdoctorsarebuildingmanually. The article presents a semi-automatic algorithm for contouring of left ventricle on echocardiographic images of the apical four-chamber heart projection. A quantitative analysis of algorithm results was conducted. The contour building by algorithm follows the contour building by experts with high accuracy. For qualitative analysis, the results of semi-automatic algorithm were compared with the results obtained by thealgorithm JSEG. This segmentation algorithm has less precision than the semi-automatic algorithm and can’t be used for solving this problem.