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The endocardial surface and the volume of the left ventricle were determined experimentally by an original noninvasive method with the goal of understanding the mechanism of the influence of the change of left ventricle shape on the execution of its pumping function. The chore parameters were studied by echocardiography and ECG at the end of diastole and systole. Three groups of patients (sportsmen, subjects taking part in no sports and dialysis patients) were evaluated. The change in the volume of left ventricle represents the frame of the left ventricle pumping action, while the change of surface can be interpreted as an indicator of the axis’ dynamics. A spherical and the cylindrical shapes of the volume ejecting left ventricle during the heart cycle and that can be understood as a principle, called »cylindricality«. In diastole the left ventricle is more spherical, in systole more tube-like. This mechanism is in pathological conditions changed. The term of cylindricality encompasses the fact that two bodies with the same volume can have different surface areas. The experimentally determined value of the cylindrical form of surface deviates from the mathematically determined spherical form of surface. Cylindricality of a normal left ventricle in diastole is 7 %, and systolic cylindicality 24 %; diastolic cylindricality of the dialysis patients is 16 %, in systole 24 %. The results obtained suggest that in pathological conditions the principle of cylindricality is replaced by the law of Laplace, which can explain the consequences of the lost of the cylindricality, principle for the left ventricle function and its prognosis.