The comprehensive study of morphometrical parameters and viscoelastic properties of right ventricle and left ventricle papillary muscles of ISIAH rats during the development of arterial hypertension has been carried out. It is established the significant increase of the index of heart mass to body mass and to tibia length of ISIAH rats in comparison with WAG rats of the same age. There are no any significant differences of "stress-strain" dependences of all experimental groups.