Some mechanical considerations in the selection and testing of papillary muscles

Measurements of segmental deformation made on papillary muscles obtained from cat, rabbit, dog and pig hearts suggest that the deformational behavior in these specimens is appreciably nonuniform both in the resting (passive) state and in the stimulated (active) state. In view of this, in the mechanical testing of papillary muscles, it is necessary to establish a minimum size of segment "sufficiently" far from the disturbing influence of end fixtures generally used to hold the specimen in the testing machine. The segment size should be large enough to average out the nonuniform aspects of deformation. Thus, the shape and size of the specimen dictated by the nonuniformities in the mechanical response, the thinness of the specimen dictated by the viability considerations and aspects of the testing machines and method dictated by the visco-elastic features of the specimen should be given due consideration in the selection and testing of papillary muscles.