A plain bearing assembly for a cardiac pump, the plain bearing assembly comprising; a rotational portion which, in use, rotates with a cardiac pump rotor, the rotational portion configured to engage a stationary portion of a cardiac pump housing, the stationary portion comprising one or more first bearing surfaces and the rotational portion comprising one or more second bearing surfaces, the one or more second bearing surfaces configured so as to be in contact with the one or more first bearing surfaces, therein defining a bearing interface between the one or more first bearing surfaces and the one or more second bearing surfaces during rotation of the rotational portion, wherein the rotational portion comprises one or more first flow channels configured to interrupt the bearing interface and permit blood to flow between an outside of the plain bearing assembly and a center of the plain bearing assembly.