A plain bearing assembly (102 202 302) for a cardiac pump (101 202 302) the plain boating assembly comprising a rotational portion (120 229 329) which in use rotates with a cardiac pump rotor (108 208 303) the rotational portion being configured to engage a stationary portion (125 225 325) of a cardiac pump housing (7 107 207 307) the stationary portion comprising one or more first hearing surfaces (127 227 327) and the rotational portion: comprising one or more second bearing surfaces (131 231 331) the one or more second hearing surfaces being configured so as to be in contact with the one or more first bearing surfaces therein defining a bearing Interface (135 235 335) 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 (133 133a 133b 233 233a 233b 333) configured to Interrupt the bearing Interface and permit blood to flow between an outside (132 132a 132b 232 232a 232b 332) of the plain bearing assembly and a centre (134 134a 134b 234 234a 234b 334) of the plain bearing assembly.
