A cardiac pump 101 with impellers 113 comprises a magnetic bearing assembly 136 providing rotatable radial support between the cardiac pump rotor 108 and the housing 107 and having first and second magnetic bearing portions 136a,136b, the axial position of which may be threadably adjustable by means of a magnetic bearing adjuster 176 to bias the cardiac pump rotor 108, 208 in an axial direction and provide a preload force to a plain bearing assembly 126 configured to rotatably support the cardiac pump rotor 108 in at least an axial direction. There may be a further magnetic bearing assembly 156, a further plain bearing assembly, and a magnetic drive coupling 140.
