In a catheter (2) to assist the performance of a heart (1) with at least one pump (7), the pump is formed as a rotary pump at the distal end of the catheter (2), the rotor (6) lying distally on the outer side being coupled via a magneto coupling with a drive wheel (21), formed as a hydraulically or pneumatically operated paddle wheel, arranged inside the catheter (2). The driving fluid is supplied to the paddle wheel via a lumen (22) of the catheter (2) and is carried off via a further lumen (23) of the catheter.