A catheter system for cryoablation is described that comprises: a catheter, which extends along its longitudinal axis； at least one cryoballoon which surrounds the catheter around its entire circumference and forms a filling lumen； a cooling lumen, which is separate from the filling lumen, within the cryoballoon, wherein the cooling lumen is arranged at the outer region of the cryoballoon away from the longitudinal axis of the catheter； at least one filling conduit which extends within the catheter and terminates in the filling lumen； and at least one cooling conduit which extends within the catheter and terminates in the cooling lumen.
