A stepped catheter comprising a distal portion of smaller diameter than a proximal portion, wherein the distal portion defines a flow aperture configured to deliver fluid passing through the catheter from the proximal portion to the flow aperture. The catheter may include a flow restrictor located within a lumen of the catheter at or near the flow aperture. A filter element may also be included and located within the lumen of the catheter at a location upstream of the flow restrictor.
