Abstract: Septum retaining means for an implantable tubular percutaneous device. The retaining means is a tubular stem insert having an integral pressure plate across an intermediate portion thereof. A modified septum fits into the insert below the pressure plate. Tabs extending outwardly from the upper edge of the insert cooperate with a grooved portion of a body exterior cavity in the T-stem to provide means for holding the insert in the T-stem cavity. Notches in the walls of the insert on either side of the tabs allow the wall portions containing the tabs to be flexed inwardly so as to permit the insert to be passed into and out of the T-stem. The insert is designed to permit a forceps or other crimping tool to obtain access to the tab containing insert wall portions for removal of the insert and septum.