The invention regards a medical device for adjustably reducing a vessel lumen. The device comprises a stent part providing a flow channel for the blood and a flexible membrane part within the stent part that closes the flow channel off except for a flow opening. A thread is arranged within the membrane part with one end exiting the device and thus being accessible. The thread forms a loop around the flow opening and by pulling on the thread the loop can be constricted which leads to a reduction of the size of the flow opening.
