First off Gangrene is a macroscopic death of tissue with surpadded putrefaction. The swelling in your fingers along with peeling of skin and blackening is due to inadequate blood supply due to the stenosis The medications given are antiplatelet drugs persantine is a medication having dypiridamole which releases adenosine , a compound causing vasodilation. Looking at how much your situation has progressed I suggest you go to your doctor immediately and get operated on the stenosis else the Gangrene may spread. Also not to alarm you but there is a possibility that the gangrenous part may have to be amputated although this is a decision for your surgeon after further examination and tests