Suggest Treatment For Pain And Clogged Artery In Knee

Situation is a 69 year old man, diabetic, had a clogged artery behind his knee- a very long stent was put in.. No check ups- 2 months later had a stress test and did well. One week after stress test developed severe pain especially in foot of affected leg.. Went to pharmacist who saw leg snd told him to go to ER. At ER he was admitted. Is in ICU. Is having clot buster fluids applied to clot/plaque. Was given 50/50 chance of keeping leg. What can be done?