###HUMAN: what is the number of patients whose discharge location is long term care hospital and procedure long title is incision of vessel, lower limb arteries?, ###ASSISTANT: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN procedures ON demographic.hadm_id = procedures.hadm_id WHERE demographic.discharge_location = "LONG TERM CARE HOSPITAL" AND procedures.long_title = "Incision of vessel, lower limb arteries"