While the patient is awake and pain-free (local anesthesia), a catheter is inserted into an artery at the top of the leg (the femoral artery). The procedure begins with the doctor injecting some local anesthesia into the groin area and putting a needle into the femoral artery (the blood vessel that runs from the heart down the leg). Once the needle is inserted, a guide wire is placed through the needle, into the blood vessel. Following this step, the guide wire is left in the blood vessel and the needle is removed. A large needle called an introducer is then placed over the guide wire and the guide wire is removed.