All participants will receive 0.25 mg/kg of ReoPro (maximum dose of 30 mg). The drug is infused into the vein over 12 hours. Some patients will also receive one of four doses of Retavase, which may boost the effectiveness of ReoPro in opening the blocked blood vessel. Retavase is given through a needle in the vein over 2 minutes. Patients will be monitored daily until discharge from the hospital, or until day 5, whichever is earlier. Assessments will include physical examinations, blood tests to examine factors involved in blood clotting, and CT scans to evaluate both the response to treatment and drug side effects. They will return for a follow-up examination and CT scan 30 days after treatment.