 VINTAGE-MI is a randomized, double blind study enrolling patients who have recently suffered their first heart attack. There are two recruitment clinics within the Johns Hopkins University Network, the Johns Hopkins Hospital and the Hopkins Bayview Medical Center. Following preliminary testing to establish eligibility and baseline function of both the heart and blood vessels, study participants will be randomly assigned to receive either L-Arginine or a placebo pill which is identical except that it does not contain L-Arginine. These pills will be taken orally 3 times a day for 6 months. Participants will return to the clinic 1, 3, and 6 months after they begin taking their medication to have the same functional testing repeated. 