The purpose of the study is to determine if the medication, ranolazine (study drug), can help improve blood flow to your heart, increase your exercise capacity and improve your quality of life (QOL). For this study, you will be asked to perform several tests in order to determine if your heart function, exercise capacity, chest pain and QOL have improved after 3 months of treatment with ranolazine. Ranolazine is approved by the U.S. Food and Drug Administration (FDA) for the treatment of angina.