This study will examine the effectiveness of the drug cyclosporine in treating hypertrophic cardiomyopathy (HCM), a condition in which the heart muscle thickens. The thickened muscle can impair the heart's pumping action or decrease its blood supply, or both. Various symptoms, such as chest pain, shortness of breath, fatigue, and palpitations, may result. In animal studies, cyclosporine prevented heart muscle from thickening in mice that had been engineered to develop thick hearts.