*Prospective study; enrolled 10 or more patients; study duration at least 6 months. Prospective study; angioplasty included stent placement; enrolled 30 or more patients; study duration at least 6 months; patients recruited in 1993 or later; patients did not have previous angioplasty. One study has data both for direct comparison of medical treatment to angioplasty and for natural history. Any study design; enrolled 10 or more patients; study duration at least 6 months. Studies with surgical intervention must have recruited patients in 1993 or later. ||Any study design; enrolled 10 or more patients; study duration at least 6 months; patients recruited in 1993 or later. ¶Any study design; enrolled 100 or more patients (10 or more if the study was prospective); study duration at least 6 months; patients recruited in 1993 or later.