I gather that you are a young man with established coronary disease, asymptomatic on medical treatment. The medical treatment is very important, continue that and keep your lipds very low - LDL Cholesterol less than 80 mgs, triglycerides less than 150 mgs and HDL Cholesterol more than 45 mgs. Statins and niacin are good for that. Keep your BP less than 140/85 mms Hg.
In addition, I think a stress thallium should be repeated to evaluate degree of ischaemia if the areas involved have increased and anterior wall also gets involved during exercise it calls for a repeat angiography. The need for revascularisation(PTCA /CABG) will depend on the area at risk.