Bypass surgery ( CABG) and Angioplasty ( PTCA) have shown to improve the quality of life in chronic stable angina patients. These modalities haven't shown to improve all-cause mortality.
Clinical trials like EAST, RITA, MASS, BARI, BARI-2D, and COURAGE has shown the limitation of bypass surgery and angioplasty in patients with chronic stable angina.
There is a huge discrepancy between what the cardiologist wants to deliver which is a reduction in symptoms and improved quality of life. What stable patients want to achieve is a decrease in the chance of myocardial infarction ( heart attack) and improved survival by doing interventional procedures like bypass surgery and angioplasty.