A 52-year-old woman with a 10-year history of type 2 diabetes mellitus, hypertension, and hypercholesterolemia undergoes coronary angiography for stable angina. Angiography reveals 70% stenosis in the left anterior descending artery, 60% stenosis in the left circumflex artery, and 85% stenosis in the right coronary artery with normal left ventricular ejection fraction. What is the most appropriate next step in management?