Under normal circumstances, the official lumen of coronary artery is smooth and elastic, and the blood flow is smooth. When severe atherosclerosis occurs in the coronary arteries or when spasm or thrombosis occurs on this basis and causes narrowing of the official lumen, the blood and oxygen delivered to the heart will be reduced, and then symptoms such as chest tightness and chest pain will appear, which is called coronary heart disease. Mild stenosis of coronary arteries <50% does not cause obvious symptoms and is not diagnosed as coronary heart disease; only when the stenosis is ≥50% is coronary heart disease diagnosed. Coronary heart disease can cause angina pectoris, myocardial infarction, and even cardiac arrest or sudden death. But you don't need to worry, there are many advanced methods of treatment available to restore normal blood flow to the narrowed coronary arteries and normal blood supply to the heart muscle, eliminating your symptoms and improving your quality of life.