An atherosclerosis index of 4.51 is not normal and indicates that atherosclerotic disease is already present. Atherosclerosis is a disease in which the inner lining of the arteries becomes diseased, with lipid accumulation, fibrous tissue proliferation, calcium deposits, and gradual degeneration and calcification of the middle layer of the arteries, which can lead to arterial stenosis or even blockage in severe cases. Atherosclerotic index is a measure of the degree of atherosclerosis. The atherosclerosis index should be below 4.0 under normal circumstances, and the higher the number above 4.0, the more serious the condition is, and the higher the risk of cardiovascular and cerebrovascular events. The atherosclerosis index of 4.51 indicates that atherosclerosis already exists, which is not normal, but the condition has not yet reached a particularly serious level.