혈관의 일부분만 좁아져 있을 때는 별다른 증상이 없는 탓에 증세가 느껴질 때면 대부분 합병증이 생긴 경우다.
Because no speical symptoms are visible when the blood vessel is partially narrowed, most of the cases show that complication is already developed by the time when the symptoms are recognized.