Is having blocked arteries a serious condition?

Depends where: A blocked artery can cause the death of the organ supplied by that artery, or a portion thereof. If the main artery of your heart is blocked, this is of course a serious condition that few survive if the blockages complete. If it is a small artery to a small portion of an unimportant organ, you may not even notice. Disease in one vessel usually means there is also disease in other vessels.